/**
 * @license
 * Copyright (c) 2015 The Polymer Project Authors. All rights reserved.
 * This code may only be used under the BSD style license found at http://polymer.github.io/LICENSE.txt
 * The complete set of authors may be found at http://polymer.github.io/AUTHORS.txt
 * The complete set of contributors may be found at http://polymer.github.io/CONTRIBUTORS.txt
 * Code distributed by Google as part of the polymer project is also
 * subject to an additional IP rights grant found at http://polymer.github.io/PATENTS.txt
 */

// jshint node:true
'use strict';

var fs = require('fs');
var path = require('path');
var pathIsAbsolute = require('path-is-absolute');
var url = require('url');

function getFile(filePath, deferred, secondPath) {
  fs.readFile(filePath, 'utf-8', function(err, content) {
    if (err) {
      if (secondPath) {
        getFile(secondPath, deferred);
      } else {
        console.log("ERROR finding " + filePath);
        deferred.reject(err);
      }
    } else {
      deferred.resolve(content);
    }
  });
}

/**
 * Returns true if `patha` is a sibling or aunt of `pathb`.
 * @return {boolean}
 */
function isSiblingOrAunt(patha, pathb) {
  var parent = path.dirname(patha);
  if (pathb.indexOf(patha) === -1 && pathb.indexOf(parent) === 0) {
    return true;
  }
  return false;
}

/**
 * Change `localPath` from a sibling of `basePath` to be a child of
 * `basePath` joined with `redirect`.
 * @return {string}
 */
function redirectSibling(basePath, localPath, redirect) {
  var parent = path.dirname(basePath);
  var redirected = path.join(basePath, redirect, localPath.slice(parent.length));
  return redirected;
}

/**
 * Resolves requests via the file system.
 * @constructor
 * @memberof hydrolysis
 * @param {Object} config  configuration options.
 * @param {string} config.host Hostname to match for absolute urls.
 *     Matches "/" by default
 * @param {string} config.basePath Prefix directory for components in url.
 *     Defaults to "/".
 * @param {string} config.root Filesystem root to search. Defaults to the
 *     current working directory.
 * @param {string} config.redirect Where to redirect lookups to siblings.
 */
function FSResolver(config) {
  this.config = config || {};
}
FSResolver.prototype = {
  accept: function(uri, deferred) {
    var parsed = url.parse(uri);
    var host = this.config.host;
    var base = this.config.basePath && decodeURIComponent(this.config.basePath);
    var root = this.config.root && path.normalize(this.config.root);
    var redirect = this.config.redirect;

    var local;

    if (!parsed.hostname || parsed.hostname === host) {
      local = parsed.pathname;
    }
    if (local) {
      // un-escape HTML escapes
      local = decodeURIComponent(local);

      if (base) {
        local = path.relative(base, local);
      }
      if (root) {
        local = path.join(root, local);
      }

      var backup;
      if (redirect && isSiblingOrAunt(root, local)) {
        backup = redirectSibling(root, local, redirect);
      }

      getFile(local, deferred, backup);
      return true;
    }

    return false;
  }
};

module.exports = FSResolver;