const fs = require("fs");
const path = require("path");
const os = require("os");
const crypto = require("crypto");
let AdmZip = null;
try {
  AdmZip = require("adm-zip");
} catch {
  AdmZip = null;
}
const { db } = require("./db");
const {
  createRecoveryMarker,
  updateRecoveryMarker,
  markRecoveryMarkerFailed,
  markRecoveryMarkerComplete
} = require("./recovery-mode");

const repoRoot = path.join(__dirname, "..", "..");
const dataDir = path.join(repoRoot, "data");
const snapshotsDir = path.join(dataDir, "snapshots");
const indexPath = path.join(snapshotsDir, "index.json");
const maxSnapshots = 20;

function ensureSnapshotsDir() {
  fs.mkdirSync(snapshotsDir, { recursive: true });
}

function loadIndex() {
  if (!fs.existsSync(indexPath)) {
    return [];
  }
  try {
    const raw = fs.readFileSync(indexPath, "utf8");
    const data = JSON.parse(raw);
    return Array.isArray(data) ? data : [];
  } catch {
    return [];
  }
}

function saveIndex(entries) {
  ensureSnapshotsDir();
  fs.writeFileSync(indexPath, JSON.stringify(entries, null, 2), "utf8");
}

async function backupDatabase(targetPath) {
  if (typeof db.backup === "function") {
    await db.backup(targetPath);
    return;
  }
  const source = path.join(dataDir, "app.db");
  if (fs.existsSync(source)) {
    fs.copyFileSync(source, targetPath);
  }
}

async function createSnapshot({ type, pluginId, metadata = {} }) {
  ensureSnapshotsDir();
  const id = `${Date.now()}-${crypto.randomUUID()}`;
  const snapshotPath = path.join(snapshotsDir, id);
  fs.mkdirSync(snapshotPath, { recursive: true });

  const dbPath = path.join(snapshotPath, "app.db");
  await backupDatabase(dbPath);

  let pluginExisted = false;
  let pluginZip = null;
  if (type === "bot") {
    const coreZip = path.join(snapshotPath, "core.zip");
    zipCore(coreZip);
  }

  if (type === "plugin" && pluginId) {
    const pluginDir = path.join(repoRoot, "plugins", pluginId);
    pluginExisted = fs.existsSync(pluginDir);
    if (pluginExisted) {
      pluginZip = path.join(snapshotPath, "plugin.zip");
      zipFolder(pluginDir, pluginZip, {
        base: pluginDir,
        ignore: new Set(["node_modules", "data"])
      });
    }
  }

  return { id, type, pluginId, pluginExisted, pluginZip, snapshotPath, metadata };
}

function finalizeSnapshot(snapshot) {
  const entries = loadIndex();
  const record = {
    id: snapshot.id,
    type: snapshot.type,
    pluginId: snapshot.pluginId || null,
    pluginExisted: snapshot.pluginExisted || false,
    createdAt: Date.now(),
    status: "available",
    path: snapshot.snapshotPath,
    target_kind: snapshot.metadata?.target_kind || snapshot.type,
    target_id: snapshot.metadata?.target_id || snapshot.pluginId || null,
    from_version: snapshot.metadata?.from_version || null,
    to_version: snapshot.metadata?.to_version || null,
    source_branch: snapshot.metadata?.source_branch || null,
    update_method: snapshot.metadata?.update_method || null,
    rollback_safe: snapshot.metadata?.rollback_safe !== false,
    recovery_marker_id: snapshot.metadata?.recovery_marker_id || null,
    major_crossing: Boolean(snapshot.metadata?.major_crossing),
    migration_notes: snapshot.metadata?.migration_notes || "",
    danger_notes: snapshot.metadata?.danger_notes || []
  };
  entries.push(record);
  saveIndex(pruneEntries(entries));
  return record;
}

function discardSnapshot(snapshot) {
  if (!snapshot?.snapshotPath) {
    return;
  }
  try {
    fs.rmSync(snapshot.snapshotPath, { recursive: true, force: true });
  } catch {
    // Ignore cleanup failures.
  }
}

function pruneEntries(entries) {
  const available = entries
    .filter((entry) => entry.status === "available")
    .sort((a, b) => b.createdAt - a.createdAt);
  const keep = new Set(available.slice(0, maxSnapshots).map((entry) => entry.id));
  const pruned = entries.filter((entry) => entry.status !== "available" || keep.has(entry.id));

  for (const entry of entries) {
    if (entry.status === "available" && !keep.has(entry.id)) {
      try {
        fs.rmSync(entry.path, { recursive: true, force: true });
      } catch {
        // Ignore cleanup failures.
      }
    }
  }

  return pruned;
}

function listSnapshots() {
  return loadIndex()
    .filter((entry) => entry.status === "available")
    .sort((a, b) => b.createdAt - a.createdAt);
}

function markSnapshotRolledBack(id) {
  const entries = loadIndex();
  const entry = entries.find((item) => item.id === id);
  if (!entry) {
    return null;
  }
  entry.status = "rolled_back";
  entry.rolledBackAt = Date.now();
  saveIndex(entries);
  return entry;
}

function extractZip(zipPath, targetDir) {
  if (!AdmZip) {
    throw new Error("adm-zip is not installed. Run npm install.");
  }
  const zip = new AdmZip(zipPath);
  zip.extractAllTo(targetDir, true);
}

function resolveZipRoot(extractedDir) {
  const packagePath = path.join(extractedDir, "package.json");
  if (fs.existsSync(packagePath)) {
    return extractedDir;
  }
  const entries = fs.readdirSync(extractedDir, { withFileTypes: true });
  const dirs = entries.filter((entry) => entry.isDirectory());
  if (dirs.length === 1) {
    const candidate = path.join(extractedDir, dirs[0].name);
    if (fs.existsSync(path.join(candidate, "package.json"))) {
      return candidate;
    }
  }
  return extractedDir;
}

function resolvePatchRoot(extractedDir) {
  const entries = fs.readdirSync(extractedDir, { withFileTypes: true });
  const dirs = entries.filter((entry) => entry.isDirectory());
  const files = entries.filter((entry) => entry.isFile());
  if (files.length > 0) {
    return extractedDir;
  }
  if (dirs.length === 1) {
    return path.join(extractedDir, dirs[0].name);
  }
  return extractedDir;
}

function resolvePluginRoot(extractedDir) {
  const pluginPath = path.join(extractedDir, "plugin.json");
  if (fs.existsSync(pluginPath)) {
    return extractedDir;
  }
  const entries = fs.readdirSync(extractedDir, { withFileTypes: true });
  const dirs = entries.filter((entry) => entry.isDirectory());
  if (dirs.length === 1) {
    const candidate = path.join(extractedDir, dirs[0].name);
    if (fs.existsSync(path.join(candidate, "plugin.json"))) {
      return candidate;
    }
  }
  return extractedDir;
}

function verifyBotPackage(rootPath) {
  const required = [
    path.join(rootPath, "package.json"),
    path.join(rootPath, "safe-mode.js"),
    path.join(rootPath, "src", "main.js"),
    path.join(rootPath, "src", "web", "server.js")
  ];
  for (const filePath of required) {
    if (!fs.existsSync(filePath)) {
      throw new Error(`Missing required file: ${path.relative(rootPath, filePath)}`);
    }
  }
  JSON.parse(fs.readFileSync(required[0], "utf8"));
}

function verifyPatchPackage(rootPath) {
  if (!hasAnyFiles(rootPath)) {
    throw new Error("Patch archive is empty.");
  }
}

function verifyPluginPackage(rootPath) {
  const pluginPath = path.join(rootPath, "plugin.json");
  if (!fs.existsSync(pluginPath)) {
    throw new Error("plugin.json not found in plugin package.");
  }
  const manifest = JSON.parse(fs.readFileSync(pluginPath, "utf8"));
  if (!manifest.id) {
    throw new Error("plugin.json must include an id.");
  }
  const mainFile = manifest.main || "index.js";
  const mainPath = path.join(rootPath, mainFile);
  if (!fs.existsSync(mainPath)) {
    throw new Error(`Plugin entry ${mainFile} not found.`);
  }
  return manifest;
}

function zipCore(destination) {
  if (!AdmZip) {
    throw new Error("adm-zip is not installed. Run npm install.");
  }
  const zip = new AdmZip();
  addFolder(zip, repoRoot, repoRoot, new Set([".git", "node_modules", "data", "plugins"]));
  zip.writeZip(destination);
}

function zipFolder(source, destination, options) {
  if (!AdmZip) {
    throw new Error("adm-zip is not installed. Run npm install.");
  }
  const zip = new AdmZip();
  const base = options?.base || source;
  addFolder(zip, source, base, options?.ignore || new Set(["node_modules"]));
  zip.writeZip(destination);
}

function addFolder(zip, folderPath, basePath, ignore) {
  const entries = fs.readdirSync(folderPath, { withFileTypes: true });
  for (const entry of entries) {
    const fullPath = path.join(folderPath, entry.name);
    const relPath = path.relative(basePath, fullPath);
    const topLevel = relPath.split(path.sep)[0];
    if (ignore.has(topLevel)) {
      continue;
    }
    if (entry.isDirectory()) {
      addFolder(zip, fullPath, basePath, ignore);
    } else if (entry.isFile()) {
      zip.addLocalFile(fullPath, path.dirname(relPath));
    }
  }
}

function resetCoreFiles() {
  const ignore = new Set([".git", "node_modules", "data", "plugins"]);
  const entries = fs.readdirSync(repoRoot, { withFileTypes: true });
  for (const entry of entries) {
    if (ignore.has(entry.name)) {
      continue;
    }
    const fullPath = path.join(repoRoot, entry.name);
    fs.rmSync(fullPath, { recursive: true, force: true });
  }
}

function copyDirectory(source, target, ignore) {
  const entries = fs.readdirSync(source, { withFileTypes: true });
  for (const entry of entries) {
    if (ignore.has(entry.name)) {
      continue;
    }
    const srcPath = path.join(source, entry.name);
    const destPath = path.join(target, entry.name);
    if (entry.isDirectory()) {
      fs.mkdirSync(destPath, { recursive: true });
      copyDirectory(srcPath, destPath, ignore);
    } else if (entry.isFile()) {
      fs.copyFileSync(srcPath, destPath);
    }
  }
}

function applyCoreUpdate(rootPath) {
  resetCoreFiles();
  copyDirectory(
    rootPath,
    repoRoot,
    new Set([".git", "node_modules", "data", "plugins"])
  );
}

function applyCorePatch(rootPath) {
  copyDirectory(
    rootPath,
    repoRoot,
    new Set([".git", "node_modules", "data", "plugins"])
  );
}

function hasAnyFiles(rootPath) {
  const entries = fs.readdirSync(rootPath, { withFileTypes: true });
  for (const entry of entries) {
    if (entry.isFile()) {
      return true;
    }
    if (entry.isDirectory()) {
      if (hasAnyFiles(path.join(rootPath, entry.name))) {
        return true;
      }
    }
  }
  return false;
}

function resetPluginCode(targetDir) {
  if (!fs.existsSync(targetDir)) {
    return;
  }
  for (const entry of fs.readdirSync(targetDir, { withFileTypes: true })) {
    if (entry.name === "data") {
      continue;
    }
    fs.rmSync(path.join(targetDir, entry.name), {
      recursive: true,
      force: true
    });
  }
}

function applyPluginFiles(rootPath, pluginId, options = {}) {
  const pluginsDir = path.join(repoRoot, "plugins");
  const targetDir = path.join(pluginsDir, pluginId);
  fs.mkdirSync(pluginsDir, { recursive: true });
  replacePluginDirectory(rootPath, targetDir, options);
}

function replacePluginDirectory(rootPath, targetDir, options = {}) {
  if (options.preserveData) {
    resetPluginCode(targetDir);
  } else {
    fs.rmSync(targetDir, { recursive: true, force: true });
  }
  fs.mkdirSync(targetDir, { recursive: true });
  copyDirectory(
    rootPath,
    targetDir,
    options.preserveData
      ? new Set(["node_modules", "data"])
      : new Set(["node_modules"])
  );
}

async function applyBotUpdate(zipPath, options = {}) {
  const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "lumi-update-"));
  try {
    extractZip(zipPath, tempDir);
    const mode = options.mode === "patch" ? "patch" : "full";
    const rootPath =
      mode === "patch" ? resolvePatchRoot(tempDir) : resolveZipRoot(tempDir);
    if (mode === "patch") {
      verifyPatchPackage(rootPath);
    } else {
      verifyBotPackage(rootPath);
    }

    const marker = createRecoveryMarker({
      target_kind: "core",
      target_id: "core",
      from_version: options.metadata?.from_version || null,
      to_version: options.metadata?.to_version || null,
      source_branch: options.metadata?.source_branch || "manual_zip",
      update_method: options.mode === "patch" ? "zip_patch" : "zip",
      rollback_safe: options.metadata?.rollback_safe !== false,
      major_crossing: Boolean(options.metadata?.major_crossing)
    });
    updateRecoveryMarker({ status: "applying" });
    const snapshot = await createSnapshot({
      type: "bot",
      metadata: {
        target_kind: "core",
        update_method: options.mode === "patch" ? "zip_patch" : "zip",
        ...options.metadata,
        recovery_marker_id: marker.id
      }
    });
    try {
      if (mode === "patch") {
        applyCorePatch(rootPath);
      } else {
        applyCoreUpdate(rootPath);
      }
      const record = finalizeSnapshot(snapshot);
      markRecoveryMarkerComplete({ snapshot_id: record.id });
      return record;
    } catch (error) {
      discardSnapshot(snapshot);
      markRecoveryMarkerFailed(error);
      throw error;
    }
  } finally {
    fs.rmSync(tempDir, { recursive: true, force: true });
  }
}

async function applyPluginUpdate(zipPath, options = {}) {
  const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "lumi-plugin-"));
  try {
    extractZip(zipPath, tempDir);
    const rootPath = resolvePluginRoot(tempDir);
    const manifest = verifyPluginPackage(rootPath);
    if (options.expectedPluginId && manifest.id !== options.expectedPluginId) {
      throw new Error(`Plugin ZIP id ${manifest.id} does not match ${options.expectedPluginId}.`);
    }

    const marker = createRecoveryMarker({
      target_kind: "plugin",
      target_id: manifest.id,
      from_version: options.metadata?.from_version || null,
      to_version: manifest.version || options.metadata?.to_version || null,
      source_branch: options.metadata?.source_branch || "manual_zip",
      update_method: "zip",
      rollback_safe: options.metadata?.rollback_safe !== false,
      major_crossing: Boolean(options.metadata?.major_crossing)
    });
    updateRecoveryMarker({ status: "applying" });
    const snapshot = await createSnapshot({
      type: "plugin",
      pluginId: manifest.id,
      metadata: {
        target_kind: "plugin",
        target_id: manifest.id,
        update_method: "zip",
        ...options.metadata,
        recovery_marker_id: marker.id
      }
    });
    try {
      applyPluginFiles(rootPath, manifest.id, {
        preserveData: snapshot.pluginExisted
      });
      const record = finalizeSnapshot(snapshot);
      markRecoveryMarkerComplete({ snapshot_id: record.id });
      return record;
    } catch (error) {
      discardSnapshot(snapshot);
      markRecoveryMarkerFailed(error);
      throw error;
    }
  } finally {
    fs.rmSync(tempDir, { recursive: true, force: true });
  }
}

function restoreDatabase(snapshotPath) {
  const source = path.join(snapshotPath, "app.db");
  const target = path.join(dataDir, "app.db");
  if (!fs.existsSync(source)) {
    throw new Error("Snapshot database not found.");
  }
  fs.copyFileSync(source, target);
  const wal = path.join(dataDir, "app.db-wal");
  const shm = path.join(dataDir, "app.db-shm");
  fs.rmSync(wal, { force: true });
  fs.rmSync(shm, { force: true });
}

function restoreSnapshot(id, options = {}) {
  const entries = loadIndex();
  const entry = entries.find((item) => item.id === id);
  if (!entry) {
    throw new Error("Snapshot not found.");
  }
  if (entry.status !== "available") {
    throw new Error("Snapshot is no longer available.");
  }
  if (options.expectedType && entry.type !== options.expectedType) {
    throw new Error("Snapshot target type does not match this revert action.");
  }
  if (options.expectedPluginId && entry.pluginId !== options.expectedPluginId) {
    throw new Error("Snapshot target plugin does not match this revert action.");
  }
  if (entry.major_crossing && entry.rollback_safe === false && !options.allowUnsafeMajorRollback) {
    throw new Error("This snapshot crossed a major version and is not marked rollback safe.");
  }
  if (options.currentVersion && entry.to_version && entry.to_version !== options.currentVersion) {
    throw new Error("Only the previous version snapshot can be reverted from this action.");
  }

  if (entry.type === "bot") {
    const coreZip = path.join(entry.path, "core.zip");
    if (!fs.existsSync(coreZip)) {
      throw new Error("Snapshot core archive missing.");
    }
    const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "lumi-restore-"));
    extractZip(coreZip, tempDir);
    const rootPath = resolveZipRoot(tempDir);
    applyCoreUpdate(rootPath);
    fs.rmSync(tempDir, { recursive: true, force: true });
  }

  if (entry.type === "plugin") {
    const pluginsDir = path.join(repoRoot, "plugins");
    const targetDir = path.join(pluginsDir, entry.pluginId);
    if (entry.pluginExisted) {
      const pluginZip = path.join(entry.path, "plugin.zip");
      if (!fs.existsSync(pluginZip)) {
        throw new Error("Snapshot plugin archive missing.");
      }
      const tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "lumi-restore-"));
      extractZip(pluginZip, tempDir);
      const rootPath = resolvePluginRoot(tempDir);
      applyPluginFiles(rootPath, entry.pluginId, { preserveData: true });
      fs.rmSync(tempDir, { recursive: true, force: true });
    } else {
      fs.rmSync(targetDir, { recursive: true, force: true });
    }
  }

  restoreDatabase(entry.path);
  markSnapshotRolledBack(id);
  return entry;
}

module.exports = {
  applyBotUpdate,
  applyPluginUpdate,
  createSnapshot,
  finalizeSnapshot,
  discardSnapshot,
  applyPluginFiles,
  resetPluginCode,
  replacePluginDirectory,
  listSnapshots,
  restoreSnapshot
};