/**
 * A linked desktop runs the features its server runs.
 *
 * For every plugin in "mirror" mode, the server decides: a plugin installed
 * there is installed here, on or off to match, with the capabilities an
 * admin granted it there. Plugins marked "local" are left to the desktop and
 * "server" ones never run on a linked desktop. A user plugin no key trusted
 * here signed is only ever switched off; the desktop's admin turns it on.
 */

import fs from "fs";
import path from "path";
import semver from "semver";
import {
  resolvePluginDesktopMode,
  type PluginDesktopMode,
} from "@termix-ssh/plugin-sdk/manifest";
import { syncLogger } from "../../utils/logger.js";
import { sendCoreAlert } from "../../notify/core-notify.js";
import {
  getPluginRuntime,
  installPluginArtifact,
  registerLoadedPlugins,
  setPluginEnabled,
  unloadPlugin,
} from "../../plugins/index.js";
import { getPluginsDir } from "../../plugins/paths.js";
import {
  isLocallyTrustedPluginKey,
  setSyncedRegistryKeys,
} from "../../plugins/registries.js";
import type { LoadedPlugin } from "../../plugins/loader.js";
import {
  createCurrentPluginPermissionGrantRepository,
  createCurrentPluginRepository,
} from "../../database/repositories/factory.js";
import { remoteFetch, remoteJson } from "./http.js";
import type { SyncLink } from "./link-store.js";

export interface RemotePlugin {
  id: string;
  name: string;
  version: string;
  source: "bundled" | "user";
  /** The server can send a signed .tmxplug for it. */
  artifact?: boolean;
  enabled: boolean;
  active: boolean;
  desktop: PluginDesktopMode;
  syncEntities: string[];
  granted: string[];
}

let lastRemote: RemotePlugin[] = [];
const alertedVersions = new Set<string>();

/** What the server ran at the last sync, for the sync panel. */
export function lastRemotePlugins(): RemotePlugin[] {
  return lastRemote;
}

async function isEnabledLocally(pluginId: string): Promise<boolean> {
  const record = await createCurrentPluginRepository().findById(pluginId);
  return record?.state === "enabled";
}

/**
 * Signed by a key this desktop trusts on its own. A key the server sent
 * would let the server's admin sign anything, so it does not count.
 */
function vouchedHere(local: LoadedPlugin): boolean {
  return !!local.signedBy && isLocallyTrustedPluginKey(local.signedBy);
}

const PLUGIN_ID_PATTERN = /^[a-z0-9][a-z0-9-]*$/;

/** Downloads next to the installed copy, which stays until the swap. */
async function download(link: SyncLink, plugin: RemotePlugin): Promise<string> {
  const response = await remoteFetch(
    link,
    `/sync/v2/plugins/${encodeURIComponent(plugin.id)}/package`,
    { timeoutMs: 120_000 },
  );
  if (!response.ok) {
    throw new Error(`Could not download ${plugin.id} (${response.status})`);
  }
  const buffer = Buffer.from(await response.arrayBuffer());
  const dir = getPluginsDir();
  await fs.promises.mkdir(dir, { recursive: true });
  const file = path.join(dir, `${plugin.id}.tmxplug.download`);
  await fs.promises.writeFile(file, buffer);
  const signature = response.headers.get("x-termix-signature");
  const sigFile = `${file}.sig`;
  if (signature) {
    await fs.promises.writeFile(
      sigFile,
      Buffer.from(signature, "base64").toString("utf8"),
    );
  } else {
    await fs.promises.rm(sigFile, { force: true });
  }
  return file;
}

async function moveIfThere(from: string, to: string): Promise<void> {
  await fs.promises.rm(to, { force: true });
  if (fs.existsSync(from)) await fs.promises.rename(from, to);
}

/**
 * Swaps a downloaded copy in for the installed one. If it fails to install,
 * the old copy goes back on disk and is loaded again, so a bad download never
 * leaves the desktop without the plugin.
 */
async function replaceWithDownload(
  pluginId: string,
  downloaded: string,
  previous: LoadedPlugin | undefined,
  wasEnabled: boolean,
): Promise<LoadedPlugin> {
  const file = path.join(getPluginsDir(), `${pluginId}.tmxplug`);
  const backup = `${file}.previous`;
  await moveIfThere(file, backup);
  await moveIfThere(`${file}.sig`, `${backup}.sig`);
  await moveIfThere(downloaded, file);
  await moveIfThere(`${downloaded}.sig`, `${file}.sig`);
  if (previous) await unloadPlugin(pluginId);
  try {
    const installed = await installPluginArtifact(file);
    // Approval belongs to the reviewed version, regardless of remote metadata.
    if (wasEnabled && installed.source === "user" && !vouchedHere(installed)) {
      await setPluginEnabled(pluginId, false);
    }
    await fs.promises.rm(backup, { force: true });
    await fs.promises.rm(`${backup}.sig`, { force: true });
    return installed;
  } catch (error) {
    await moveIfThere(backup, file);
    await moveIfThere(`${backup}.sig`, `${file}.sig`);
    if (previous) await restorePrevious(pluginId, previous, file, wasEnabled);
    throw error;
  }
}

async function restorePrevious(
  pluginId: string,
  previous: LoadedPlugin,
  file: string,
  wasEnabled: boolean,
): Promise<void> {
  const { loader } = getPluginRuntime();
  if (loader.get(pluginId)) return;
  try {
    if (fs.existsSync(file)) {
      await installPluginArtifact(file);
    } else if (previous.source === "bundled") {
      await registerLoadedPlugins([await loader.loadBundled(pluginId)]);
    }
    if (wasEnabled && loader.get(pluginId)) {
      await setPluginEnabled(pluginId, true);
    }
  } catch (error) {
    syncLogger.warn("Could not restore a feature after a failed update", {
      operation: "sync_plugin_restore",
      pluginId,
      error: error instanceof Error ? error.message : String(error),
    });
  }
}

async function matchGrants(plugin: RemotePlugin): Promise<void> {
  const repository = createCurrentPluginPermissionGrantRepository();
  const local = getPluginRuntime().loader.get(plugin.id);
  if (!local || local.source !== "user") return;
  // Grants are only copied for code a trusted key signed. Anything else the
  // desktop's own admin has to review, as with any plugin dropped on disk.
  if (!vouchedHere(local)) return;
  const declared = new Set(local.manifest.capabilities);
  const wanted = new Set(plugin.granted.filter((cap) => declared.has(cap)));
  const existing = await repository.listByPlugin(plugin.id);
  for (const grant of existing) {
    if (!wanted.has(grant.capability)) {
      await repository.revoke(plugin.id, grant.capability);
    }
  }
  const have = new Set(existing.map((grant) => grant.capability));
  for (const capability of wanted) {
    if (have.has(capability)) continue;
    await repository.grant({
      pluginId: plugin.id,
      capability,
      grantedBy: null,
      source: "admin",
    });
  }
}

async function alertOlderDesktop(plugin: RemotePlugin): Promise<void> {
  const key = `${plugin.id}@${plugin.version}`;
  if (alertedVersions.has(key)) return;
  alertedVersions.add(key);
  await sendCoreAlert({
    title: "Update the desktop app",
    body: `The server runs a newer ${plugin.name} (${plugin.version}) than this app has. Update the app to get it.`,
    severity: "info",
    category: "termix.sync.desktop_outdated",
    dedupeKey: `sync:outdated:${key}`,
    audience: "admins",
  });
}

async function alertUnsigned(plugin: RemotePlugin): Promise<void> {
  const key = `unsigned:${plugin.id}@${plugin.version}`;
  if (alertedVersions.has(key)) return;
  alertedVersions.add(key);
  await sendCoreAlert({
    title: "Review a feature from your server",
    body: `${plugin.name} (${plugin.version}) was copied from your server but is not signed by a key this app trusts, so it stays off here until you turn it on.`,
    severity: "warning",
    category: "termix.sync.unsigned_plugin",
    dedupeKey: `sync:${key}`,
    audience: "admins",
  });
}

async function mirrorOne(link: SyncLink, plugin: RemotePlugin): Promise<void> {
  // The id becomes a file name below, so it must be a real plugin id.
  if (typeof plugin.id !== "string" || !PLUGIN_ID_PATTERN.test(plugin.id)) {
    throw new Error("The server sent a plugin with an invalid id");
  }
  const { loader } = getPluginRuntime();
  let local = loader.get(plugin.id);
  const mode = local
    ? resolvePluginDesktopMode(local.manifest)
    : (plugin.desktop ?? "mirror");

  if (mode === "server") {
    if (local && (await isEnabledLocally(plugin.id))) {
      await setPluginEnabled(plugin.id, false);
    }
    return;
  }
  if (mode !== "mirror") return;

  if (plugin.source === "bundled") {
    const newer = !local || semver.gt(plugin.version, local.manifest.version);
    if (newer && plugin.artifact && local?.state !== "activating") {
      // A signed update of a bundled plugin. The loader checks the signature
      // and that the version really is newer.
      const wasEnabled = await isEnabledLocally(plugin.id);
      try {
        const downloaded = await download(link, plugin);
        local = await replaceWithDownload(
          plugin.id,
          downloaded,
          local,
          wasEnabled,
        );
      } catch (error) {
        await alertOlderDesktop(plugin);
        throw error;
      }
      if (wasEnabled && local.source === "bundled") {
        await setPluginEnabled(plugin.id, true);
      }
    } else if (newer) {
      await alertOlderDesktop(plugin);
    }
    if (!local) return;
  } else if (plugin.enabled || local) {
    const outdated =
      !local ||
      local.source !== "user" ||
      local.manifest.version !== plugin.version;
    if (outdated && (!local || local.source === "user")) {
      const wasEnabled = local ? await isEnabledLocally(plugin.id) : false;
      const downloaded = await download(link, plugin);
      local = await replaceWithDownload(
        plugin.id,
        downloaded,
        local,
        wasEnabled,
      );
      if (wasEnabled && !plugin.enabled) {
        await setPluginEnabled(plugin.id, false);
      }
    }
    await matchGrants(plugin);
  }

  if (!local) return;
  // Remote metadata cannot confer bundled trust on a locally loaded user plugin.
  if (local.source === "user" && !vouchedHere(local)) {
    const enabledHere = await isEnabledLocally(plugin.id);
    if (!plugin.enabled && enabledHere) {
      await setPluginEnabled(plugin.id, false);
    } else if (plugin.enabled && !enabledHere) {
      await alertUnsigned(plugin);
    }
    return;
  }
  if (plugin.enabled !== (await isEnabledLocally(plugin.id))) {
    await setPluginEnabled(plugin.id, plugin.enabled);
  } else if (plugin.enabled && local.state !== "active") {
    await setPluginEnabled(plugin.id, true);
  }
}

export async function mirrorPlugins(link: SyncLink): Promise<void> {
  const { serialized } = await import("../../plugins/manage.js");
  const { plugins, registryKeys } = await remoteJson<{
    plugins: RemotePlugin[];
    registryKeys?: unknown[];
  }>(link, "/sync/v2/plugins");
  // Before any download: a plugin from a custom registry needs its key.
  await setSyncedRegistryKeys(Array.isArray(registryKeys) ? registryKeys : []);
  lastRemote = plugins;
  const remoteIds = new Set(plugins.map((plugin) => plugin.id));

  for (const plugin of plugins) {
    try {
      // Share the consent/enable lock so an update cannot swap code mid-approval.
      await serialized(() => mirrorOne(link, plugin));
    } catch (error) {
      syncLogger.warn("Could not match a feature to the server", {
        operation: "sync_plugin_mirror",
        pluginId: plugin.id,
        error: error instanceof Error ? error.message : String(error),
      });
    }
  }

  // A plugin the server no longer has is switched off here. Its data stays.
  for (const local of getPluginRuntime().loader.list()) {
    if (remoteIds.has(local.id) || local.source !== "user") continue;
    if (resolvePluginDesktopMode(local.manifest) !== "mirror") continue;
    if (await isEnabledLocally(local.id)) {
      await setPluginEnabled(local.id, false).catch(() => {});
    }
  }
}

/**
 * Whether a plugin's on/off state belongs to the linked server. Code no key
 * trusted here vouches for is the desktop's own admin's call to turn on.
 */
export function isServerManaged(pluginId: string): boolean {
  const local = getPluginRuntime().loader.get(pluginId);
  const mode = local ? resolvePluginDesktopMode(local.manifest) : "mirror";
  if (mode !== "mirror") return mode === "server";
  return local?.source !== "user" || vouchedHere(local);
}