import fs from 'fs';
import path from 'path';
import { fileURLToPath } from 'url';

const __dirname = path.dirname(fileURLToPath(import.meta.url));

/**
 * 미리보기 이미지 저장 디렉터리
 * @returns {string}
 */
export function getPreviewsDir() {
    const dir = process.env.PREVIEWS_PATH || path.join(__dirname, '..', '..', 'data', 'previews');
    if (!fs.existsSync(dir)) {
        fs.mkdirSync(dir, { recursive: true });
    }
    return dir;
}

/**
 * base64 data URL을 PNG 파일로 저장
 * @param {string} shareCode
 * @param {string} dataUrl
 * @returns {string} 파일명
 */
export function savePreviewImage(shareCode, dataUrl) {
    if (!dataUrl || !dataUrl.startsWith('data:image')) {
        return null;
    }
    const base64 = dataUrl.replace(/^data:image\/\w+;base64,/, '');
    const fileName = `${shareCode}.png`;
    fs.writeFileSync(path.join(getPreviewsDir(), fileName), Buffer.from(base64, 'base64'));
    return fileName;
}

/**
 * @param {string} shareCode
 * @returns {string|null}
 */
export function getPreviewFilePath(shareCode) {
    const filePath = path.join(getPreviewsDir(), `${shareCode}.png`);
    return fs.existsSync(filePath) ? filePath : null;
}

/**
 * @param {string} shareCode
 * @param {string|null} [previewImageRecord] DB preview_image 컬럼
 * @returns {string|null}
 */
export function getPreviewUrl(shareCode, previewImageRecord = null) {
    const hasFile = Boolean(getPreviewFilePath(shareCode));
    if (hasFile || previewImageRecord) {
        return `/api/v1/decks/${shareCode}/preview`;
    }
    return null;
}