'use strict'
module.exports = writeFile
module.exports.sync = writeFileSync
module.exports._getTmpname = getTmpname // for testing
module.exports._cleanupOnExit = cleanupOnExit

var fs = require('graceful-fs')
var MurmurHash3 = require('imurmurhash')
var onExit = require('signal-exit')
var path = require('path')
var activeFiles = {}

var invocations = 0
function getTmpname (filename) {
  return filename + '.' +
    MurmurHash3(__filename)
      .hash(String(process.pid))
      .hash(String(++invocations))
      .result()
}

function cleanupOnExit (tmpfile) {
  return function () {
    try {
      fs.unlinkSync(typeof tmpfile === 'function' ? tmpfile() : tmpfile)
    } catch (_) {}
  }
}

function writeFile (filename, data, options, callback) {
  if (options instanceof Function) {
    callback = options
    options = null
  }
  if (!options) options = {}

  var Promise = options.Promise || global.Promise
  var truename
  var fd
  var tmpfile
  var removeOnExit = cleanupOnExit(() => tmpfile)
  var absoluteName = path.resolve(filename)

  new Promise(function serializeSameFile (resolve) {
    // make a queue if it doesn't already exist
    if (!activeFiles[absoluteName]) activeFiles[absoluteName] = []

    activeFiles[absoluteName].push(resolve) // add this job to the queue
    if (activeFiles[absoluteName].length === 1) resolve() // kick off the first one
  }).then(function getRealPath () {
    return new Promise(function (resolve) {
      fs.realpath(filename, function (_, realname) {
        truename = realname || filename
        tmpfile = getTmpname(truename)
        resolve()
      })
    })
  }).then(function stat () {
    return new Promise(function stat (resolve) {
      if (options.mode && options.chown) resolve()
      else {
        // Either mode or chown is not explicitly set
        // Default behavior is to copy it from original file
        fs.stat(truename, function (err, stats) {
          if (err || !stats) resolve()
          else {
            options = Object.assign({}, options)

            if (!options.mode) {
              options.mode = stats.mode
            }
            if (!options.chown && process.getuid) {
              options.chown = { uid: stats.uid, gid: stats.gid }
            }
            resolve()
          }
        })
      }
    })
  }).then(function thenWriteFile () {
    return new Promise(function (resolve, reject) {
      fs.open(tmpfile, 'w', options.mode, function (err, _fd) {
        fd = _fd
        if (err) reject(err)
        else resolve()
      })
    })
  }).then(function write () {
    return new Promise(function (resolve, reject) {
      if (Buffer.isBuffer(data)) {
        fs.write(fd, data, 0, data.length, 0, function (err) {
          if (err) reject(err)
          else resolve()
        })
      } else if (data != null) {
        fs.write(fd, String(data), 0, String(options.encoding || 'utf8'), function (err) {
          if (err) reject(err)
          else resolve()
        })
      } else resolve()
    })
  }).then(function syncAndClose () {
    if (options.fsync !== false) {
      return new Promise(function (resolve, reject) {
        fs.fsync(fd, function (err) {
          if (err) reject(err)
          else fs.close(fd, resolve)
        })
      })
    }
  }).then(function chown () {
    if (options.chown) {
      return new Promise(function (resolve, reject) {
        fs.chown(tmpfile, options.chown.uid, options.chown.gid, function (err) {
          if (err) reject(err)
          else resolve()
        })
      })
    }
  }).then(function chmod () {
    if (options.mode) {
      return new Promise(function (resolve, reject) {
        fs.chmod(tmpfile, options.mode, function (err) {
          if (err) reject(err)
          else resolve()
        })
      })
    }
  }).then(function rename () {
    return new Promise(function (resolve, reject) {
      fs.rename(tmpfile, truename, function (err) {
        if (err) reject(err)
        else resolve()
      })
    })
  }).then(function success () {
    removeOnExit()
    callback()
  }).catch(function fail (err) {
    removeOnExit()
    fs.unlink(tmpfile, function () {
      callback(err)
    })
  }).then(function checkQueue () {
    activeFiles[absoluteName].shift() // remove the element added by serializeSameFile
    if (activeFiles[absoluteName].length > 0) {
      activeFiles[absoluteName][0]() // start next job if one is pending
    } else delete activeFiles[absoluteName]
  })
}

function writeFileSync (filename, data, options) {
  if (!options) options = {}
  try {
    filename = fs.realpathSync(filename)
  } catch (ex) {
    // it's ok, it'll happen on a not yet existing file
  }
  var tmpfile = getTmpname(filename)

  try {
    if (!options.mode || !options.chown) {
      // Either mode or chown is not explicitly set
      // Default behavior is to copy it from original file
      try {
        var stats = fs.statSync(filename)
        options = Object.assign({}, options)
        if (!options.mode) {
          options.mode = stats.mode
        }
        if (!options.chown && process.getuid) {
          options.chown = { uid: stats.uid, gid: stats.gid }
        }
      } catch (ex) {
        // ignore stat errors
      }
    }

    var removeOnExit = onExit(cleanupOnExit(tmpfile))
    var fd = fs.openSync(tmpfile, 'w', options.mode)
    if (Buffer.isBuffer(data)) {
      fs.writeSync(fd, data, 0, data.length, 0)
    } else if (data != null) {
      fs.writeSync(fd, String(data), 0, String(options.encoding || 'utf8'))
    }
    if (options.fsync !== false) {
      fs.fsyncSync(fd)
    }
    fs.closeSync(fd)
    if (options.chown) fs.chownSync(tmpfile, options.chown.uid, options.chown.gid)
    if (options.mode) fs.chmodSync(tmpfile, options.mode)
    fs.renameSync(tmpfile, filename)
    removeOnExit()
  } catch (err) {
    removeOnExit()
    try { fs.unlinkSync(tmpfile) } catch (e) {}
    throw err
  }
}