'use strict';

const Buffer = require('buffer').Buffer;
const Writable = require('stream').Writable;
const fs = require('fs');
const util = require('util');

const {
  O_APPEND,
  O_CREAT,
  O_EXCL,
  O_RDONLY,
  O_RDWR,
  O_SYNC,
  O_TRUNC,
  O_WRONLY
} = process.binding('constants').fs;

function assertEncoding(encoding) {
  if (encoding && !Buffer.isEncoding(encoding)) {
    throw new Error(`Unknown encoding: ${encoding}`);
  }
}

function stringToFlags(flag) {
  if (typeof flag === 'number') {
    return flag;
  }

  switch (flag) {
    case 'r' : return O_RDONLY;
    case 'rs' : // Fall through.
    case 'sr' : return O_RDONLY | O_SYNC;
    case 'r+' : return O_RDWR;
    case 'rs+' : // Fall through.
    case 'sr+' : return O_RDWR | O_SYNC;

    case 'w' : return O_TRUNC | O_CREAT | O_WRONLY;
    case 'wx' : // Fall through.
    case 'xw' : return O_TRUNC | O_CREAT | O_WRONLY | O_EXCL;

    case 'w+' : return O_TRUNC | O_CREAT | O_RDWR;
    case 'wx+': // Fall through.
    case 'xw+': return O_TRUNC | O_CREAT | O_RDWR | O_EXCL;

    case 'a' : return O_APPEND | O_CREAT | O_WRONLY;
    case 'ax' : // Fall through.
    case 'xa' : return O_APPEND | O_CREAT | O_WRONLY | O_EXCL;

    case 'a+' : return O_APPEND | O_CREAT | O_RDWR;
    case 'ax+': // Fall through.
    case 'xa+': return O_APPEND | O_CREAT | O_RDWR | O_EXCL;
  }

  throw new Error('Unknown file open flag: ' + flag);
}

// Temporary hack for process.stdout and process.stderr when piped to files.
function SyncWriteStream(fd, options) {
  Writable.call(this);

  options = options || {};

  this.fd = fd;
  this.readable = false;
  this.autoClose = options.autoClose === undefined ? true : options.autoClose;

  this.on('end', () => this._destroy());
}

util.inherits(SyncWriteStream, Writable);

SyncWriteStream.prototype._write = function(chunk, encoding, cb) {
  fs.writeSync(this.fd, chunk, 0, chunk.length);
  cb();
  return true;
};

SyncWriteStream.prototype._destroy = function() {
  if (this.fd === null) // already destroy()ed
    return;

  if (this.autoClose)
    fs.closeSync(this.fd);

  this.fd = null;
  return true;
};

SyncWriteStream.prototype.destroySoon =
SyncWriteStream.prototype.destroy = function() {
  this._destroy();
  this.emit('close');
  return true;
};

module.exports = {
  assertEncoding,
  stringToFlags,
  SyncWriteStream,
  realpathCacheKey: Symbol('realpathCacheKey')
};