var common = require('./common');
var _cd = require('./cd');
var path = require('path');

// Pushd/popd/dirs internals
var _dirStack = [];

function _isStackIndex(index) {
  return (/^[\-+]\d+$/).test(index);
}

function _parseStackIndex(index) {
  if (_isStackIndex(index)) {
    if (Math.abs(index) < _dirStack.length + 1) { // +1 for pwd
      return (/^-/).test(index) ? Number(index) - 1 : Number(index);
    } else {
      common.error(index + ': directory stack index out of range');
    }
  } else {
    common.error(index + ': invalid number');
  }
}

function _actualDirStack() {
  return [process.cwd()].concat(_dirStack);
}

//@
//@ ### pushd([options,] [dir | '-N' | '+N'])
//@
//@ Available options:
//@
//@ + `-n`: Suppresses the normal change of directory when adding directories to the stack, so that only the stack is manipulated.
//@
//@ Arguments:
//@
//@ + `dir`: Makes the current working directory be the top of the stack, and then executes the equivalent of `cd dir`.
//@ + `+N`: Brings the Nth directory (counting from the left of the list printed by dirs, starting with zero) to the top of the list by rotating the stack.
//@ + `-N`: Brings the Nth directory (counting from the right of the list printed by dirs, starting with zero) to the top of the list by rotating the stack.
//@
//@ Examples:
//@
//@ ```javascript
//@ // process.cwd() === '/usr'
//@ pushd('/etc'); // Returns /etc /usr
//@ pushd('+1');   // Returns /usr /etc
//@ ```
//@
//@ Save the current directory on the top of the directory stack and then cd to `dir`. With no arguments, pushd exchanges the top two directories. Returns an array of paths in the stack.
function _pushd(options, dir) {
  if (_isStackIndex(options)) {
    dir = options;
    options = '';
  }

  options = common.parseOptions(options, {
    'n' : 'no-cd'
  });

  var dirs = _actualDirStack();

  if (dir === '+0') {
    return dirs; // +0 is a noop
  } else if (!dir) {
    if (dirs.length > 1) {
      dirs = dirs.splice(1, 1).concat(dirs);
    } else {
      return common.error('no other directory');
    }
  } else if (_isStackIndex(dir)) {
    var n = _parseStackIndex(dir);
    dirs = dirs.slice(n).concat(dirs.slice(0, n));
  } else {
    if (options['no-cd']) {
      dirs.splice(1, 0, dir);
    } else {
      dirs.unshift(dir);
    }
  }

  if (options['no-cd']) {
    dirs = dirs.slice(1);
  } else {
    dir = path.resolve(dirs.shift());
    _cd('', dir);
  }

  _dirStack = dirs;
  return _dirs('');
}
exports.pushd = _pushd;

//@
//@ ### popd([options,] ['-N' | '+N'])
//@
//@ Available options:
//@
//@ + `-n`: Suppresses the normal change of directory when removing directories from the stack, so that only the stack is manipulated.
//@
//@ Arguments:
//@
//@ + `+N`: Removes the Nth directory (counting from the left of the list printed by dirs), starting with zero.
//@ + `-N`: Removes the Nth directory (counting from the right of the list printed by dirs), starting with zero.
//@
//@ Examples:
//@
//@ ```javascript
//@ echo(process.cwd()); // '/usr'
//@ pushd('/etc');       // '/etc /usr'
//@ echo(process.cwd()); // '/etc'
//@ popd();              // '/usr'
//@ echo(process.cwd()); // '/usr'
//@ ```
//@
//@ When no arguments are given, popd removes the top directory from the stack and performs a cd to the new top directory. The elements are numbered from 0 starting at the first directory listed with dirs; i.e., popd is equivalent to popd +0. Returns an array of paths in the stack.
function _popd(options, index) {
  if (_isStackIndex(options)) {
    index = options;
    options = '';
  }

  options = common.parseOptions(options, {
    'n' : 'no-cd'
  });

  if (!_dirStack.length) {
    return common.error('directory stack empty');
  }

  index = _parseStackIndex(index || '+0');

  if (options['no-cd'] || index > 0 || _dirStack.length + index === 0) {
    index = index > 0 ? index - 1 : index;
    _dirStack.splice(index, 1);
  } else {
    var dir = path.resolve(_dirStack.shift());
    _cd('', dir);
  }

  return _dirs('');
}
exports.popd = _popd;

//@
//@ ### dirs([options | '+N' | '-N'])
//@
//@ Available options:
//@
//@ + `-c`: Clears the directory stack by deleting all of the elements.
//@
//@ Arguments:
//@
//@ + `+N`: Displays the Nth directory (counting from the left of the list printed by dirs when invoked without options), starting with zero.
//@ + `-N`: Displays the Nth directory (counting from the right of the list printed by dirs when invoked without options), starting with zero.
//@
//@ Display the list of currently remembered directories. Returns an array of paths in the stack, or a single path if +N or -N was specified.
//@
//@ See also: pushd, popd
function _dirs(options, index) {
  if (_isStackIndex(options)) {
    index = options;
    options = '';
  }

  options = common.parseOptions(options, {
    'c' : 'clear'
  });

  if (options['clear']) {
    _dirStack = [];
    return _dirStack;
  }

  var stack = _actualDirStack();

  if (index) {
    index = _parseStackIndex(index);

    if (index < 0) {
      index = stack.length + index;
    }

    common.log(stack[index]);
    return stack[index];
  }

  common.log(stack.join(' '));

  return stack;
}
exports.dirs = _dirs;