Support sqlite mode flags (#73)

* Update mbtiles.js

* some reading

* remove seemingly unused/dead code

* core api functionality

* test note

* grids

* remove index test

* add tilelive example

* vNext

* follow sqlite3 URI filenames

* add mode test

* add mode test

* fix ci

* fix ci

* Update mbtiles.js

* follow sqlite3 URI filenames

* add mode test

* add mode test

* fix ci

* fix ci

* Update readme on mode flags

README.md

@@ -22,11 +22,17 @@ var MBTiles = require('@mapbox/mbtiles');
 All MBTiles instances need to be constructed before any of the methods become available. *NOTE: All methods described below assume you've taken this step.*
 
 ```javascript
-new MBTiles('./path/to/file.mbtiles', function(err, mbtiles) {
+new MBTiles('./path/to/file.mbtiles?mode={ro, rw, rwc}', function(err, mbtiles) {
   console.log(mbtiles) // mbtiles object with methods listed below
 });
 ```
 
+The `mode` query parameter is a opening flag of mbtiles. It is optional, default as `rwc`. Available flags are:
+
+- `ro`: readonly mode, will throw error if the mbtiles is not existed.
+- `rw`: read and write mode, will throw error if the mbtiles is not existed.
+- `rwc`: read, write and create mode, will create a new mbtiles if the mbtiles is not existed.
+
 ### Reading
 
 **`getTile(z, x, y, callback)`**

lib/mbtiles.js

@@ -51,11 +51,22 @@ function MBTiles(uri, callback) {
     uri.query = uri.query || {};
     if (!uri.query.batch) uri.query.batch = 100;
 
+    if (!uri.query.mode) uri.query.mode = 'rwc';
+    var flagEnum = {
+        ro: sqlite3.OPEN_READONLY,
+        rw: sqlite3.OPEN_READWRITE,
+        rwc: sqlite3.OPEN_READWRITE | sqlite3.OPEN_CREATE
+    };
+    var mode = flagEnum[uri.query.mode];
+    if (!mode) {
+        return callback(new Error('Only supports "ro", "rw", or "rwc" mode.'));
+    }
+
     var mbtiles = this;
     this.setMaxListeners(0);
     this.filename = uri.pathname;
     this._batchSize = +uri.query.batch;
-    mbtiles._db = new sqlite3.Database(mbtiles.filename, function(err) {
+    mbtiles._db = new sqlite3.Database(mbtiles.filename, mode, function(err) {
         if (err) return callback(err);
         fs.stat(mbtiles.filename, function(err, stat) {
             if (err) return callback(err);

test/mode.test.js

@@ -0,0 +1,32 @@
+require('sqlite3').verbose();
+
+var fs = require('fs');
+var MBTiles = require('..');
+var tape = require('tape');
+
+var non_existent = __dirname + '/fixtures/non_existent.mbtiles';
+
+try { fs.unlinkSync(non_existent); } catch (err) {}
+
+tape('Open with ro mode', function(assert) {
+  new MBTiles(non_existent + '?mode=ro', function(err, mbtiles) {
+    assert.ok(err);
+    assert.ok(err.message.match(/SQLITE_CANTOPEN: unable to open database file/));
+    assert.end();
+  })
+})
+
+tape('Open with rw mode', function(assert) {
+  new MBTiles(non_existent + '?mode=rw', function(err, mbtiles) {
+    assert.ok(err);
+    assert.ok(err.message.match(/SQLITE_CANTOPEN: unable to open database file/));
+    assert.end();
+  })
+})
+
+tape('Open with rwc mode', function(assert) {
+  new MBTiles(non_existent + '?mode=rwc', function(err, mbtiles) {
+    assert.notOk(err);
+    assert.end();
+  })
+})