'use strict';

var Command = require('ember-cli/lib/models/command');
var chalk   = require('chalk');
var path    = require('path');
var Q       = require("q");
var request = require("request");
var _       = require('lodash');
var fs      = require('fs');

// taken from http://stackoverflow.com/a/17238793
// `condition` is a function that returns a boolean
// `body` is a function that returns a promise
// returns a promise for the completion of the loop
function promiseWhile(condition, body) {

    var done = Q.defer();

    function loop() {
        // When the result of calling `condition` is no longer true, we are
        // done.
        if (!condition()) return done.resolve();
        // Use `when`, in case `body` does not return a promise.
        // When it completes loop again otherwise, if it fails, reject the
        // done promise
        Q.when(body(), loop, done.reject);
    }

    // Start running the loop in the next tick so that this function is
    // completely async. It would be unexpected if `body` was called
    // synchronously the first time.
    Q.nextTick(loop);

    // The promise
    return done.promise;
}


module.exports = Command.extend({
  name: 'dl-fixtures',
  description: "Download fixtures",
  works: 'everywhere',
  availableOptions: [
    { name: 'type', type: String, default: 'documents', aliases: ['t'], description: "type of obejcts to downloads" },
    { name: 'url',  type: String, aliases: ['u'], description: "Source url" },
    { name: 'dest', type: String, aliases: ['d'], description: "File destination"  },
    { name: 'page', type: Number, default: 1 , aliases: ['p'], description: "number of page to download"},
    { name: 'format', type: String, default: 'es6' , aliases: ['f'], description: "Format for module export, es6 or require"},
  ],
  run: function(commandOptions, rawArgs) {

    //TODO: check that commandOptions.url is not empty

    var dest = commandOptions.dest || "." + path.sep + commandOptions.type + ".js"
    var format = commandOptions.format || 'es6';

    var ids = [];
    var pageIndex = 1;
    var nextPageUrl = commandOptions.url;

    return promiseWhile(
      function() { return pageIndex <= commandOptions.page && nextPageUrl },
      function() {
        var deferred = Q.defer();
        request.get({url: nextPageUrl, json: true}, function (err, res, body) {
          if (err) {
              return deferred.reject(err);
          } else if (res.statusCode !== 200) {
              err = new Error("Unexpected status code: " + res.statusCode);
              err.res = res;
              return deferred.reject(err);
          }
          nextPageUrl = body.next_page_url;
          pageIndex++;

          ids = _.reduce(
            body.documents,
            function(res, doc) {
              res.push(doc.id);
              return res;
            },
            ids
          );
          deferred.resolve(ids);
        });
        return deferred.promise;
      }
    ).then(function() {
      return Q.all(_.map(ids, function(id) {
        var deferred = Q.defer();
        request.get({url: commandOptions.url + id, json: true}, function (err, res, body) {
          if (err) {
              return deferred.reject(err);
          } else if (res.statusCode !== 200) {
              err = new Error("Unexpected status code: " + res.statusCode);
              err.res = res;
              return deferred.reject(err);
          }
          deferred.resolve(body.document);
        });
        return deferred.promise;
      }));
    }).then(function(res) {
      var deferred = Q.defer();
      var prefix = (format==='es6')?'export default ':"module.exports = ";
      fs.writeFile(dest, prefix + JSON.stringify(res,null,2) + ";", function(err) {
        if(err) {
          return deferred.reject(err);
        }
        deferred.resolve();
      });
      return deferred.promise;
    });
  }
});