// Each command has a completion function that takes an options object and a cb
// The callback gets called with an error and an array of possible completions.
// The options object is built up based on the environment variables set by
// zsh or bash when calling a function for completion, based on the cursor
// position and the command line thus far.  These are:
// COMP_CWORD: the index of the "word" in the command line being completed
// COMP_LINE: the full command line thusfar as a string
// COMP_POINT: the cursor index at the point of triggering completion
//
// We parse the command line with nopt, like npm does, and then create an
// options object containing:
// words: array of words in the command line
// w: the index of the word being completed (ie, COMP_CWORD)
// word: the word being completed
// line: the COMP_LINE
// lineLength
// point: the COMP_POINT, usually equal to line length, but not always, eg if
// the user has pressed the left-arrow to complete an earlier word
// partialLine: the line up to the point
// partialWord: the word being completed (which might be ''), up to the point
// conf: a nopt parse of the command line
//
// When the implementation completion method returns its list of strings,
// and arrays of strings, we filter that by any that start with the
// partialWord, since only those can possibly be valid matches.
//
// Matches are wrapped with ' to escape them, if necessary, and then printed
// one per line for the shell completion method to consume in IFS=$'\n' mode
// as an array.
//

const { definitions, shorthands } = require('./utils/config/index.js')
const deref = require('./utils/deref-command.js')
const { aliases, cmdList, plumbing } = require('./utils/cmd-list.js')
const aliasNames = Object.keys(aliases)
const fullList = cmdList.concat(aliasNames).filter(c => !plumbing.includes(c))
const nopt = require('nopt')
const configNames = Object.keys(definitions)
const shorthandNames = Object.keys(shorthands)
const allConfs = configNames.concat(shorthandNames)
const isWindowsShell = require('./utils/is-windows-shell.js')
const fileExists = require('./utils/file-exists.js')

const { promisify } = require('util')
const BaseCommand = require('./base-command.js')

class Completion extends BaseCommand {
  /* istanbul ignore next - see test/lib/load-all-commands.js */
  static get name () {
    return 'completion'
  }

  /* istanbul ignore next - see test/lib/load-all-commands.js */
  static get description () {
    return 'npm command completion script. save to ~/.bashrc or ~/.zshrc'
  }

  // completion for the completion command
  async completion (opts) {
    if (opts.w > 2)
      return

    const { resolve } = require('path')
    const [bashExists, zshExists] = await Promise.all([
      fileExists(resolve(process.env.HOME, '.bashrc')),
      fileExists(resolve(process.env.HOME, '.zshrc')),
    ])
    const out = []
    if (zshExists)
      out.push(['>>', '~/.zshrc'])

    if (bashExists)
      out.push(['>>', '~/.bashrc'])

    return out
  }

  exec (args, cb) {
    this.compl(args).then(() => cb()).catch(cb)
  }

  async compl (args) {
    if (isWindowsShell) {
      const msg = 'npm completion supported only in MINGW / Git bash on Windows'
      throw Object.assign(new Error(msg), {
        code: 'ENOTSUP',
      })
    }

    const { COMP_CWORD, COMP_LINE, COMP_POINT } = process.env

    // if the COMP_* isn't in the env, then just dump the script.
    if (COMP_CWORD === undefined ||
      COMP_LINE === undefined ||
      COMP_POINT === undefined)
      return dumpScript()

    // ok we're actually looking at the envs and outputting the suggestions
    // get the partial line and partial word,
    // if the point isn't at the end.
    // ie, tabbing at: npm foo b|ar
    const w = +COMP_CWORD
    const words = args.map(unescape)
    const word = words[w]
    const line = COMP_LINE
    const point = +COMP_POINT
    const partialLine = line.substr(0, point)
    const partialWords = words.slice(0, w)

    // figure out where in that last word the point is.
    const partialWordRaw = args[w]
    let i = partialWordRaw.length
    while (partialWordRaw.substr(0, i) !== partialLine.substr(-1 * i) && i > 0)
      i--

    const partialWord = unescape(partialWordRaw.substr(0, i))
    partialWords.push(partialWord)

    const opts = {
      words,
      w,
      word,
      line,
      lineLength: line.length,
      point,
      partialLine,
      partialWords,
      partialWord,
      raw: args,
    }

    if (partialWords.slice(0, -1).indexOf('--') === -1) {
      if (word.charAt(0) === '-')
        return this.wrap(opts, configCompl(opts))

      if (words[w - 1] &&
        words[w - 1].charAt(0) === '-' &&
        !isFlag(words[w - 1])) {
        // awaiting a value for a non-bool config.
        // don't even try to do this for now
        return this.wrap(opts, configValueCompl(opts))
      }
    }

    // try to find the npm command.
    // it's the first thing after all the configs.
    // take a little shortcut and use npm's arg parsing logic.
    // don't have to worry about the last arg being implicitly
    // boolean'ed, since the last block will catch that.
    const types = Object.entries(definitions).reduce((types, [key, def]) => {
      types[key] = def.type
      return types
    }, {})
    const parsed = opts.conf =
      nopt(types, shorthands, partialWords.slice(0, -1), 0)
    // check if there's a command already.
    const cmd = parsed.argv.remain[1]
    if (!cmd)
      return this.wrap(opts, cmdCompl(opts))

    Object.keys(parsed).forEach(k => this.npm.config.set(k, parsed[k]))

    // at this point, if words[1] is some kind of npm command,
    // then complete on it.
    // otherwise, do nothing
    const impl = this.npm.commands[cmd]
    if (impl && impl.completion) {
      const comps = await impl.completion(opts)
      return this.wrap(opts, comps)
    }
  }

  // The command should respond with an array.  Loop over that,
  // wrapping quotes around any that have spaces, and writing
  // them to stdout.
  // If any of the items are arrays, then join them with a space.
  // Ie, returning ['a', 'b c', ['d', 'e']] would allow it to expand
  // to: 'a', 'b c', or 'd' 'e'
  wrap (opts, compls) {
    if (!Array.isArray(compls))
      compls = compls ? [compls] : []

    compls = compls.map(c =>
      Array.isArray(c) ? c.map(escape).join(' ') : escape(c))

    if (opts.partialWord)
      compls = compls.filter(c => c.startsWith(opts.partialWord))

    if (compls.length > 0)
      this.npm.output(compls.join('\n'))
  }
}

const dumpScript = async () => {
  const fs = require('fs')
  const readFile = promisify(fs.readFile)
  const { resolve } = require('path')
  const p = resolve(__dirname, 'utils/completion.sh')

  const d = (await readFile(p, 'utf8')).replace(/^#!.*?\n/, '')
  await new Promise((res, rej) => {
    let done = false
    process.stdout.write(d, () => {
      if (done)
        return

      done = true
      res()
    })

    process.stdout.on('error', er => {
      if (done)
        return

      done = true

      // Darwin is a pain sometimes.
      //
      // This is necessary because the "source" or "." program in
      // bash on OS X closes its file argument before reading
      // from it, meaning that you get exactly 1 write, which will
      // work most of the time, and will always raise an EPIPE.
      //
      // Really, one should not be tossing away EPIPE errors, or any
      // errors, so casually.  But, without this, `. <(npm completion)`
      // can never ever work on OS X.
      if (er.errno === 'EPIPE')
        res()
      else
        rej(er)
    })
  })
}

const unescape = w => w.charAt(0) === '\'' ? w.replace(/^'|'$/g, '')
  : w.replace(/\\ /g, ' ')

const escape = w => !/\s+/.test(w) ? w
  : '\'' + w + '\''

// the current word has a dash.  Return the config names,
// with the same number of dashes as the current word has.
const configCompl = opts => {
  const word = opts.word
  const split = word.match(/^(-+)((?:no-)*)(.*)$/)
  const dashes = split[1]
  const no = split[2]
  const flags = configNames.filter(isFlag)
  return allConfs.map(c => dashes + c)
    .concat(flags.map(f => dashes + (no || 'no-') + f))
}

// expand with the valid values of various config values.
// not yet implemented.
const configValueCompl = opts => []

// check if the thing is a flag or not.
const isFlag = word => {
  // shorthands never take args.
  const split = word.match(/^(-*)((?:no-)+)?(.*)$/)
  const no = split[2]
  const conf = split[3]
  const {type} = definitions[conf]
  return no ||
    type === Boolean ||
    (Array.isArray(type) && type.includes(Boolean)) ||
    shorthands[conf]
}

// complete against the npm commands
// if they all resolve to the same thing, just return the thing it already is
const cmdCompl = opts => {
  const matches = fullList.filter(c => c.startsWith(opts.partialWord))
  if (!matches.length)
    return matches

  const derefs = new Set([...matches.map(c => deref(c))])
  if (derefs.size === 1)
    return [...derefs]

  return fullList
}

module.exports = Completion