import * as db from '../../db/pic.js';

const FULL_HASH_RE = /^[a-fA-F0-9]{64}$/;
/** Content-addressed by SHA-256 — safe for long-lived browser cache (auth still required on first fetch). */
const CACHE_CONTROL = 'private, max-age=31536000, immutable';

function parseFullHash(value) {
    const fullHash = typeof value === 'string' ? value.trim() : '';
    if (!FULL_HASH_RE.test(fullHash)) {
        return { error: 'fullHash must be a 64-char hex SHA-256' };
    }
    return { fullHash: fullHash.toLowerCase() };
}

function picErrorStatus(error) {
    if (error.message === 'Not authorized') return 403;
    if (error.message === 'Image not found') return 404;
    return 500;
}

function sendImmutableAvif(req, res, { buffer, contentType, fullHash }) {
    const etag = `"${fullHash}"`;
    res.setHeader('Content-Type', contentType);
    res.setHeader('Cache-Control', CACHE_CONTROL);
    res.setHeader('ETag', etag);
    res.setHeader('Content-Length', String(buffer.length));

    const ifNoneMatch = req.headers['if-none-match'];
    if (ifNoneMatch === etag || ifNoneMatch === fullHash) {
        return res.status(304).end();
    }

    return res.status(200).send(buffer);
}

/**
 * Registers content-addressed image routes (requires auth).
 * @param {import('express').Application} app
 * @param {string} [basePath='']
 */
export function register(app, basePath = '') {
    /**
     * @openapi
     * /image/{fullHash}:
     *   get:
     *     tags: [Image]
     *     summary: Full image by hash
     *     description: |
     *       Returns the full AVIF by `pic.hash` (SHA-256 hex).
     *       Auth via article category access. Browser-cacheable (`private`, `immutable`, `ETag`).
     *     security:
     *       - cookieAuth: []
     *     x-markdown: image/get.md
     *     parameters:
     *       - in: path
     *         name: fullHash
     *         required: true
     *         schema:
     *           type: string
     *           pattern: '^[a-fA-F0-9]{64}$'
     *         description: SHA-256 hex of the full image bytes
     *     responses:
     *       200:
     *         description: AVIF image bytes
     *         headers:
     *           Cache-Control:
     *             schema:
     *               type: string
     *               example: private, max-age=31536000, immutable
     *           ETag:
     *             schema:
     *               type: string
     *         content:
     *           image/avif:
     *             schema:
     *               type: string
     *               format: binary
     *       304:
     *         description: Not modified (If-None-Match matched ETag)
     *       400:
     *         description: Invalid hash
     *         content:
     *           application/json:
     *             schema:
     *               $ref: '#/components/schemas/Error'
     *       401:
     *         description: Unauthorized
     *         content:
     *           application/json:
     *             schema:
     *               $ref: '#/components/schemas/Error'
     *       403:
     *         description: Not authorized
     *         content:
     *           application/json:
     *             schema:
     *               $ref: '#/components/schemas/Error'
     *       404:
     *         description: Image not found
     *         content:
     *           application/json:
     *             schema:
     *               $ref: '#/components/schemas/Error'
     */
    app.get(`${basePath}/image/:fullHash`, async (req, res) => {
        const parsed = parseFullHash(req.params.fullHash);
        if (parsed.error) {
            return res.status(400).json({ error: parsed.error });
        }

        try {
            const image = await db.getImageByHash(req.user.id, parsed.fullHash);
            sendImmutableAvif(req, res, {
                buffer: image.buffer,
                contentType: image.contentType,
                fullHash: parsed.fullHash,
            });
        } catch (error) {
            const status = picErrorStatus(error);
            if (status === 500) console.error('Get image by hash failed:', error);
            res.status(status).json({ error: error.message });
        }
    });

    /**
     * @openapi
     * /thumb/{fullHash}:
     *   get:
     *     tags: [Image]
     *     summary: Thumb image by hash
     *     description: |
     *       Returns the thumb AVIF for `pic.hash` (fullHash — not thumbhash).
     *       Auth via article category access. Browser-cacheable (`private`, `immutable`, `ETag`).
     *     security:
     *       - cookieAuth: []
     *     x-markdown: thumb/get.md
     *     parameters:
     *       - in: path
     *         name: fullHash
     *         required: true
     *         schema:
     *           type: string
     *           pattern: '^[a-fA-F0-9]{64}$'
     *         description: SHA-256 hex of the full image bytes
     *     responses:
     *       200:
     *         description: AVIF thumb bytes
     *         headers:
     *           Cache-Control:
     *             schema:
     *               type: string
     *               example: private, max-age=31536000, immutable
     *           ETag:
     *             schema:
     *               type: string
     *         content:
     *           image/avif:
     *             schema:
     *               type: string
     *               format: binary
     *       304:
     *         description: Not modified (If-None-Match matched ETag)
     *       400:
     *         description: Invalid hash
     *         content:
     *           application/json:
     *             schema:
     *               $ref: '#/components/schemas/Error'
     *       401:
     *         description: Unauthorized
     *         content:
     *           application/json:
     *             schema:
     *               $ref: '#/components/schemas/Error'
     *       403:
     *         description: Not authorized
     *         content:
     *           application/json:
     *             schema:
     *               $ref: '#/components/schemas/Error'
     *       404:
     *         description: Image not found
     *         content:
     *           application/json:
     *             schema:
     *               $ref: '#/components/schemas/Error'
     */
    app.get(`${basePath}/thumb/:fullHash`, async (req, res) => {
        const parsed = parseFullHash(req.params.fullHash);
        if (parsed.error) {
            return res.status(400).json({ error: parsed.error });
        }

        try {
            const image = await db.getThumbByHash(req.user.id, parsed.fullHash);
            sendImmutableAvif(req, res, {
                buffer: image.buffer,
                contentType: image.contentType,
                fullHash: parsed.fullHash,
            });
        } catch (error) {
            const status = picErrorStatus(error);
            if (status === 500) console.error('Get thumb by hash failed:', error);
            res.status(status).json({ error: error.message });
        }
    });
}