text: const path = require('path')
  const inspect = require('util').inspect
  const camelCase = require('camelcase')
  
  const DEFAULT_MARKER = '*'
  
  // handles parsing positional arguments,
  // and populating argv with said positional
  // arguments.
  module.exports = function (yargs, usage, validation) {
    const self = {}
  
    var handlers = {}
    var aliasMap = {}
    var defaultCommand
    self.addHandler = function (cmd, description, builder, handler) {
      var aliases = []
      if (Array.isArray(cmd)) {
        aliases = cmd.slice(1)
        cmd = cmd[0]
      } else if (typeof cmd === 'object') {
        var command = (Array.isArray(cmd.command) || typeof cmd.command === 'string') ? cmd.command : moduleName(cmd)
        if (cmd.aliases) command = [].concat(command).concat(cmd.aliases)
        self.addHandler(command, extractDesc(cmd), cmd.builder, cmd.handler)
        return
      }
  
      // allow a module to be provided instead of separate builder and handler
      if (typeof builder === 'object' && builder.builder && typeof builder.handler === 'function') {
        self.addHandler([cmd].concat(aliases), description, builder.builder, builder.handler)
        return
      }
  
      // parse positionals out of cmd string
      var parsedCommand = self.parseCommand(cmd)
  
      // remove positional args from aliases only
      aliases = aliases.map(function (alias) {
        return self.parseCommand(alias).cmd
      })
  
      // check for default and filter out '*''
      var isDefault = false
      var parsedAliases = [parsedCommand.cmd].concat(aliases).filter(function (c) {
        if (c === DEFAULT_MARKER) {
          isDefault = true
          return false
        }
        return true
      })
  
      // short-circuit if default with no aliases
      if (isDefault && parsedAliases.length === 0) {
        defaultCommand = {
          original: cmd.replace(DEFAULT_MARKER, '').trim(),
          handler: handler,
          builder: builder || {},
          demanded: parsedCommand.demanded,
          optional: parsedCommand.optional
        }
        return
      }
  
      // shift cmd and aliases after filtering out '*'
      if (isDefault) {
        parsedCommand.cmd = parsedAliases[0]
        aliases = parsedAliases.slice(1)
        cmd = cmd.replace(DEFAULT_MARKER, parsedCommand.cmd)
      }
  
      // populate aliasMap
      aliases.forEach(function (alias) {
        aliasMap[alias] = parsedCommand.cmd
      })
  
      if (description !== false) {
        usage.command(cmd, description, isDefault, aliases)
      }
  
      handlers[parsedCommand.cmd] = {
        original: cmd,
        handler: handler,
        builder: builder || {},
        demanded: parsedCommand.demanded,
        optional: parsedCommand.optional
      }
  
      if (isDefault) defaultCommand = handlers[parsedCommand.cmd]
    }
  
    self.addDirectory = function (dir, context, req, callerFile, opts) {
      opts = opts || {}
      // disable recursion to support nested directories of subcommands
      if (typeof opts.recurse !== 'boolean') opts.recurse = false
      // exclude 'json', 'coffee' from require-directory defaults
      if (!Array.isArray(opts.extensions)) opts.extensions = ['js']
      // allow consumer to define their own visitor function
      const parentVisit = typeof opts.visit === 'function' ? opts.visit : function (o) { return o }
      // call addHandler via visitor function
      opts.visit = function (obj, joined, filename) {
        const visited = parentVisit(obj, joined, filename)
        // allow consumer to skip modules with their own visitor
        if (visited) {
          // check for cyclic reference
          // each command file path should only be seen once per execution
          if (~context.files.indexOf(joined)) return visited
          // keep track of visited files in context.files
          context.files.push(joined)
          self.addHandler(visited)
        }
        return visited
      }
      require('require-directory')({ require: req, filename: callerFile }, dir, opts)
    }
  
    // lookup module object from require()d command and derive name
    // if module was not require()d and no name given, throw error
    function moduleName (obj) {
      const mod = require('which-module')(obj)
      if (!mod) throw new Error('No command name given for module: ' + inspect(obj))
      return commandFromFilename(mod.filename)
    }
  
    // derive command name from filename
    function commandFromFilename (filename) {
      return path.basename(filename, path.extname(filename))
    }
  
    function extractDesc (obj) {
      for (var keys = ['describe', 'description', 'desc'], i = 0, l = keys.length, test; i < l; i++) {
        test = obj[keys[i]]
        if (typeof test === 'string' || typeof test === 'boolean') return test
      }
      return false
    }
  
    self.parseCommand = function (cmd) {
      var extraSpacesStrippedCommand = cmd.replace(/\s{2,}/g, ' ')
      var splitCommand = extraSpacesStrippedCommand.split(/\s+(?![^[]*]|[^<]*>)/)
      var bregex = /\.*[\][<>]/g
      var parsedCommand = {
        cmd: (splitCommand.shift()).replace(bregex, ''),
        demanded: [],
        optional: []
      }
      splitCommand.forEach(function (cmd, i) {
        var variadic = false
        cmd = cmd.replace(/\s/g, '')
        if (/\.+[\]>]/.test(cmd) && i === splitCommand.length - 1) variadic = true
        if (/^\[/.test(cmd)) {
          parsedCommand.optional.push({
            cmd: cmd.replace(bregex, '').split('|'),
            variadic: variadic
          })
        } else {
          parsedCommand.demanded.push({
            cmd: cmd.replace(bregex, '').split('|'),
            variadic: variadic
          })
        }
      })
      return parsedCommand
    }
  
    self.getCommands = function () {
      return Object.keys(handlers).concat(Object.keys(aliasMap))
    }
  
    self.getCommandHandlers = function () {
      return handlers
    }
  
    self.hasDefaultCommand = function () {
      return !!defaultCommand
    }
  
    self.runCommand = function (command, yargs, parsed) {
      var aliases = parsed.aliases
      var commandHandler = handlers[command] || handlers[aliasMap[command]] || defaultCommand
      var currentContext = yargs.getContext()
      var numFiles = currentContext.files.length
      var parentCommands = currentContext.commands.slice()
  
      // what does yargs look like after the buidler is run?
      var innerArgv = parsed.argv
      var innerYargs = null
      var positionalMap = {}
  
      if (command) currentContext.commands.push(command)
      if (typeof commandHandler.builder === 'function') {
        // a function can be provided, which builds
        // up a yargs chain and possibly returns it.
        innerYargs = commandHandler.builder(yargs.reset(parsed.aliases))
        // if the builder function did not yet parse argv with reset yargs
        // and did not explicitly set a usage() string, then apply the
        // original command string as usage() for consistent behavior with
        // options object below.
        if (yargs.parsed === false) {
          if (typeof yargs.getUsageInstance().getUsage() === 'undefined') {
            yargs.usage('$0 ' + (parentCommands.length ? parentCommands.join(' ') + ' ' : '') + commandHandler.original)
          }
          innerArgv = innerYargs ? innerYargs._parseArgs(null, null, true) : yargs._parseArgs(null, null, true)
        } else {
          innerArgv = yargs.parsed.argv
        }
  
        if (innerYargs && yargs.parsed === false) aliases = innerYargs.parsed.aliases
        else aliases = yargs.parsed.aliases
      } else if (typeof commandHandler.builder === 'object') {
        // as a short hand, an object can instead be provided, specifying
        // the options that a command takes.
        innerYargs = yargs.reset(parsed.aliases)
        innerYargs.usage('$0 ' + (parentCommands.length ? parentCommands.join(' ') + ' ' : '') + commandHandler.original)
        Object.keys(commandHandler.builder).forEach(function (key) {
          innerYargs.option(key, commandHandler.builder[key])
        })
        innerArgv = innerYargs._parseArgs(null, null, true)
        aliases = innerYargs.parsed.aliases
      }
  
      if (!yargs._hasOutput()) {
        positionalMap = populatePositionals(commandHandler, innerArgv, currentContext, yargs)
      }
  
      // we apply validation post-hoc, so that custom
      // checks get passed populated positional arguments.
      if (!yargs._hasOutput()) yargs._runValidation(innerArgv, aliases, positionalMap, yargs.parsed.error)
  
      if (commandHandler.handler && !yargs._hasOutput()) {
        yargs._setHasOutput()
        commandHandler.handler(innerArgv)
      }
  
      if (command) currentContext.commands.pop()
      numFiles = currentContext.files.length - numFiles
      if (numFiles > 0) currentContext.files.splice(numFiles * -1, numFiles)
  
      return innerArgv
    }
  
    // transcribe all positional arguments "command <foo> <bar> [apple]"
    // onto argv.
    function populatePositionals (commandHandler, argv, context, yargs) {
      argv._ = argv._.slice(context.commands.length) // nuke the current commands
      var demanded = commandHandler.demanded.slice(0)
      var optional = commandHandler.optional.slice(0)
      var positionalMap = {}
  
      validation.positionalCount(demanded.length, argv._.length)
  
      while (demanded.length) {
        var demand = demanded.shift()
        populatePositional(demand, argv, yargs, positionalMap)
      }
  
      while (optional.length) {
        var maybe = optional.shift()
        populatePositional(maybe, argv, yargs, positionalMap)
      }
  
      argv._ = context.commands.concat(argv._)
      return positionalMap
    }
  
    // populate a single positional argument and its
    // aliases onto argv.
    function populatePositional (positional, argv, yargs, positionalMap) {
      // "positional" consists of the positional.cmd, an array representing
      // the positional's name and aliases, and positional.variadic
      // indicating whether or not it is a variadic array.
      var variadics = null
      var value = null
      for (var i = 0, cmd; (cmd = positional.cmd[i]) !== undefined; i++) {
        if (positional.variadic) {
          if (variadics) argv[cmd] = variadics.slice(0)
          else argv[cmd] = variadics = argv._.splice(0)
        } else {
          if (!value && !argv._.length) continue
          if (value) argv[cmd] = value
          else argv[cmd] = value = argv._.shift()
        }
        positionalMap[cmd] = true
        postProcessPositional(yargs, argv, cmd)
        addCamelCaseExpansions(argv, cmd)
      }
    }
  
    // TODO move positional arg logic to yargs-parser and remove this duplication
    function postProcessPositional (yargs, argv, key) {
      var coerce = yargs.getOptions().coerce[key]
      if (typeof coerce === 'function') {
        try {
          argv[key] = coerce(argv[key])
        } catch (err) {
          yargs.getUsageInstance().fail(err.message, err)
        }
      }
    }
  
    function addCamelCaseExpansions (argv, option) {
      if (/-/.test(option)) {
        const cc = camelCase(option)
        if (typeof argv[option] === 'object') argv[cc] = argv[option].slice(0)
        else argv[cc] = argv[option]
      }
    }
  
    self.reset = function () {
      handlers = {}
      aliasMap = {}
      defaultCommand = undefined
      return self
    }
  
    // used by yargs.parse() to freeze
    // the state of commands such that
    // we can apply .parse() multiple times
    // with the same yargs instance.
    var frozen
    self.freeze = function () {
      frozen = {}
      frozen.handlers = handlers
      frozen.aliasMap = aliasMap
      frozen.defaultCommand = defaultCommand
    }
    self.unfreeze = function () {
      handlers = frozen.handlers
      aliasMap = frozen.aliasMap
      defaultCommand = frozen.defaultCommand
      frozen = undefined
    }
  
    return self
  }
  