/***********************************************************************************************************************************************************************
 * File Name: task_download.controller.js  (client)
 * Type of Program: Controller
 * Description: Proxies file downloads for task completion attachments through
 *              the backend, so the raw Garage/S3 URL is never exposed to the
 *              browser. Sets Content-Disposition: attachment with the original
 *              filename.
 *
 *              storage_key is DERIVED from file_url at request time (no schema
 *              change needed) by stripping the known S3_PUBLIC_URL + bucket
 *              prefix, since both are constants defined in s3.service.js / .env.
 *
 * Route: GET /client/groups/:groupId/task-lists/:taskListId/tasks/:taskId/completions/:completionId/files/:fileId/download
 *
 * Access: only the completion's owner (req.user.user_id === completion.user_id)
 *         can download — admin downloads go through a separate admin route.
 *
 * Author: Kenneth Obsequio (@lash0000)
 * Date Created: Jun. 15, 2026
 ***********************************************************************************************************************************************************************/
const { Task, TaskList, TaskListGroup } = require('../../models/task/task.mdl');
const { TaskCompletion, TaskCompletionFile } = require('../../models/task/task_completion.mdl');
const { mdl_UserGroups, mdl_UserGroupMembers } = require('../../models/users/user_groups.mdl');
const { getObjectStream } = require('../../services/s3.service');
const R = require('../../utils/response.util');

// ─── Helper: verify user is a member of the group ─────────────────────────────
const isMember = async (userId, groupId) => {
    const membership = await mdl_UserGroupMembers.findOne({
        where: { user_id: userId, group_id: groupId, deletedAt: null },
    });
    return !!membership;
};

// ─── Helper: derive S3 storage_key from a public file_url ─────────────────────
// Strips "{S3_PUBLIC_URL}/{S3_BUCKET}/" prefix, leaving e.g. "images/uuid.jpg"
const deriveStorageKey = (fileUrl) => {
    const publicUrl = (process.env.S3_PUBLIC_URL || '').replace(/\/$/, '');
    const bucket    = process.env.S3_BUCKET || 'philproperties';
    const prefix    = `${publicUrl}/${bucket}/`;

    if (fileUrl && fileUrl.startsWith(prefix)) {
        return fileUrl.slice(prefix.length);
    }
    return null;
};

// =============================================================================
// ── STREAM FILE (inline preview — no Content-Disposition: attachment) ────────
// =============================================================================
//
// GET /client/groups/:groupId/task-lists/:taskListId/tasks/:taskId/completions/:completionId/files/:fileId/stream
//
// Used by FilePreview.jsx for <img>/<video>/<audio>/<iframe> src — proxies the
// object inline so the raw Garage/S3 URL never appears, but does NOT force
// download (no Content-Disposition: attachment).

exports.streamCompletionFile = async (req, res) => {
    try {
        const { groupId, taskListId, taskId, completionId, fileId } = req.params;

        const member = await isMember(req.user.user_id, groupId);
        if (!member) return R.error(res, 'Group not found or you are not a member.', 403);

        const task = await Task.findOne({
            where: { task_id: taskId, task_list_id: taskListId },
            include: [{
                model: TaskList,
                as: 'taskList',
                required: true,
                include: [{
                    model: mdl_UserGroups,
                    as: 'groups',
                    where: { group_id: groupId },
                    required: true,
                    attributes: [],
                    through: { model: TaskListGroup, attributes: [] },
                }],
            }],
        });
        if (!task) return R.error(res, 'Task not found or not accessible.', 404);

        const completion = await TaskCompletion.findOne({
            where: { completion_id: completionId, task_id: taskId, user_id: req.user.user_id },
        });
        if (!completion) return R.error(res, 'Completion not found.', 404);

        const file = await TaskCompletionFile.findOne({
            where: { file_id: fileId, completion_id: completionId },
        });
        if (!file) return R.error(res, 'File not found.', 404);

        const storageKey = deriveStorageKey(file.file_url);
        if (!storageKey) {
            return R.error(res, 'This file cannot be previewed (unrecognized storage URL).', 422);
        }

        const { stream, contentType, contentLength } = await getObjectStream(storageKey);

        res.setHeader('Content-Type', contentType || file.mime_type || 'application/octet-stream');
        if (contentLength) res.setHeader('Content-Length', contentLength);
        // No Content-Disposition — browser renders inline based on Content-Type

        stream.pipe(res);
    } catch (err) {
        console.error('[CLIENT][STREAM COMPLETION FILE]', err);
        return R.error(res, 'Could not load file.', 500);
    }
};

// =============================================================================
// ── DOWNLOAD FILE ──────────────────────────────────────────────────────────────
// =============================================================================

exports.downloadCompletionFile = async (req, res) => {
    try {
        const { groupId, taskListId, taskId, completionId, fileId } = req.params;

        // ── Validate member ───────────────────────────────────────────────────
        const member = await isMember(req.user.user_id, groupId);
        if (!member) return R.error(res, 'Group not found or you are not a member.', 403);

        // ── Validate task belongs to task list + group ────────────────────────
        const task = await Task.findOne({
            where: { task_id: taskId, task_list_id: taskListId },
            include: [{
                model: TaskList,
                as: 'taskList',
                required: true,
                include: [{
                    model: mdl_UserGroups,
                    as: 'groups',
                    where: { group_id: groupId },
                    required: true,
                    attributes: [],
                    through: { model: TaskListGroup, attributes: [] },
                }],
            }],
        });
        if (!task) return R.error(res, 'Task not found or not accessible.', 404);

        // ── Validate completion belongs to this user + task ───────────────────
        const completion = await TaskCompletion.findOne({
            where: { completion_id: completionId, task_id: taskId, user_id: req.user.user_id },
        });
        if (!completion) return R.error(res, 'Completion not found.', 404);

        // ── Validate file belongs to completion ───────────────────────────────
        const file = await TaskCompletionFile.findOne({
            where: { file_id: fileId, completion_id: completionId },
        });
        if (!file) return R.error(res, 'File not found.', 404);

        // ── Derive storage_key from file_url ──────────────────────────────────
        const storageKey = deriveStorageKey(file.file_url);
        if (!storageKey) {
            return R.error(res, 'This file cannot be downloaded (unrecognized storage URL).', 422);
        }

        // ── Stream from S3/Garage ──────────────────────────────────────────────
        const { stream, contentType, contentLength } = await getObjectStream(storageKey);

        res.setHeader('Content-Type', contentType || file.mime_type || 'application/octet-stream');
        if (contentLength) res.setHeader('Content-Length', contentLength);
        res.setHeader('Content-Disposition', `attachment; filename="${encodeURIComponent(file.file_name)}"`);

        stream.pipe(res);
    } catch (err) {
        console.error('[CLIENT][DOWNLOAD COMPLETION FILE]', err);
        return R.error(res, 'Could not download file.', 500);
    }
};