var absURLRegEx = /^[^\/]+:\/\//;

function readMemberExpression(p, value) {
  var pParts = p.split('.');
  while (pParts.length)
    value = value[pParts.shift()];
  return value;
}

var baseURLCache = {};
function getBaseURLObj() {
  if (baseURLCache[this.baseURL])
    return baseURLCache[this.baseURL];

  // normalize baseURL if not already
  if (this.baseURL[this.baseURL.length - 1] != '/')
    this.baseURL += '/';

  var baseURL = new URL(this.baseURL, baseURI);

  this.baseURL = baseURL.href;

  return (baseURLCache[this.baseURL] = baseURL);
}

function getMapMatch(map, name) {
  var bestMatch, bestMatchLength = 0;

  for (var p in map) {
    if (name.substr(0, p.length) == p && (name.length == p.length || name[p.length] == '/')) {
      var curMatchLength = p.split('/').length;
      if (curMatchLength <= bestMatchLength)
        continue;
      bestMatch = p;
      bestMatchLength = curMatchLength;
    }
  }

  return bestMatch;
}

function setProduction(isProduction) {
  this.set('@system-env', this.newModule({
    browser: isBrowser,
    node: !!this._nodeRequire,
    production: isProduction
  }));
}

var baseURIObj = new URL(baseURI);

hookConstructor(function(constructor) {
  return function() {
    constructor.call(this);

    // support baseURL
    this.baseURL = baseURI.substr(0, baseURI.lastIndexOf('/') + 1);

    // support map and paths
    this.map = {};
    this.paths = {};

    // global behaviour flags
    this.warnings = false;
    this.defaultJSExtensions = false;
    this.pluginFirst = false;

    // by default load ".json" files as json
    // leading * meta doesn't need normalization
    // NB add this in next breaking release
    // this.meta['*.json'] = { format: 'json' };

    // support the empty module, as a concept
    this.set('@empty', this.newModule({}));

    setProduction.call(this, false);
  };
});

// include the node require since we're overriding it
if (typeof require != 'undefined' && typeof process != 'undefined' && !process.browser)
  SystemJSLoader.prototype._nodeRequire = require;

var nodeCoreModules = ['assert', 'buffer', 'child_process', 'cluster', 'console', 'constants', 
    'crypto', 'dgram', 'dns', 'domain', 'events', 'fs', 'http', 'https', 'module', 'net', 'os', 'path', 
    'process', 'punycode', 'querystring', 'readline', 'repl', 'stream', 'string_decoder', 'sys', 'timers', 
    'tls', 'tty', 'url', 'util', 'vm', 'zlib'];

/*
  Core SystemJS Normalization

  If a name is relative, we apply URL normalization to the page
  If a name is an absolute URL, we leave it as-is

  Plain names (neither of the above) run through the map and paths
  normalization phases.

  The paths normalization phase applies last (paths extension), which
  defines the `decanonicalize` function and normalizes everything into
  a URL.
 */

function applyMap(name) {
  // first run map config
  if (name[0] != '.' && name[0] != '/' && !name.match(absURLRegEx)) {
    var mapMatch = getMapMatch(this.map, name);
    if (mapMatch)
      return this.map[mapMatch] + name.substr(mapMatch.length);
  }
  return name;
}

hook('normalize', function(normalize) {
  return function(name, parentName, skipExt) {
    name = applyMap.call(this, name);

    // dynamically load node-core modules when requiring `@node/fs` for example
    if (name.substr(0, 6) == '@node/' && nodeCoreModules.indexOf(name.substr(6)) != -1) {
      if (!this._nodeRequire)
        throw new TypeError('Error loading ' + name + '. Can only load node core modules in Node.');
      this.set(name, this.newModule(getESModule(this._nodeRequire(name.substr(6)))));
    }
    
    // relative URL-normalization
    if (name[0] == '.' || name[0] == '/') {
      if (parentName)
        name = new URL(name, parentName.replace(/#/g, '%05')).href.replace(/%05/g, '#');
      else
        name = new URL(name, baseURIObj).href;
    }

    // if the module is in the registry already, use that
    if (this.has(name))
      return name;

    if (name.match(absURLRegEx)) {
      // defaultJSExtensions backwards compatibility
      if (this.defaultJSExtensions && name.substr(name.length - 3, 3) != '.js' && !skipExt)
        name += '.js';
      return name;
    }

    // applyPaths implementation provided from ModuleLoader system.js source
    name = applyPaths(this.paths, name) || name;

    // defaultJSExtensions backwards compatibility
    if (this.defaultJSExtensions && name.substr(name.length - 3, 3) != '.js' && !skipExt)
      name += '.js';

    // ./x, /x -> page-relative
    if (name[0] == '.' || name[0] == '/')
      return new URL(name, baseURIObj).href;
    // x -> baseURL-relative
    else
      return new URL(name, getBaseURLObj.call(this)).href;
  };
});

// percent encode just '#' in urls if using HTTP requests
var httpRequest = typeof XMLHttpRequest != 'undefined';
hook('locate', function(locate) {
  return function(load) {
    return Promise.resolve(locate.call(this, load))
    .then(function(address) {
      if (httpRequest)
        return address.replace(/#/g, '%23');
      return address;
    });
  };
});

/*
 * Fetch with authorization
 */
hook('fetch', function() {
  return function(load) {
    return new Promise(function(resolve, reject) {
      fetchTextFromURL(load.address, load.metadata.authorization, resolve, reject);
    });
  };
});

/*
  __useDefault
  
  When a module object looks like:
  newModule(
    __useDefault: true,
    default: 'some-module'
  })

  Then importing that module provides the 'some-module'
  result directly instead of the full module.

  Useful for eg module.exports = function() {}
*/
hook('import', function(systemImport) {
  return function(name, parentName, parentAddress) {
    if (parentName && parentName.name)
      warn.call(this, 'SystemJS.import(name, { name: parentName }) is deprecated for SystemJS.import(name, parentName), while importing ' + name + ' from ' + parentName.name);
    return systemImport.call(this, name, parentName, parentAddress).then(function(module) {
      return module.__useDefault ? module['default'] : module;
    });
  };
});

/*
 * Allow format: 'detect' meta to enable format detection
 */
hook('translate', function(systemTranslate) {
  return function(load) {
    if (load.metadata.format == 'detect')
      load.metadata.format = undefined;
    return systemTranslate.call(this, load);
  };
});


/*
 * JSON format support
 *
 * Supports loading JSON files as a module format itself
 *
 * Usage:
 *
 * SystemJS.config({
 *   meta: {
 *     '*.json': { format: 'json' }
 *   }
 * });
 *
 * Module is returned as if written:
 *
 * export default {JSON}
 *
 * No named exports are provided
 *
 * Files ending in ".json" are treated as json automatically by SystemJS
 */
hook('instantiate', function(instantiate) {
  return function(load) {
    if (load.metadata.format == 'json' && !this.builder) {
      var entry = load.metadata.entry = createEntry();
      entry.deps = [];
      entry.execute = function() {
        try {
          return JSON.parse(load.source);
        }
        catch(e) {
          throw new Error("Invalid JSON file " + load.name);
        }
      };
    }
  };
})

/*
 Extend config merging one deep only

  loader.config({
    some: 'random',
    config: 'here',
    deep: {
      config: { too: 'too' }
    }
  });

  <=>

  loader.some = 'random';
  loader.config = 'here'
  loader.deep = loader.deep || {};
  loader.deep.config = { too: 'too' };


  Normalizes meta and package configs allowing for:

  SystemJS.config({
    meta: {
      './index.js': {}
    }
  });

  To become

  SystemJS.meta['https://thissite.com/index.js'] = {};

  For easy normalization canonicalization with latest URL support.

*/
SystemJSLoader.prototype.env = 'development';

SystemJSLoader.prototype.config = function(cfg) {
  var loader = this;

  if ('warnings' in cfg)
    loader.warnings = cfg.warnings;

  // transpiler deprecation path
  if (cfg.transpilerRuntime === false)
    loader._loader.loadedTranspilerRuntime = true;

  // always configure baseURL first
  if (cfg.baseURL) {
    var hasConfig = false;
    function checkHasConfig(obj) {
      for (var p in obj)
        if (hasOwnProperty.call(obj, p))
          return true;
    }
    if (checkHasConfig(loader.packages) || checkHasConfig(loader.meta) || checkHasConfig(loader.depCache) || checkHasConfig(loader.bundles) || checkHasConfig(loader.packageConfigPaths))
      throw new TypeError('Incorrect configuration order. The baseURL must be configured with the first SystemJS.config call.');

    loader.baseURL = cfg.baseURL;

    // sanitize baseURL
    getBaseURLObj.call(loader);
  }

  if (cfg.defaultJSExtensions) {
    loader.defaultJSExtensions = cfg.defaultJSExtensions;
    warn.call(loader, 'The defaultJSExtensions configuration option is deprecated, use packages configuration instead.');
  }

  if (cfg.pluginFirst)
    loader.pluginFirst = cfg.pluginFirst;

  if (cfg.production)
    setProduction.call(loader, true);

  if (cfg.paths) {
    for (var p in cfg.paths)
      loader.paths[p] = cfg.paths[p];
  }

  if (cfg.map) {
    var objMaps = '';
    for (var p in cfg.map) {
      var v = cfg.map[p];

      // object map backwards-compat into packages configuration
      if (typeof v !== 'string') {
        objMaps += (objMaps.length ? ', ' : '') + '"' + p + '"';

        var defaultJSExtension = loader.defaultJSExtensions && p.substr(p.length - 3, 3) != '.js';
        var prop = loader.decanonicalize(p);
        if (defaultJSExtension && prop.substr(prop.length - 3, 3) == '.js')
          prop = prop.substr(0, prop.length - 3);

        // if a package main, revert it
        var pkgMatch = '';
        for (var pkg in loader.packages) {
          if (prop.substr(0, pkg.length) == pkg 
              && (!prop[pkg.length] || prop[pkg.length] == '/') 
              && pkgMatch.split('/').length < pkg.split('/').length)
            pkgMatch = pkg;
        }
        if (pkgMatch && loader.packages[pkgMatch].main)
          prop = prop.substr(0, prop.length - loader.packages[pkgMatch].main.length - 1);

        var pkg = loader.packages[prop] = loader.packages[prop] || {};
        pkg.map = v;
      }
      else {
        loader.map[p] = v;
      }
    }
    if (objMaps)
      warn.call(loader, 'The map configuration for ' + objMaps + ' uses object submaps, which is deprecated in global map.\nUpdate this to use package contextual map with configs like SystemJS.config({ packages: { "' + p + '": { map: {...} } } }).');
  }

  if (cfg.packageConfigPaths) {
    var packageConfigPaths = [];
    for (var i = 0; i < cfg.packageConfigPaths.length; i++) {
      var path = cfg.packageConfigPaths[i];
      var packageLength = Math.max(path.lastIndexOf('*') + 1, path.lastIndexOf('/'));
      var defaultJSExtension = loader.defaultJSExtensions && path.substr(packageLength - 3, 3) != '.js';
      var normalized = loader.decanonicalize(path.substr(0, packageLength));
      if (defaultJSExtension && normalized.substr(normalized.length - 3, 3) == '.js')
        normalized = normalized.substr(0, normalized.length - 3);
      packageConfigPaths[i] = normalized + path.substr(packageLength);
    }
    loader.packageConfigPaths = packageConfigPaths;
  }

  if (cfg.bundles) {
    for (var p in cfg.bundles) {
      var bundle = [];
      for (var i = 0; i < cfg.bundles[p].length; i++) {
        var defaultJSExtension = loader.defaultJSExtensions && cfg.bundles[p][i].substr(cfg.bundles[p][i].length - 3, 3) != '.js';
        var normalizedBundleDep = loader.decanonicalize(cfg.bundles[p][i]);
        if (defaultJSExtension && normalizedBundleDep.substr(normalizedBundleDep.length - 3, 3) == '.js')
          normalizedBundleDep = normalizedBundleDep.substr(0, normalizedBundleDep.length - 3);
        bundle.push(normalizedBundleDep);
      }
      loader.bundles[p] = bundle;
    }
  }

  if (cfg.packages) {
    for (var p in cfg.packages) {
      if (p.match(/^([^\/]+:)?\/\/$/))
        throw new TypeError('"' + p + '" is not a valid package name.');

      var defaultJSExtension = loader.defaultJSExtensions && p.substr(p.length - 3, 3) != '.js';
      var prop = loader.decanonicalize(applyMap(p));
      if (defaultJSExtension && prop.substr(prop.length - 3, 3) == '.js')
        prop = prop.substr(0, prop.length - 3);

      // allow trailing slash in packages
      if (prop[prop.length - 1] == '/')
        prop = prop.substr(0, prop.length - 1);

      loader.packages[prop] = loader.packages[prop] || {};

      // meta backwards compatibility
      if (cfg.packages[p].modules) {
        warn.call(loader, 'Package ' + p + ' is configured with "modules", which is deprecated as it has been renamed to "meta".');
        cfg.packages[p].meta = cfg.packages[p].modules;
        delete cfg.packages[p].modules;
      }

      for (var q in cfg.packages[p])
        if (indexOf.call(packageProperties, q) == -1)
          warn.call(loader, '"' + q + '" is not a valid package configuration option in package ' + p);

      extendMeta(loader.packages[prop], cfg.packages[p]);
    }
  }

  for (var c in cfg) {
    var v = cfg[c];

    if (c == 'baseURL' || c == 'map' || c == 'packages' || c == 'bundles' || c == 'paths' || c == 'warnings' || c == 'packageConfigPaths')
      continue;

    if (typeof v != 'object' || v instanceof Array) {
      loader[c] = v;
    }
    else {
      loader[c] = loader[c] || {};

      for (var p in v) {
        // base-level wildcard meta does not normalize to retain catch-all quality
        if (c == 'meta' && p[0] == '*') {
          loader[c][p] = v[p];
        }
        else if (c == 'meta') {
          // meta can go through global map
          loader[c][loader.decanonicalize(applyMap(p))] = v[p];
        }
        else if (c == 'depCache') {
          var defaultJSExtension = loader.defaultJSExtensions && p.substr(p.length - 3, 3) != '.js';
          var prop = loader.decanonicalize(p);
          if (defaultJSExtension && prop.substr(prop.length - 3, 3) == '.js')
            prop = prop.substr(0, prop.length - 3);
          loader[c][prop] = v[p];
        }
        else {
          loader[c][p] = v[p];
        }
      }
    }
  }
};