'use strict'

const fs = require('fs')
const path = require('path')
const EE = require('events').EventEmitter
const Minimatch = require('minimatch').Minimatch

class Walker extends EE {
  constructor (opts) {
    opts = opts || {}
    super(opts)
    this.path = opts.path || process.cwd()
    this.basename = path.basename(this.path)
    this.ignoreFiles = opts.ignoreFiles || [ '.ignore' ]
    this.ignoreRules = {}
    this.parent = opts.parent || null
    this.includeEmpty = !!opts.includeEmpty
    this.root = this.parent ? this.parent.root : this.path
    this.follow = !!opts.follow
    this.result = this.parent ? this.parent.result : []
    this.entries = null
    this.sawError = false
  }

  sort (a, b) {
    return a.localeCompare(b)
  }

  emit (ev, data) {
    let ret = false
    if (!(this.sawError && ev === 'error')) {
      if (ev === 'error')
        this.sawError = true
      else if (ev === 'done' && !this.parent)
        data = data.sort(this.sort)
      if (ev === 'error' && this.parent)
        ret = this.parent.emit('error', data)
      else
        ret = super.emit(ev, data)
    }
    return ret
  }

  start () {
    fs.readdir(this.path, (er, entries) =>
      er ? this.emit('error', er) : this.onReaddir(entries))
    return this
  }

  isIgnoreFile (e) {
    return e !== "." &&
      e !== ".." &&
      -1 !== this.ignoreFiles.indexOf(e)
  }

  onReaddir (entries) {
    this.entries = entries
    if (entries.length === 0) {
      if (this.includeEmpty)
        this.result.push(this.path.substr(this.root.length + 1))
      this.emit('done', this.result)
    } else {
      const hasIg = this.entries.some(e =>
        this.isIgnoreFile(e))

      if (hasIg)
        this.addIgnoreFiles()
      else
        this.filterEntries()
    }
  }

  addIgnoreFiles () {
    const newIg = this.entries
      .filter(e => this.isIgnoreFile(e))

    let igCount = newIg.length
    const then = _ => {
      if (--igCount === 0)
        this.filterEntries()
    }

    newIg.forEach(e => this.addIgnoreFile(e, then))
  }

  addIgnoreFile (file, then) {
    const ig = path.resolve(this.path, file)
    fs.readFile(ig, 'utf8', (er, data) =>
      er ? this.emit('error', er) : this.onReadIgnoreFile(file, data, then))
  }

  onReadIgnoreFile (file, data, then) {
    const mmopt = {
      matchBase: true,
      dot: true,
      flipNegate: true,
      nocase: true
    }
    const rules = data.split(/\r?\n/)
      .filter(line => !/^#|^$/.test(line.trim()))
      .map(r => new Minimatch(r, mmopt))

    if (rules.length)
      this.ignoreRules[file] = rules

    then()
  }

  filterEntries () {
    // at this point we either have ignore rules, or just inheriting
    // this exclusion is at the point where we know the list of
    // entries in the dir, but don't know what they are.  since
    // some of them *might* be directories, we have to run the
    // match in dir-mode as well, so that we'll pick up partials
    // of files that will be included later.  Anything included
    // at this point will be checked again later once we know
    // what it is.
    const filtered = this.entries.map(entry => {
      // at this point, we don't know if it's a dir or not.
      const passFile = this.filterEntry(entry)
      const passDir = this.filterEntry(entry, true)
      return (passFile || passDir) ? [entry, passFile, passDir] : false
    }).filter(e => e)

    // now we stat them all
    // if it's a dir, and passes as a dir, then recurse
    // if it's not a dir, but passes as a file, add to set
    let entryCount = filtered.length
    if (entryCount === 0) {
      this.emit('done', this.result)
    } else {
      const then = _ => {
        if (-- entryCount === 0)
          this.emit('done', this.result)
      }
      filtered.forEach(filt => {
        const entry = filt[0]
        const file = filt[1]
        const dir = filt[2]
        this.stat(entry, file, dir, then)
      })
    }
  }

  onstat (st, entry, file, dir, then) {
    const abs = this.path + '/' + entry
    if (!st.isDirectory()) {
      if (file)
        this.result.push(abs.substr(this.root.length + 1))
      then()
    } else {
      // is a directory
      if (dir)
        this.walker(entry, then)
      else
        then()
    }
  }

  stat (entry, file, dir, then) {
    const abs = this.path + '/' + entry
    fs[this.follow ? 'stat' : 'lstat'](abs, (er, st) => {
      if (er)
        this.emit('error', er)
      else
        this.onstat(st, entry, file, dir, then)
    })
  }

  walkerOpt (entry) {
    return {
      path: this.path + '/' + entry,
      parent: this,
      ignoreFiles: this.ignoreFiles,
      follow: this.follow,
      includeEmpty: this.includeEmpty
    }
  }

  walker (entry, then) {
    new Walker(this.walkerOpt(entry)).on('done', then).start()
  }

  filterEntry (entry, partial) {
    let included = true

    // this = /a/b/c
    // entry = d
    // parent /a/b sees c/d
    if (this.parent && this.parent.filterEntry) {
      var pt = this.basename + "/" + entry
      included = this.parent.filterEntry(pt, partial)
    }

    this.ignoreFiles.forEach(f => {
      if (this.ignoreRules[f]) {
        this.ignoreRules[f].forEach(rule => {
          // negation means inclusion
          // so if it's negated, and already included, no need to check
          // likewise if it's neither negated nor included
          if (rule.negate !== included) {
            // first, match against /foo/bar
            // then, against foo/bar
            // then, in the case of partials, match with a /
            const match = rule.match('/' + entry) ||
              rule.match(entry) ||
              (!!partial && (
                rule.match('/' + entry + '/') ||
                rule.match(entry + '/'))) ||
              (!!partial && rule.negate && (
                rule.match('/' + entry, true) ||
                rule.match(entry, true)))

            if (match)
              included = rule.negate
          }
        })
      }
    })

    return included
  }
}

class WalkerSync extends Walker {
  constructor (opt) {
    super(opt)
  }

  start () {
    this.onReaddir(fs.readdirSync(this.path))
    return this
  }

  addIgnoreFile (file, then) {
    const ig = path.resolve(this.path, file)
    this.onReadIgnoreFile(file, fs.readFileSync(ig, 'utf8'), then)
  }

  stat (entry, file, dir, then) {
    const abs = this.path + '/' + entry
    const st = fs[this.follow ? 'statSync' : 'lstatSync'](abs)
    this.onstat(st, entry, file, dir, then)
  }

  walker (entry, then) {
    new WalkerSync(this.walkerOpt(entry)).start()
    then()
  }
}

const walk = (options, callback) => {
  const p = new Promise((resolve, reject) => {
    new Walker(options).on('done', resolve).on('error', reject).start()
  })
  return callback ? p.then(res => callback(null, res), callback) : p
}

const walkSync = options => {
  return new WalkerSync(options).start().result
}

module.exports = walk
walk.sync = walkSync
walk.Walker = Walker
walk.WalkerSync = WalkerSync
