/**
 * ─────────────────────────────────────────────
 *  SPB Drive — Personal Cloud Drive
 * ─────────────────────────────────────────────
 *  Author  : Simon-Pierre Boucher
 *  Contact : contact@spboucher.ai
 *  File    : src/storage/upload.mjs
 *  Purpose : Chunked + resumable uploads (init / chunk / complete / status)
 *  License : MIT © Simon-Pierre Boucher
 * ─────────────────────────────────────────────
 */

import { randomBytes } from 'node:crypto';
import { createReadStream, createWriteStream, existsSync } from 'node:fs';
import { mkdir, readdir, rm } from 'node:fs/promises';
import path from 'node:path';
import { pipeline } from 'node:stream/promises';
import { config } from '../config.mjs';
import { getDb } from '../db/db.mjs';
import { putBlob } from './blobs.mjs';
import { createFileNode, mustGetNode, validateName } from './nodes.mjs';

const uploadDir = (id) => path.join(config.uploadsDir, id);

/**
 * Start (or describe) an upload session.
 * @returns {{uploadId: string, chunkSize: number, nChunks: number, have: number[]}}
 */
export async function initUpload({ parentId, name, size }) {
  validateName(name);
  mustGetNode(parentId);
  const sz = Number(size);
  if (!Number.isFinite(sz) || sz < 0) throw Object.assign(new Error('Bad size'), { statusCode: 400 });

  const id = randomBytes(16).toString('hex');
  const nChunks = Math.max(1, Math.ceil(sz / config.chunkSize));
  getDb()
    .prepare(
      `INSERT INTO uploads (id, parent_id, name, size, chunk_size, n_chunks, created)
       VALUES (?, ?, ?, ?, ?, ?, ?)`,
    )
    .run(id, parentId, name, sz, config.chunkSize, nChunks, Date.now());
  await mkdir(uploadDir(id), { recursive: true, mode: 0o700 });
  return { uploadId: id, chunkSize: config.chunkSize, nChunks, have: [] };
}

/**
 * Tag an upload session with its origin (e.g. 'req:<fileRequestId>') so
 * public file-request endpoints can only touch their own sessions.
 */
export function markUploadSource(id, source) {
  getDb().prepare('UPDATE uploads SET source = ? WHERE id = ?').run(source, String(id));
}

/** Look up an upload session row or throw 404. */
export function getUpload(id) {
  const row = getDb().prepare('SELECT * FROM uploads WHERE id = ?').get(String(id));
  if (!row) throw Object.assign(new Error('Unknown upload'), { statusCode: 404 });
  return row;
}

/** Which chunk indexes are already on disk (for resume). */
export async function chunksPresent(id) {
  getUpload(id);
  try {
    const entries = await readdir(uploadDir(id));
    return entries
      .filter((e) => /^\d+$/.test(e))
      .map(Number)
      .sort((a, b) => a - b);
  } catch {
    return [];
  }
}

/** Persist one chunk from a request stream. */
export async function writeChunk(id, n, stream) {
  const up = getUpload(id);
  const idx = Number(n);
  if (!Number.isInteger(idx) || idx < 0 || idx >= up.n_chunks) {
    throw Object.assign(new Error('Chunk index out of range'), { statusCode: 400 });
  }
  await mkdir(uploadDir(id), { recursive: true, mode: 0o700 });
  const tmp = path.join(uploadDir(id), `${idx}.part`);
  await pipeline(stream, createWriteStream(tmp, { mode: 0o600 }));
  const { rename } = await import('node:fs/promises');
  await rename(tmp, path.join(uploadDir(id), String(idx)));
}

/**
 * Assemble chunks → CAS blob → file node. Cleans up the session.
 * @param {'keep-both'|'replace'|'skip'} conflict
 */
export async function completeUpload(id, { conflict = 'keep-both', mime = null, ip = '' } = {}) {
  const up = getUpload(id);
  const have = await chunksPresent(id);
  if (have.length !== up.n_chunks) {
    throw Object.assign(
      new Error(`Missing chunks: have ${have.length}/${up.n_chunks}`),
      { statusCode: 409 },
    );
  }

  async function* concat() {
    for (let i = 0; i < up.n_chunks; i += 1) {
      const chunkFile = path.join(uploadDir(id), String(i));
      if (!existsSync(chunkFile)) throw new Error(`Chunk ${i} vanished`);
      yield* createReadStream(chunkFile);
    }
  }

  const { sha, size } = await putBlob(concat());
  if (size !== up.size) {
    throw Object.assign(
      new Error(`Size mismatch: expected ${up.size}, got ${size}`),
      { statusCode: 409 },
    );
  }

  const node = createFileNode(up.parent_id, up.name, { sha, size, mime, conflict, ip });
  await abortUpload(id);
  return node;
}

/** Drop an upload session and its chunk files. */
export async function abortUpload(id) {
  getDb().prepare('DELETE FROM uploads WHERE id = ?').run(String(id));
  await rm(uploadDir(String(id)), { recursive: true, force: true });
}

/** Remove upload sessions older than 48 h (daily job). */
export async function pruneUploads() {
  const stale = getDb()
    .prepare('SELECT id FROM uploads WHERE created < ?')
    .all(Date.now() - 48 * 3_600_000);
  for (const { id } of stale) await abortUpload(id);
  return stale.length;
}