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import { anchor, captureStack, derive, microtask, type StateUnsubscribe } from '@anchorlib/core';
import {
type DBEvent,
type DBUnsubscribe,
IDBStatus,
type KVEvent,
type KVFn,
type KVSeed,
type KVState,
type KVSubscriber,
type Operation,
type Storable,
} from './types.js';
import { put, remove } from './helper.js';
/**
* IndexedKV is an optimistic KV Storage that uses IndexedDB as its backend.
* It provides a simple key-value store with optimistic concurrency control.
*
* This class extends IndexedStore and provides methods to set, get, and delete
* key-value pairs. It also supports subscribing to changes in the store.
*
* @template T The type of values stored in the key-value store.
*/
export class IndexedKv<T> extends IndexedStore {
/**
* In-memory storage for the key-value pairs.
*/
#storage = new Map<string, T>();
/**
* Set of awaiter functions to resolve when operations complete.
*/
#awaiters = new Set<() => void>();
/**
* Counter for ongoing operations.
*/
#operations = 0;
/**
* Gets a readonly object store for reading data.
* @protected
*/
protected get reader(): IDBObjectStore {
return this.instance?.transaction(this.name, 'readonly').objectStore(this.name) as IDBObjectStore;
}
/**
* Gets a readwrite object store for writing data.
* @protected
*/
protected get writer(): IDBObjectStore {
return this.instance?.transaction(this.name, 'readwrite').objectStore(this.name) as IDBObjectStore;
}
/**
* Indicates whether there are ongoing operations.
* @returns True if there are ongoing operations, false otherwise.
*/
public get busy(): boolean {
return this.#operations > 0;
}
/**
* Creates a new IndexedKv instance.
* @param name - The name of the object store.
* @param version - The version of the database.
* @param dbName - The name of the database.
* @param seeds - An optional array of seed objects to initialize the database.
*/
constructor(
protected name: string,
protected version = 1,
dbName = `${name}.kv`,
protected seeds?: KVSeed<T>[]
) {
super(dbName, version);
this.init().open();
}
/**
* Sets up the initial data by reading from the IndexedDB.
* @protected
*/
protected async setup() {
await new Promise((resolve, reject) => {
const request = this.reader.openCursor();
request.onsuccess = (event) => {
const cursor = (event.target as IDBRequest)?.result;
if (cursor) {
this.#storage.set(cursor.key, cursor.value);
cursor.continue();
} else {
resolve(true);
}
};
request.onerror = () => {
reject(request.error);
};
});
}
protected finalize(): void {
if (!this.#storage.size && this.seeds) {
for (const [key, value] of this.seeds) {
this.set(key, value);
}
}
super.finalize();
}
/**
* Waits for all ongoing operations to complete.
* @returns A promise that resolves when all operations are completed.
*/
public async completed(): Promise<true> {
if (this.busy) {
return await new Promise((resolve) => {
const handler = () => {
if (!this.busy) {
resolve(true);
this.#awaiters.delete(handler);
}
};
this.#awaiters.add(handler);
});
}
return true;
}
/**
* Upgrades the database by creating the object store if it doesn't exist.
* @param event - The version change event.
* @protected
*/
protected upgrade(event: IDBVersionChangeEvent): Promise<void> | void {
const db = (event.target as IDBOpenDBRequest)?.result as IDBDatabase;
if (db && !db.objectStoreNames.contains(this.name)) {
db.createObjectStore(this.name);
}
}
/**
* Publishes an event to subscribers.
* @param event - The event to publish.
* @protected
*/
protected publish(event: KVEvent<T>) {
super.publish(event as DBEvent);
}
/**
* Gets the value associated with the specified key.
* @param name - The key to look up.
* @returns The value associated with the key, or undefined if not found.
*/
public get(name: string): T | undefined {
return this.#storage.get(name);
}
/**
* Sets the value for the specified key.
* @param key - The key to set.
* @param value - The value to set.
* @param onerror - Optional error handler.
* @returns An operation object with a promise that resolves when the operation completes.
*/
public set(key: string, value: T, onerror?: (error: Error) => void): Operation {
if (this.status !== IDBStatus.Open) {
const error = new Error(`Database is in "${this.status}" state.`);
captureStack.error.external(`Cannot perform "set" operation during "${this.status}" state.`, error, this.set);
onerror?.(error);
return { promise: () => Promise.resolve() };
}
const current = this.#storage.get(key);
let resolved: Error | boolean = false;
let resolver: () => void;
let rejector: (error: Error) => void;
this.setBusy();
this.#storage.set(key, value);
put(this.writer, key, value)
.then(() => {
this.publish({ type: 'set', key, value });
resolver?.();
resolved = true;
})
.catch((error) => {
captureStack.error.external(`Unable to set value of "${key}":`, error, put, this.set);
if (current) {
this.#storage.set(key, current);
} else {
this.#storage.delete(key);
}
onerror?.(error);
rejector?.(error);
resolved = error;
})
.finally(() => {
this.setFree();
});
return {
promise: () => {
if (resolved) {
return resolved === true ? Promise.resolve() : Promise.reject(resolved);
}
return new Promise((resolve, reject) => {
resolver = resolve as never;
rejector = reject;
});
},
} as Operation;
}
/**
* Deletes the value associated with the specified key.
* @param key - The key to delete.
* @param onerror - Optional error handler.
* @returns An operation object with a promise that resolves when the operation completes.
*/
public delete(key: string, onerror?: (error: Error) => void): Operation {
if (this.status !== IDBStatus.Open) {
const error = new Error(`Database is in "${this.status}" state.`);
captureStack.error.external(
`Cannot perform "delete" operation during "${this.status}" state.`,
error,
this.delete
);
onerror?.(error);
return { promise: () => Promise.resolve() };
}
const current = this.#storage.get(key);
if (current) {
let resolved: Error | boolean = false;
let resolver: (value: true) => void;
let rejector: (error: Error) => void;
this.setBusy();
this.#storage.delete(key);
remove(this.writer, key)
.then(() => {
this.publish({ type: 'delete', key });
resolver?.(true);
resolved = true;
})
.catch((error) => {
captureStack.error.external(`Unable to delete "${key}":`, error, remove, this.delete);
this.#storage.set(key, current);
onerror?.(error);
rejector?.(error);
resolved = error;
})
.finally(() => {
this.setFree();
});
return {
promise: () => {
if (resolved) {
return resolved === true ? Promise.resolve() : Promise.reject(resolved);
}
return new Promise((resolve, reject) => {
resolver = resolve as never;
rejector = reject as never;
});
},
} as Operation;
}
return { promise: () => Promise.resolve() };
}
/**
* Subscribes to changes in the store.
* @param handler - The handler function to call when changes occur.
* @returns A function to unsubscribe from changes.
*/
public subscribe(handler: KVSubscriber<T>): DBUnsubscribe {
return super.subscribe(handler);
}
/**
* Increments the operation counter.
* @private
*/
private setBusy() {
this.#operations += 1;
}
/**
* Decrements the operation counter and notifies awaiters.
* @private
*/
private setFree() {
this.#operations -= 1;
if (this.#operations <= 0) {
this.#operations = 0;
}
this.#awaiters.forEach((handler) => handler());
}
}
const KV_STORES = new Map<string, KVFn>();
/**
* Creates a key-value store function that provides reactive state management synchronized with IndexedDB.
*
* This factory function initializes an IndexedKv storage instance and returns a KVFn function
* that can be used to create reactive state objects. Each state object automatically syncs
* with the underlying IndexedDB storage and maintains its own initialization status.
*
* The returned function manages state lifecycle including:
* - Caching states by key to prevent duplicate instances
* - Tracking usage counts for memory management
* - Automatically synchronizing reactive changes to IndexedDB with debouncing
* - Handling database initialization and readiness states
*
* @param name - The name of the object store in IndexedDB
* @param version - The version of the database schema (default: 1)
* @param dbName - The name of the database (default: `${name}.kv`)
* @param seeds - An initial set of key-value pairs to seed the database.
* @returns A KVFn function that can create and manage reactive key-value states
*/
export function createKVStore<T extends Storable>(
name: string,
version = 1,
dbName = `${name}.kv`,
seeds?: KVSeed<T>[]
): KVFn {
const key = `${name}@${version}`;
if (KV_STORES.has(key)) {
return KV_STORES.get(key) as KVFn;
}
const store = new IndexedKv<T>(name, version, dbName, seeds);
const stateMap = new Map<string, KVState<Storable>>();
const stateUsage = new Map<KVState<Storable>, number>();
const stateSubscriptions = new WeakMap<KVState<Storable>, StateUnsubscribe>();
function kvFn(key: string, init: T): KVState<T> {
// Make sure access to the same key is pointing to the same state.
// One key will have one state that in charge of synchronization.
if (stateMap.has(key)) {
const state = stateMap.get(key) as KVState<T>;
// Track the usage count to prevent unnecessary unsubscribes.
const usage = stateUsage.get(state) as number;
stateUsage.set(state, usage + 1);
return state;
}
const state = anchor.raw({ data: init, status: 'init' } as KVState<T>);
const [schedule] = microtask(DB_SYNC_DELAY);
const readKv = () => {
const value = store.get(key);
// Maintain optimistic behavior.
state.status = 'ready';
if (typeof value !== 'undefined') {
state.data = value;
} else {
store.set(key, init, (error) => {
anchor.assign(state, { error, status: 'error' });
});
}
// Create synchronization if the given state data is a linkable value.
const stateUnsubscribe = derive(state, (snapshot, event) => {
if (event.type !== 'init' && event.keys.includes('data')) {
schedule(() => {
const prev = event.prev as T;
store.set(key, snapshot.data, (error) => {
anchor.assign(state, { data: prev, error, status: 'error' });
});
});
}
});
const unsubscribe = () => {
let usage = stateUsage.get(state) as number;
usage -= 1;
if (usage <= 0) {
stateUnsubscribe();
stateMap.delete(key);
stateUsage.delete(state);
stateSubscriptions.delete(state);
} else {
stateUsage.set(state, usage);
}
};
stateSubscriptions.set(state, unsubscribe);
};
if (store.status === IDBStatus.Init) {
const unsubscribe = store.subscribe((event) => {
if (event.type === IDBStatus.Open) {
readKv();
unsubscribe();
} else if (event.type === IDBStatus.Closed) {
anchor.assign(state, { status: 'error', error: store.error });
unsubscribe();
}
});
} else {
readKv();
}
if (!stateMap.has(key)) {
stateMap.set(key, state);
stateUsage.set(state, 1);
}
return state;
}
kvFn.store = () => {
return store;
};
kvFn.leave = <T extends Storable>(state: KVState<T>) => {
if (stateSubscriptions.has(state)) {
stateSubscriptions.get(state)?.();
}
};
kvFn.remove = (key: string) => {
const state = stateMap.get(key);
if (state) {
state.status = 'removed';
}
store
.delete(key)
.promise()
.then(() => {
if (state) {
const unsubscribe = stateSubscriptions.get(state);
stateUsage.set(state, 1);
unsubscribe?.();
anchor.assign(state, { data: undefined });
}
})
.catch((error) => {
if (state) {
anchor.assign(state, { error, status: 'error' });
}
});
};
kvFn.ready = async () => {
await store.promise();
return await store.completed();
};
KV_STORES.set(key, kvFn as KVFn);
return kvFn as KVFn;
}
// Creates default KV store.
export const kv = createKVStore('anchor');
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