// The shared HTTP machinery behind every api.* domain module: the fetch wrapper (`req`), the typed
// error, structured-error localization, the connectivity toast, the per-tab active-account plumbing,
// and the keepalive beacon. Domain modules import from here; nothing here imports a domain module,
// so the runtime graph is a clean barrel → domain → core with no cycles.
import { notify, remove } from "../notifications";
import i18n from "../../i18n";
import { reportError } from "../errorDialog";
import { activeAccountId, ACTIVE_ACCOUNT_KEY } from "../storage";

export class HttpError extends Error {
  status: number;
  detail?: string; // server-provided reason (FastAPI's `detail`), when present
  detailData?: unknown; // structured detail ({ code, reason, ... }) when the server sent an object
  constructor(status: number, detail?: string, detailData?: unknown) {
    super(detail || `HTTP ${status}`);
    this.status = status;
    this.detail = detail;
    this.detailData = detailData;
  }
}

// Localize a STRUCTURED server error ({ code, reason, ... }) into the user's language. FastAPI
// usually returns a plain string `detail`, but some routes (e.g. download quota/edit) return a
// structured object with an i18n reason key + numbers so HU/DE users don't get hardcoded English
// with a dot-decimal separator. Falls back to a generic message for unknown shapes.
function localizeDetail(d: unknown): string {
  const t = i18n.t.bind(i18n);
  // FastAPI request-validation errors: `detail` is an ARRAY of { loc, msg, type }. The UI sends
  // well-formed requests, so this only fires on genuinely malformed input. The per-field `msg` and
  // `loc` field names are English, snake_case internal tokens — surface a clean, fully localized
  // "check your input" message rather than leaking them into a translated sentence.
  if (Array.isArray(d)) return t("errors.validation");
  const o = d as { code?: string; reason?: string; limit?: number } | null | undefined;
  if (o?.code === "quota") {
    if (o.reason === "max_bytes") {
      const gb = new Intl.NumberFormat(i18n.language, { maximumFractionDigits: 1 }).format(
        (o.limit || 0) / 1_073_741_824,
      );
      return t("downloads.errors.quota.max_bytes", { size: gb });
    }
    if (o.reason === "max_jobs") return t("downloads.errors.quota.max_jobs", { limit: o.limit });
    return t("downloads.errors.quota.generic");
  }
  if (o?.code === "edit")
    return t(`downloads.errors.edit.${o.reason}`, t("downloads.errors.edit.generic"));
  return t("errors.generic");
}

// A single, self-resolving "connection lost" status: while the server is unreachable we
// show one sticky, transient (non-persisted) notice; the moment any request reaches the
// server again we remove it. This makes good on its "clears once it's back" copy and keeps
// bursts of concurrent failures from stacking up — there's only ever one live handle.
let connectivityNotifId: number | null = null;
function markConnectivityLost(): void {
  if (connectivityNotifId !== null) return;
  connectivityNotifId = notify({
    level: "error",
    title: i18n.t("errors.offline.title"),
    message: i18n.t("errors.offline.body"),
    transient: true,
  });
}
function markConnectivityRestored(): void {
  if (connectivityNotifId === null) return;
  remove(connectivityNotifId);
  connectivityNotifId = null;
}

// Gateway statuses that mean "the upstream connection failed", not "the app rejected the
// request" — typically a reverse-proxy ↔ uvicorn keepalive connection reset before the
// request was processed. Safe to retry an idempotent call once on a fresh connection.
const RETRIABLE_GATEWAY = new Set([502, 503, 504]);
const delay = (ms: number) => new Promise((res) => window.setTimeout(res, ms));

// `idempotent`: may this request be replayed after a transient gateway/network failure?
// GETs always can; non-GET callers opt in (e.g. the player's progress/state writes, which
// are safe to repeat). Used to recover from the keepalive race without surfacing a 502.
export interface ReqConfig {
  idempotent?: boolean;
  // Suppress the global error modal for 4xx/5xx so the caller can show the error inline
  // (used by the auth forms — a wrong password shouldn't pop a blocking dialog).
  quiet?: boolean;
}

// Set by the app shell. Invoked whenever any request returns 401 so a session that ended
// server-side (account suspended/deleted while the tab was open) can drop the user to the login
// page. The handler itself guards against firing when we were never signed in, so it's safe to
// call for every 401. (The bootstrap /api/me probe no longer 401s — it returns 200 with a null
// user when logged out — but other protected endpoints still do.)
let onUnauthorized: (() => void) | null = null;
export function setUnauthorizedHandler(fn: (() => void) | null): void {
  onUnauthorized = fn;
}

// Headers for install-wizard calls: the one-time setup token plus the JSON content type (req
// replaces — not merges — its default headers when opts.headers is given, so include both).
export const setupHeaders = (token: string) => ({
  "Content-Type": "application/json",
  "X-Setup-Token": token,
});

// --- Per-tab active account --------------------------------------------------------------
// The signed session cookie is the browser's account "wallet"; which account a given TAB acts
// as is chosen here and sent per-request, so two tabs can run two accounts at once. Stored in
// sessionStorage (per-tab, survives F5, not shared across tabs). null = use the session default.
// The storage key + reader live in storage.ts (so its per-account helpers can use them too).
const ACTIVE_ACCOUNT_HEADER = "X-Siftlode-Account";

export const getActiveAccount = activeAccountId;

// Fire-and-forget POST that survives page unload (keepalive) — shared by the resume-position
// beacons (YT + Plex players). A normal fetch is cancelled on unload and React effect cleanup
// doesn't run on a full reload, so without keepalive the last position (esp. right after a seek)
// would be lost.
export function beacon(url: string, body: Record<string, unknown>): void {
  const active = getActiveAccount();
  try {
    void fetch(url, {
      method: "POST",
      keepalive: true,
      credentials: "include",
      headers: {
        "Content-Type": "application/json",
        ...(active != null ? { [ACTIVE_ACCOUNT_HEADER]: String(active) } : {}),
      },
      body: JSON.stringify(body),
    }).catch(() => {});
  } catch {
    /* ignore */
  }
}

export function setActiveAccount(id: number): void {
  try {
    sessionStorage.setItem(ACTIVE_ACCOUNT_KEY, String(id));
  } catch {
    /* ignore */
  }
}
export function clearActiveAccount(): void {
  try {
    sessionStorage.removeItem(ACTIVE_ACCOUNT_KEY);
  } catch {
    /* ignore */
  }
}

export async function req<T = unknown>(
  url: string,
  opts: RequestInit = {},
  cfg: ReqConfig = {},
): Promise<T> {
  const method = opts.method ?? "GET";
  const canRetry = cfg.idempotent ?? method === "GET";
  let attempt = 0;

  for (;;) {
    let r: Response;
    try {
      const active = getActiveAccount();
      r = await fetch(url, {
        credentials: "include",
        headers: {
          "Content-Type": "application/json",
          // Per-tab identity override (only setup calls pass their own headers, and those are
          // pre-auth, so this is safe to put in the defaults that `...opts` may replace).
          ...(active != null ? { [ACTIVE_ACCOUNT_HEADER]: String(active) } : {}),
        },
        ...opts,
      });
    } catch (e) {
      // Network-level failure (incl. a keepalive connection reset surfacing as a TypeError).
      if (canRetry && attempt === 0) {
        attempt++;
        await delay(250);
        continue;
      }
      markConnectivityLost();
      throw e;
    }

    // A gateway error usually means the upstream connection was reset before our request
    // was processed — retry idempotent calls once on a fresh connection before surfacing it.
    if (!r.ok && canRetry && attempt === 0 && RETRIABLE_GATEWAY.has(r.status)) {
      attempt++;
      await delay(250);
      continue;
    }

    // The server answered (anything that isn't a gateway error means it's reachable) —
    // clear a standing "connection lost" status if one is showing.
    if (!RETRIABLE_GATEWAY.has(r.status)) markConnectivityRestored();

    if (!r.ok) {
      // Capture the server's reason (FastAPI returns `{ detail }`) so callers can react.
      let detail: string | undefined;
      let detailData: unknown;
      try {
        const body = await r.json();
        if (body && typeof body.detail === "string") detail = body.detail;
        else if (body && body.detail && typeof body.detail === "object") {
          detailData = body.detail;
          detail = localizeDetail(body.detail); // structured error → localized message
        }
      } catch {
        /* no JSON body */
      }
      // 502/503/504 mean the gateway couldn't reach the app (restarting / connection reset),
      // not a request the app refused — treat them like a network blip with the soft,
      // self-clearing toast rather than a blocking modal the user must acknowledge.
      // A genuine 500 (real fault, carries a JSON detail) still gets the modal, as do
      // 400/409/422 (validation/conflict). 401/403/404 are caller-handled control flow.
      if (RETRIABLE_GATEWAY.has(r.status)) {
        markConnectivityLost();
      } else if (r.status === 401) {
        // Session ended server-side (e.g. the account was suspended or deleted mid-visit). Let the
        // app shell decide what to do (drop to the login page if we were signed in). Not a modal.
        onUnauthorized?.();
      } else if (cfg.quiet) {
        /* caller handles the error inline — no global modal */
      } else if (r.status >= 500) {
        reportError(detail || `${i18n.t("errors.server")} (${r.status})`);
      } else if (r.status === 400 || r.status === 409 || r.status === 422) {
        reportError(detail);
      }
      throw new HttpError(r.status, detail, detailData);
    }
    // The single audited cast in this layer: the server contract is asserted here, once, so
    // every typed api.* method (T comes from its declared return type) is checked from here up.
    return (r.status === 204 ? null : await r.json()) as T;
  }
}
