const fs = require('fs')
const path = require('path')
const zlib = require('zlib')
const stream = require('stream/promises')
const EventEmitter = require('events')

const fileExists = require('./file_exists')
const colorCodeStringify = require('../util/chat/stringify/color_code')
const ansiStringify = require('../util/chat/stringify/ansi')

class Console extends EventEmitter {
  #writeStream = null
  #forks = []

  logdir = null
  filename = null
  parent = null

  constructor ({ lang = {}, namespace = '', stdout = process.stdout, stderr = process.stderr, readline = null } = {}) {
    super()

    this.language = lang
    this.namespace = namespace
    this.stdout = stdout
    this.stderr = stderr
    this.readline = readline

    this.readline?.on('line', line => {
      this.emit('line', line)
      this.readline.prompt(true)
    })

    this.on('local_error', error => this.emit('error', error))

    this.on('error', error => this.#forks.forEach(fork => fork.emit('error', error)))
    this.on('line', line => this.#forks.forEach(fork => fork.emit('line', line)))
    this.on('end', () => this.#forks.forEach(fork => fork.emit('end')))
  }

  info (text) {
    this.#log(text, '\xa72INFO', this.stdout)
  }

  warn (text) {
    this.#log(text, '\xa7eWARN', this.stderr)
  }

  error (text) {
    this.#log(text, '\xa7cERROR', this.stderr)
  }

  log (text) {
    this.info(text)
  }

  #log (text, prefix, stdout) {
    const raw = [`[${formatTimestamp()} ${prefix}\xa7r] `, text]
    if (this.namespace) raw[0] += `[${this.namespace}] `

    const options = { lang: this.language }
    const colorStr = colorCodeStringify(raw, options)
    const ansiStr = ansiStringify(raw, options)

    if (stdout) stdout.write(ansiStr + '\x1b[0m\n')
    this.#writeToLog(colorStr + '\n') 
  }

  #writeToLog (text) {
    if (this.parent) return this.parent.#writeToLog(text)
    this.#writeStream?.write(text)
  }

  fork (namespace) {
    if (this.namespace) namespace = this.namespace + '/' + namespace

    const fork = new Console({ lang: this.language, namespace })
    fork.parent = this

    this.#forks.push(fork)
    fork.on('end', () => (this.#forks = this.#forks.filter(_fork => _fork !== fork)))

    return fork
  }

  end () {
    this.#writeStream?.end()
    this.stdout = null
    this.stderr = null
    this.parent = null

    this.emit('end')
  }

  async createLogFile (logdir) {
    this.logdir = logdir
    const filename = path.join(logdir, 'latest.log')

    if (await fileExists(filename)) await copyLatestLog(this.logdir, filename)

    this.filename = filename
    this.#writeStream = fs.createWriteStream(filename)
    this.#writeStream.setDefaultEncoding('utf-8')
    this.#writeStream.write(formatDate() + '\n')
  }
}

async function copyLatestLog (logdir, filename) {
  const input = fs.createReadStream(filename)
  let out
  let gzip

  input.on('data', chunk => {
    if (gzip) {
      gzip.write(chunk)
      return
    }

    // Attempt to read the first line (assumed to have a date)
    let idx = -1
    for (let i = 0; i < chunk.length; i++) {
      if (chunk[i] === 0x0a || chunk[i] === 0x0d) {
        idx = i + 1
        break
      }
    }
    if (chunk[idx] === 0x0d && chunk[idx + 1] === 0x0a) idx++

    let date
    if (idx !== -1) {
      date = chunk.subarray(0, idx).toString().trim()

      // sanity checking
      const parts = date.split('-').map(Number)
      if (parts.length !== 3) idx = -1
      else if (parts.some(part => Number.isNaN(part))) idx = -1
    }

    if (idx !== -1) {
      // The sanity checks passed, so we can skip the date now
      chunk = chunk.subarray(idx)
    } else {
      // stat the file for the creation date
      const stat = fs.statSync(filename)
      date = formatDate(stat.birthtime)
    }

    // handle duplicates
    const prefix = logdir + '/'
    const suffix = '.log.gz'
    let outFilename = prefix + date + suffix
    let count = 1
    while (fs.existsSync(outFilename)) {
      outFilename = prefix + date + '-' + count++ + suffix
    }

    // so much for just some output streams...
    out = fs.createWriteStream(outFilename)
    gzip = zlib.createGzip()

    gzip.pipe(out)
    gzip.write(chunk)
  })

  await stream.finished(input)
  gzip?.end()
}

function formatDate (date = new Date()) {
  const year = date.getFullYear()
  const month = date.getMonth() + 1
  const day = date.getDate()
  return `${year.toString().padStart(4, '0')}-${month.toString().padStart(2, '0')}-${day.toString().padStart(2, '0')}`
}

function formatTimestamp (date = new Date()) {
  const hours = date.getHours()
  const minutes = date.getMinutes()
  const seconds = date.getSeconds()
  return `${hours.toString().padStart(2, '0')}:${minutes.toString().padStart(2, '0')}:${seconds.toString().padStart(2, '0')}`
}

module.exports = Console