/* globals require, module */

  'use strict';

  /**
   * Module dependencies.
   */

  var pathtoRegexp = require('path-to-regexp');

  /**
   * Short-cuts for global-object checks
   */

  var hasDocument = ('undefined' !== typeof document);
  var hasWindow = ('undefined' !== typeof window);
  var hasHistory = ('undefined' !== typeof history);
  var hasProcess = typeof process !== 'undefined';

  /**
   * Detect click event
   */
  var clickEvent = hasDocument && document.ontouchstart ? 'touchstart' : 'click';

  /**
   * To work properly with the URL
   * history.location generated polyfill in https://github.com/devote/HTML5-History-API
   */

  var isLocation = hasWindow && !!(window.history.location || window.location);

  /**
   * The page instance
   * @api private
   */
  function Page() {
    // public things
    this.callbacks = [];
    this.exits = [];
    this.current = '';
    this.len = 0;

    // private things
    this._decodeURLComponents = true;
    this._base = '';
    this._strict = false;
    this._running = false;
    this._hashbang = false;

    // bound functions
    this.clickHandler = this.clickHandler.bind(this);
    this._onpopstate = this._onpopstate.bind(this);
  }

  /**
   * Configure the instance of page. This can be called multiple times.
   *
   * @param {Object} options
   * @api public
   */

  Page.prototype.configure = function(options) {
    var opts = options || {};

    this._window = opts.window || (hasWindow && window);
    this._decodeURLComponents = opts.decodeURLComponents !== false;
    this._popstate = opts.popstate !== false && hasWindow;
    this._click = opts.click !== false && hasDocument;
    this._hashbang = !!opts.hashbang;

    var _window = this._window;
    if(this._popstate) {
      _window.addEventListener('popstate', this._onpopstate, false);
    } else if(hasWindow) {
      _window.removeEventListener('popstate', this._onpopstate, false);
    }

    if (this._click) {
      _window.document.addEventListener(clickEvent, this.clickHandler, false);
    } else if(hasDocument) {
      _window.document.removeEventListener(clickEvent, this.clickHandler, false);
    }

    if(this._hashbang && hasWindow && !hasHistory) {
      _window.addEventListener('hashchange', this._onpopstate, false);
    } else if(hasWindow) {
      _window.removeEventListener('hashchange', this._onpopstate, false);
    }
  };

  /**
   * Get or set basepath to `path`.
   *
   * @param {string} path
   * @api public
   */

  Page.prototype.base = function(path) {
    if (0 === arguments.length) return this._base;
    this._base = path;
  };

  /**
   * Gets the `base`, which depends on whether we are using History or
   * hashbang routing.

   * @api private
   */
  Page.prototype._getBase = function() {
    var base = this._base;
    if(!!base) return base;
    var loc = hasWindow && this._window && this._window.location;

    if(hasWindow && this._hashbang && loc && loc.protocol === 'file:') {
      base = loc.pathname;
    }

    return base;
  };

  /**
   * Get or set strict path matching to `enable`
   *
   * @param {boolean} enable
   * @api public
   */

  Page.prototype.strict = function(enable) {
    if (0 === arguments.length) return this._strict;
    this._strict = enable;
  };


  /**
   * Bind with the given `options`.
   *
   * Options:
   *
   *    - `click` bind to click events [true]
   *    - `popstate` bind to popstate [true]
   *    - `dispatch` perform initial dispatch [true]
   *
   * @param {Object} options
   * @api public
   */

  Page.prototype.start = function(options) {
    var opts = options || {};
    this.configure(opts);

    if (false === opts.dispatch) return;
    this._running = true;

    var url;
    if(isLocation) {
      var window = this._window;
      var loc = window.location;

      if(this._hashbang && ~loc.hash.indexOf('#!')) {
        url = loc.hash.substr(2) + loc.search;
      } else if (this._hashbang) {
        url = loc.search + loc.hash;
      } else {
        url = loc.pathname + loc.search + loc.hash;
      }
    }

    this.replace(url, null, true, opts.dispatch);
  };

  /**
   * Unbind click and popstate event handlers.
   *
   * @api public
   */

  Page.prototype.stop = function() {
    if (!this._running) return;
    this.current = '';
    this.len = 0;
    this._running = false;

    var window = this._window;
    this._click && window.document.removeEventListener(clickEvent, this.clickHandler, false);
    hasWindow && window.removeEventListener('popstate', this._onpopstate, false);
    hasWindow && window.removeEventListener('hashchange', this._onpopstate, false);
  };

  /**
   * Show `path` with optional `state` object.
   *
   * @param {string} path
   * @param {Object=} state
   * @param {boolean=} dispatch
   * @param {boolean=} push
   * @return {!Context}
   * @api public
   */

  Page.prototype.show = function(path, state, dispatch, push) {
    var ctx = new Context(path, state, this),
      prev = this.prevContext;
    this.prevContext = ctx;
    this.current = ctx.path;
    if (false !== dispatch) this.dispatch(ctx, prev);
    if (false !== ctx.handled && false !== push) ctx.pushState();
    return ctx;
  };

  /**
   * Goes back in the history
   * Back should always let the current route push state and then go back.
   *
   * @param {string} path - fallback path to go back if no more history exists, if undefined defaults to page.base
   * @param {Object=} state
   * @api public
   */

  Page.prototype.back = function(path, state) {
    var page = this;
    if (this.len > 0) {
      var window = this._window;
      // this may need more testing to see if all browsers
      // wait for the next tick to go back in history
      hasHistory && window.history.back();
      this.len--;
    } else if (path) {
      setTimeout(function() {
        page.show(path, state);
      });
    } else {
      setTimeout(function() {
        page.show(page._getBase(), state);
      });
    }
  };

  /**
   * Register route to redirect from one path to other
   * or just redirect to another route
   *
   * @param {string} from - if param 'to' is undefined redirects to 'from'
   * @param {string=} to
   * @api public
   */
  Page.prototype.redirect = function(from, to) {
    var inst = this;

    // Define route from a path to another
    if ('string' === typeof from && 'string' === typeof to) {
      page.call(this, from, function(e) {
        setTimeout(function() {
          inst.replace(/** @type {!string} */ (to));
        }, 0);
      });
    }

    // Wait for the push state and replace it with another
    if ('string' === typeof from && 'undefined' === typeof to) {
      setTimeout(function() {
        inst.replace(from);
      }, 0);
    }
  };

  /**
   * Replace `path` with optional `state` object.
   *
   * @param {string} path
   * @param {Object=} state
   * @param {boolean=} init
   * @param {boolean=} dispatch
   * @return {!Context}
   * @api public
   */


  Page.prototype.replace = function(path, state, init, dispatch) {
    var ctx = new Context(path, state, this),
      prev = this.prevContext;
    this.prevContext = ctx;
    this.current = ctx.path;
    ctx.init = init;
    ctx.save(); // save before dispatching, which may redirect
    if (false !== dispatch) this.dispatch(ctx, prev);
    return ctx;
  };

  /**
   * Dispatch the given `ctx`.
   *
   * @param {Context} ctx
   * @api private
   */

  Page.prototype.dispatch = function(ctx, prev) {
    var i = 0, j = 0, page = this;

    function nextExit() {
      var fn = page.exits[j++];
      if (!fn) return nextEnter();
      fn(prev, nextExit);
    }

    function nextEnter() {
      var fn = page.callbacks[i++];

      if (ctx.path !== page.current) {
        ctx.handled = false;
        return;
      }
      if (!fn) return unhandled.call(page, ctx);
      fn(ctx, nextEnter);
    }

    if (prev) {
      nextExit();
    } else {
      nextEnter();
    }
  };

  /**
   * Register an exit route on `path` with
   * callback `fn()`, which will be called
   * on the previous context when a new
   * page is visited.
   */
  Page.prototype.exit = function(path, fn) {
    if (typeof path === 'function') {
      return this.exit('*', path);
    }

    var route = new Route(path, null, this);
    for (var i = 1; i < arguments.length; ++i) {
      this.exits.push(route.middleware(arguments[i]));
    }
  };

  /**
   * Handle "click" events.
   */

  /* jshint +W054 */
  Page.prototype.clickHandler = function(e) {
    if (1 !== this._which(e)) return;

    if (e.metaKey || e.ctrlKey || e.shiftKey) return;
    if (e.defaultPrevented) return;

    // ensure link
    // use shadow dom when available if not, fall back to composedPath()
    // for browsers that only have shady
    var el = e.target;
    var eventPath = e.path || (e.composedPath ? e.composedPath() : null);

    if(eventPath) {
      for (var i = 0; i < eventPath.length; i++) {
        if (!eventPath[i].nodeName) continue;
        if (eventPath[i].nodeName.toUpperCase() !== 'A') continue;
        if (!eventPath[i].href) continue;

        el = eventPath[i];
        break;
      }
    }

    // continue ensure link
    // el.nodeName for svg links are 'a' instead of 'A'
    while (el && 'A' !== el.nodeName.toUpperCase()) el = el.parentNode;
    if (!el || 'A' !== el.nodeName.toUpperCase()) return;

    // check if link is inside an svg
    // in this case, both href and target are always inside an object
    var svg = (typeof el.href === 'object') && el.href.constructor.name === 'SVGAnimatedString';

    // Ignore if tag has
    // 1. "download" attribute
    // 2. rel="external" attribute
    if (el.hasAttribute('download') || el.getAttribute('rel') === 'external') return;

    // ensure non-hash for the same path
    var link = el.getAttribute('href');
    if(!this._hashbang && this._samePath(el) && (el.hash || '#' === link)) return;

    // Check for mailto: in the href
    if (link && link.indexOf('mailto:') > -1) return;

    // check target
    // svg target is an object and its desired value is in .baseVal property
    if (svg ? el.target.baseVal : el.target) return;

    // x-origin
    // note: svg links that are not relative don't call click events (and skip page.js)
    // consequently, all svg links tested inside page.js are relative and in the same origin
    if (!svg && !this.sameOrigin(el.href)) return;

    // rebuild path
    // There aren't .pathname and .search properties in svg links, so we use href
    // Also, svg href is an object and its desired value is in .baseVal property
    var path = svg ? el.href.baseVal : (el.pathname + el.search + (el.hash || ''));

    path = path[0] !== '/' ? '/' + path : path;

    // strip leading "/[drive letter]:" on NW.js on Windows
    if (hasProcess && path.match(/^\/[a-zA-Z]:\//)) {
      path = path.replace(/^\/[a-zA-Z]:\//, '/');
    }

    // same page
    var orig = path;
    var pageBase = this._getBase();

    if (path.indexOf(pageBase) === 0) {
      path = path.substr(pageBase.length);
    }

    if (this._hashbang) path = path.replace('#!', '');

    if (pageBase && orig === path && (!isLocation || this._window.location.protocol !== 'file:')) {
      return;
    }

    e.preventDefault();
    this.show(orig);
  };

  /**
   * Handle "populate" events.
   * @api private
   */

  Page.prototype._onpopstate = (function () {
    var loaded = false;
    if ( ! hasWindow ) {
      return function () {};
    }
    if (hasDocument && document.readyState === 'complete') {
      loaded = true;
    } else {
      window.addEventListener('load', function() {
        setTimeout(function() {
          loaded = true;
        }, 0);
      });
    }
    return function onpopstate(e) {
      if (!loaded) return;
      var page = this;
      if (e.state) {
        var path = e.state.path;
        page.replace(path, e.state);
      } else if (isLocation) {
        var loc = page._window.location;
        page.show(loc.pathname + loc.search + loc.hash, undefined, undefined, false);
      }
    };
  })();

  /**
   * Event button.
   */
  Page.prototype._which = function(e) {
    e = e || (hasWindow && this._window.event);
    return null == e.which ? e.button : e.which;
  };

  /**
   * Convert to a URL object
   * @api private
   */
  Page.prototype._toURL = function(href) {
    var window = this._window;
    if(typeof URL === 'function' && isLocation) {
      return new URL(href, window.location.toString());
    } else if (hasDocument) {
      var anc = window.document.createElement('a');
      anc.href = href;
      return anc;
    }
  };

  /**
   * Check if `href` is the same origin.
   * @param {string} href
   * @api public
   */
  Page.prototype.sameOrigin = function(href) {
    if(!href || !isLocation) return false;

    var url = this._toURL(href);
    var window = this._window;

    var loc = window.location;

    /*
       When the port is the default http port 80 for http, or 443 for
       https, internet explorer 11 returns an empty string for loc.port,
       so we need to compare loc.port with an empty string if url.port
       is the default port 80 or 443.
       Also the comparition with `port` is changed from `===` to `==` because
       `port` can be a string sometimes. This only applies to ie11.
    */
    return loc.protocol === url.protocol &&
      loc.hostname === url.hostname &&
      (loc.port === url.port || loc.port === '' && (url.port == 80 || url.port == 443)); // jshint ignore:line
  };

  /**
   * @api private
   */
  Page.prototype._samePath = function(url) {
    if(!isLocation) return false;
    var window = this._window;
    var loc = window.location;
    return url.pathname === loc.pathname &&
      url.search === loc.search;
  };

  /**
   * Remove URL encoding from the given `str`.
   * Accommodates whitespace in both x-www-form-urlencoded
   * and regular percent-encoded form.
   *
   * @param {string} val - URL component to decode
   * @api private
   */
  Page.prototype._decodeURLEncodedURIComponent = function(val) {
    if (typeof val !== 'string') { return val; }
    return this._decodeURLComponents ? decodeURIComponent(val.replace(/\+/g, ' ')) : val;
  };

  /**
   * Create a new `page` instance and function
   */
  function createPage() {
    var pageInstance = new Page();

    function pageFn(/* args */) {
      return page.apply(pageInstance, arguments);
    }

    // Copy all of the things over. In 2.0 maybe we use setPrototypeOf
    pageFn.callbacks = pageInstance.callbacks;
    pageFn.exits = pageInstance.exits;
    pageFn.base = pageInstance.base.bind(pageInstance);
    pageFn.strict = pageInstance.strict.bind(pageInstance);
    pageFn.start = pageInstance.start.bind(pageInstance);
    pageFn.stop = pageInstance.stop.bind(pageInstance);
    pageFn.show = pageInstance.show.bind(pageInstance);
    pageFn.back = pageInstance.back.bind(pageInstance);
    pageFn.redirect = pageInstance.redirect.bind(pageInstance);
    pageFn.replace = pageInstance.replace.bind(pageInstance);
    pageFn.dispatch = pageInstance.dispatch.bind(pageInstance);
    pageFn.exit = pageInstance.exit.bind(pageInstance);
    pageFn.configure = pageInstance.configure.bind(pageInstance);
    pageFn.sameOrigin = pageInstance.sameOrigin.bind(pageInstance);
    pageFn.clickHandler = pageInstance.clickHandler.bind(pageInstance);

    pageFn.create = createPage;

    Object.defineProperty(pageFn, 'len', {
      get: function(){
        return pageInstance.len;
      },
      set: function(val) {
        pageInstance.len = val;
      }
    });

    Object.defineProperty(pageFn, 'current', {
      get: function(){
        return pageInstance.current;
      },
      set: function(val) {
        pageInstance.current = val;
      }
    });

    // In 2.0 these can be named exports
    pageFn.Context = Context;
    pageFn.Route = Route;

    return pageFn;
  }

  /**
   * Register `path` with callback `fn()`,
   * or route `path`, or redirection,
   * or `page.start()`.
   *
   *   page(fn);
   *   page('*', fn);
   *   page('/user/:id', load, user);
   *   page('/user/' + user.id, { some: 'thing' });
   *   page('/user/' + user.id);
   *   page('/from', '/to')
   *   page();
   *
   * @param {string|!Function|!Object} path
   * @param {Function=} fn
   * @api public
   */

  function page(path, fn) {
    // <callback>
    if ('function' === typeof path) {
      return page.call(this, '*', path);
    }

    // route <path> to <callback ...>
    if ('function' === typeof fn) {
      var route = new Route(/** @type {string} */ (path), null, this);
      for (var i = 1; i < arguments.length; ++i) {
        this.callbacks.push(route.middleware(arguments[i]));
      }
      // show <path> with [state]
    } else if ('string' === typeof path) {
      this['string' === typeof fn ? 'redirect' : 'show'](path, fn);
      // start [options]
    } else {
      this.start(path);
    }
  }

  /**
   * Unhandled `ctx`. When it's not the initial
   * popstate then redirect. If you wish to handle
   * 404s on your own use `page('*', callback)`.
   *
   * @param {Context} ctx
   * @api private
   */
  function unhandled(ctx) {
    if (ctx.handled) return;
    var current;
    var page = this;
    var window = page._window;

    if (page._hashbang) {
      current = isLocation && this._getBase() + window.location.hash.replace('#!', '');
    } else {
      current = isLocation && window.location.pathname + window.location.search;
    }

    if (current === ctx.canonicalPath) return;
    page.stop();
    ctx.handled = false;
    isLocation && (window.location.href = ctx.canonicalPath);
  }

  /**
   * Escapes RegExp characters in the given string.
   *
   * @param {string} s
   * @api private
   */
  function escapeRegExp(s) {
    return s.replace(/([.+*?=^!:${}()[\]|/\\])/g, '\\$1');
  }

  /**
   * Initialize a new "request" `Context`
   * with the given `path` and optional initial `state`.
   *
   * @constructor
   * @param {string} path
   * @param {Object=} state
   * @api public
   */

  function Context(path, state, pageInstance) {
    var _page = this.page = pageInstance || page;
    var window = _page._window;
    var hashbang = _page._hashbang;

    var pageBase = _page._getBase();
    if ('/' === path[0] && 0 !== path.indexOf(pageBase)) path = pageBase + (hashbang ? '#!' : '') + path;
    var i = path.indexOf('?');

    this.canonicalPath = path;
    var re = new RegExp('^' + escapeRegExp(pageBase));
    this.path = path.replace(re, '') || '/';
    if (hashbang) this.path = this.path.replace('#!', '') || '/';

    this.title = (hasDocument && window.document.title);
    this.state = state || {};
    this.state.path = path;
    this.querystring = ~i ? _page._decodeURLEncodedURIComponent(path.slice(i + 1)) : '';
    this.pathname = _page._decodeURLEncodedURIComponent(~i ? path.slice(0, i) : path);
    this.params = {};

    // fragment
    this.hash = '';
    if (!hashbang) {
      if (!~this.path.indexOf('#')) return;
      var parts = this.path.split('#');
      this.path = this.pathname = parts[0];
      this.hash = _page._decodeURLEncodedURIComponent(parts[1]) || '';
      this.querystring = this.querystring.split('#')[0];
    }
  }

  /**
   * Push state.
   *
   * @api private
   */

  Context.prototype.pushState = function() {
    var page = this.page;
    var window = page._window;
    var hashbang = page._hashbang;

    page.len++;
    if (hasHistory) {
        window.history.pushState(this.state, this.title,
          hashbang && this.path !== '/' ? '#!' + this.path : this.canonicalPath);
    }
  };

  /**
   * Save the context state.
   *
   * @api public
   */

  Context.prototype.save = function() {
    var page = this.page;
    if (hasHistory) {
        page._window.history.replaceState(this.state, this.title,
          page._hashbang && this.path !== '/' ? '#!' + this.path : this.canonicalPath);
    }
  };

  /**
   * Initialize `Route` with the given HTTP `path`,
   * and an array of `callbacks` and `options`.
   *
   * Options:
   *
   *   - `sensitive`    enable case-sensitive routes
   *   - `strict`       enable strict matching for trailing slashes
   *
   * @constructor
   * @param {string} path
   * @param {Object=} options
   * @api private
   */

  function Route(path, options, page) {
    var _page = this.page = page || globalPage;
    var opts = options || {};
    opts.strict = opts.strict || _page._strict;
    this.path = (path === '*') ? '(.*)' : path;
    this.method = 'GET';
    this.regexp = pathtoRegexp(this.path, this.keys = [], opts);
  }

  /**
   * Return route middleware with
   * the given callback `fn()`.
   *
   * @param {Function} fn
   * @return {Function}
   * @api public
   */

  Route.prototype.middleware = function(fn) {
    var self = this;
    return function(ctx, next) {
      if (self.match(ctx.path, ctx.params)) {
        ctx.routePath = self.path;
        return fn(ctx, next);
      }
      next();
    };
  };

  /**
   * Check if this route matches `path`, if so
   * populate `params`.
   *
   * @param {string} path
   * @param {Object} params
   * @return {boolean}
   * @api private
   */

  Route.prototype.match = function(path, params) {
    var keys = this.keys,
      qsIndex = path.indexOf('?'),
      pathname = ~qsIndex ? path.slice(0, qsIndex) : path,
      m = this.regexp.exec(decodeURIComponent(pathname));

    if (!m) return false;

    delete params[0];

    for (var i = 1, len = m.length; i < len; ++i) {
      var key = keys[i - 1];
      var val = this.page._decodeURLEncodedURIComponent(m[i]);
      if (val !== undefined || !(hasOwnProperty.call(params, key.name))) {
        params[key.name] = val;
      }
    }

    return true;
  };


  /**
   * Module exports.
   */

  var globalPage = createPage();
  module.exports = globalPage;
  module.exports.default = globalPage;