Add Windshaft Server components

Previously Windshaft included a built-in server. That must now
be specified explicitly, as done in OpenTreeMap/otm-tiler#116,
and as shown in their examples https://github.com/CartoDB/Windshaft/tree/be55cb931a157be3e7da9e9c810929f48c342789/examples

The beforeTileRender and afterTileRender hooks are gone,
so that functionality is moved in to the server code.

Some of this code has been updated / adapted from the examples
to make more sense, and be less redundant. Other parts remain
from the examples. It could use a proper overhaul.

src/tiler/http/mapController.js

@@ -0,0 +1,145 @@
+'use strict';
+
+var step = require('step');
+var windshaft = require('windshaft');
+var _ = require('underscore');
+
+var MapConfig = windshaft.model.MapConfig;
+var DummyMapConfigProvider = require('windshaft/lib/windshaft/models/providers/dummy_mapconfig_provider');
+var MapStoreMapConfigProvider = windshaft.model.provider.MapStoreMapConfig;
+
+/**
+ * @param app
+ * @param {MapStore} mapStore
+ * @param {MapBackend} mapBackend
+ * @param {TileBackend} tileBackend
+ * @constructor
+ */
+function MapController(app, mapStore, mapBackend, tileBackend) {
+    this._app = app;
+    this.mapStore = mapStore;
+    this.mapBackend = mapBackend;
+    this.tileBackend = tileBackend;
+}
+
+MapController.prototype.register = function(app) {
+    var tile = this.tile.bind(this);
+    var cors = this.cors.bind(this);
+
+    app.get(app.base_url + '/:z/:x/:y@:scale_factor?x.:format(png|grid\.json)', tile);
+    app.get(app.base_url + '/:z/:x/:y.:format(png|grid\.json)', tile);
+    app.options(app.base_url, cors);
+};
+
+// send CORS headers when client send options.
+MapController.prototype.cors = function(req, res, next) {
+    this._app.doCORS(res, 'Content-Type');
+    return next();
+};
+
+MapController.prototype.create = function initLayergroup(req, mapConfig, callback) {
+    this.mapBackend.createLayergroup(
+        mapConfig, req.params, new DummyMapConfigProvider(mapConfig, req.params), callback
+    );
+};
+
+// Gets a tile for a given token and set of tile ZXY coords. (OSM style)
+MapController.prototype.tile = function(req, res) {
+    var self = this;
+    var mapConfig;
+
+    this._app.doCORS(res);
+    step(
+        function mapController$prepareParams() {
+            self._app.req2params(req, this);
+        },
+        function mapController$getMapConfig(err) {
+            mapConfig = MapConfig.create({
+                layers: [{
+                    type: 'mapnik',
+                    options: {
+                        sql: req.params.sql,
+                        cartocss: req.params.style,
+                        cartocss_version: '2.0.1',
+                        interactivity: req.params.interactivity,
+                        geom_column: 'geom',
+                    }
+                }]
+            });
+            self.mapStore.load(mapConfig.id(), this);
+        },
+        function mapController$saveMapConfig(err, layer) {
+            if (layer) {
+                this(null, layer);
+            } else {
+                self.create(req, mapConfig, this);
+            }
+        },
+        function mapController$getTile(err, layer) {
+            if ( err ) {
+                throw err;
+            }
+            req.params.token = layer.layergroupid;
+            self.tileBackend.getTile(new MapStoreMapConfigProvider(self.mapStore, req.params), req.params, this);
+        },
+        function mapController$finalize(err, tile, headers) {
+            self.finalizeGetTileOrGrid(err, req, res, tile, headers);
+            self._app.cacheTile(req, tile);
+            return null;
+        },
+        function finish(err) {
+            if ( err ) {
+                // TODO Replace with Rollbar
+                console.error("windshaft.tiles: " + err);
+            }
+        }
+    );
+};
+
+// This function is meant for being called as the very last
+// step by all endpoints serving tiles or grids
+MapController.prototype.finalizeGetTileOrGrid = function(err, req, res, tile, headers) {
+    if (err) {
+        // See https://github.com/Vizzuality/Windshaft-cartodb/issues/68
+        var errMsg = err.message ? ( '' + err.message ) : ( '' + err );
+
+        // Rewrite mapnik parsing errors to start with layer number
+        var matches = errMsg.match("(.*) in style 'layer([0-9]+)'");
+        if (matches) {
+            errMsg = 'style'+matches[2]+': ' + matches[1];
+        }
+
+        var status = err.http_status || statusFromErrorMessage(errMsg);
+
+        this._app.sendError(res, { errors: [errMsg] }, status, 'TILE', err);
+    } else {
+        res.status(200)
+            // Add cache header for 30 days
+            .set(_.extend(headers, { 'Cache-Control': 'max-age=2592000' }))
+            .send(tile);
+    }
+};
+
+function statusFromErrorMessage(errMsg) {
+    // Find an appropriate statusCode based on message
+    var statusCode = 400;
+    if ( -1 !== errMsg.indexOf('permission denied') ) {
+        statusCode = 403;
+    }
+    else if ( -1 !== errMsg.indexOf('authentication failed') ) {
+        statusCode = 403;
+    }
+    else if (errMsg.match(/Postgis Plugin.*[\s|\n].*column.*does not exist/)) {
+        statusCode = 400;
+    }
+    else if ( -1 !== errMsg.indexOf('does not exist') ) {
+        if ( -1 !== errMsg.indexOf(' role ') ) {
+            statusCode = 403; // role 'xxx' does not exist
+        } else {
+            statusCode = 404;
+        }
+    }
+    return statusCode;
+}
+
+module.exports = MapController;