/**
 * ─────────────────────────────────────────────
 *  SPB Drive — Personal Cloud Drive
 * ─────────────────────────────────────────────
 *  Author  : Simon-Pierre Boucher
 *  Contact : contact@spboucher.ai
 *  File    : src/storage/versions.mjs
 *  Purpose : File version history — keep superseded blobs on replace/edit,
 *            list, restore, prune (each version row holds one blob ref)
 *  License : MIT © Simon-Pierre Boucher
 * ─────────────────────────────────────────────
 */

import { getDb, logActivity } from '../db/db.mjs';
import { refBlob, unrefBlob } from './blobs.mjs';

/** Versions kept per node; older ones are pruned (blob unref'd). */
export const MAX_VERSIONS = 20;

function fileNode(id) {
  const node = getDb().prepare("SELECT * FROM nodes WHERE id = ? AND type = 'file'").get(id);
  if (!node) throw Object.assign(new Error('No such file'), { statusCode: 404 });
  return node;
}

/** Version history for a node, newest first. */
export function listVersions(nodeId) {
  return getDb()
    .prepare('SELECT * FROM node_versions WHERE node_id = ? ORDER BY replaced_at DESC, id DESC')
    .all(nodeId);
}

export function getVersion(nodeId, versionId) {
  return getDb()
    .prepare('SELECT * FROM node_versions WHERE id = ? AND node_id = ?')
    .get(versionId, nodeId) ?? null;
}

/**
 * Snapshot a node's CURRENT blob into its history (called just before the
 * blob is swapped). Takes its own ref on the blob and prunes old versions.
 */
function pushVersion(node, origin) {
  if (!node.blob_sha) return;
  const db = getDb();
  db.prepare(
    `INSERT INTO node_versions (node_id, blob_sha, size, mime, created, replaced_at, origin)
     VALUES (?, ?, ?, ?, ?, ?, ?)`,
  ).run(node.id, node.blob_sha, node.size, node.mime, node.modified, Date.now(), origin);
  refBlob(node.blob_sha);
  // Prune beyond the cap, oldest first.
  const excess = db
    .prepare(
      `SELECT id, blob_sha FROM node_versions WHERE node_id = ?
       ORDER BY replaced_at DESC, id DESC LIMIT -1 OFFSET ?`,
    )
    .all(node.id, MAX_VERSIONS);
  for (const row of excess) deleteVersionRow(row);
}

function deleteVersionRow(row) {
  unrefBlob(row.blob_sha);
  getDb().prepare('DELETE FROM node_versions WHERE id = ?').run(row.id);
}

/**
 * Swap a file node's content to a new stored blob, archiving the current one.
 * The caller must have already put the blob in the CAS (no ref taken yet).
 * @param {'replace'|'edit'|'restore'} origin
 * @returns {object} the updated node row
 */
export function setNodeBlob(nodeId, { sha, size, mime, origin = 'replace', ip = '' }) {
  const node = fileNode(nodeId);
  const now = Date.now();
  const db = getDb();
  if (node.blob_sha === sha) {
    db.prepare('UPDATE nodes SET modified = ? WHERE id = ?').run(now, nodeId);
    return fileNode(nodeId);
  }
  pushVersion(node, origin);
  refBlob(sha);
  unrefBlob(node.blob_sha);
  db.prepare('UPDATE nodes SET blob_sha = ?, size = ?, mime = ?, modified = ? WHERE id = ?')
    .run(sha, size, mime ?? node.mime, now, nodeId);
  logActivity(`file.${origin}`, { nodeId, detail: node.name, ip });
  return fileNode(nodeId);
}

/**
 * Make an old version current again. The current content is archived
 * (origin 'restore') and the version row stays in the history.
 */
export function restoreVersion(nodeId, versionId, { ip = '' } = {}) {
  const version = getVersion(nodeId, versionId);
  if (!version) throw Object.assign(new Error('No such version'), { statusCode: 404 });
  return setNodeBlob(nodeId, {
    sha: version.blob_sha, size: version.size, mime: version.mime, origin: 'restore', ip,
  });
}

/** Delete one version from history (releases its blob ref). */
export function deleteVersion(nodeId, versionId) {
  const version = getVersion(nodeId, versionId);
  if (!version) return false;
  deleteVersionRow(version);
  return true;
}

/** Release every version blob for a node (used by hard delete). */
export function dropVersionsForNode(nodeId) {
  for (const row of listVersions(nodeId)) deleteVersionRow(row);
}