first stab at online tiles

lib/mbtiles.js

@@ -3,6 +3,7 @@ var _ = require('underscore'),
     Step = require('step'),
     crypto = require('crypto'),
     zlib = require('zlib'),
+    get = require('get'),
     sqlite3 = require('sqlite3');
 
 // MBTiles
@@ -10,8 +11,16 @@ var _ = require('underscore'),
 // MBTiles class for doing common operations (schema setup, tile reading,
 // insertion, etc.)
 function MBTiles(filename, callback) {
+    var mbtiles = this;
     this.filename = filename;
-    this.db = new sqlite3.Database(filename, callback);
+    this.db = new sqlite3.Database(filename, function(err) {
+        if (err) return callback(err);
+        mbtiles.metadata('online', function(err, value) {
+            // Ignore not-existant key.
+            mbtiles.online = value;
+            if (callback) callback(null);
+        });
+    });
 };
 
 // Retrieve the schema of the current mbtiles database and inform the caller of
@@ -208,16 +217,39 @@ MBTiles.prototype.insertGridTiles = function(map, callback) {
 // - @param {Number} z tile z coordinate.
 // - @param {Function} callback
 MBTiles.prototype.tile = function(x, y, z, callback) {
+    var mbtiles = this;
     this.db.get('SELECT tile_data FROM tiles WHERE ' +
         'zoom_level = ? AND tile_column = ? AND tile_row = ?',
         z, x, y,
         function(err, row) {
             if (err) callback(err);
-            else if (!row || !row.tile_data) callback(new Error('Tile does not exist'));
+            else if (!row || !row.tile_data) mbtiles.onlineTile(x, y, z, callback);
             else callback(null, row.tile_data);
         });
 };
 
+// Requests a tile from an online source and cache it to the database.
+//
+// - @param {Number} x tile x coordinate.
+// - @param {Number} y tile y coordinate.
+// - @param {Number} z tile z coordinate.
+// - @param {Function} callback
+MBTiles.prototype.onlineTile = function(x, y, z, callback) {
+    var mbtiles = this;
+    if (!this.online) {
+        return callback(new Error('Tile does not exist'));
+    }
+
+    var url = this.online.replace(/%x/g, x).replace(/%y/g, Math.pow(2, z) - 1 - y).replace(/%z/g, z);
+    new get(url).asBuffer(function(err, result) {
+        if (err) return callback(new Error(err));
+
+        // Cache image.
+        mbtiles.insertTiles([{ x: x, y: y, z: z, data: result }], function() {});
+        callback(null, result);
+    });
+};
+
 // Select a grid and its data from an mbtiles database.
 //
 // - @param {Number} x tile x coordinate

package.json

@@ -26,6 +26,7 @@
         "optimist": "0.2.x",
         "sqlite3": "2.0.x",
         "step": "0.0.x",
+        "get": "0.3.x",
         "underscore": "1.1.x",
         "zlib": "1.0.x"
     },

test/online.test.js

@@ -0,0 +1,61 @@
+var assert = require('assert');
+var MBTiles = require('..').MBTiles;
+
+var fixture = __dirname + '/fixtures/online.mbtiles';
+
+exports['get online metadata'] = function(beforeExit) {
+    var completion = {};
+
+    var mbtiles = new MBTiles(fixture);
+    mbtiles.metadata('name', function(err, value) { if (err) throw err; completion.name = value; });
+    mbtiles.metadata('type', function(err, value) { if (err) throw err; completion.type = value; });
+    mbtiles.metadata('description', function(err, value) { if (err) throw err; completion.description = value; });
+    mbtiles.metadata('version', function(err, value) { if (err) throw err; completion.version = value; });
+    mbtiles.metadata('formatter', function(err, value) { if (err) throw err; completion.formatter = value; });
+    mbtiles.metadata('bounds', function(err, value) { if (err) throw err; completion.bounds = value; });
+    mbtiles.metadata('online', function(err, value) { if (err) throw err; completion.online = value; });
+    mbtiles.metadata('invalid', function(err, value) { completion.invalid = err.message; });
+
+    beforeExit(function() {
+        assert.deepEqual(completion, {
+            name: 'MapQuest streets',
+            type: 'baselayer',
+            description: 'MapQuest’s OpenStreetMap based street level tiles.',
+            version: '1.0.0',
+            formatter: null,
+            bounds: '-180,-90,180,90',
+            online: 'http://otile1.mqcdn.com/tiles/1.0.0/osm/%z/%x/%y.png',
+            invalid: 'Key does not exist'
+        });
+    });
+};
+
+
+exports['get online tiles'] = function(beforeExit) {
+    var status = {
+        success: 0,
+        error: 0
+    };
+
+    var mbtiles = new MBTiles(fixture);
+
+    mbtiles.db.serialize(function() {
+        mbtiles.db.run("DELETE FROM map");
+        mbtiles.db.run("DELETE FROM images");
+    });
+
+    mbtiles.tile(0, 0, 0, function(err, tile) {
+        if (err) throw new Error(err);
+        status.success++;
+    });
+
+    mbtiles.tile(0, 0, 18, function(err, tile) {
+        if (err) throw new Error(err);
+        status.success++;
+    });
+
+    beforeExit(function() {
+        assert.equal(status.success, 2);
+        assert.equal(status.error, 0);
+    });
+};