Start refactoring channel storage

src/channel-storage/channelstore.js

@@ -0,0 +1,11 @@
+import { FileStore } from './filestore';
+
+var CHANNEL_STORE = new FileStore();
+
+export function load(channelName) {
+    return CHANNEL_STORE.load(channelName);
+}
+
+export function save(channelName, data) {
+    return CHANNEL_STORE.save(channelName, data);
+}

src/channel-storage/filestore.js

@@ -0,0 +1,46 @@
+import * as Promise from 'bluebird';
+import { stat } from 'fs';
+import * as fs from 'graceful-fs';
+import path from 'path';
+
+const readFileAsync = Promise.promisify(fs.readFile);
+const writeFileAsync = Promise.promisify(fs.writeFile);
+const statAsync = Promise.promisify(stat);
+const SIZE_LIMIT = 1048576;
+const CHANDUMP_DIR = path.resolve(__dirname, '..', '..', 'chandump');
+
+export class FileStore {
+    filenameForChannel(channelName) {
+        return path.join(CHANDUMP_DIR, channelName);
+    }
+
+    load(channelName) {
+        const filename = this.filenameForChannel(channelName);
+        return statAsync(filename).then(stats => {
+            if (stats.size > SIZE_LIMIT) {
+                throw new Error('Channel state file is too large: ' + stats.size);
+            } else {
+                return readFileAsync(filename);
+            }
+        }).then(fileContents => {
+            try {
+                return JSON.parse(fileContents);
+            } catch (e) {
+                throw new Error('Channel state file is not valid JSON: ' + e);
+            }
+        });
+    }
+
+    save(channelName, data) {
+        const filename = this.filenameForChannel(channelName);
+        const fileContents = new Buffer(JSON.stringify(data), 'utf8');
+        if (fileContents.length > SIZE_LIMIT) {
+            let error = new Error('Channel state size is too large');
+            error.limit = SIZE_LIMIT;
+            error.size = fileContents.length;
+            return Promise.reject(error);
+        }
+
+        return writeFileAsync(filename, fileContents);
+    }
+}