text: '''
  Generate Operations (Query and Mutations) using Python
  ======================================================
  
  .. note::
  
    This module could be called "query", however it should also generate
    mutations and a class ``Query`` could lead to mistakes, since the
    users should define their own root ``Query`` class with the
    top-level queries in their GraphQL schema.
  
  Users create instance of :class:`Operation` using the
  ``Schema.Query`` or ``Schema.Mutation`` types. From there they proceed
  accessing members, which will produce :class:`Selector` instances,
  that once called will produce :class:`Selection` instances, which are
  automatically added to a :class:`SelectionList` in the parent
  (operation or selection). The following annotated GraphQL code helps
  to understand the Python mapping::
  
     query { # Operation
        parent(arg: "value") { # Selector, called with arguments
           child { # Selector, called without arguments
              field # Selector called without arguments, Selection without alias
              alias: field(other: 123)
           }
           sibling { x { y } }
        }
     }
  
  .. code-block:: python
  
     op = Operation(Query)
     parent = op.parent(arg='value')
  
     child = parent.child
     child.field()
     child.field(other=123, __alias__='alias')
  
     parent.sibling.x.y()
  
  :class:`Operation` implements ``__str__()`` and ``__repr__()`` to
  generate the GraphQL query for you. It also provide ``__bytes__()`` to
  produce compact output, without indentation. It can be passed to
  :class:`sgqlc.endpoint.base.BaseEndpoint.__call__()` as is.
  
  Another convenience is the ``__add__()`` to apply the operation to a
  resulting JSON data, interpreting the results and producing convenient
  objects:
  
  .. code-block:: python
  
     endpoint = HTTPEndpoint(url)
     data = endpoint(op)
  
     obj = op + data
     print(obj.parent.child.field)
     print(obj.parent.sibling.x.y)
  
  
  Examples
  --------
  
  Let's start defining the types, including the schema root ``Query``:
  
  >>> from sgqlc.types import *
  >>> from datetime import datetime
  >>> class Actor(Interface):
  ...    login = non_null(str)
  ...
  >>> class User(Type, Actor):
  ...    name = str
  ...
  >>> class Organization(Type, Actor):
  ...    location = str
  ...
  >>> class ActorConnection(Type):
  ...    actors = Field(list_of(non_null(Actor)), args={'login': non_null(str)})
  ...
  >>> class Assignee(Type):
  ...    email = non_null(str)
  ...
  >>> class UserOrAssignee(Union):
  ...    __types__ = (User, Assignee)
  ...
  >>> class Issue(Type):
  ...     number = non_null(int)
  ...     title = non_null(str)
  ...     body = str
  ...     reporter = non_null(User)
  ...     assigned = UserOrAssignee
  ...     commenters = ActorConnection
  ...
  >>> class ReporterFilterInput(Input):
  ...     name_contains = str
  ...
  >>> class IssuesFilter(Input):
  ...     reporter = list_of(ReporterFilterInput)
  ...     start_date = non_null(datetime)
  ...     end_date = datetime
  ...
  >>> class Repository(Type):
  ...     id = ID
  ...     name = non_null(str)
  ...     owner = non_null(Actor)
  ...     issues = Field(list_of(non_null(Issue)), args={
  ...         'title_contains': str,
  ...         'reporter_login': str,
  ...         'filter': IssuesFilter,
  ...     })
  ...
  >>> class Query(Type):
  ...     repository = Field(Repository, args={'id': non_null(ID)})
  ...
  >>> class Mutation(Type):
  ...     add_issue = Field(Issue, args={
  ...         'repository_id': non_null(ID),
  ...         'title': non_null(str),
  ...         'body': str,
  ...     })
  ...
  >>> global_schema  # doctest: +ELLIPSIS
  schema {
    ...
    interface Actor {
      login: String!
    }
    type User implements Actor {
      login: String!
      name: String
    }
    type Organization implements Actor {
      login: String!
      location: String
    }
    type ActorConnection {
      actors(login: String!): [Actor!]
    }
    type Assignee {
      email: String!
    }
    union UserOrAssignee = User | Assignee
    type Issue {
      number: Int!
      title: String!
      body: String
      reporter: User!
      assigned: UserOrAssignee
      commenters: ActorConnection
    }
    input ReporterFilterInput {
      nameContains: String
    }
    input IssuesFilter {
      reporter: [ReporterFilterInput]
      startDate: DateTime!
      endDate: DateTime
    }
    type Repository {
      id: ID
      name: String!
      owner: Actor!
      issues(titleContains: String, reporterLogin: String, filter: IssuesFilter): [Issue!]
    }
    type Query {
      repository(id: ID!): Repository
    }
    type Mutation {
      addIssue(repositoryId: ID!, title: String!, body: String): Issue
    }
  }
  
  Selecting to Generate Queries
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  Then let's select numbers and titles of issues of repository with
  identifier ``repo1``:
  
  >>> op = Operation(Query)
  >>> repository = op.repository(id='repo1')
  >>> repository.issues.number()
  number
  >>> repository.issues.title()
  title
  >>> op # or repr(), prints out GraphQL!
  query {
    repository(id: "repo1") {
      issues {
        number
        title
      }
    }
  }
  
  You can see we stored ``op.repository(id='repo1')`` result in a
  variable, later reusing it. Executing this statement will emit a new
  :class:`Selection` and only one field selection is allowed in the
  selection list (unless an alias is used). Trying the code below will
  **error**:
  
  >>> op = Operation(Query)
  >>> op.repository(id='repo1').issues.number() # ok!
  number
  >>> op.repository(id='repo1').issues.title() # fails
  Traceback (most recent call last):
    ...
  ValueError: repository already have a selection repository(id: "repo1") {
    issues {
      number
    }
  }. Maybe use __alias__ as param?
  
  That is, if you wanted to query for two repositories, you should use
  ``__alias__`` argument in the call. But here would **not** produce the
  query we want, as seen below:
  
  >>> op = Operation(Query)
  >>> op.repository(id='repo1').issues.number()
  number
  >>> op.repository(id='repo1', __alias__='alias').issues.title()
  title
  >>> op  # not what we want in this example, 2 independent queries
  query {
    repository(id: "repo1") {
      issues {
        number
      }
    }
    alias: repository(id: "repo1") {
      issues {
        title
      }
    }
  }
  
  In our case, to get the correct query, do as in the first example and
  save the result of ``op.repository(id='repo1')``.
  
  Aliases may be used to rename fields everywhere, not just in the topmost
  query, and for other reasons other than allow two calls with the same
  name. One may use it to translate API fields to something else, example:
  
  >>> op = Operation(Query)
  >>> repository = op.repository(id='repo1')
  >>> repository.issues.number(__alias__='code')
  code: number
  >>> op # or repr(), prints out GraphQL!
  query {
    repository(id: "repo1") {
      issues {
        code: number
      }
    }
  }
  
  Last but not least, in the first example you can also note that we're
  not calling ``issues``, just accessing its members. This is a shortcut
  for an empty call, and the handle is saved for you (ease of use):
  
  >>> op = Operation(Query)
  >>> repository = op.repository(id='repo1')
  >>> repository.issues().number()
  number
  >>> repository.issues().title()
  title
  >>> op # or repr(), prints out GraphQL!
  query {
    repository(id: "repo1") {
      issues {
        number
        title
      }
    }
  }
  
  This could be rewritten saving the issues selector:
  
  >>> op = Operation(Query)
  >>> issues = op.repository(id='repo1').issues()
  >>> issues.number()
  number
  >>> issues.title()
  title
  >>> op
  query {
    repository(id: "repo1") {
      issues {
        number
        title
      }
    }
  }
  
  Or even simpler with ``__fields__(*names, **names_and_args)``:
  
  >>> op = Operation(Query)
  >>> op.repository(id='repo1').issues.__fields__('number', 'title')
  >>> op
  query {
    repository(id: "repo1") {
      issues {
        number
        title
      }
    }
  }
  >>> op = Operation(Query)
  >>> op.repository(id='repo1').issues.__fields__(
  ...     number=True,
  ...     title=True,
  ... )
  >>> op
  query {
    repository(id: "repo1") {
      issues {
        number
        title
      }
    }
  }
  
  Which also allows to include all but some fields:
  
  >>> op = Operation(Query)
  >>> op.repository(id='repo1').issues.__fields__(
  ...     __exclude__=('body', 'reporter', 'commenters'),
  ... )
  >>> op
  query {
    repository(id: "repo1") {
      issues {
        number
        title
        assigned {
          __typename
          ... on User {
            login
            name
          }
          ... on Assignee {
            email
          }
        }
      }
    }
  }
  
  Or using named arguments:
  
  >>> op = Operation(Query)
  >>> op.repository(id='repo1').issues.__fields__(
  ...     body=False,
  ...     reporter=False,
  ...     commenters=False,
  ... )
  >>> op
  query {
    repository(id: "repo1") {
      issues {
        number
        title
        assigned {
          __typename
          ... on User {
            login
            name
          }
          ... on Assignee {
            email
          }
        }
      }
    }
  }
  
  If no arguments are given to ``__fields__()``, then it defaults to
  include every member, and this is done recursively:
  
  >>> op = Operation(Query)
  >>> op.repository(id='repo1').issues.__fields__()
  >>> op
  query {
    repository(id: "repo1") {
      issues {
        number
        title
        body
        reporter {
          login
          name
        }
        assigned {
          __typename
          ... on User {
            login
            name
          }
          ... on Assignee {
            email
          }
        }
        commenters {
          actors {
            login
          }
        }
      }
    }
  }
  
  Named arguments may be used to provide fields with argument values:
  
  >>> op = Operation(Query)
  >>> op.repository(id='repo1').__fields__(
  ...    issues={'title_contains': 'bug'}, # adds field and children
  ... )
  >>> op
  query {
    repository(id: "repo1") {
      issues(titleContains: "bug") {
        number
        title
        body
        reporter {
          login
          name
        }
        assigned {
          __typename
        }
      }
    }
  }
  
  Arguments can be given as tuple of key-value pairs as well:
  
  >>> op = Operation(Query)
  >>> op.repository(id='repo1').__fields__(
  ...    issues=(('title_contains', 'bug'),), # adds field and children
  ... )
  >>> op
  query {
    repository(id: "repo1") {
      issues(titleContains: "bug") {
        number
        title
        body
        reporter {
          login
          name
        }
        assigned {
          __typename
        }
      }
    }
  }
  
  If a field of a container type (interface or type) is used without explicit
  fields as documented above, all of its fields will be added automatically.
  It will avoid dependency loops and limit the allowed nest depth to 2 by
  default, but that can be overridden with an explicit ``auto_select_depth``
  to ``__to_graphql__()`` (which is used by ``str()``, ``repr()`` and the
  likes):
  
  >>> op = Operation(Query)
  >>> op.repository(id='repo1') # printed with depth=2 (default)
  repository(id: "repo1") {
    id
    name
    owner {
      login
    }
    issues {
      number
      title
      body
    }
  }
  >>> op # the whole query printed with depth=2 (default)
  query {
    repository(id: "repo1") {
      id
      name
      owner {
        login
      }
      issues {
        number
        title
        body
      }
    }
  }
  
  >>> print(op.__to_graphql__(auto_select_depth=1)) # omits owner/issues
  query {
    repository(id: "repo1") {
      id
      name
    }
  }
  >>> print(op.__to_graphql__(auto_select_depth=3)) # shows reporter
  query {
    repository(id: "repo1") {
      id
      name
      owner {
        login
      }
      issues {
        number
        title
        body
        reporter {
          login
          name
        }
        assigned {
          __typename
        }
      }
    }
  }
  >>> print(op.__to_graphql__(auto_select_depth=4)) # shows assigned sub-types
  query {
    repository(id: "repo1") {
      id
      name
      owner {
        login
      }
      issues {
        number
        title
        body
        reporter {
          login
          name
        }
        assigned {
          __typename
          ... on User {
            login
            name
          }
          ... on Assignee {
            email
          }
        }
        commenters {
          actors {
            login
          }
        }
      }
    }
  }
  
  
  
  
  
  Interpret Query Results
  ~~~~~~~~~~~~~~~~~~~~~~~
  
  Given the operation explained above:
  
  >>> op = Operation(Query)
  >>> op.repository(id='repo1').issues.__fields__('number', 'title')
  >>> op
  query {
    repository(id: "repo1") {
      issues {
        number
        title
      }
    }
  }
  
  After calling the GraphQL endpoint, you should get a JSON object that
  matches the one below:
  
  >>> json_data = {'data': {
  ...     'repository': {'issues': [
  ...         {'number': 1, 'title': 'found a bug'},
  ...         {'number': 2, 'title': 'a feature request'},
  ...     ]},
  ... }}
  
  To interpret this, simply add the data to the operation:
  
  >>> obj = op + json_data
  >>> repository = obj.repository
  >>> for issue in repository.issues:
  ...     print(issue)
  Issue(number=1, title=found a bug)
  Issue(number=2, title=a feature request)
  
  Which are instances of classes declared in the beginning of example
  section:
  
  >>> repository.__class__ is Repository
  True
  >>> repository.issues[0].__class__ is Issue
  True
  
  While it's mostly the same as creating instances yourself:
  
  >>> repository = Repository(json_data['data']['repository'])
  >>> for issue in repository.issues:
  ...     print(issue)
  Issue(number=1, title=found a bug)
  Issue(number=2, title=a feature request)
  
  The difference is that it will handle **aliases** for you:
  
  >>> op = Operation(Query)
  >>> op.repository(id='repo1', __alias__='r_name1').issues.__fields__(
  ...     number='code', title='headline',
  ... )
  >>> op.repository(id='repo2', __alias__='r_name2').issues.__fields__(
  ...     'number', 'title',
  ... )
  >>> op
  query {
    r_name1: repository(id: "repo1") {
      issues {
        code: number
        headline: title
      }
    }
    r_name2: repository(id: "repo2") {
      issues {
        number
        title
      }
    }
  }
  
  >>> json_data = {'data': {
  ...     'r_name1': {'issues': [
  ...         {'code': 1, 'headline': 'found a bug'},
  ...         {'code': 2, 'headline': 'a feature request'},
  ...     ]},
  ...     'r_name2': {'issues': [
  ...         {'number': 10, 'title': 'something awesome'},
  ...         {'number': 20, 'title': 'other thing broken'},
  ...     ]},
  ... }}
  >>> obj = op + json_data
  >>> for issue in obj.r_name1.issues:
  ...     print(issue)
  Issue(code=1, headline=found a bug)
  Issue(code=2, headline=a feature request)
  >>> for issue in obj.r_name2.issues:
  ...     print(issue)
  Issue(number=10, title=something awesome)
  Issue(number=20, title=other thing broken)
  
  Updating also reflects on the correct backing store:
  
  >>> obj.r_name2.name = 'repo2 name'
  >>> json_data['data']['r_name2']['name']
  'repo2 name'
  
  It also works with auto selection:
  
  >>> op = Operation(Query)
  >>> op.repository(id='repo1')
  repository(id: "repo1") {
    id
    name
    owner {
      login
    }
    issues {
      number
      title
      body
    }
  }
  >>> json_data = {'data': {
  ...     'repository': {'id': 'repo1', 'name': 'Repo #1'},
  ... }}
  >>> obj = op + json_data
  >>> obj.repository.name
  'Repo #1'
  
  
  Error Reporting
  ~~~~~~~~~~~~~~~
  
  If the returned data contains only ``errors`` and no ``data``,
  the interpretation will raise an error :class:`GraphQLErrors`:
  
  >>> json_data = {'errors': [{'message': 'some message'}]}
  >>> try:  # doctest: +ELLIPSIS
  ...     obj = op + json_data
  ... except GraphQLErrors as ex:
  ...     print('Got error:', repr(ex))
  ...     print(ex.errors)
  Got error: GraphQLErrors('some message'...
  [{'message': 'some message'}]
  
  If there are mixed data and errors, the object is returned with
  ``__errors__`` attribute set to the errors:
  
  >>> json_data = {
  ...     'errors': [{'message': 'some message'}],
  ...     'data': {
  ...         'repository': {'id': 'repo1', 'name': 'Repo #1'},
  ...     },
  ... }
  >>> obj = op + json_data
  >>> obj.repository.name
  'Repo #1'
  >>> obj.__errors__
  [{'message': 'some message'}]
  
  
  Mutations
  ~~~~~~~~~
  
  Mutations are handled as well, just use that as :class:`Operation`
  root type:
  
  >>> op = Operation(Mutation)
  >>> op.add_issue(repository_id='repo1', title='an issue').__fields__()
  >>> op
  mutation {
    addIssue(repositoryId: "repo1", title: "an issue") {
      number
      title
      body
      reporter {
        login
        name
      }
      assigned {
        __typename
        ... on User {
          login
          name
        }
        ... on Assignee {
          email
        }
      }
      commenters {
        actors {
          login
        }
      }
    }
  }
  
  
  Inline Fragments & Interfaces
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  When a field specifies an interface such as the ``Repository.owner``
  in our example, only the interface fields can be queried. However,
  the actual type may implement much more, and to solve that in GraphQL
  we usually do an inline fragment ``... on ActualType { field1, field2 }``.
  
  To achieve that we use the ``__as__(ActualType)`` on the selection list,
  example:
  
  >>> op = Operation(Query)
  >>> repo = op.repository(id='repo1')
  >>> repo.owner.login() # interface fields can be declared as usual
  login
  >>> repo.owner().__as__(Organization).location() # location field for Orgs
  location
  >>> repo.owner.__as__(User).name() # name field for Users
  name
  >>> repo.issues().assigned.__as__(Assignee).email()
  email
  >>> repo.issues().assigned.__as__(User).login()
  login
  >>> repo.issues().commenters().actors().login()
  login
  >>> repo.issues().commenters().actors().__as__(Organization).location()
  location
  >>> repo.issues().commenters().actors().__as__(User).name()
  name
  >>> op
  query {
    repository(id: "repo1") {
      owner {
        login
        __typename
        ... on Organization {
          location
        }
        ... on User {
          name
        }
      }
      issues {
        assigned {
          __typename
          ... on Assignee {
            email
          }
          ... on User {
            login
          }
        }
        commenters {
          actors {
            login
            __typename
            ... on Organization {
              location
            }
            ... on User {
              name
            }
          }
        }
      }
    }
  }
  
  Note that ``__typename`` is automatically selected so it can create the
  proper type when interprets the results:
  
  >>> json_data = {'data': {'repository': {'owner': {
  ...    '__typename': 'User',
  ...    'login': 'user',
  ...    'name': 'User Name',
  ...    },
  ...    'issues': [
  ...      {
  ...          'assigned': {'__typename': 'Assignee', 'email': 'e@mail.com'},
  ...          'commenters': {
  ...              'actors': [
  ...                  {'login': 'user', '__typename': 'User', 'name': 'User Name'},
  ...                  {'login': 'a-company', '__typename': 'Organization', 'location': 'that place'}
  ...              ]
  ...          }
  ...      },
  ...      {
  ...          'assigned': {'__typename': 'User', 'login': 'xpto'},
  ...          'commenters': {
  ...              'actors': [
  ...                  {'login': 'user', '__typename': 'User', 'name': 'User Name'},
  ...                  {'login': 'xpto', '__typename': 'User'}
  ...              ]
  ...          }
  ...      },
  ...    ],
  ... }}}
  >>> obj = op + json_data
  >>> obj.repository.owner
  User(login='user', __typename__='User', name='User Name')
  >>> for i in obj.repository.issues:
  ...     print(i)
  Issue(assigned=Assignee(__typename__=Assignee, email=e@mail.com), commenters=ActorConnection(actors=[User(login='user', __typename__='User', name='User Name'), Organization(login='a-company', __typename__='Organization', location='that place')]))
  Issue(assigned=User(__typename__=User, login=xpto), commenters=ActorConnection(actors=[User(login='user', __typename__='User', name='User Name'), User(login='xpto', __typename__='User')]))
  
  >>> json_data = {'data': {'repository': {'owner': {
  ...    '__typename': 'Organization',
  ...    'login': 'a-company',
  ...    'name': 'A Company',
  ... }}}}
  >>> obj = op + json_data
  >>> obj.repository.owner
  Organization(login='a-company', __typename__='Organization')
  
  If the returned type doesn't have an explicit type fields, the
  Interface field is returned:
  
  >>> json_data = {'data': {'repository': {'owner': {
  ...    '__typename': 'SomethingElse',
  ...    'login': 'something-else',
  ...    'field': 'value',
  ... }}}}
  >>> obj = op + json_data
  >>> obj.repository.owner
  Actor(login='something-else', __typename__='SomethingElse')
  
  In the unusual situation where ``__typename`` is not returned,
  it's going to behave as the interface type as well:
  
  >>> json_data = {'data': {'repository': {'owner': {
  ...    'login': 'user',
  ...    'name': 'User Name',
  ... }}}}
  >>> obj = op + json_data
  >>> obj.repository.owner
  Actor(login='user')
  
  
  Named Fragments
  ~~~~~~~~~~~~~~~
  
  Named fragments are a way to reuse selection blocks and allow
  optimizations to be employed. They also allow shorter documents
  if the fragment is used more than once.
  
  They are similar to Inline Fragments described above as they
  allow selecting on interfaces and unions.
  
  >>> org_loc_frag = Fragment(Organization, 'OrganizationLocationFragment')
  >>> org_loc_frag.location()
  location
  >>> org_login_frag = Fragment(Organization, 'OrganizationLoginFragment')
  >>> org_login_frag.login()
  login
  >>> user_frag = Fragment(User, 'UserFragment')
  >>> user_frag.name()
  name
  >>> assignee_frag = Fragment(Assignee, 'AssigneeFragment')
  >>> assignee_frag.email()
  email
  >>> op = Operation(Query)
  >>> repo = op.repository(id='repo1')
  >>> repo.owner.login() # interface fields can be declared as usual
  login
  >>> repo.owner().__fragment__(org_loc_frag)
  >>> repo.owner().__fragment__(org_login_frag)  # can do many on the same type
  >>> repo.owner.__fragment__(user_frag)
  >>> repo.issues().assigned.__fragment__(assignee_frag)
  >>> repo.issues().assigned.__fragment__(user_frag)
  >>> repo.issues().commenters().actors().login()
  login
  >>> repo.issues().commenters().actors().__fragment__(org_loc_frag)
  >>> repo.issues().commenters().actors().__fragment__(user_frag)
  >>> op
  query {
    repository(id: "repo1") {
      owner {
        login
        __typename
        ...OrganizationLocationFragment
        ...OrganizationLoginFragment
        ...UserFragment
      }
      issues {
        assigned {
          __typename
          ...AssigneeFragment
          ...UserFragment
        }
        commenters {
          actors {
            login
            __typename
            ...OrganizationLocationFragment
            ...UserFragment
          }
        }
      }
    }
  }
  fragment OrganizationLocationFragment on Organization {
    location
  }
  fragment OrganizationLoginFragment on Organization {
    login
  }
  fragment UserFragment on User {
    name
  }
  fragment AssigneeFragment on Assignee {
    email
  }
  
  Note that ``__typename`` is automatically selected so it can create the
  proper type when interprets the results:
  
  >>> json_data = {'data': {'repository': {'owner': {
  ...    '__typename': 'User',
  ...    'login': 'user',
  ...    'name': 'User Name',
  ...    },
  ...    'issues': [
  ...      {
  ...          'assigned': {'__typename': 'Assignee', 'email': 'e@mail.com'},
  ...          'commenters': {
  ...              'actors': [
  ...                  {'login': 'user', '__typename': 'User', 'name': 'User Name'},
  ...                  {'login': 'a-company', '__typename': 'Organization', 'location': 'that place'}
  ...              ]
  ...          }
  ...      },
  ...      {
  ...          'assigned': {'__typename': 'User', 'name': 'User'},
  ...          'commenters': {
  ...              'actors': [
  ...                  {'login': 'user', '__typename': 'User', 'name': 'User Name'},
  ...                  {'login': 'xpto', '__typename': 'User'}
  ...              ]
  ...          }
  ...      },
  ...    ],
  ... }}}
  >>> obj = op + json_data
  >>> obj.repository.owner
  User(login='user', __typename__='User', name='User Name')
  >>> for i in obj.repository.issues:
  ...     print(i)
  Issue(assigned=Assignee(__typename__=Assignee, email=e@mail.com), commenters=ActorConnection(actors=[User(login='user', __typename__='User', name='User Name'), Organization(login='a-company', __typename__='Organization', location='that place')]))
  Issue(assigned=User(__typename__=User, name=User), commenters=ActorConnection(actors=[User(login='user', __typename__='User', name='User Name'), User(login='xpto', __typename__='User')]))
  
  >>> json_data = {'data': {'repository': {'owner': {
  ...    '__typename': 'Organization',
  ...    'login': 'a-company',
  ...    'location': 'somewhere',
  ...    'name': 'A Company',
  ... }}}}
  >>> obj = op + json_data
  >>> obj.repository.owner
  Organization(login='a-company', __typename__='Organization', location='somewhere')
  
  If the returned type doesn't have an explicit type fields, the
  Interface field is returned:
  
  >>> json_data = {'data': {'repository': {'owner': {
  ...    '__typename': 'SomethingElse',
  ...    'login': 'something-else',
  ...    'field': 'value',
  ... }}}}
  >>> obj = op + json_data
  >>> obj.repository.owner
  Actor(login='something-else', __typename__='SomethingElse')
  
  In the unusual situation where ``__typename`` is not returned,
  it's going to behave as the interface type as well:
  
  >>> json_data = {'data': {'repository': {'owner': {
  ...    'login': 'user',
  ...    'name': 'User Name',
  ... }}}}
  >>> obj = op + json_data
  >>> obj.repository.owner
  Actor(login='user')
  
  
  Utilities
  ~~~~~~~~~
  
  Starting with the first selection example:
  
  >>> op = Operation(Query)
  >>> repository = op.repository(id='repo1')
  >>> repository.issues.number()
  number
  >>> repository.issues.title()
  title
  
  One can get a indented print out using ``repr()``:
  
  >>> print(repr(op))
  query {
    repository(id: "repo1") {
      issues {
        number
        title
      }
    }
  }
  >>> print(repr(repository))
  repository(id: "repo1") {
    issues {
      number
      title
    }
  }
  >>> print(repr(repository.issues.number()))
  number
  
  Note that :class:`Selector` is different:
  
  >>> print(repr(repository.issues.number))
  Selector(field=number)
  
  Or can get a compact print out without indentation using ``bytes()``:
  
  >>> print(bytes(op).decode('utf-8'))
  query {
  repository(id: "repo1") {
  issues {
  number
  title
  }
  }
  }
  >>> print(bytes(repository).decode('utf-8'))
  repository(id: "repo1") {
  issues {
  number
  title
  }
  }
  >>> print(bytes(repository.issues.number()).decode('utf-8'))
  number
  
  
  :class:`Selection` and :class:`Selector` both implement ``len()``:
  
  >>> len(op)                        # number of selections (here: top level)
  1
  >>> len(repository.issues())       # number of selections
  2
  >>> len(repository.issues)         # number of selections (implicit empty call)
  2
  >>> len(repository.issues.title()) # leaf is always 1
  1
  
  :class:`Selection` and :class:`Selector` both implement ``dir()`` to
  also list fields:
  
  >>> for name in dir(repository.issues()): # on selection also yields fields
  ...     if not name.startswith('_'):
  ...         print(name)
  assigned
  body
  commenters
  number
  reporter
  title
  >>> for name in dir(repository.issues): # same for selector
  ...     if not name.startswith('_'):
  ...         print(name)
  assigned
  body
  commenters
  number
  reporter
  title
  >>> for name in dir(repository.issues.number()): # no fields for scalar
  ...     if not name.startswith('_'):
  ...         print(name)
  >>> for name in dir(repository.issues.number): # no fields for scalar
  ...     if not name.startswith('_'):
  ...         print(name)
  
  Classes also implement ``iter()`` to iterate over selections:
  
  >>> for i, sel in enumerate(op):
  ...     print('#%d: %s' % (i, sel))
  #0: repository(id: "repo1") {
    issues {
      number
      title
    }
  }
  >>> for i, sel in enumerate(repository):
  ...     print('#%d: %s' % (i, sel))
  #0: issues {
    number
    title
  }
  >>> for i, sel in enumerate(repository.issues):
  ...     print('#%d: %s' % (i, sel))
  #0: number
  #1: title
  >>> for i, sel in enumerate(repository.issues()):
  ...     print('#%d: %s' % (i, sel))
  #0: number
  #1: title
  >>> for i, sel in enumerate(repository.issues.number()):
  ...     print('#%d: %s' % (i, sel))
  #0: number
  
  Given a :class:`Selector` one can query a **selection** given its alias:
  
  >>> op = Operation(Query)
  >>> op.repository(id='repo1').issues.number()
  number
  >>> op.repository(id='repo2', __alias__='alias').issues.title()
  title
  >>> type(op['repository'])  # it's the selector, not a selection!
  <class 'sgqlc.operation.Selector'>
  >>> op['repository'].__selection__() # default selection
  repository(id: "repo1") {
    issues {
      number
    }
  }
  >>> op['repository'].__selection__('alias') # aliased selection
  alias: repository(id: "repo2") {
    issues {
      title
    }
  }
  
  Which is useful to query the selection alias and arguments:
  
  >>> op['repository'].__selection__('alias').__alias__
  'alias'
  >>> op['repository'].__selection__('alias').__args__
  {'id': 'repo2'}
  >>> op['repository'].__selection__().__args__
  {'id': 'repo1'}
  
  To get the arguments of the default (non-aliased) one can use the shortcut:
  
  >>> op['repository'].__args__
  {'id': 'repo1'}
  
  :license: ISC
  '''  # noqa: E501
  
  __docformat__ = 'reStructuredText en'
  
  __all__ = ('Operation',)
  
  from collections import OrderedDict
  
  from ..types import BaseTypeWithTypename, Union, ContainerType, ArgDict, \
      global_schema
  
  
  DEFAULT_AUTO_SELECT_DEPTH = 2
  PROXIED_FIELDS = {
      '__type__', '__casts__', '__as__', '__fragment__', '__fragments__',
  }
  
  
  class Selection:
      '''Select a field with in a container type.
  
      .. warning::
  
        Do not create instances directly, use
        :class:`sgqlc.operation.Selector` instead.
  
      A selection matches the GraphQL statement to select a field from a
      type, it may contain an alias and parameters::
  
        query {
          parent {
            field
            field(param1: value1, param2: value2)
            alias: field(param1: value1, param2: value2)
          }
        }
  
      Attributes or items access will result in :class:`sgqlc.operation.Selector`
      matching the **target type** field:
  
      .. code-block:: python
  
        parent.field.child
  
  
      For container types one can provide a batch of fields using
      :func:`sgqlc.operation.Selection.__fields__()`:
  
      .. code-block:: python
  
        # just field1 and field2
        parent.field.child.__fields__('field1', 'field2')
        parent.field.child.__fields__(field1=True, field2=True)
  
        # field1 with parameters
        parent.field.child.__fields__(field1=dict(param1='value1'))
  
        # all but field2
        parent.field.child.__fields__(field2=False)
        parent.field.child.__fields__(field2=None)
        parent.field.child.__fields__(__exclude__=('field2',))
  
      If ``__fields__()`` is not explicitly called, then all fields
      are included. Note that this may lead to huge queries since it
      will result in recursive inclusion of all fields.
  
      Selectors will create selections when items or attributes are
      accessed, this is done by implicitly calling the selector with
      empty parameters.
  
      However leafs (ie: scalars) must be **explicitly** called,
      otherwise they won't generate a selection
  
      .. code-block:: python
  
        # OK
        parent.field.child()
        # NOT OK: doesn't create a selection for child.
        parent.field.child
  
      '''
  
      __slots__ = (
          '__alias__', '__field__', '__args__', '__field_selector',
          '__selection_list',
      )
  
      def __init__(self, alias, field, args):
          self.__alias__ = alias
          self.__field__ = field
          self.__args__ = args
          self.__field_selector = {}
          self.__selection_list = None
          if issubclass(field.type, BaseTypeWithTypename):
              self.__selection_list = SelectionList(field.type)
  
      def __get_selections_or_auto_select__(
              self, auto_select_depth=DEFAULT_AUTO_SELECT_DEPTH):
          selections = self.__selection_list
          if selections is None or selections:
              return selections
          return self.__get_all_fields_selection_list(
              auto_select_depth, [])
  
      def __len__(self):
          if self.__selection_list is not None:
              return len(self.__selection_list)
          return 1
  
      def __iter__(self):
          if self.__selection_list is not None:
              return iter(self.__selection_list)
          return iter((self,))
  
      def __select_all_types(cls, union_type, depth, trail):
          recursive = len(trail) < depth
  
          q = SelectionList(union_type)
          q.__typename__()
          for t in union_type:
              if recursive and t not in trail:
                  sel = q.__as__(t)
                  for x in cls.__select_all_fields(t, depth, trail):
                      sel += x
          return q
  
      def __select_all_fields(cls, container_type, depth, trail):
          recursive = len(trail) < depth
  
          q = SelectionList(container_type)
          for f in container_type:
              sel = Selection(None, f, {})
              if issubclass(f.type, BaseTypeWithTypename):
                  if recursive and f.type not in trail:
                      # change the locally created selection list to the
                      # auto-selected one. This must be explicit here so
                      # it doesn't affect __to_graphql__(), that one must not
                      # affect the actual selection it's operating on!
                      sel.__selection_list = \
                          sel.__get_all_fields_selection_list(depth, trail)
                  else:
                      sel = None
  
              if sel:
                  q += sel
          return q
  
      def __get_all_fields_selection_list(self, depth, trail):
          t = self.__field__.type
          trail.append(t)
  
          if issubclass(t, Union):
              q = self.__select_all_types(t, depth, trail)
          else:
              q = self.__select_all_fields(t, depth, trail)
  
          trail.pop()
          return q
  
      def __fields__(self, *names, **names_and_args):
          '''Select fields of a container type.
  
          This is a helper to automate selection of fields of container
          types, such as giving a list of names to include, with or
          without parameters (passed as a mapping ``name=args``).
  
          If no arguments are given, all fields are included.
  
          If the keyword argument ``__exclude__`` is given a list of
          names, then all but those fields will be
          included. Alternatively one can exclude fields using
          ``name=None`` or ``name=False`` as keyword argument.
  
          If a list of names is given as positional arguments, then only
          those names will be included. Alternatively one can include
          fields using ``name=True``. To include fields with selection
          parameters, then use ``name=dict(...)`` or ``name=list(...)``.
          To include fields without arguments and with aliases, use the
          shortcut ``name='alias'``.
  
          .. code-block:: python
  
            # just field1 and field2
            parent.field.child.__fields__('field1', 'field2')
            parent.field.child.__fields__(field1=True, field2=True)
  
            # field1 with parameters
            parent.field.child.__fields__(field1=dict(param1='value1'))
  
            # field1 renamed (aliased) to alias1
            parent.field.child.__fields__(field1='alias1')
  
            # all but field2
            parent.field.child.__fields__(field2=False)
            parent.field.child.__fields__(field2=None)
            parent.field.child.__fields__(__exclude__=('field2',))
          '''
          exclude = self.__fields_gen_excludes(names_and_args)
  
          if not names and not names_and_args:
              self.__fields_add_all(exclude)
              return
  
          self.__fields_add_names(names)
          self.__fields_add_names_and_args(names_and_args)
  
      def __fields_gen_excludes(self, names_and_args):
          exclude = []
          if '__exclude__' in names_and_args:
              exclude = names_and_args.pop('__exclude__')
  
          for k, v in tuple(names_and_args.items()):  # force copy
              if v is False or v is None:
                  exclude.append(k)
                  del names_and_args[k]
  
          return exclude
  
      def __fields_add_all(self, exclude):
          for f in self.__field__.type:
              if f.name not in exclude:
                  self[f.name]()
  
      def __fields_add_names(self, names):
          for n in names:
              self[n]()
  
      def __fields_add_names_and_args(self, names_and_args):
          for n, args in names_and_args.items():
              if args and not isinstance(args, dict):
                  if isinstance(args, (tuple, list)):
                      args = dict(args)
                  elif isinstance(args, str):
                      args = {'__alias__': args}
                  else:
                      args = {}
              self[n](**args)
  
      def __to_graphql__(self, indent=0, indent_string='  ',
                         auto_select_depth=DEFAULT_AUTO_SELECT_DEPTH):
          prefix = indent_string * indent
  
          alias = ''
          if self.__alias__:
              alias = self.__alias__ + ': '
  
          args = self.__field__.args.__to_graphql_input__(
              self.__args__, indent, indent_string)
  
          query = ''
          if self.__selection_list is not None:
              selections = self.__selection_list
              if not selections:
                  selections = self.__get_all_fields_selection_list(
                      auto_select_depth, [])
              query = ' ' + selections.__to_graphql__(
                  indent, indent_string, auto_select_depth)
          return prefix + alias + self.__field__.graphql_name + args + query
  
      def __collect_fragments__(self, fragments):
          if self.__selection_list:
              self.__selection_list.__collect_fragments__(fragments)
  
      def __dir__(self):
          original_dir = super(Selection, self).__dir__()
          t = self.__field__.type
          if not issubclass(t, ContainerType):
              return original_dir
          fields = [f.name for f in t]
          return sorted(original_dir + fields)
  
      def __getattr__(self, name):
          if name.startswith('_'):
              sl = self.__selection_list
              if name in PROXIED_FIELDS:
                  if sl is None:
                      return None
                  return getattr(sl, name)
  
          try:
              return self[name]
          except KeyError as exc:
              raise AttributeError('%s has no field %s' % (self, name)) from exc
          except ValueError as exc:
              raise AttributeError('%s failed to get field %s' %
                                   (self, name)) from exc
  
      def __getitem__(self, name):
          if self.__selection_list is None:
              raise ValueError('Field %r of %s is not a container type.' %
                               (self.__field__, self.__field__.container))
  
          selector = self.__field_selector.get(name)
          if selector is None:
              selector = self.__field_selector[name] = Selector(
                  self.__selection_list, self.__field__.type[name])
  
          return selector
  
      def __str__(self):
          return self.__to_graphql__()
  
      def __repr__(self):
          return str(self)
  
      def __bytes__(self):
          return bytes(self.__to_graphql__(indent_string=''), 'utf-8')
  
  
  class Selector:
      '''Creates selection for a given field.
  
      .. warning::
  
        Do not create instances directly, use
        :class:`sgqlc.operation.SelectionList` instead.
  
      Selectors are callable objects that will create
      :class:`sgqlc.operation.Selection` entries in the parent
      :class:`sgqlc.operation.SelectionList`.
  
      Selectors will create selections when items or attributes are
      accessed, this is done by implicitly calling the selector with
      empty parameters.
  
      However leafs (ie: scalars) must be **explicitly** called,
      otherwise they won't generate a selection
  
      .. code-block:: python
  
        # OK
        parent.field.child()
        # NOT OK: doesn't create a selection for child.
        parent.field.child
  
      To select all fields from a container type, use
      :func:`sgqlc.operation.Selection.__fields__()`, example:
  
      .. code-block:: python
  
        # just field1 and field2
        parent.field.child.__fields__('field1', 'field2')
        parent.field.child.__fields__(field1=True, field2=True)
  
        # field1 with parameters
        parent.field.child.__fields__(field1=dict(param1='value1'))
  
        # all but field2
        parent.field.child.__fields__(field2=False)
        parent.field.child.__fields__(field2=None)
        parent.field.child.__fields__(__exclude__=('field2',))
  
      .. note::
  
         GraphQL limits a single selection per type, as the field name
         is used in the return object. If you want to select the same
         field multiple times, like as using different parameters, then
         provide the ``__alias__`` parameter to the selector:
  
          .. code-block:: python
  
            # FAILS:
            parent.field.child(param1='value1')
            parent.field.child(param2='value2')
  
            # OK
            parent.field.child(param1='value1')
            parent.field.child(param2='value2', __alias__='child2')
      '''
  
      __slots__ = (
          '__parent__', '__field__', '__selections',
      )
  
      def __init__(self, parent, field):
          self.__parent__ = parent
          self.__field__ = field
          self.__selections = {}
  
      def __call__(self, **args):
          '''Create a selection with the given parameters.
  
          To provide an alias, use ``__alias__`` keyword argument.
          '''
          alias = None
          if '__alias__' in args:
              alias = args.pop('__alias__')
  
          s = self.__selections.get(alias)
          if s is not None:
              if not args:
                  return s
              raise ValueError(
                  ('%s already have a selection %s. '
                   'Maybe use __alias__ as param?') % (self.__field__, s))
  
          s = self.__selections[alias] = Selection(alias, self.__field__, args)
          self.__parent__ += s
          return s
  
      def __as__(self, typ):
          '''Create a selection list on the given type.
  
          The selection list will be result in an inline fragment
          in the query with an additional query for ``__typename``,
          which is later used to create the proper type when
          the results are interpreted.
          '''
          return self().__as__(typ)
  
      def __fragment__(self, fragment):
          '''Spread the given fragment in the selection list.
          '''
          return self().__fragment__(fragment)
  
      def __dir__(self):
          original_dir = super(Selector, self).__dir__()
          t = self.__field__.type
          if not issubclass(t, ContainerType):
              return original_dir
          fields = [f.name for f in t]
          return sorted(original_dir + fields)
  
      @property
      def __fields__(self):
          '''Calls the selector without arguments, creating a
          :class:`Selection` instance and return
          :func:`Selection.__fields__` method, ready to be called.
  
          To query the actual field this selector operates, use
          ``self.__field__``
          '''
          return self().__fields__
  
      def __len__(self):
          return len(self())
  
      def __iter__(self):
          return iter(self())
  
      def __getattr__(self, name):
          try:
              return self[name]
          except KeyError as exc:
              raise AttributeError('%s has no field %s' % (self, name)) from exc
          except ValueError as exc:
              raise AttributeError('%s failed to get field %s' %
                                   (self, name)) from exc
  
      def __getitem__(self, name):
          return self()[name]
  
      def __str__(self):
          return '%s(field=%s)' % (self.__class__.__name__, self.__field__)
  
      def __repr__(self):
          return str(self)
  
      def __selection__(self, alias=None):
          'Return the selection given its alias'
          return self.__selections[alias]
  
      @property
      def __args__(self):
          'Shortcut for self.__selection__().__args__'
          return self.__selection__().__args__
  
  
  class SelectionList:
      '''List of :class:`sgqlc.operation.Selection` in a type.
  
      .. warning::
  
        Do not create instances directly, use
        :class:`sgqlc.operation.Operation` instead.
  
      Create a selection list using a type to query its fields. Once
      fields are accessed, they will create
      :class:`sgqlc.operation.Selector` object for that field, this
      allows to match the type structure, with easy to use API:
  
      .. code-block:: python
  
        parent.field.child()
        parent.field(param1=value1).child()
  
      Direct usage example (not recommended):
  
      >>> sl = SelectionList(global_schema.Repository)
      >>> sl += Selection('x', global_schema.Repository.id, {})
      >>> sl # or repr()
      {
        x: id
      }
      >>> print(bytes(sl).decode('utf-8')) # no indentation
      {
      x: id
      }
      >>> sl.id    # or any other field from Repository returns a Selector
      Selector(field=id)
      >>> sl['id'] # also as get item
      Selector(field=id)
      >>> sl.x    # not the alias
      Traceback (most recent call last):
        ...
      AttributeError: {
        x: id
      } has no field x
      >>> sl['x'] #
      Traceback (most recent call last):
        ...
      KeyError: 'Repository has no field x'
      >>> sl.__type__ # returns the type the selection operates on
      type Repository {
        id: ID
        name: String!
        owner: Actor!
        issues(titleContains: String, reporterLogin: String, filter: IssuesFilter): [Issue!]
      }
  
      '''  # noqa: E501
  
      __slots__ = ('__type', '__selectors', '__selections', '__casts',
                   '__fragments')
  
      def __init__(self, typ):
          assert issubclass(typ, BaseTypeWithTypename), \
              str(typ) + ': not a selection list type (container or union)'
          self.__type = typ
          self.__selectors = {}
          self.__selections = []
          self.__casts = OrderedDict()
          self.__fragments = OrderedDict()
  
      def __str__(self):
          return self.__to_graphql__()
  
      def __repr__(self):
          return str(self)
  
      def __bytes__(self):
          return bytes(self.__to_graphql__(indent_string=''), 'utf-8')
  
      def __to_graphql__(self, indent=0, indent_string='  ',
                         auto_select_depth=DEFAULT_AUTO_SELECT_DEPTH):
          prefix = indent_string * indent
          next_indent = indent + 1
  
          s = ['{']
          for v in self.__selections:
              s.append(v.__to_graphql__(
                  next_indent, indent_string, auto_select_depth,
              ))
  
          next_prefix = prefix + indent_string
          for v in self.__casts.values():
              s.append(next_prefix + v.__to_graphql__(
                  next_indent, indent_string, auto_select_depth,
              ))
          for lst in self.__fragments.values():
              for v in lst:
                  s.append(next_prefix + v.__spread__())
  
          s.append(prefix + '}')
          return '\n'.join(s)
  
      def __get_selections_or_auto_select__(self):
          return self.__selections
  
      def __iter__(self):
          return iter(self.__selections)
  
      def __len__(self):
          return len(self.__selections)
  
      def __getitem__(self, name):
          s = self.__selectors.get(name)
          if s is None:
              s = self.__selectors[name] = Selector(self, self.__type[name])
          return s
  
      def __getattr__(self, name):
          try:
              return self[name]
          except KeyError as exc:
              raise AttributeError('%s has no field %s' % (self, name)) from exc
  
      def __iadd__(self, selection):
          assert isinstance(selection, Selection)
          self.__selections.append(selection)
          return self
  
      @property
      def __type__(self):
          return self.__type
  
      @property
      def __casts__(self):
          return self.__casts
  
      @property
      def __fragments__(self):
          return self.__fragments
  
      def __collect_fragments__(self, fragments=None):
          if fragments is None:
              fragments = OrderedDict()
  
          for lst in self.__fragments.values():
              for frag in lst:
                  fragments.setdefault(frag.__name__, frag)
                  frag.__collect_fragments__(fragments)
  
          for sel in self.__selections:
              sel.__collect_fragments__(fragments)
  
          return fragments
  
      def __as__(self, typ):
          '''Create a child selection list on the given type.
  
          The selection list will be result in an inline fragment
          in the query with an additional query for ``__typename``,
          which is later used to create the proper type when
          the results are interpreted.
  
          The newly created selection list is shared for all users
          of the same type in this selection list.
          '''
          try:
              return self.__casts[typ.__name__]
          except KeyError:
              pass
  
          sl = InlineFragmentSelectionList(typ)
          self.__casts[typ.__name__] = sl
          self['__typename__']()
          return sl
  
      def __fragment__(self, fragment):
          assert isinstance(fragment, Fragment)
          self.__fragments.setdefault(
              fragment.__type__.__name__, []
          ).append(fragment)
          self['__typename__']()
  
  
  class InlineFragmentSelectionList(SelectionList):
      def __to_graphql__(self, indent=0, indent_string='  ',
                         auto_select_depth=DEFAULT_AUTO_SELECT_DEPTH):
          selection = SelectionList.__to_graphql__(
              self, indent, indent_string, auto_select_depth)
          return '... on %s %s' % (self.__type__, selection)
  
  
  class Fragment(SelectionList):
      __slots__ = ('__name',)
  
      def __init__(self, typ, name):
          super(Fragment, self).__init__(typ)
          self.__name = name
  
      @property
      def __name__(self):
          return self.__name
  
      def __spread__(self):
          return '...%s' % (self.__name,)
  
      def __to_graphql__(self, indent=0, indent_string='  ',
                         auto_select_depth=DEFAULT_AUTO_SELECT_DEPTH):
          selection = SelectionList.__to_graphql__(
              self, indent, indent_string, auto_select_depth)
          return 'fragment %s on %s %s' % (
              self.__name, self.__type__, selection)
  
  
  class GraphQLErrors(RuntimeError):
      def __init__(self, errors):
          assert len(errors) > 0
          msg = str(errors[0].get('message'))
          super(RuntimeError, self).__init__(msg)
          self.errors = errors
  
  
  class Operation:
      '''GraphQL Operation: query or mutation.
  
      The given type must be one of ``schema.Query`` or
      ``schema.Mutation``, defaults to ``global_schema.Query`` or
      whatever is defined as ``global_schema.query_type``.
  
      The operation has an internal
      :class:`sgqlc.operation.SelectionList` and will proxy attributes
      and item access to it, thus offering selectors and automatically
      handling selections:
  
      .. code-block:: python
  
        op = Operation()
        op.parent.field.child()
        op.parent.field(param1=value1, __alias__'q2').child()
  
      Once data is fetched and parsed as JSON object containing the
      field ``data``, the operation can be used to interpret this data
      using the addition operator (no clearly named method to avoid
      clashing with selections):
  
      .. code-block:: python
  
        op = Operation()
        op.parent.field.child()
  
        endpoint = HTTPEndpoint('http://my.server.com/graphql')
        json_data = endpoint(op)
  
        parent = op + json_data
        print(parent.field.child)
  
      Example usage:
  
      >>> op = Operation(global_schema.Query)
      >>> op.repository
      Selector(field=repository)
      >>> repository = op.repository(id='repo1')
      >>> repository.issues.number()
      number
      >>> repository.issues.title()
      title
      >>> op # or repr(), prints out GraphQL!
      query {
        repository(id: "repo1") {
          issues {
            number
            title
          }
        }
      }
  
      The root type can be omitted, then ``global_schema.Query`` or
      whatever is defined as ```global_schema.query_type`` is used:
  
      >>> op = Operation()  # same as Operation(global_schema.Query)
      >>> op.repository
      Selector(field=repository)
  
      Operations can be named:
  
      >>> op = Operation(name='MyOp')
      >>> repository = op.repository(id='repo1')
      >>> repository.issues.number()
      number
      >>> repository.issues.title()
      title
      >>> op # or repr(), prints out GraphQL!
      query MyOp {
        repository(id: "repo1") {
          issues {
            number
            title
          }
        }
      }
  
      Operations can also have argument (variables), in this case it
      must be named (otherwise a name is created based on root type
      name, such as ``"Query"``):
  
      >>> from sgqlc.types import Variable
      >>> op = Operation(repo_id=str, reporter_login=str)
      >>> repository = op.repository(id=Variable('repo_id'))
      >>> issues = repository.issues(reporter_login=Variable('reporter_login'))
      >>> issues.__fields__('number', 'title')
      >>> op # or repr(), prints out GraphQL!
      query Query($repoId: String, $reporterLogin: String) {
        repository(id: $repoId) {
          issues(reporterLogin: $reporterLogin) {
            number
            title
          }
        }
      }
  
      If variable name conflicts with the parameter, you can pass
      them as a single ``variables`` parameter containing a dict.
  
      >>> from sgqlc.types import Variable
      >>> op = Operation(name='MyOperation', variables={'name': str})
      >>> op.repository(id=Variable('name')).name()
      name
      >>> op # or repr(), prints out GraphQL!
      query MyOperation($name: String) {
        repository(id: $name) {
          name
        }
      }
  
      Complex argument types are also supported as JSON object (GraphQL names
      and raw types) or actual types:
  
      >>> op = Operation()
      >>> repository = op.repository(id='sgqlc')
      >>> issues = repository.issues(filter={
      ...     'reporter': [{'nameContains': 'Gustavo'}],
      ...     'startDate': '2019-01-01T00:00:00+00:00',
      ... })
      >>> issues.__fields__('number', 'title')
      >>> op # or repr(), prints out GraphQL!
      query {
        repository(id: "sgqlc") {
          issues(filter: {reporter: [{nameContains: "Gustavo"}], startDate: "2019-01-01T00:00:00+00:00"}) {
            number
            title
          }
        }
      }
  
      >>> from datetime import datetime, timezone
      >>> from sgqlc.types import global_schema
      >>> op = Operation()
      >>> repository = op.repository(id='sgqlc')
      >>> issues = repository.issues(filter=global_schema.IssuesFilter(
      ...     reporter=[global_schema.ReporterFilterInput(name_contains='Gustavo')],
      ...     start_date=datetime(2019, 1, 1, tzinfo=timezone.utc),
      ... ))
      >>> issues.__fields__('number', 'title')
      >>> op # or repr(), prints out GraphQL!
      query {
        repository(id: "sgqlc") {
          issues(filter: {reporter: [{nameContains: "Gustavo"}], startDate: "2019-01-01T00:00:00+00:00"}) {
            number
            title
          }
        }
      }
  
      Selectors can be acquired as attributes or items, but they must
      exist in the target type:
  
      >>> op = Operation()
      >>> op.repository
      Selector(field=repository)
      >>> op['repository']
      Selector(field=repository)
      >>> op.does_not_exist
      Traceback (most recent call last):
        ...
      AttributeError: query {
      } has no field does_not_exist
      >>> op['does_not_exist']
      Traceback (most recent call last):
        ...
      KeyError: 'Query has no field does_not_exist'
  
      '''  # noqa: E501
  
      def __init__(self, typ=None, name=None, **args):
          if typ is None:
              typ = global_schema.query_type
  
          variable_args = OrderedDict()
          if len(args) == 1 and 'variables' in args:
              args = args['variables']
          for k, v in args.items():
              variable_args['$' + k] = v
  
          if variable_args and not name:
              name = typ.__name__
  
          self.__type = typ
          self.__kind = self._get_kind()
          self.__name = name
          self.__args = ArgDict(variable_args)
          self.__args._set_container(typ.__schema__, self)
          self.__selection_list = SelectionList(typ)
  
      def _get_kind(self):
          typ = self.__type
          schema = typ.__schema__
          if schema.query_type is typ:
              return 'query'
          elif schema.mutation_type is typ:
              return 'mutation'
          elif schema.subscription_type is typ:  # pragma: no cover
              return 'subscription'
          else:  # pragma: no cover
              raise ValueError(
                  "schema doesn't define %s as query, mutation "
                  "or subscription type"
                  % (typ.__name__,)
              )
  
      def __to_graphql__(self, indent=0, indent_string='  ',
                         auto_select_depth=DEFAULT_AUTO_SELECT_DEPTH):
          prefix = indent_string * indent
          kind = self.__kind
          name = ''
          if self.__name:
              name = ' ' + self.__name
  
          args = self.__args.__to_graphql__(indent, indent_string)
          selections = self.__selection_list.__to_graphql__(
              indent, indent_string, auto_select_depth)
  
          frags_gql = []
          fragments = self.__selection_list.__collect_fragments__()
          for fragment in fragments.values():
              frags_gql.append(fragment.__to_graphql__(indent, indent_string,
                               auto_select_depth))
  
          frags = ''
          if frags_gql:
              frags = '\n' + '\n'.join(frags_gql)
          return prefix + kind + name + args + ' ' + selections + frags
  
      def __iter__(self):
          return iter(self.__selection_list)
  
      def __len__(self):
          return len(self.__selection_list)
  
      def __getattr__(self, name):
          try:
              return self.__selection_list[name]
          except KeyError as exc:
              raise AttributeError('%s has no field %s' % (self, name)) from exc
  
      def __getitem__(self, name):
          return self.__selection_list[name]
  
      def __str__(self):
          return self.__to_graphql__()
  
      def __repr__(self):
          return str(self)
  
      def __bytes__(self):
          return bytes(self.__to_graphql__(indent_string=''), 'utf-8')
  
      def __add__(self, other):
          errors = other.get('errors')
          ex = None
          if errors:
              ex = GraphQLErrors(errors)
  
          data = other.get('data')
          if not data:
              if not ex:  # pragma: no cover
                  ex = ValueError('no data and no errors')
              raise ex
          o = self.__type(other.get('data'), self.__selection_list)
          o.__errors__ = errors
          return o
  