import { Capacitor } from "@capacitor/core";
import { useEffect, useState } from "react";
import { apiClient } from "../../api/client";
import { isNewerVersion } from "./version-compare";

/** How often a background check is allowed to actually hit the network — cold start and every resume-from-background otherwise re-checks needlessly. */
const CHECK_INTERVAL_MS = 6 * 60 * 60 * 1000; // 6h

const LAST_CHECKED_KEY = "appUpdate_lastCheckedAt";
const DISMISSED_VERSION_KEY = "appUpdate_dismissedVersion";

/** Outcome of a single version comparison — shared by the silent background check and {@link useAppUpdateCheck}'s manual `checkNow`, so a caller showing immediate feedback (issue #86's "Vérifier les mises à jour" button) can switch on it directly instead of re-deriving it from `availableVersion`. */
export type AppUpdateCheckResult =
  | { status: "up-to-date" }
  | { status: "update-available"; version: string }
  | { status: "error" };

/**
 * Fetches the installed version (native `App.getInfo()`) and the latest
 * tagged release, and compares them — the one place this comparison
 * happens, shared by the background effect below and `checkNow`. No
 * throttling and no `Preferences` side effects of its own; callers decide
 * what to do with the result (persist a last-checked timestamp, filter
 * against a dismissed version, etc.).
 */
async function fetchLatestVersionResult(): Promise<AppUpdateCheckResult> {
  try {
    const { App } = await import("@capacitor/app");
    const [{ version: installedVersion }, { version: latestTag }] = await Promise.all([
      App.getInfo(),
      apiClient.getLatestMobileVersion(),
    ]);
    if (!latestTag || !isNewerVersion(installedVersion, latestTag)) {
      return { status: "up-to-date" };
    }
    return { status: "update-available", version: latestTag };
  } catch {
    return { status: "error" };
  }
}

/**
 * Detects whether a newer version of the Android app has been tagged than
 * the one currently installed, and offers a way to dismiss the notice for
 * that specific version — plus, since issue #86, a manual `checkNow` for a
 * "Vérifier les mises à jour" button (`AppSettingsPage`) that surfaces this
 * same check's result immediately instead of waiting on the silent
 * background timer.
 *
 * **Native only** — on the web, "the app" is just whatever the server is
 * currently serving; there is no "installed version" to compare against,
 * and reloading the page always gets the latest build. `Capacitor`/
 * `@capacitor/app`/`@capacitor/preferences` stay dynamically imported so
 * none of them enter the web bundle (same pattern as `main.tsx`'s own
 * `capacitor-token-store` bootstrap) — this hook is safe to call
 * unconditionally from `AppLayout`, which renders on both platforms.
 * `checkNow` itself still resolves on the web (`{ status: "error" }`,
 * nothing to check) rather than rejecting — callers gate the *button* that
 * would invoke it behind `Capacitor.isNativePlatform()` themselves
 * (`AppSettingsPage` does), so this never actually runs there in practice.
 *
 * No Play Store integration exists (this app isn't distributed there) —
 * Google's In-App Update API has no purchase here at all, so this is a
 * from-scratch check, not a wrapper around it.
 *
 * The background effect fails silently on any network/parsing error — it
 * must never surface an error banner or block anything, same posture as
 * `ThemeContext`'s own preferences fetch. `checkNow` is the opposite: it's
 * a direct response to an explicit click, so it returns its outcome
 * (including `"error"`) for the caller to actually display.
 */
export function useAppUpdateCheck(): {
  /** The newer version's tag (e.g. `"v1.4.2"`), or `null` when none is available (or none has been checked/parsed yet). */
  availableVersion: string | null;
  /** Hides the banner for `availableVersion` specifically — it reappears only once an even newer version ships, never just on the next app start. */
  dismiss: () => void;
  /**
   * Runs the check immediately, bypassing the background check's own
   * throttle — an explicit "Vérifier les mises à jour" click should always
   * hit the network, not silently no-op because a background check already
   * ran recently. Also bypasses the dismissed-version filter: re-asking is
   * itself a reason to show the result again, even for a version dismissed
   * earlier. Updates `availableVersion` on `"update-available"` so the
   * persistent {@link UpdateBanner} picks it up too, not just this call's
   * own return value.
   */
  checkNow: () => Promise<AppUpdateCheckResult>;
} {
  const [availableVersion, setAvailableVersion] = useState<string | null>(null);

  useEffect(() => {
    if (!Capacitor.isNativePlatform()) return;

    let cancelled = false;

    async function backgroundCheck() {
      try {
        const { Preferences } = await import("@capacitor/preferences");
        const { value: lastCheckedRaw } = await Preferences.get({ key: LAST_CHECKED_KEY });
        const lastCheckedAt = lastCheckedRaw ? Number(lastCheckedRaw) : 0;
        if (Date.now() - lastCheckedAt < CHECK_INTERVAL_MS) return;

        const result = await fetchLatestVersionResult();
        await Preferences.set({ key: LAST_CHECKED_KEY, value: String(Date.now()) });
        if (result.status !== "update-available") return;

        const { value: dismissedVersion } = await Preferences.get({ key: DISMISSED_VERSION_KEY });
        if (dismissedVersion === result.version) return;

        if (!cancelled) setAvailableVersion(result.version);
      } catch {
        // Silent — see this hook's own doc comment. Nothing to log to
        // (apps/web has no client-side LoggerService equivalent yet), and a
        // failed version check is never actionable for the visitor anyway.
      }
    }

    void backgroundCheck();

    // Re-check whenever the app comes back to the foreground — the listener
    // itself is cheap to keep registered, `backgroundCheck`'s own throttle
    // above is what actually keeps this from hitting the network every time.
    let removeListener: (() => void) | undefined;
    void import("@capacitor/app").then(({ App }) => {
      if (cancelled) return;
      App.addListener("appStateChange", ({ isActive }) => {
        if (isActive) void backgroundCheck();
      }).then((handle) => {
        removeListener = () => void handle.remove();
      });
    });

    return () => {
      cancelled = true;
      removeListener?.();
    };
  }, []);

  function dismiss() {
    if (!availableVersion) return;
    const dismissed = availableVersion;
    setAvailableVersion(null);
    void import("@capacitor/preferences").then(({ Preferences }) =>
      Preferences.set({ key: DISMISSED_VERSION_KEY, value: dismissed }),
    );
  }

  async function checkNow(): Promise<AppUpdateCheckResult> {
    try {
      const result = await fetchLatestVersionResult();
      if (result.status === "update-available") setAvailableVersion(result.version);
      // Best-effort — a manual check shouldn't make the *next* background
      // check fire again immediately after. Not awaited: nothing the
      // caller needs to wait on, and native-only anyway (a no-op import on
      // the web build would just resolve to nothing useful).
      void import("@capacitor/preferences").then(({ Preferences }) =>
        Preferences.set({ key: LAST_CHECKED_KEY, value: String(Date.now()) }),
      );
      return result;
    } catch {
      // `fetchLatestVersionResult` already turns every failure it can hit
      // into `{ status: "error" }` rather than throwing — this only exists
      // to keep `checkNow`'s own contract (a result, never a rejection)
      // true in case that ever changes, per the repo's async/try-catch
      // convention (see specs/dev-conventions.md).
      return { status: "error" };
    }
  }

  return { availableVersion, dismiss, checkNow };
}