text: var assert = require('assert'),
    path = require('path'),
    Completion = require('./lib/completion'),
    Parser = require('./lib/parser'),
    Usage = require('./lib/usage'),
    Validation = require('./lib/validation')
  
  Argv(process.argv.slice(2))
  
  var exports = module.exports = Argv
  function Argv (processArgs, cwd) {
    processArgs = processArgs || [] // handle calling yargs().
  
    var self = {}
    var completion = null
    var usage = null
    var validation = null
  
    if (!cwd) cwd = process.cwd()
  
    self.$0 = process.argv
      .slice(0, 2)
      .map(function (x, i) {
        // ignore the node bin, specify this in your
        // bin file with #!/usr/bin/env node
        if (i === 0 && /\b(node|iojs)$/.test(x)) return
        var b = rebase(cwd, x)
        return x.match(/^\//) && b.length < x.length
        ? b : x
      })
      .join(' ').trim()
  
    if (process.env._ !== undefined && process.argv[1] === process.env._) {
      self.$0 = process.env._.replace(
        path.dirname(process.execPath) + '/', ''
      )
    }
  
    var options
    self.resetOptions = self.reset = function () {
      // put yargs back into its initial
      // state, this is useful for creating a
      // nested CLI.
      options = {
        array: [],
        boolean: [],
        string: [],
        narg: {},
        key: {},
        alias: {},
        default: {},
        defaultDescription: {},
        requiresArg: [],
        count: [],
        normalize: [],
        config: []
      }
  
      usage = Usage(self) // handle usage output.
      validation = Validation(self, usage) // handle arg validation.
      completion = Completion(self, usage)
  
      demanded = {}
  
      exitProcess = true
      strict = false
      helpOpt = null
      versionOpt = null
      completionOpt = null
  
      return self
    }
    self.resetOptions()
  
    self.boolean = function (bools) {
      options.boolean.push.apply(options.boolean, [].concat(bools))
      return self
    }
  
    self.array = function (arrays) {
      options.array.push.apply(options.array, [].concat(arrays))
      return self
    }
  
    self.nargs = function (key, n) {
      if (typeof key === 'object') {
        Object.keys(key).forEach(function (k) {
          self.nargs(k, key[k])
        })
      } else {
        options.narg[key] = n
      }
      return self
    }
  
    self.normalize = function (strings) {
      options.normalize.push.apply(options.normalize, [].concat(strings))
      return self
    }
  
    self.config = function (configs) {
      options.config.push.apply(options.config, [].concat(configs))
      return self
    }
  
    self.example = function (cmd, description) {
      usage.example(cmd, description)
      return self
    }
  
    self.command = function (cmd, description) {
      usage.command(cmd, description)
      return self
    }
  
    self.string = function (strings) {
      options.string.push.apply(options.string, [].concat(strings))
      return self
    }
  
    self.default = function (key, value, defaultDescription) {
      if (typeof key === 'object') {
        Object.keys(key).forEach(function (k) {
          self.default(k, key[k])
        })
      } else {
        if (typeof value === 'function') {
          defaultDescription = usage.functionDescription(value, defaultDescription)
          value = value.call()
        }
        options.defaultDescription[key] = defaultDescription
        options.default[key] = value
      }
      return self
    }
  
    self.alias = function (x, y) {
      if (typeof x === 'object') {
        Object.keys(x).forEach(function (key) {
          self.alias(key, x[key])
        })
      } else {
        options.alias[x] = (options.alias[x] || []).concat(y)
      }
      return self
    }
  
    self.count = function (counts) {
      options.count.push.apply(options.count, [].concat(counts))
      return self
    }
  
    var demanded = {}
    self.demand = self.required = self.require = function (keys, msg) {
      if (typeof keys === 'number') {
        if (!demanded._) demanded._ = { count: 0, msg: null }
        demanded._.count += keys
        demanded._.msg = msg
      } else if (Array.isArray(keys)) {
        keys.forEach(function (key) {
          self.demand(key, msg)
        })
      } else {
        if (typeof msg === 'string') {
          demanded[keys] = { msg: msg }
        } else if (msg === true || typeof msg === 'undefined') {
          demanded[keys] = { msg: undefined }
        }
      }
  
      return self
    }
    self.getDemanded = function () {
      return demanded
    }
  
    self.requiresArg = function (requiresArgs) {
      options.requiresArg.push.apply(options.requiresArg, [].concat(requiresArgs))
      return self
    }
  
    self.implies = function (key, value) {
      validation.implies(key, value)
      return self
    }
  
    self.usage = function (msg, opts) {
      if (!opts && typeof msg === 'object') {
        opts = msg
        msg = null
      }
  
      usage.usage(msg)
  
      if (opts) self.options(opts)
  
      return self
    }
  
    self.epilogue = self.epilog = function (msg) {
      usage.epilog(msg)
      return self
    }
  
    self.fail = function (f) {
      usage.failFn(f)
      return self
    }
  
    self.check = function (f) {
      validation.check(f)
      return self
    }
  
    self.defaults = self.default
  
    self.describe = function (key, desc) {
      options.key[key] = true
      usage.describe(key, desc)
      return self
    }
  
    self.parse = function (args) {
      return parseArgs(args)
    }
  
    self.option = self.options = function (key, opt) {
      if (typeof key === 'object') {
        Object.keys(key).forEach(function (k) {
          self.options(k, key[k])
        })
      } else {
        assert(typeof opt === 'object', 'second argument to option must be an object')
  
        options.key[key] = true // track manually set keys.
  
        if (opt.alias) self.alias(key, opt.alias)
  
        var demand = opt.demand || opt.required || opt.require
  
        if (demand) {
          self.demand(key, demand)
        } if ('default' in opt) {
          self.default(key, opt.default)
        } if ('nargs' in opt) {
          self.nargs(key, opt.nargs)
        } if (opt.boolean || opt.type === 'boolean') {
          self.boolean(key)
          if (opt.alias) self.boolean(opt.alias)
        } if (opt.array || opt.type === 'array') {
          self.array(key)
          if (opt.alias) self.array(opt.alias)
        } if (opt.string || opt.type === 'string') {
          self.string(key)
          if (opt.alias) self.string(opt.alias)
        } if (opt.count || opt.type === 'count') {
          self.count(key)
        }
  
        var desc = opt.describe || opt.description || opt.desc
        if (desc) {
          self.describe(key, desc)
        }
  
        if (opt.requiresArg) {
          self.requiresArg(key)
        }
      }
  
      return self
    }
    self.getOptions = function () {
      return options
    }
  
    self.wrap = function (cols) {
      usage.wrap(cols)
      return self
    }
  
    var strict = false
    self.strict = function () {
      strict = true
      return self
    }
    self.getStrict = function () {
      return strict
    }
  
    self.showHelp = function (level) {
      if (!self.parsed) parseArgs(processArgs) // run parser, if it has not already been executed.
      usage.showHelp(level)
      return self
    }
  
    var versionOpt = null
    self.version = function (ver, opt, msg) {
      versionOpt = opt || 'version'
      usage.version(ver)
      self.describe(versionOpt, msg || 'Show version number')
      return self
    }
  
    var helpOpt = null
    self.addHelpOpt = function (opt, msg) {
      helpOpt = opt
      self.describe(opt, msg || 'Show help')
      return self
    }
  
    self.showHelpOnFail = function (enabled, message) {
      usage.showHelpOnFail(enabled, message)
      return self
    }
  
    var exitProcess = true
    self.exitProcess = function (enabled) {
      if (typeof enabled !== 'boolean') {
        enabled = true
      }
      exitProcess = enabled
      return self
    }
    self.getExitProcess = function () {
      return exitProcess
    }
  
    self.help = function () {
      if (arguments.length > 0) return self.addHelpOpt.apply(self, arguments)
  
      if (!self.parsed) parseArgs(processArgs) // run parser, if it has not already been executed.
  
      return usage.help()
    }
  
    var completionOpt = null,
    completionCommand = null
    self.completion = function (cmd, desc, fn) {
      // a function to execute when generating
      // completions can be provided as the second
      // or third argument to completion.
      if (typeof desc === 'function') {
        fn = desc
        desc = null
      }
  
      // register the completion command.
      completionCommand = cmd
      completionOpt = completion.completionKey
      self.command(completionCommand, desc || 'generate bash completion script')
  
      // a function can be provided
      if (fn) completion.registerFunction(fn)
  
      return self
    }
  
    self.showCompletionScript = function ($0) {
      $0 = $0 || self.$0
      console.log(completion.generateCompletionScript($0))
      return self
    }
  
    self.getUsageInstance = function () {
      return usage
    }
  
    self.getValidationInstance = function () {
      return validation
    }
  
    Object.defineProperty(self, 'argv', {
      get: function () {
        var args = null
  
        try {
          args = parseArgs(processArgs)
        } catch (err) {
          usage.fail(err.message)
        }
  
        return args
      },
      enumerable: true
    })
  
    function parseArgs (args) {
      var parsed = Parser(args, options),
      argv = parsed.argv,
      aliases = parsed.aliases
  
      argv.$0 = self.$0
  
      self.parsed = parsed
  
      // generate a completion script for adding to ~/.bashrc.
      if (completionCommand && ~argv._.indexOf(completionCommand)) {
        self.showCompletionScript()
        if (exitProcess) {
          process.exit(0)
        }
      }
  
      Object.keys(argv).forEach(function (key) {
        if (key === helpOpt) {
          self.showHelp('log')
          if (exitProcess) {
            process.exit(0)
          }
        } else if (key === versionOpt) {
          usage.showVersion()
          if (exitProcess) {
            process.exit(0)
          }
        } else if (key === completionOpt) {
          // we allow for asynchronous completions,
          // e.g., loading in a list of commands from an API.
          completion.getCompletion(function (completions) {
            ;(completions || []).forEach(function (completion) {
              console.log(completion)
            })
  
            if (exitProcess) {
              process.exit(0)
            }
          })
          return
        }
      })
  
      validation.nonOptionCount(argv)
      validation.missingArgumentValue(argv)
      validation.requiredArguments(argv)
  
      if (strict) {
        validation.unknownArguments(argv, aliases)
      }
  
      validation.customChecks(argv, aliases)
      validation.implications(argv)
      setPlaceholderKeys(argv)
  
      return argv
    }
  
    function setPlaceholderKeys (argv) {
      Object.keys(options.key).forEach(function (key) {
        if (typeof argv[key] === 'undefined') argv[key] = undefined
      })
    }
  
    sigletonify(self)
    return self
  }
  
  // rebase an absolute path to a relative one with respect to a base directory
  // exported for tests
  exports.rebase = rebase
  function rebase (base, dir) {
    return path.relative(base, dir)
  }
  
  /*  Hack an instance of Argv with process.argv into Argv
      so people can do
      require('yargs')(['--beeble=1','-z','zizzle']).argv
      to parse a list of args and
      require('yargs').argv
      to get a parsed version of process.argv.
  */
  function sigletonify (inst) {
    Object.keys(inst).forEach(function (key) {
      if (key === 'argv') {
        Argv.__defineGetter__(key, inst.__lookupGetter__(key))
      } else {
        Argv[key] = typeof inst[key] === 'function'
        ? inst[key].bind(inst)
        : inst[key]
      }
    })
  }
  