[Persistence] Copy CouchDB adapter

Copy CouchDB adapter to use as a basis for an adapter to
ElasticSearch, WTD-1033.

platform/persistence/elastic/src/ElasticPersistenceProvider.js

@@ -0,0 +1,162 @@
+/*global define*/
+
+define(
+    ["./CouchDocument"],
+    function (CouchDocument) {
+        'use strict';
+
+        // JSLint doesn't like dangling _'s, but CouchDB uses these, so
+        // hide this behind variables.
+        var REV = "_rev",
+            ID = "_id";
+
+        /**
+         * The CouchPersistenceProvider reads and writes JSON documents
+         * (more specifically, domain object models) to/from a CouchDB
+         * instance.
+         * @constructor
+         */
+        function ElasticPersistenceProvider($http, $q, SPACE, PATH) {
+            var spaces = [ SPACE ],
+                revs = {};
+
+            // Convert a subpath to a full path, suitable to pass
+            // to $http.
+            function url(subpath) {
+                return PATH + '/' + subpath;
+            }
+
+            // Issue a request using $http; get back the plain JS object
+            // from the expected JSON response
+            function request(subpath, method, value) {
+                return $http({
+                    method: method,
+                    url: url(subpath),
+                    data: value
+                }).then(function (response) {
+                    return response.data;
+                }, function () {
+                    return undefined;
+                });
+            }
+
+            // Shorthand methods for GET/PUT methods
+            function get(subpath) {
+                return request(subpath, "GET");
+            }
+            function put(subpath, value) {
+                return request(subpath, "PUT", value);
+            }
+
+            // Pull out a list of document IDs from CouchDB's
+            // _all_docs response
+            function getIdsFromAllDocs(allDocs) {
+                return allDocs.rows.map(function (r) { return r.id; });
+            }
+
+            // Get a domain object model out of CouchDB's response
+            function getModel(response) {
+                if (response && response.model) {
+                    revs[response[ID]] = response[REV];
+                    return response.model;
+                } else {
+                    return undefined;
+                }
+            }
+
+            // Check the response to a create/update/delete request;
+            // track the rev if it's valid, otherwise return false to
+            // indicate that the request failed.
+            function checkResponse(response) {
+                if (response && response.ok) {
+                    revs[response.id] = response.rev;
+                    return response.ok;
+                } else {
+                    return false;
+                }
+            }
+
+            return {
+                /**
+                 * List all persistence spaces which this provider
+                 * recognizes.
+                 *
+                 * @returns {Promise.<string[]>} a promise for a list of
+                 *          spaces supported by this provider
+                 */
+                listSpaces: function () {
+                    return $q.when(spaces);
+                },
+                /**
+                 * List all objects (by their identifiers) that are stored
+                 * in the given persistence space, per this provider.
+                 * @param {string} space the space to check
+                 * @returns {Promise.<string[]>} a promise for the list of
+                 *          identifiers
+                 */
+                listObjects: function (space) {
+                    return get("_all_docs").then(getIdsFromAllDocs);
+                },
+                /**
+                 * Create a new object in the specified persistence space.
+                 * @param {string} space the space in which to store the object
+                 * @param {string} key the identifier for the persisted object
+                 * @param {object} value a JSONifiable object that should be
+                 *        stored and associated with the provided identifier
+                 * @returns {Promise.<boolean>} a promise for an indication
+                 *          of the success (true) or failure (false) of this
+                 *          operation
+                 */
+                createObject: function (space, key, value) {
+                    return put(key, new CouchDocument(key, value))
+                        .then(checkResponse);
+                },
+
+                /**
+                 * Read an existing object back from persistence.
+                 * @param {string} space the space in which to look for
+                 *        the object
+                 * @param {string} key the identifier for the persisted object
+                 * @returns {Promise.<object>} a promise for the stored
+                 *          object; this will resolve to undefined if no such
+                 *          object is found.
+                 */
+                readObject: function (space, key) {
+                    return get(key).then(getModel);
+                },
+                /**
+                 * Update an existing object in the specified persistence space.
+                 * @param {string} space the space in which to store the object
+                 * @param {string} key the identifier for the persisted object
+                 * @param {object} value a JSONifiable object that should be
+                 *        stored and associated with the provided identifier
+                 * @returns {Promise.<boolean>} a promise for an indication
+                 *          of the success (true) or failure (false) of this
+                 *          operation
+                 */
+                updateObject: function (space, key, value) {
+                    return put(key, new CouchDocument(key, value, revs[key]))
+                        .then(checkResponse);
+                },
+                /**
+                 * Delete an object in the specified persistence space.
+                 * @param {string} space the space from which to delete this
+                 *        object
+                 * @param {string} key the identifier of the persisted object
+                 * @param {object} value a JSONifiable object that should be
+                 *        deleted
+                 * @returns {Promise.<boolean>} a promise for an indication
+                 *          of the success (true) or failure (false) of this
+                 *          operation
+                 */
+                deleteObject: function (space, key, value) {
+                    return put(key, new CouchDocument(key, value, revs[key], true))
+                        .then(checkResponse);
+                }
+            };
+
+        }
+
+        return ElasticPersistenceProvider;
+    }
+);