/**
 * Plugin host: the `window.registerKandevPlugin` global + the loader that
 * imports plugin bundles from the boot payload (docs/plans/plugins/PLUGIN-API.md).
 *
 * Loading sequence per bundle: inject `styleUrls` as `<link>` tags, dynamically
 * `import(/* @vite-ignore *\/ bundleUrl)` the bundle (module-level side effect
 * calls `window.registerKandevPlugin`), then call the registered plugin's
 * `initialize(registry, host)`. A bad plugin (throwing bundle, missing
 * registration, or throwing `initialize`) is logged and swallowed — it never
 * breaks boot or blocks other plugins.
 *
 * `registeredPlugins` is never cleared on disable — only on a fresh import
 * (see `resolveRegistration`). The browser's ES module cache means a repeat
 * `import(bundleUrl)` after disable would resolve without re-running the
 * bundle's top-level `registerKandevPlugin` call, so re-enabling in the same
 * tab must reuse the cached registration instead of relying on re-import.
 */
import { getBackendConfig } from "@/lib/config";
import { pluginModalManager } from "./modal-manager";
import { pluginRegistry } from "./registry";
import { generationFencedHost, PluginLoadResources } from "./host-runtime-resources";
import type { ActivePlugin, KandevPlugin, PluginHostApi, PluginRegistry } from "./types";

/** Builds the per-plugin `PluginHostApi` for a given pluginId. */
export type PluginHostFactory = (pluginId: string) => PluginHostApi;

/** Injectable bundle loader — defaults to a real dynamic import. Tests pass a fake. */
export type BundleImporter = (url: string) => Promise<unknown>;

const defaultImporter: BundleImporter = (url) => import(/* @vite-ignore */ url);

/**
 * How long `loadPlugin` waits for a single plugin's `initialize(registry, host)`
 * to settle before giving up on it and moving on to the next plugin in the
 * boot list. A plugin whose `initialize()` never resolves must not be able to
 * stall every plugin queued behind it.
 */
const DEFAULT_INITIALIZE_TIMEOUT_MS = 10_000;

/**
 * Races `promise` against a `timeoutMs` timer. Resolves with the settled value
 * (or rejects with its error) if it settles first; otherwise calls `onTimeout`
 * and resolves with `timedOut: true` — a timeout is deliberately not a
 * rejection, so the caller's loop can continue to the next plugin instead of
 * routing a hang through the same error-handling path as a thrown/rejected
 * `initialize()`. The original promise is not cancelled; if it eventually
 * settles nothing observes it.
 */
function raceTimeout<T>(
  promise: Promise<T>,
  timeoutMs: number,
  onTimeout: () => void,
): Promise<{ value?: T; timedOut: boolean }> {
  return new Promise((resolve, reject) => {
    const timer = setTimeout(() => {
      onTimeout();
      resolve({ timedOut: true });
    }, timeoutMs);
    promise.then(
      (value) => {
        clearTimeout(timer);
        resolve({ value, timedOut: false });
      },
      (error: unknown) => {
        clearTimeout(timer);
        reject(error as Error);
      },
    );
  });
}

type PluginGlobalWindow = Window & {
  registerKandevPlugin?: (id: string, plugin: KandevPlugin) => void;
};

/** Bundles registered via `window.registerKandevPlugin`, keyed by pluginId. */
const registeredPlugins = new Map<string, KandevPlugin>();

/**
 * Latest load "generation" claimed per pluginId. `loadPlugin` claims a fresh
 * generation the moment it starts (before it awaits the dynamic import), so a
 * later-initiated load always outranks an earlier one for the same plugin.
 * Registry mutations are then fenced on this: a load that has been superseded
 * — an older boot import resolving after a newer install/update already loaded
 * (bootPlugins fires loadPlugins without awaiting it, and the settings update
 * path calls loadPlugins independently) — must not revoke the successor's
 * registrations or append its own stale ones. See `loadPlugin`.
 */
const loadGenerations = new Map<string, number>();

type ActivePluginRuntime = {
  generation: number;
  plugin: KandevPlugin;
  resources: PluginLoadResources;
};

/** Currently initialized (or initializing) runtime per plugin id. */
const activePluginRuntimes = new Map<string, ActivePluginRuntime>();

/** Claims and returns a new, strictly-increasing load generation for `id`. */
function claimLoadGeneration(id: string): number {
  const next = (loadGenerations.get(id) ?? 0) + 1;
  loadGenerations.set(id, next);
  return next;
}

/** True while `generation` is still the newest claimed load for `id`. */
function isCurrentLoad(id: string, generation: number): boolean {
  return loadGenerations.get(id) === generation;
}

/**
 * Wraps a scoped `PluginRegistry` so every register* call is dropped once this
 * load has been superseded by a newer one (`isCurrent()` is false). Guards the
 * window where a plugin registers *after* an `await` inside `initialize()`: a
 * stale async initializer must not append onto the successor's registrations.
 *
 * Wraps every method reflectively rather than naming each one, so any register*
 * added to the `PluginRegistry` contract (e.g. `registerKeybinding`) is fenced
 * automatically instead of being silently dropped from the forwarded object.
 */
function generationFencedRegistry(
  registry: PluginRegistry,
  isCurrent: () => boolean,
): PluginRegistry {
  const fenced: Record<string, unknown> = {};
  for (const [key, value] of Object.entries(registry)) {
    fenced[key] =
      typeof value === "function"
        ? (...args: unknown[]) => {
            if (isCurrent()) (value as (...callArgs: unknown[]) => unknown)(...args);
          }
        : value;
  }
  return fenced as unknown as PluginRegistry;
}

/** Defines `window.registerKandevPlugin` before any bundle loads. Idempotent. */
export function installPluginGlobal(win: Window = window): void {
  (win as PluginGlobalWindow).registerKandevPlugin = (id, plugin) => {
    registeredPlugins.set(id, plugin);
  };
}

/**
 * Loads every plugin from the boot payload: injects styles, imports the
 * bundle, then runs `initialize(registry, host)`. Each plugin is isolated —
 * a failure anywhere in its load path is logged and does not affect the
 * others or the boot sequence. `initTimeoutMs` (default
 * `DEFAULT_INITIALIZE_TIMEOUT_MS`) bounds how long a single plugin's
 * `initialize()` can block the (sequential) loop before the loader gives up
 * on it and moves on — tests inject a short value instead of waiting out the
 * real default.
 */
export async function loadPlugins(
  bootPlugins: ActivePlugin[],
  hostFactory: PluginHostFactory,
  importer: BundleImporter = defaultImporter,
  win: Window = window,
  initTimeoutMs: number = DEFAULT_INITIALIZE_TIMEOUT_MS,
): Promise<void> {
  installPluginGlobal(win);
  for (const plugin of bootPlugins) {
    await loadPlugin(plugin, hostFactory, importer, initTimeoutMs);
  }
}

async function loadPlugin(
  plugin: ActivePlugin,
  hostFactory: PluginHostFactory,
  importer: BundleImporter,
  initTimeoutMs: number,
): Promise<void> {
  const { apiBaseUrl } = getBackendConfig();
  // Claim a generation before the (awaited) import so entry order — not
  // import-resolve order — decides which load owns the registry.
  const generation = claimLoadGeneration(plugin.id);
  // A replacement generation owns the id immediately. Abort and destroy the
  // prior runtime before loading new code so its requests/listeners cannot run
  // concurrently with the successor.
  deactivatePluginRuntime(plugin.id);
  pluginRegistry.markPluginLoading(plugin.id, generation);
  let generationOpen = true;
  const isActiveGeneration = () => generationOpen && isCurrentLoad(plugin.id, generation);
  try {
    injectStyles(plugin.id, plugin.styleUrls, apiBaseUrl);
    const registered = await resolveRegistration(plugin, importer, apiBaseUrl);
    if (!registered) {
      console.error(`[plugins] "${plugin.id}" bundle did not call registerKandevPlugin`);
      generationOpen = false;
      if (isCurrentLoad(plugin.id, generation)) {
        pluginRegistry.markPluginFailed(plugin.id, generation);
        revokeFailedLoad(plugin.id, generation);
      }
      return;
    }
    // A newer load for this plugin started while we awaited the import — it now
    // owns the registry. Bail before mutating anything so this stale load can't
    // revoke the successor's registrations or initialize an older bundle over
    // them (the boot-vs-update race Codex flagged).
    if (!isCurrentLoad(plugin.id, generation)) {
      generationOpen = false;
      return;
    }
    const resources = new PluginLoadResources(plugin.id);
    activePluginRuntimes.set(plugin.id, { generation, plugin: registered, resources });
    const host = generationFencedHost(
      hostFactory(plugin.id),
      () => isCurrentLoad(plugin.id, generation),
      resources,
    );
    // Idempotent (re)load. The nav/route/slot registry is append-only, so
    // running a plugin's initialize() a second time while its previous
    // registrations are still live leaves duplicates — e.g. a plugin's
    // chat-input-actions icon rendered twice. The disable/update paths already
    // call unloadPlugin() first, but boot does not, and it can re-enter for a
    // plugin that is already registered: a boot race (bootPlugins' fire-and-
    // forget loadPlugins still in flight when an install/update reload runs), a
    // dev HMR re-boot (fresh bootedStores guard against the persistent registry
    // singleton), or a fresh store instance. Because resolveRegistration reuses
    // the cached bundle registration, that re-entry re-runs initialize() and
    // re-registers on top of the old entries. Revoke this plugin's prior
    // registrations here so a reload always converges to exactly one set,
    // whatever the caller did — a no-op on a genuine first load.
    pluginRegistry.unregisterPlugin(plugin.id);
    // Newer boot payloads carry manifest-owned provider IDs. Set them after
    // revoking prior state and before plugin initialize(), so a re-enable
    // cannot retain stale declarations and registration is checked eagerly.
    // Omit this call for older payloads to preserve their existing registry API.
    if (plugin.repositoryProviderIds) {
      pluginRegistry.setDeclaredRepositoryProviderIds(plugin.id, plugin.repositoryProviderIds);
    }
    // Fence the scoped registry on this generation so that if an even-newer
    // load supersedes us while initialize() is awaiting, a plugin that
    // registers post-await can't append onto the successor.
    const registry = generationFencedRegistry(
      pluginRegistry.forPlugin(plugin.id, plugin.name),
      isActiveGeneration,
    );
    const result = await raceTimeout(
      Promise.resolve(registered.initialize(registry, host)),
      initTimeoutMs,
      () => {
        console.warn(
          `[plugins] "${plugin.id}" initialize() timed out after ${initTimeoutMs}ms; continuing without it`,
        );
      },
    );
    generationOpen = false;
    if (isCurrentLoad(plugin.id, generation)) {
      if (result.timedOut) {
        pluginRegistry.markPluginFailed(plugin.id, generation);
        revokeFailedLoad(plugin.id, generation);
      } else {
        pluginRegistry.markPluginReady(plugin.id, generation);
      }
    }
  } catch (error) {
    generationOpen = false;
    if (isCurrentLoad(plugin.id, generation)) {
      pluginRegistry.markPluginFailed(plugin.id, generation);
    }
    console.error(`[plugins] failed to load plugin "${plugin.id}"`, error);
    revokeFailedLoad(plugin.id, generation);
  }
}

/**
 * Removes a failed generation without disturbing a newer concurrent load.
 * Leaves the plugin's registry entries (nav items, routes, etc.) in place: a
 * registration made before `initialize()` threw or timed out must survive —
 * only the runtime (resources, styles, modals) is torn down. `loadPlugin`
 * already marked the plugin `"failed"` before calling this.
 */
function revokeFailedLoad(pluginId: string, generation: number): void {
  if (!isCurrentLoad(pluginId, generation)) return;
  deactivatePluginRuntime(pluginId, generation, { unregister: false });
  // Fence delayed registrations from an initializer that timed out.
  claimLoadGeneration(pluginId);
}

/**
 * Revokes one active runtime without changing its published lifecycle state.
 * Pass `unregister: false` to keep the plugin's existing registry entries —
 * used by the failed-load path (see `revokeFailedLoad`) so a nav item
 * registered before `initialize()` failed is retained, per the
 * partial-initialization-failure retention contract (spec.md's AC).
 */
function deactivatePluginRuntime(
  pluginId: string,
  expectedGeneration?: number,
  options?: { unregister?: boolean },
): void {
  if (expectedGeneration !== undefined && !isCurrentLoad(pluginId, expectedGeneration)) return;
  const runtime = activePluginRuntimes.get(pluginId);
  if (runtime && expectedGeneration !== undefined && runtime.generation !== expectedGeneration) {
    return;
  }
  if (runtime) {
    activePluginRuntimes.delete(pluginId);
    runtime.resources.revoke();
    try {
      runtime.plugin.destroy?.();
    } catch (error) {
      console.error(`[plugins] error destroying plugin "${pluginId}"`, error);
    }
  }
  if (options?.unregister ?? true) {
    pluginRegistry.unregisterPlugin(pluginId);
  }
  pluginModalManager.closeAllForPlugin(pluginId);
  removeStyles(pluginId);
}

/**
 * Returns the plugin's registration, importing the bundle only when it
 * isn't already cached from a prior load in this tab (see module doc for
 * why re-enable must not blindly re-import).
 */
async function resolveRegistration(
  plugin: ActivePlugin,
  importer: BundleImporter,
  apiBaseUrl: string,
): Promise<KandevPlugin | undefined> {
  const cached = registeredPlugins.get(plugin.id);
  if (cached) return cached;
  await importer(resolvePluginUrl(plugin.bundleUrl, apiBaseUrl));
  return registeredPlugins.get(plugin.id);
}

/**
 * Prefixes a root-relative plugin asset URL with the backend origin. Plain
 * root-relative URLs only resolve correctly when the SPA and the API share
 * an origin (same-origin production); split-origin dev and the Tauri
 * desktop shell need the explicit `apiBaseUrl`, same as `host.api.fetch`.
 */
function resolvePluginUrl(url: string, apiBaseUrl: string): string {
  if (!apiBaseUrl || !url.startsWith("/")) return url;
  return `${apiBaseUrl}${url}`;
}

function injectStyles(pluginId: string, styleUrls: string[] | undefined, apiBaseUrl: string): void {
  if (!styleUrls) return;
  for (const href of styleUrls) {
    const link = document.createElement("link");
    link.rel = "stylesheet";
    link.href = resolvePluginUrl(href, apiBaseUrl);
    link.dataset.pluginId = pluginId;
    document.head.appendChild(link);
  }
}

/** Removes every `<link>` this plugin injected via `injectStyles`. */
function removeStyles(pluginId: string): void {
  document.querySelectorAll(`link[data-plugin-id="${pluginId}"]`).forEach((link) => link.remove());
}

/**
 * Disables a plugin: calls `destroy?.()`, bulk-revokes its registry
 * registrations, and removes its injected stylesheets. By default this
 * keeps the `registeredPlugins` entry — see module doc — so a later
 * re-enable in the same tab can re-run `initialize` without depending on the
 * browser re-executing the bundle's module-eval side effect.
 *
 * Pass `evictCache: true` for the install/update path specifically: an
 * updated package can ship new bundle code under the same `bundleUrl`, so
 * the cached registration (and, with it, the stale `initialize`/`destroy`
 * closures from the previous version) must be dropped so the next
 * `loadPlugin` re-imports it. This is opt-in — unconditional eviction here
 * would break the plain disable/re-enable cycle's cached-registration reuse.
 */
export function unloadPlugin(
  id: string,
  options?: { evictCache?: boolean; transition?: "reload" | "removed" },
): void {
  const generation = claimLoadGeneration(id);
  if (options?.transition === "reload") {
    pluginRegistry.markPluginLoading(id, generation);
  } else {
    pluginRegistry.markPluginRemoved(id, generation);
  }
  // Supersede any in-flight load so a plugin whose initialize() is still
  // awaiting can't re-register after we've disabled/uninstalled it.
  deactivatePluginRuntime(id);
  if (options?.evictCache) {
    registeredPlugins.delete(id);
  }
}