feature: emit events

fsdb.ts

@@ -34,6 +34,7 @@ export interface FSDB_INDEXER<T> {
 export class FSDB_COLLECTION<T extends Record<string, any>> {
 	private config: FSDB_COLLECTION_CONFIG;
 	public INDEX: Record<string, FSDB_INDEXER<any>>;
+	private event_listeners: Record<string, []>;
 
 	constructor(input_config: FSDB_COLLECTION_CONFIG_INPUT) {
 		this.config = {
@@ -45,6 +46,8 @@ export class FSDB_COLLECTION<T extends Record<string, any>> {
 			...(input_config ?? {})
 		};
 
+		this.event_listeners = {};
+
 		this.INDEX = this.config.indexers ?? {};
 		for (const indexer of Object.values(this.INDEX)) {
 			indexer.set_fsdb_root(this.config.root);
@@ -84,7 +87,7 @@ export class FSDB_COLLECTION<T extends Record<string, any>> {
 		}
 
 		const collection_info_file_path: string = path.resolve(path.join(this.config.root, '.fsdb.collection.json'));
-		const collection_info_json: string = JSON.stringify(this.config, null, 4);
+		const collection_info_json: string = JSON.stringify(this.config, null, '\t');
 		Deno.mkdirSync(path.dirname(collection_info_file_path), {
 			recursive: true
 		});
@@ -114,26 +117,43 @@ export class FSDB_COLLECTION<T extends Record<string, any>> {
 
 	private async write_item(item: T, override_path?: string): Promise<void> {
 		const item_path: string = override_path ?? await this.ensure_item_path(item, this.config.id_field);
-		Deno.writeTextFileSync(item_path, JSON.stringify(item, null, 1));
+		Deno.writeTextFileSync(item_path, JSON.stringify(item, null, '\t'));
+
+		this.emit('write', {
+			item,
+			item_path
+		});
 
 		if (this.config.indexers) {
 			for (const indexer of Object.values(this.config.indexers)) {
 				await (indexer as FSDB_INDEXER<T>).index(item, item_path);
+				this.emit('index', {
+					item,
+					item_path,
+					indexer
+				});
 			}
 		}
 	}
 
 	/** Get an item from the collection given its id. */
 	async get(id: string): Promise<T | null> {
-		const id_path: string = this.get_organized_id_path(id);
-		const item_exists: boolean = await fs.exists(id_path);
+		const item_path: string = this.get_organized_id_path(id);
+		const item_exists: boolean = await fs.exists(item_path);
 
 		if (!item_exists) {
 			return null;
 		}
 
-		const content: string = await Deno.readTextFile(id_path);
-		return JSON.parse(content);
+		const content: string = await Deno.readTextFile(item_path);
+		const item: T = JSON.parse(content);
+
+		this.emit('get', {
+			item,
+			item_path
+		});
+
+		return item;
 	}
 
 	/** Create an item in the collection. */
@@ -149,15 +169,21 @@ export class FSDB_COLLECTION<T extends Record<string, any>> {
 
 		await this.write_item(item);
 
+		this.emit('create', {
+			item,
+			item_path
+		});
+
 		return item;
 	}
 
 	/** Update the given item in the collection, requiring the id to be stable. */
 	async update(item: T): Promise<T> {
 		const item_path: string = this.get_organized_item_path(item);
-		const item_exists: boolean = await fs.exists(item_path);
+		const id: string = item[this.config.id_field];
+		const previous: T | null = await this.get(id);
 
-		if (!item_exists) {
+		if (!previous) {
 			throw new Error('item does not exist', {
 				cause: 'item_does_not_exist'
 			});
@@ -165,6 +191,12 @@ export class FSDB_COLLECTION<T extends Record<string, any>> {
 
 		await this.write_item(item, item_path);
 
+		this.emit('update', {
+			item,
+			previous,
+			item_path
+		});
+
 		return item;
 	}
 
@@ -202,6 +234,11 @@ export class FSDB_COLLECTION<T extends Record<string, any>> {
 			await Deno.remove(dir);
 			dir = path.dirname(dir);
 		} while (dir.length);
+
+		this.emit('delete', {
+			item
+		});
+
 		return item;
 	}
 
@@ -302,6 +339,11 @@ export class FSDB_COLLECTION<T extends Record<string, any>> {
 		if (Deno.env.get('FSDB_PERF')) performance.mark('fsdb_all_end');
 		if (Deno.env.get('FSDB_PERF')) console.dir(performance.measure('fsdb all items time', 'fsdb_all_begin', 'fsdb_all_end'));
 
+		this.emit('all', {
+			options,
+			results
+		});
+
 		return results;
 	}
 
@@ -350,6 +392,64 @@ export class FSDB_COLLECTION<T extends Record<string, any>> {
 		if (Deno.env.get('FSDB_PERF')) performance.mark('fsdb_find_end');
 		if (Deno.env.get('FSDB_PERF')) console.dir(performance.measure('fsdb find time', 'fsdb_find_begin', 'fsdb_find_end'));
 
+		this.emit('find', {
+			criteria,
+			options,
+			results
+		});
+
 		return results;
 	}
+
+	public on(event: string, handler: (event_data: any) => void) {
+		const listeners: ((event: any) => void)[] = this.event_listeners[event] = this.event_listeners[event] ?? [];
+		if (!listeners.includes(handler)) {
+			listeners.push(handler);
+		}
+
+		if (Deno.env.get('FSDB_LOG_EVENTS')) {
+			console.dir({
+				on: {
+					event,
+					handler
+				},
+				listeners
+			});
+		}
+	}
+
+	public off(event: string, handler: (event_data: any) => void) {
+		const listeners: ((event: any) => void)[] = this.event_listeners[event] = this.event_listeners[event] ?? [];
+		if (listeners.includes(handler)) {
+			listeners.splice(listeners.indexOf(handler), 1);
+		}
+
+		if (Deno.env.get('FSDB_LOG_EVENTS')) {
+			console.dir({
+				off: {
+					event: event,
+					handler
+				},
+				listeners
+			});
+		}
+	}
+
+	private emit(event_name: string, event_data: any) {
+		const listeners: ((event: any) => void)[] = this.event_listeners[event_name] = this.event_listeners[event_name] ?? [];
+
+		if (Deno.env.get('FSDB_LOG_EVENTS')) {
+			console.dir({
+				emitting: {
+					event_name,
+					event_data,
+					listeners
+				}
+			});
+		}
+
+		for (const listener of listeners) {
+			listener(event_data);
+		}
+	}
 }