private_image/frontend/src/stores/exiftool.ts

import { defineStore } from 'pinia';
import { ref } from 'vue';
import type { ExiftoolInitStatus } from '@/types/metadata/ExiftoolInitStatus';
import type { ExiftoolWorkerOutMessage } from '@/types/workers/exiftoolWorkerOutMessage';

export const useExiftoolStore = defineStore('exiftool', () => {
    const initStatus = ref<ExiftoolInitStatus>('idle');
    const initErrorMessage = ref<string | null>(null);

    const worker = ref<Worker | null>(null);

    let initPromise: Promise<void> | null = null;
    let initPromiseResolve: (() => void) | null = null;
    let initPromiseReject: ((error: Error) => void) | null = null;

    const readMetadataWaiters = new Map<
        string,
        { resolve: (output: string) => void; reject: (error: Error) => void }
    >();

    const initializeExiftool = async (): Promise<void> => {
        if (initStatus.value === 'ready') {
            return;
        }

        if (initStatus.value === 'error') {
            throw new Error(initErrorMessage.value ?? 'ExifTool is unavailable');
        }

        if (initStatus.value === 'idle') {
            initStatus.value = 'loading';
            initErrorMessage.value = null;
            initPromise = new Promise<void>((resolve, reject) => {
                initPromiseResolve = resolve;
                initPromiseReject = reject;
            });

            if (!worker.value) {
                worker.value = new Worker(new URL('../workers/exiftoolWorker.ts', import.meta.url), {
                    type: 'module'
                });

                worker.value.addEventListener('message', handleWorkerMessage);
            }

            worker.value.postMessage({ type: 'init' });
        }

        if (!initPromise) {
            throw new Error('ExifTool is not initializing');
        }

        await initPromise;
    };

    const handleWorkerMessage = (event: MessageEvent<ExiftoolWorkerOutMessage>): void => {
        const message = event.data;

        if (message.type === 'init-done') {
            initStatus.value = 'ready';
            initPromiseResolve?.();
            initPromiseResolve = null;
            initPromiseReject = null;

            return;
        }

        if (message.type === 'init-error') {
            initStatus.value = 'error';
            initErrorMessage.value = message.message;
            initPromiseReject?.(new Error(message.message));
            initPromiseResolve = null;
            initPromiseReject = null;

            return;
        }

        if (message.type === 'read-metadata-done') {
            const waiter = readMetadataWaiters.get(message.id);

            if (!waiter) {
                return;
            }

            readMetadataWaiters.delete(message.id);
            waiter.resolve(message.output);

            return;
        }

        if (message.type === 'read-metadata-error') {
            const waiter = readMetadataWaiters.get(message.id);

            if (!waiter) {
                return;
            }

            readMetadataWaiters.delete(message.id);
            waiter.reject(new Error(message.message));
        }
    };

    const readMetadata = async (file: File): Promise<string> => {
        await initializeExiftool();

        const id = crypto.randomUUID();

        const workerInstance = worker.value;

        if (!workerInstance) {
            throw new Error('ExifTool worker is unavailable');
        }

        return new Promise<string>((resolve, reject) => {
            readMetadataWaiters.set(id, { resolve, reject });
            workerInstance.postMessage({ type: 'read-metadata', id, file });
        });
    };

    return {
        initStatus,
        initErrorMessage,
        initializeExiftool,
        readMetadata
    };
});