"use client";

export class ApiError extends Error {
  status: number;
  code: string;
  detail: unknown;
  constructor(status: number, message: string, code = "ERROR", detail?: unknown) {
    super(message);
    this.status = status;
    this.code = code;
    this.detail = detail;
  }
}

async function request<T>(method: string, path: string, body?: unknown, init?: RequestInit): Promise<T> {
  const headers: Record<string, string> = { Accept: "application/json" };
  if (method !== "GET" && method !== "HEAD") headers["X-LLM-CSRF"] = "1";
  if (body !== undefined) headers["Content-Type"] = "application/json";
  const res = await fetch(path, {
    method,
    headers,
    credentials: "same-origin",
    body: body !== undefined ? JSON.stringify(body) : undefined,
    ...init,
  });
  const text = await res.text();
  let data: unknown = null;
  try {
    data = text ? JSON.parse(text) : null;
  } catch {
    data = text;
  }
  if (!res.ok) {
    const err = (data as { error?: { message?: string; code?: string } })?.error;
    if (res.status === 401 && typeof window !== "undefined" && !location.pathname.startsWith("/login")) {
      location.href = `/login?next=${encodeURIComponent(location.pathname)}`;
    }
    throw new ApiError(res.status, err?.message || `HTTP ${res.status}`, err?.code || "ERROR", data);
  }
  return data as T;
}

export const api = {
  get: <T,>(path: string) => request<T>("GET", path),
  post: <T,>(path: string, body?: unknown) => request<T>("POST", path, body),
  put: <T,>(path: string, body?: unknown) => request<T>("PUT", path, body),
  patch: <T,>(path: string, body?: unknown) => request<T>("PATCH", path, body),
  del: <T,>(path: string, body?: unknown) => request<T>("DELETE", path, body),
};

/** Stream an OpenAI chat completion from the local API using the admin session. */
export async function* streamChat(body: Record<string, unknown>, signal?: AbortSignal): AsyncGenerator<Record<string, unknown>> {
  const res = await fetch("/v1/chat/completions", {
    method: "POST",
    headers: { "Content-Type": "application/json", "X-LLM-CSRF": "1" },
    credentials: "same-origin",
    body: JSON.stringify({ ...body, stream: true }),
    signal,
  });
  if (!res.ok || !res.body) {
    const t = await res.text();
    let msg = t;
    try {
      msg = JSON.parse(t).error?.message || t;
    } catch {}
    throw new ApiError(res.status, msg);
  }
  const reader = res.body.getReader();
  const dec = new TextDecoder();
  let buf = "";
  while (true) {
    const { value, done } = await reader.read();
    if (done) break;
    buf += dec.decode(value, { stream: true });
    let idx: number;
    while ((idx = buf.indexOf("\n\n")) >= 0) {
      const chunk = buf.slice(0, idx);
      buf = buf.slice(idx + 2);
      for (const line of chunk.split("\n")) {
        if (!line.startsWith("data: ")) continue;
        const payload = line.slice(6).trim();
        if (payload === "[DONE]") return;
        try {
          yield JSON.parse(payload);
        } catch {}
      }
    }
  }
}