import type {
  CurveState,
  GpuInfo,
  MonitoringSample,
  SnapshotInfo,
  LimitsState,
  ProfileData,
  FanState,
  FanPoint,
  DashboardInfo,
  ProcessListResponse,
} from "../types.js";

export class ApiError extends Error {
  status: number;
  constructor(status: number, message: string) {
    super(message);
    this.status = status;
  }
}

// Global handler invoked when any API call returns 401 (not logged in, or the
// 24-hour session expired). The app uses it to re-show the login screen.
let unauthorizedHandler: (() => void) | null = null;
export function onUnauthorized(handler: (() => void) | null): void {
  unauthorizedHandler = handler;
}

function handleUnauthorized(res: Response): void {
  if (res.status === 401 && unauthorizedHandler) {
    unauthorizedHandler();
  }
}

async function get<T>(path: string, gpuIndex?: number): Promise<T> {
  const url =
    gpuIndex !== undefined
      ? `/api${path}?gpu_index=${gpuIndex}`
      : `/api${path}`;
  const res = await fetch(url);
  if (!res.ok) {
    handleUnauthorized(res);
    const text = await res.text().catch(() => res.statusText);
    throw new ApiError(res.status, `GET ${url}: ${res.status} — ${text}`);
  }
  return res.json() as Promise<T>;
}

async function post<T = void>(
  path: string,
  body?: unknown,
  gpuIndex?: number,
): Promise<T> {
  const url =
    gpuIndex !== undefined
      ? `/api${path}?gpu_index=${gpuIndex}`
      : `/api${path}`;
  const res = await fetch(url, {
    method: "POST",
    headers: body != null ? { "Content-Type": "application/json" } : {},
    body: body != null ? JSON.stringify(body) : undefined,
  });
  if (!res.ok) {
    handleUnauthorized(res);
    const text = await res.text().catch(() => res.statusText);
    throw new ApiError(res.status, `POST ${url}: ${res.status} — ${text}`);
  }
  // Some endpoints return no body (204)
  const ct = res.headers.get("content-type") ?? "";
  if (ct.includes("application/json")) return res.json() as Promise<T>;
  // SAFETY: non-JSON responses (e.g. 204) carry no body; callers of these
  // endpoints use T = void and ignore the result, so undefined is a valid T.
  return undefined as unknown as T;
}

async function del<T = void>(path: string, gpuIndex?: number): Promise<T> {
  const url =
    gpuIndex !== undefined
      ? `/api${path}?gpu_index=${gpuIndex}`
      : `/api${path}`;
  const res = await fetch(url, { method: "DELETE" });
  if (!res.ok) {
    handleUnauthorized(res);
    const text = await res.text().catch(() => res.statusText);
    throw new ApiError(res.status, `DELETE ${url}: ${res.status} — ${text}`);
  }
  const ct = res.headers.get("content-type") ?? "";
  if (ct.includes("application/json")) return res.json() as Promise<T>;
  // SAFETY: non-JSON responses (e.g. 204) carry no body; callers of these
  // endpoints use T = void and ignore the result, so undefined is a valid T.
  return undefined as unknown as T;
}

export interface AuthStatus {
  auth_required: boolean;
  authenticated: boolean;
  username: string | null;
  expires_at: number | null;
}

export const api = {
  /** Auth */
  authStatus: () => get<AuthStatus>("/auth/status"),
  login: (username: string, password: string) =>
    post<{ ok: boolean; username: string; expires_at: number; token: string }>(
      "/auth/login",
      { username, password },
    ),
  logout: () => post("/auth/logout"),

  gpus: () => get<GpuInfo[]>("/gpus"),
  gpu: (gpuIndex: number) => get<GpuInfo>("/gpu", gpuIndex),
  dashboard: (gpuIndex: number) => get<DashboardInfo>("/dashboard", gpuIndex),
  curve: (gpuIndex: number) => get<CurveState>("/curve", gpuIndex),
  ranges: (gpuIndex: number) =>
    get<Record<string, { min_khz: number; max_khz: number }>>(
      "/ranges",
      gpuIndex,
    ),
  voltage: (gpuIndex: number) =>
    get<{ voltage_uv: number; voltage_mv: number }>("/voltage", gpuIndex),
  monitor: (gpuIndex: number) => get<MonitoringSample>("/monitor", gpuIndex),
  processes: (gpuIndex: number) =>
    get<ProcessListResponse>("/processes", gpuIndex),
  killProcess: (
    pid: number,
    signal: "TERM" | "KILL" = "TERM",
    parent = false,
  ) =>
    post<{ ok: boolean; pid: number; signal: string; parent: boolean }>(
      "/processes/kill",
      { pid, signal, parent },
    ),
  snapshots: (gpuIndex: number) => get<SnapshotInfo[]>("/snapshots", gpuIndex),

  /** Write per-point frequency deltas. deltas: { pointIndex: deltaKhz } */
  writeDeltas: (deltas: Record<number, number>, gpuIndex: number) =>
    post<{ ok: boolean; freq_warnings?: string[] }>(
      "/curve/write",
      { deltas },
      gpuIndex,
    ),

  /** Reset all frequency deltas to zero. */
  resetCurve: (gpuIndex: number) => post("/curve/reset", undefined, gpuIndex),

  /** Get performance limits mapping */
  limits: (gpuIndex: number) => get<LimitsState>("/limits", gpuIndex),

  /** Set performance limits */
  updateLimits: (updates: Partial<LimitsState>, gpuIndex: number) =>
    post("/limits", updates, gpuIndex),

  /** Reset power limit and memory offset to hardware defaults */
  resetLimits: (gpuIndex: number) => post("/limits/reset", undefined, gpuIndex),

  /** Profile Management */
  profiles: (gpuIndex: number) =>
    get<{
      profiles: ProfileData[];
      active: string | null;
      auto_load: string | null;
    }>("/profiles", gpuIndex),
  saveProfile: (name: string, gpuIndex: number) =>
    post<{ ok: boolean; filepath: string }>("/profiles", { name }, gpuIndex),
  applyProfile: (name: string, gpuIndex: number) =>
    post(`/profiles/${encodeURIComponent(name)}/apply`, undefined, gpuIndex),
  deleteProfile: (name: string) => del(`/profiles/${encodeURIComponent(name)}`),
  renameProfile: (oldName: string, newName: string) =>
    post(`/profiles/${encodeURIComponent(oldName)}/rename`, {
      new_name: newName,
    }),

  /** Server config */
  setAutoLoadProfile: (name: string | null, gpuIndex: number) =>
    post<{ ok: boolean; auto_load_profile: string | null }>("/config", {
      auto_load_profile: name,
      gpu_index: gpuIndex,
    }),

  /** Fan control */
  fans: (gpuIndex: number) => get<FanState>("/fans", gpuIndex),
  updateFans: (curve: FanPoint[], gpuIndex: number, fans?: number[] | null) =>
    post("/fans", { curve, fans: fans ?? null }, gpuIndex),
  resetFans: (gpuIndex: number) => post("/fans/reset", undefined, gpuIndex),
  setFanSpeed: (fanPct: number, gpuIndex: number, fan?: number | null) =>
    post("/fans/speed", { fan_pct: fanPct, fan: fan ?? null }, gpuIndex),
};