from collections import namedtuple
from copy import deepcopy
from itertools import combinations

import torch
from torch.fx.operator_schemas import normalize_function
from torch.testing._internal.jit_utils import clone_inputs
from torch.utils._python_dispatch import TorchDispatchMode
from torch.utils._pytree import tree_flatten, tree_map

# Named Tuples used within SchemaCheckMode
Mutation = namedtuple("Mutation", ["op_name", "arg_name"])
Aliasing = namedtuple("Aliasing", ["op_name", "arg_name", "output_number"])

# Simplified naming for C++ classes
SchemaArgument = torch._C._SchemaArgument
SchemaArgType = torch._C._SchemaArgType
SchemaInfo = torch._C._SchemaInfo

# This TorchDispatchMode Subclass is used to verify op schemas
# This TorchDispatchMode Scubclass currently:
#  - Records the called ops
#  - Checks for mutations on all inputs
#  - Checks for aliasing on all inputs


class SchemaCheckMode(TorchDispatchMode):
    def __init__(self):
        # Information recorded for testing purposes. For example:
        #  - incorrect schemas
        #  - overly conservative schemas
        self.ops = []
        self.mutated = []
        self.aliasing = []

    def reset_cache(self):
        self.ops.clear()
        self.mutated.clear()
        self.aliasing.clear()

    def display_ops(self):
        print(*self.ops, sep=",")

    def __torch_dispatch__(self, func, types, args=(), kwargs=None):
        def has_mutated(before, after, md):
            are_tensors = type(before) == torch.Tensor and type(after) == torch.Tensor
            if (
                are_tensors
                and before.layout != torch.sparse_csr
                and after.layout != torch.sparse_csr
            ):
                return not (
                    before.size() == after.size()
                    and torch.allclose(before, after, equal_nan=True)
                    and md[0] == after.stride()
                    and md[1] == after._typed_storage()._cdata
                )
            return False

        def has_aliased(lhs, rhs):
            try:
                return torch._C._overlaps(lhs, rhs)
            except Exception as exception:
                if str(exception).startswith("Cannot inspect value of type "):
                    return False
                else:
                    raise exception

        def standardize_name(name):
            return name if name != "self" else "input"

        def unwrap(e):
            if isinstance(e, torch.Tensor) and not type(e) == torch.Tensor:
                try:
                    return e.elem
                except AttributeError as t:
                    return e
            return e

        def parse_metadata(e):
            if isinstance(e, torch.Tensor):
                if not type(e) == torch.Tensor:
                    try:
                        current = e.elem
                        return (
                            deepcopy(current.stride()),
                            current._typed_storage()._cdata,
                        )
                    except AttributeError as t:
                        return None
                # Sparse CSR tensors do not have strides or storage
                elif e.layout != torch.sparse_csr:
                    return (deepcopy(e.stride()), e._typed_storage()._cdata)
            return None

        self.ops.append(func._schema.name)

        # Clone and process arguments and outputs
        pre_arguments = normalize_function(
            func, args, kwargs, normalize_to_only_use_kwargs=True
        ).kwargs

        c_p_args = dict(zip(pre_arguments.keys(), clone_inputs(pre_arguments.values())))
        cloned_arguments = {
            name: tree_map(unwrap, c_p_args.get(name)) for name in c_p_args
        }
        cloned_metadata = {
            name: tree_map(parse_metadata, tree_flatten(pre_arguments.get(name))[0])
            for name in pre_arguments
        }

        out = func(*args, **kwargs)
        arguments = {
            name: tree_map(unwrap, pre_arguments.get(name)) for name in pre_arguments
        }
        tuple_out = out if isinstance(out, tuple) else (out,)
        tuple_out = tree_map(unwrap, tuple_out)

        schema_info = SchemaInfo(func._schema)
        schema_info.add_argument_values(pre_arguments)

        # Process arguments with outputs
        for i in range(len(func._schema.arguments)):
            arg = func._schema.arguments[i]
            name = standardize_name(arg.name)
            if arguments.get(name) is not None:
                before = cloned_arguments.get(name)
                md = cloned_metadata.get(name)
                after = arguments.get(name)
                for j in range(len(tuple_out)):
                    # aten::_unsafe_view is intended to have incorrect aliasing notation (hence unsafe)
                    unsafe_ops = ("aten::_unsafe_view", "aten::unsafe_split")
                    if (
                        has_aliased(tuple_out[j], after)
                        and func._schema.name not in unsafe_ops
                    ):
                        if not schema_info.may_contain_alias(
                            SchemaArgument(SchemaArgType.output, j),
                            SchemaArgument(SchemaArgType.input, i),
                        ):
                            raise RuntimeError(
                                f"Argument {name} is not defined to alias output but was aliasing"
                            )
                        else:
                            self.aliasing.append(
                                Aliasing(func._schema.name, name, f"output_{j}")
                            )
                    if after is tuple_out[j] and isinstance(after, torch.Tensor):
                        # Only mutable ops e.g. (add_, add.out) are allowed to directly return inputs.
                        if not schema_info.is_mutable(
                            SchemaArgument(SchemaArgType.input, i)
                        ) and func not in [
                            torch.ops.aten.lift.default,
                            torch.ops.aten.lift_fresh.default,
                        ]:
                            raise RuntimeError(
                                f"""\
Dispatcher operators below autograd are not allowed to directly return inputs.
However, we found that `outputs[{str(j)}] is {name}"""
                            )
                if any(
                    has_mutated(a, b, c)
                    for a, b, c in zip(
                        tree_flatten(before)[0], tree_flatten(after)[0], md
                    )
                ):
                    if not schema_info.is_mutable(
                        SchemaArgument(SchemaArgType.input, i)
                    ):
                        raise RuntimeError(
                            f"Argument {name} is not defined as mutable but was mutated"
                        )
                    else:
                        self.mutated.append(Mutation(func._schema.name, name))

        # Aliasing between outputs
        for i, j in combinations(range(len(func._schema.returns)), 2):
            if has_aliased(tuple_out[i], tuple_out[j]):
                if not schema_info.may_contain_alias(
                    SchemaArgument(SchemaArgType.output, i),
                    SchemaArgument(SchemaArgType.output, j),
                ):
                    raise RuntimeError(f"Outputs {i} and {j} alias unexpectedly")

        return out
