'use strict';
/**
 * Expose the `Swagger` plugin.
 */
module.exports = Swagger;

/**
 * Module dependencies.
 */
var debug = require('debug')('loopback:explorer:swagger');
var path = require('path');
var urlJoin = require('./url-join');
var _defaults = require('lodash.defaults');
var classHelper = require('./class-helper');
var modelHelper = require('./model-helper');
var routeHelper = require('./route-helper');

/**
 * Create a remotable Swagger module for plugging into `RemoteObjects`.
 *
 * @param {Application} loopbackApplication Host loopback application.
 * @param {Application} swaggerApp Swagger application used for hosting
 *                                 these files.
 * @param {Object} opts Options.
 */
function Swagger(loopbackApplication, swaggerApp, opts) {
  opts = _defaults({}, opts, {
    swaggerVersion: '1.2',
    basePath: loopbackApplication.get('restApiRoot') || '/api',
    resourcePath: 'resources',
    version: getVersion()
  });

  // We need a temporary REST adapter to discover our available routes.
  var remotes = loopbackApplication.remotes();
  var adapter = remotes.handler('rest').adapter;
  var routes = adapter.allRoutes();
  var classes = remotes.classes();

  // These are the docs we will be sending from the /swagger endpoints.
  var resourceDoc = generateResourceDoc(opts);
  var apiDocs = {};

  // A class is an endpoint root; e.g. /users, /products, and so on.
  classes.forEach(function (aClass) {
    var doc = apiDocs[aClass.name] = classHelper.generateAPIDoc(aClass, opts);
    resourceDoc.apis.push(classHelper.generateResourceDocAPIEntry(aClass));

    // Add the getter for this doc.
    var docPath = urlJoin(opts.resourcePath, aClass.http.path);
    addRoute(swaggerApp, docPath, doc);
  });

  // A route is an endpoint, such as /users/findOne.
  routes.forEach(function(route) {
    // Get the API doc matching this class name.
    var className = route.method.split('.')[0];
    var doc = apiDocs[className];
    if (!doc) {
      console.error('Route exists with no class: %j', route);
      return;
    }
    // Get the class definition matching this route.
    var classDef = classes.filter(function (item) {
      return item.name === className;
    })[0];

    routeHelper.addRouteToAPIDeclaration(route, classDef, doc);
  });

  /**
   * The topmost Swagger resource is a description of all (non-Swagger) 
   * resources available on the system, and where to find more 
   * information about them.
   */
  addRoute(swaggerApp, opts.resourcePath, resourceDoc);
}

/**
 * Add a route to this remoting extension.
 * @param {Application} app       Express application.
 * @param {String} uri            Path from which to serve the doc.
 * @param {Object} doc            Doc to serve.
 */
function addRoute(app, uri, doc) {

  var hasBasePath = Object.keys(doc).indexOf('basePath') !== -1;
  var initialPath = doc.basePath || '';

  app.get(urlJoin('/', uri), function(req, res) {

    // There's a few forces at play that require this "hack". The Swagger spec
    // requires a `basePath` to be set in the API descriptions. However, we 
    // can't guarantee this path is either reachable or desirable if it's set 
    // as a part of the options.
    // 
    // The simplest way around this is to reflect the value of the `Host` HTTP
    // header as the `basePath`. Because we pre-build the Swagger data, we don't
    // know that header at the time the data is built.
    if (hasBasePath) {
      var headers = req.headers;
      var host = headers.Host || headers.host;
      doc.basePath = req.protocol + '://' + host + initialPath;
    }
    res.send(200, doc);
  });
}

/**
 * Generate a top-level resource doc. This is the entry point for swagger UI
 * and lists all of the available APIs.
 * @param  {Object} opts Swagger options.
 * @return {Object}      Resource doc.
 */
function generateResourceDoc(opts) {
  return {
    swaggerVersion: opts.swaggerVersion,
    apiVersion: opts.version,
    apis: [],
    // See https://github.com/wordnik/swagger-spec/blob/master/versions/1.2.md#513-info-object
    info: opts.apiInfo
    // TODO Authorizations
    // https://github.com/wordnik/swagger-spec/blob/master/versions/1.2.md#514-authorizations-object
    // TODO Produces/Consumes
    // https://github.com/wordnik/swagger-spec/blob/master/versions/1.2.md#52-api-declaration
  };
}

/**
 * Attempt to get the current API version from package.json.
 * @return {String} API Version.
 */
function getVersion() {
  var version;
  try {
    version = require(path.join(process.cwd(), 'package.json')).version;
  } catch(e) {
    version = '';
  }
  return version;
}