/** Copyright Stewart Allen -- All Rights Reserved */

// https://developer.mozilla.org/en-US/docs/Web/API/IndexedDB_API

export const data = {
    Index: IDBStore,
    open() {
        return new IDBStore(...arguments);
    }
};

let IDB, IRR, local = null;

try {
    IDB = self.indexedDB || self.mozIndexedDB || self.webkitIndexedDB || self.msIndexedDB;
    IRR = self.IDBKeyRange;
} catch (e) {
    console.log("IndexedDB disabled: application may not function properly");
}

/**
 * @param {String} dbname
 * @param {number} [version]
 * @constructor
 */
function IDBStore(dbname, options = {}) {
    this.db = null;
    this.name = dbname;
    this.stores = options.stores || [ dbname ];
    this.version = options.version || 1;
    this.queue = [];
    this.idle = [];
    this.initCalled = false;
    this.created = {};
}

IDBStore.delete = function(dbname) {
    IDB.deleteDatabase(dbname);
};

let SP = IDBStore.prototype;

/** ******************************************************************
 * indexedDB implementation
 ******************************************************************* */

SP.onIdle = function(fn) {
    if (this.queue.length) {
        this.idle.push(fn);
    } else {
        fn();
    }
    return this;
};

SP.promise = function(store) {
    let db = this;
    let pc = {
        iterate: (opt = {}) => new Promise(function(resolve, reject) {
            let { lower, upper, collect } = opt;
            if (!collect) {
                let rval = opt.map ? {} : [];
                collect = (key, value) => {
                    if (key !== null) {
                        if (opt.map) {
                            rval[key] = value;
                        } else {
                            rval.push({key, value});
                        }
                    } else {
                        resolve(rval);
                    }
                };
            } else {
                resolve();
            }
            db.iterate(collect, lower, upper, true, store);
        }),

        get: (key) => new Promise(function(resolve, reject) {
            db.get(key, resolve, store);
        }),

        put: (key, value) => new Promise(function(resolve, reject) {
            db.put(key, value, resolve, store);
        }),

        remove: (key) => new Promise(function(resolve, reject) {
            db.remove(key, resolve, store);
        }),

        // wait for all outstanding transactions to complete
        wait: () => new Promise(function(resolve, reject) {
            db.onIdle(promise);
        }),

        use: (store) => {
            db.use(store);
            return pc;
        },
    };
    return pc;
}

SP.keys = function(callback, lower, upper, store = this.current) {
    if (!this.db) {
        this.init();
        return this.queue.push(["keys", callback, lower, upper, store]);
    }
    let out = [];
    this.iterate(function(k,v) {
        if (k === null) {
            callback(out);
        } else {
            out.push(k);
        }
    }, lower, upper, true, store);
};

SP.iterate = function(callback, lower, upper, nullterm, store = this.current) {
    if (!this.db) {
        this.init();
        return this.queue.push(["iterate", callback, lower, upper, nullterm, store]);
    }
    let range = lower && upper ? IRR.bound(lower,upper) :
                lower ? IRR.lowerBound(lower) :
                upper ? IRR.upperBound(upper) : undefined;
    // iterate over all db values for debugging
    this.db
        .transaction(store)
        .objectStore(store)
        .openCursor(range).onsuccess = function(event) {
            let cursor = event.target.result;
            if (cursor) {
                callback(cursor.key, cursor.value);
                cursor.continue();
            } else if (nullterm) {
                callback(null);
            }
        };
};

SP.deleteStore = function() {
    if (this.initCalled) throw "cannot delete ObjectStore after init() called";
    this.version = Number.MAX_SAFE_INTEGER || Number.MAX_VALUE;
    return this.init(true);
};

SP.use = function(store) {
    this.current = store;
    return this;
}

SP.init = function(options = {}) {
    if (this.initCalled) return;

    let storage = this,
        name = this.name,
        request = null;

    function fallback() {
        console.log(`IndexedDB disabled: unable to initialize '${name}'`);
        local = {};
        storage.runQueue();
    }

    try {
        request = IDB.open(name, this.version);

        request.onupgradeneeded = function(event) {
            let db = storage.db = request.result;
            let current = [...db.objectStoreNames];
            let stores = storage.stores;
            // add missing stores
            for (let store of stores) {
                if (current.indexOf(store) >= 0) {
                    continue;
                }
                storage.created[store] = db.createObjectStore(store);
                storage.current = store;
                current.push(store);
                console.log({index_added: store});
            }
            // remove obsolete stores
            for (let curr of current) {
                if (stores.indexOf(curr) < 0) {
                    storage.db.deleteObjectStore(curr);
                    console.log({index_dropped: curr});
                }
            }
            event.target.transaction.oncomplete = function(event) {
                storage.runQueue();
            };
        };

        request.onsuccess = function(event) {
            storage.current = storage.stores[0];
            storage.db = request.result;
            storage.runQueue();
        };

        request.onerror = function(event) {
            console.log({error: event});
            fallback();
        };
    } catch (e) {
        fallback();
        return;
    }

    this.initCalled = true;
    return this;
};

SP.runQueue = function() {
    if (this.queue.length > 0) {
        let i = 0, q = this.queue, e;
        while (i < q.length) {
            e = q[i++];
            switch (e.shift()) {
                case 'iterate': this.iterate(...e); break;
                case 'keys': this.keys(...e); break;
                case 'put': this.put(...e); break;
                case 'get': this.get(...e); break;
                case 'remove': this.remove(...e); break;
                case 'clear': this.clear(...e);
            }
        }
        this.queue = [];
    }
    while (this.idle.length) {
        this.idle.shift()();
    }
};

SP.put = function(key, value, callback, store = this.current) {
    if (local) {
        local[key] = value;
        if (callback) callback(true);
        return;
    }
    if (!this.db) {
        this.init();
        return this.queue.push(['put', key, value, callback, store]);
    }
    try {
        let req = this.db
            .transaction(store, "readwrite")
            .objectStore(store).put(value, key);
        if (callback) {
            req.onsuccess = function(event) { callback(true) };
            req.onerror = function(event) { callback(false) };
        }
    } catch (e) {
        console.log(e);
        if (callback) callback(false);
    }
};

SP.get = function(key, callback, store = this.current) {
    if (local) {
        if (callback) callback(local[key]);
        return;
    }
    if (!this.db) {
        this.init();
        return this.queue.push(['get', key, callback, store]);
    }
    try {
        let req = this.db
            .transaction(store)
            .objectStore(store).get(key);
        if (callback) {
            req.onsuccess = function(event) { callback(req.result) };
            req.onerror = function(event) { callback(null) };
        }
    } catch (e) {
        console.log(e);
        if (callback) callback(null);
    }
};

SP.remove = function(key, callback, store = this.current) {
    if (local) {
        delete local[key];
        if (callback) callback(true);
        return;
    }
    if (!this.db) {
        this.init();
        return this.queue.push(['remove', key, callback, store]);
    }
    try {
        let req = this.db
            .transaction(store, "readwrite")
            .objectStore(store).delete(key);
        if (callback) {
            req.onsuccess = function(event) { callback(true) };
            req.onerror = function(event) { callback(false) };
        }
    } catch (e) {
        console.log(e);
        if (callback) callback(false);
    }
};

SP.clear = function(key, store = this.current) {
    if (!this.db) {
        this.init();
        return this.queue.push(['clear', store]);
    }
    this.db
        .transaction(store, "readwrite")
        .objectStore(store).clear();
};

export const open = data.open;
export const Index = IDBStore;