export type Tone = "Neutral" | "Casual" | "Formal" | "Academic";
export type StrengthLabel = "Light" | "Normal" | "Heavy";

export const TONES: Tone[] = ["Neutral", "Casual", "Formal", "Academic"];
export const STRENGTHS: StrengthLabel[] = ["Light", "Normal", "Heavy"];

export const STRENGTH_MAP: Record<StrengthLabel, number> = {
  Light: 0,
  Normal: 1,
  Heavy: 2,
};

export type RewriteMeta = {
  input_words: number;
  output_words: number;
  seconds: number;
  lexical_refined: number;
  ml_polish_requested: boolean;
  tone: string;
  strength: number;
};

export type AccountInfo = {
  email: string | null;
  display_name: string | null;
  role: string;
  plan: {
    id: string;
    name: string;
    daily_rewrites: number;
    max_words_per_request: number;
    daily_word_cap: number;
    price_inr_monthly: number;
  };
  usage: {
    date: string;
    rewrite_count: number;
    word_count: number;
    remaining_rewrites: number;
    remaining_words: number;
  };
};

export type RewriteResponse = {
  rewrite: string;
  meta: RewriteMeta;
  account?: AccountInfo | null;
};

export type ApiError = Error & { status?: number; code?: string };

function detailMessage(detail: unknown, fallback: string): string {
  if (typeof detail === "string") return detail;
  if (Array.isArray(detail)) {
    return detail
      .map((d) => (typeof d === "object" && d && "msg" in d ? String(d.msg) : String(d)))
      .join(" ");
  }
  return fallback;
}

export async function rewriteText(
  payload: {
    text: string;
    tone: Tone;
    strength: number;
    preserve_length: boolean;
    ml_polish?: boolean;
  },
  accessToken?: string | null,
): Promise<RewriteResponse> {
  const headers: Record<string, string> = { "Content-Type": "application/json" };
  if (accessToken) headers.Authorization = `Bearer ${accessToken}`;

  const res = await fetch("/v1/rewrite", {
    method: "POST",
    headers,
    body: JSON.stringify(payload),
  });
  if (!res.ok) {
    let detail: unknown = "Rewrite failed.";
    try {
      const data = await res.json();
      detail = data.detail ?? detail;
    } catch {
      /* ignore */
    }
    const err = new Error(detailMessage(detail, "Rewrite failed.")) as ApiError;
    err.status = res.status;
    if (res.status === 401 || res.status === 429 || res.status === 413) {
      err.code = "limit";
    }
    throw err;
  }
  return res.json();
}

export type GrammarIssue = {
  id: string;
  start: number;
  end: number;
  message: string;
  suggestion: string | null;
  category: string;
};

export type GrammarResponse = {
  issues: GrammarIssue[];
  input_words: number;
  engine: string;
  language?: string;
  note?: string;
};

export async function checkGrammar(
  text: string,
  options?: { language?: string; accessToken?: string | null },
): Promise<GrammarResponse> {
  const headers: Record<string, string> = { "Content-Type": "application/json" };
  const accessToken = options?.accessToken;
  if (accessToken) headers.Authorization = `Bearer ${accessToken}`;

  let res: Response;
  try {
    res = await fetch("/v1/grammar", {
      method: "POST",
      headers,
      body: JSON.stringify({
        text,
        language: options?.language || "en-US",
      }),
    });
  } catch {
    const err = new Error(
      "Could not reach the grammar API. Is the ZuZu server running?",
    ) as ApiError;
    err.code = "network";
    throw err;
  }

  if (!res.ok) {
    let detail: unknown = `Grammar check failed (HTTP ${res.status}).`;
    try {
      const data = await res.json();
      detail = data.detail ?? detail;
    } catch {
      /* non-JSON body — often means the Space/app build is missing /v1/grammar */
      if (res.status === 404) {
        detail =
          "Grammar API not found (404). Restart/redeploy the app so /v1/grammar is available.";
      }
    }
    const err = new Error(detailMessage(detail, `Grammar check failed (HTTP ${res.status}).`)) as ApiError;
    err.status = res.status;
    throw err;
  }
  return res.json();
}

export async function fetchMe(accessToken?: string | null): Promise<{
  auth_enabled: boolean;
  account: AccountInfo | null;
}> {
  const headers: Record<string, string> = {};
  if (accessToken) headers.Authorization = `Bearer ${accessToken}`;
  const res = await fetch("/v1/me", { headers });
  if (!res.ok) {
    throw new Error("Could not load account.");
  }
  return res.json();
}