var {promisify} = require('es6-promisify');
var Path = require('../path.js');
var Errors = require('../errors.js');
var Environment = require('./environment.js');
var async = require('../../lib/async.js');
var minimatch = require('minimatch');

function Shell(fs, options) {
  options = options || {};

  var env = new Environment(options.env);
  var cwd = '/';

  /**
   * The bound FileSystem (cannot be changed)
   */
  Object.defineProperty(this, 'fs', {
    get: function() { return fs; },
    enumerable: true
  });

  /**
   * The shell's environment (e.g., for things like
   * path, tmp, and other env vars). Use env.get()
   * and env.set() to work with variables.
   */
  Object.defineProperty(this, 'env', {
    get: function() { return env; },
    enumerable: true
  });

  /**
   * Change the current working directory. We
   * include `cd` on the `this` vs. proto so that
   * we can access cwd without exposing it externally.
   */
  this.cd = function(path, callback) {
    path = Path.resolve(cwd, path);
    // Make sure the path actually exists, and is a dir
    fs.stat(path, function(err, stats) {
      if(err) {
        callback(new Errors.ENOTDIR(null, path));
        return;
      }
      if(stats.type === 'DIRECTORY') {
        cwd = path;
        callback();
      } else {
        callback(new Errors.ENOTDIR(null, path));
      }
    });
  };

  /**
   * Get the current working directory (changed with `cd()`)
   */
  this.pwd = function() {
    return cwd;
  };

  this.promises = {};
  /**
  * Public API for Shell converted to Promise based
  */
  [
    'cd',
    'exec',
    'touch',
    'cat',
    'ls',
    'rm',
    'tempDir',
    'mkdirp',
    'find'
  ].forEach((methodName)=>{
    this.promises[methodName] = promisify(this[methodName].bind(this));
  });
}

/**
 * Execute the .js command located at `path`. Such commands
 * should assume the existence of 3 arguments, which will be
 * defined at runtime:
 *
 *   * fs - the current shell's bound filesystem object
 *   * args - a list of arguments for the command, or an empty list if none
 *   * callback - a callback function(error, result) to call when done.
 *
 * The .js command's contents should be the body of a function
 * that looks like this:
 *
 * function(fs, args, callback) {
 *   // .js code here
 * }
 */
Shell.prototype.exec = function(path, args, callback) {
  /* jshint evil:true */
  var sh = this;
  var fs = sh.fs;
  if(typeof args === 'function') {
    callback = args;
    args = [];
  }
  args = args || [];
  callback = callback || function(){};
  path = Path.resolve(sh.pwd(), path);

  fs.readFile(path, 'utf8', function(error, data) {
    if(error) {
      callback(error);
      return;
    }
    try {
      var cmd = new Function('fs', 'args', 'callback', data);
      cmd(fs, args, callback);
    } catch(e) {
      callback(e);
    }
  });
};

/**
 * Create a file if it does not exist, or update access and
 * modified times if it does. Valid options include:
 *
 *  * updateOnly - whether to create the file if missing (defaults to false)
 *  * date - use the provided Date value instead of current date/time
 */
Shell.prototype.touch = function(path, options, callback) {
  var sh = this;
  var fs = sh.fs;
  if(typeof options === 'function') {
    callback = options;
    options = {};
  }
  options = options || {};
  callback = callback || function(){};
  path = Path.resolve(sh.pwd(), path);

  function createFile(path) {
    fs.writeFile(path, '', callback);
  }

  function updateTimes(path) {
    var now = Date.now();
    var atime = options.date || now;
    var mtime = options.date || now;

    fs.utimes(path, atime, mtime, callback);
  }

  fs.stat(path, function(error) {
    if(error) {
      if(options.updateOnly === true) {
        callback();
      } else {
        createFile(path);
      }
    } else {
      updateTimes(path);
    }
  });
};

/**
 * Concatenate multiple files into a single String, with each
 * file separated by a newline. The `files` argument should
 * be a String (path to single file) or an Array of Strings
 * (multiple file paths).
 */
Shell.prototype.cat = function(files, callback) {
  var sh = this;
  var fs = sh.fs;
  var all = '';
  callback = callback || function(){};

  if(!files) {
    callback(new Errors.EINVAL('Missing files argument'));
    return;
  }

  files = typeof files === 'string' ? [ files ] : files;

  function append(item, callback) {
    var filename = Path.resolve(sh.pwd(), item);
    fs.readFile(filename, 'utf8', function(error, data) {
      if(error) {
        callback(error);
        return;
      }
      all += data + '\n';
      callback();
    });
  }

  async.eachSeries(files, append, function(error) {
    if(error) {
      callback(error);
    } else {
      callback(null, all.replace(/\n$/, ''));
    }
  });
};

/**
 * Get the listing of a directory, returning an array of
 * file entries in the following form:
 *
 * {
 *   path: <String> the basename of the directory entry
 *   links: <Number> the number of links to the entry
 *   size: <Number> the size in bytes of the entry
 *   modified: <Number> the last modified date/time
 *   type: <String> the type of the entry
 *   contents: <Array> an optional array of child entries
 * }
 *
 * By default ls() gives a shallow listing. If you want
 * to follow directories as they are encountered, use
 * the `recursive=true` option.
 */
Shell.prototype.ls = function(dir, options, callback) {
  var sh = this;
  var fs = sh.fs;
  if(typeof options === 'function') {
    callback = options;
    options = {};
  }
  options = options || {};
  callback = callback || function(){};

  if(!dir) {
    callback(new Errors.EINVAL('Missing dir argument'));
    return;
  }

  function list(path, callback) {
    var pathname = Path.resolve(sh.pwd(), path);
    var result = [];

    fs.readdir(pathname, function(error, entries) {
      if(error) {
        callback(error);
        return;
      }

      function getDirEntry(name, callback) {
        name = Path.join(pathname, name);
        fs.stat(name, function(error, stats) {
          if(error) {
            callback(error);
            return;
          }
          var entry = stats;

          if(options.recursive && stats.type === 'DIRECTORY') {
            list(Path.join(pathname, entry.name), function(error, items) {
              if(error) {
                callback(error);
                return;
              }
              entry.contents = items;
              result.push(entry);
              callback();
            });
          } else {
            result.push(entry);
            callback();
          }
        });
      }

      async.eachSeries(entries, getDirEntry, function(error) {
        callback(error, result);
      });
    });
  }

  list(dir, callback);
};

/**
 * Removes the file or directory at `path`. If `path` is a file
 * it will be removed. If `path` is a directory, it will be
 * removed if it is empty, otherwise the callback will receive
 * an error. In order to remove non-empty directories, use the
 * `recursive=true` option.
 */
Shell.prototype.rm = function(path, options, callback) {
  var sh = this;
  var fs = sh.fs;
  if(typeof options === 'function') {
    callback = options;
    options = {};
  }
  options = options || {};
  callback = callback || function(){};

  if(!path) {
    callback(new Errors.EINVAL('Missing path argument'));
    return;
  }

  function remove(pathname, callback) {
    pathname = Path.resolve(sh.pwd(), pathname);
    fs.stat(pathname, function(error, stats) {
      if(error) {
        callback(error);
        return;
      }

      // If this is a file, delete it and we're done
      if(stats.type === 'FILE') {
        fs.unlink(pathname, callback);
        return;
      }

      // If it's a dir, check if it's empty
      fs.readdir(pathname, function(error, entries) {
        if(error) {
          callback(error);
          return;
        }

        // If dir is empty, delete it and we're done
        if(entries.length === 0) {
          fs.rmdir(pathname, callback);
          return;
        }

        // If not, see if we're allowed to delete recursively
        if(!options.recursive) {
          callback(new Errors.ENOTEMPTY(null, pathname));
          return;
        }

        // Remove each dir entry recursively, then delete the dir.
        entries = entries.map(function(filename) {
          // Root dir entries absolutely
          return Path.join(pathname, filename);
        });
        async.eachSeries(entries, remove, function(error) {
          if(error) {
            callback(error);
            return;
          }
          fs.rmdir(pathname, callback);
        });
      });
    });
  }

  remove(path, callback);
};

/**
 * Gets the path to the temporary directory, creating it if not
 * present. The directory used is the one specified in
 * env.TMP. The callback receives (error, tempDirName).
 */
Shell.prototype.tempDir = function(callback) {
  var sh = this;
  var fs = sh.fs;
  var tmp = sh.env.get('TMP');
  callback = callback || function(){};

  // Try and create it, and it will either work or fail
  // but either way it's now there.
  fs.mkdir(tmp, function() {
    callback(null, tmp);
  });
};

/**
 * Recursively creates the directory at `path`. If the parent
 * of `path` does not exist, it will be created.
 * Based off EnsureDir by Sam X. Xu
 * https://www.npmjs.org/package/ensureDir
 * MIT License
 */
Shell.prototype.mkdirp = function(path, callback) {
  var sh = this;
  var fs = sh.fs;
  callback = callback || function(){};

  if(!path) {
    callback(new Errors.EINVAL('Missing path argument'));
    return;
  }
  else if (path === '/') {
    callback();
    return;
  }
  function _mkdirp(path, callback) {
    fs.stat(path, function (err, stat) {
      if(stat) {
        if(stat.isDirectory()) {
          callback();
          return;
        }
        else if (stat.isFile()) {
          callback(new Errors.ENOTDIR(null, path));
          return;
        }
      }
      else if (err && err.code !== 'ENOENT') {
        callback(err);
        return;
      }
      else {
        var parent = Path.dirname(path);
        if(parent === '/') {
          fs.mkdir(path, function (err) {
            if (err && err.code !== 'EEXIST') {
              callback(err);
              return;
            }
            callback();
            return;
          });
        }
        else {
          _mkdirp(parent, function (err) {
            if (err) return callback(err);
            fs.mkdir(path, function (err) {
              if (err && err.code !== 'EEXIST') {
                callback(err);
                return;
              }
              callback();
              return;
            });
          });
        }
      }
    });
  }

  _mkdirp(path, callback);
};

/**
 * Recursively walk a directory tree, reporting back all paths
 * that were found along the way. The `path` must be a dir.
 * Valid options include a `regex` for pattern matching paths
 * and an `exec` function of the form `function(path, next)` where
 * `path` is the current path that was found (dir paths have an '/'
 * appended) and `next` is a callback to call when done processing
 * the current path, passing any error object back as the first argument.
 * `find` returns a flat array of absolute paths for all matching/found
 * paths as the final argument to the callback.
 */
Shell.prototype.find = function(path, options, callback) {
  var sh = this;
  var fs = sh.fs;
  if(typeof options === 'function') {
    callback = options;
    options = {};
  }
  options = options || {};
  callback = callback || function(){};

  var exec = options.exec || function(path, next) { next(); };
  var found = [];

  if(!path) {
    callback(new Errors.EINVAL('Missing path argument'));
    return;
  }

  function processPath(path, callback) {
    exec(path, function(err) {
      if(err) {
        callback(err);
        return;
      }

      found.push(path);
      callback();
    });
  }

  function maybeProcessPath(path, callback) {
    // Test the path against the user's regex, name, path primaries (if any)
    // and remove any trailing slashes added previously.
    var rawPath = Path.removeTrailing(path);

    // Check entire path against provided regex, if any
    if(options.regex && !options.regex.test(rawPath)) {
      callback();
      return;
    }

    // Check basename for matches against name primary, if any
    if(options.name && !minimatch(Path.basename(rawPath), options.name)) {
      callback();
      return;
    }

    // Check dirname for matches against path primary, if any
    if(options.path && !minimatch(Path.dirname(rawPath), options.path)) {
      callback();
      return;
    }

    processPath(path, callback);
  }

  function walk(path, callback) {
    path = Path.resolve(sh.pwd(), path);

    // The path is either a file or dir, and instead of doing
    // a stat() to determine it first, we just try to readdir()
    // and it will either work or not, and we handle the non-dir error.
    fs.readdir(path, function(err, entries) {
      if(err) {
        if(err.code === 'ENOTDIR' /* file case, ignore error */) {
          maybeProcessPath(path, callback);
        } else {
          callback(err);
        }
        return;
      }

      // Path is really a dir, add a trailing / and report it found
      maybeProcessPath(Path.addTrailing(path), function(err) {
        if(err) {
          callback(err);
          return;
        }

        entries = entries.map(function(entry) {
          return Path.join(path, entry);
        });

        async.eachSeries(entries, walk, function(err) {
          callback(err, found);
        });
      });
    });
  }

  // Make sure we are starting with a dir path
  fs.stat(path, function(err, stats) {
    if(err) {
      callback(err);
      return;
    }
    if(!stats.isDirectory()) {
      callback(new Errors.ENOTDIR(null, path));
      return;
    }

    walk(path, callback);
  });
};

module.exports = Shell;