"use client";

import { localeHeader, t } from "./i18n";
import type { Activity, Difficulty } from "./schemas";
import { API_KEY_HEADER, authHeaders } from "./settings";

export type GenerateInput = {
  images?: string[];
  text?: string;
  difficulty: Difficulty;
  count?: number;
  focus?: string;
  language?: string;
  mode?: "create" | "more";
  existing?: { title: string; types: string[]; count: number };
};

export type StreamedDeck = {
  title: string;
  subject?: string;
  summary?: string;
  language?: string;
  sourceText: string;
  difficulty: Difficulty;
  activities: Activity[];
};

export type GenerateProgress = {
  stage: "vision" | "generation" | "done";
  message: string;
};

type StreamEvent =
  | { type: "stage"; stage: "vision" | "generation" | "done"; message: string }
  | { type: "deck"; deck: StreamedDeck; meta: Record<string, unknown> }
  | { type: "error"; error: string; kind?: string };

export class ApiError extends Error {
  kind: string;
  constructor(message: string, kind = "unknown") {
    super(message);
    this.name = "ApiError";
    this.kind = kind;
  }
}

/**
 * Calls POST /api/generate and consumes the NDJSON progress stream.
 * Progress events arrive between the vision and generation steps.
 */
export async function generateDeck(
  input: GenerateInput,
  options: { onProgress?: (progress: GenerateProgress) => void; signal?: AbortSignal } = {},
): Promise<{ deck: StreamedDeck; meta: Record<string, unknown> }> {
  let response: Response;
  try {
    response = await fetch("/api/generate", {
      method: "POST",
      headers: { "Content-Type": "application/json", ...authHeaders(), ...localeHeader() },
      body: JSON.stringify(input),
      signal: options.signal,
    });
  } catch (error) {
    if (error instanceof Error && error.name === "AbortError") {
      throw new ApiError(t("api.cancelled"), "aborted");
    }
    throw new ApiError(t("api.unreachable"), "network");
  }

  if (!response.ok) {
    const body = (await response.json().catch(() => null)) as { error?: string; kind?: string } | null;
    throw new ApiError(body?.error ?? t("api.httpError", { status: response.status }), body?.kind);
  }
  if (!response.body) {
    throw new ApiError(t("api.empty"), "bad_response");
  }

  const reader = response.body.getReader();
  const decoder = new TextDecoder();
  let buffer = "";
  let deck: StreamedDeck | null = null;
  let meta: Record<string, unknown> = {};
  let streamError: ApiError | null = null;
  let sawActivity = false;

  const handleLine = (line: string) => {
    if (!line.trim()) return;
    let event: StreamEvent;
    try {
      event = JSON.parse(line) as StreamEvent;
    } catch {
      return;
    }
    if (event.type === "stage") {
      options.onProgress?.({ stage: event.stage, message: event.message });
    } else if (event.type === "deck") {
      deck = event.deck;
      meta = event.meta ?? {};
      sawActivity = true;
      options.onProgress?.({ stage: "done", message: t("api.almost") });
    } else if (event.type === "error") {
      streamError = new ApiError(event.error, event.kind);
    }
  };

  while (true) {
    const { done, value } = await reader.read();
    if (done) break;
    buffer += decoder.decode(value, { stream: true });
    let newline = buffer.indexOf("\n");
    while (newline !== -1) {
      handleLine(buffer.slice(0, newline));
      buffer = buffer.slice(newline + 1);
      newline = buffer.indexOf("\n");
    }
  }
  handleLine(buffer);

  if (streamError) throw streamError;
  if (!deck) {
    throw new ApiError(
      sawActivity
        ? t("api.incomplete")
        : t("api.noDeck"),
      "bad_response",
    );
  }

  const valid = (deck as StreamedDeck).activities?.filter(
    (activity) => activity && typeof activity.type === "string" && typeof activity.id === "string",
  );
  if (!valid || valid.length === 0) {
    throw new ApiError(t("api.noActivities"), "bad_response");
  }

  return { deck: { ...(deck as StreamedDeck), activities: valid }, meta };
}

export async function gradeAnswer(input: {
  question: string;
  referenceAnswer: string;
  keyPoints: string[];
  userAnswer: string;
  language?: string;
  signal?: AbortSignal;
}): Promise<{ correct: boolean; score: number; feedback: string; missing: string[] }> {
  let response: Response;
  try {
    response = await fetch("/api/grade", {
      method: "POST",
      headers: { "Content-Type": "application/json", ...authHeaders(), ...localeHeader() },
      body: JSON.stringify(input),
      signal: input.signal,
    });
  } catch (error) {
    if (error instanceof Error && error.name === "AbortError") {
      throw new ApiError(t("api.gradingCancelled"), "aborted");
    }
    throw new ApiError(t("api.unreachableShort"), "network");
  }

  const body = (await response.json().catch(() => null)) as
    | { correct: boolean; score: number; feedback: string; missing?: string[]; error?: string; kind?: string }
    | null;

  if (!response.ok || !body || body.error) {
    throw new ApiError(body?.error ?? t("api.gradingFailed", { status: response.status }), body?.kind);
  }

  return {
    correct: Boolean(body.correct),
    score: Math.max(0, Math.min(100, Math.round(body.score))),
    feedback: body.feedback,
    missing: body.missing ?? [],
  };
}

export type HealthModel = {
  configured: string;
  resolved: string;
  available: boolean | null;
  note?: string;
};

export type Health = {
  ok: boolean;
  reachable: boolean;
  mode: "local-daemon" | "direct-cloud";
  authMode: "user-key" | "server" | "local";
  needsKey: boolean;
  keyAccepted: boolean | null;
  baseUrl: string;
  hasApiKey: boolean;
  vision: HealthModel;
  text: HealthModel;
  latencyMs: number | null;
  modelCount: number | null;
  error: string | null;
  kind?: string;
  checkedAt: string;
};

export async function fetchHealth(): Promise<Health> {
  let response: Response;
  try {
    response = await fetch("/api/health", { cache: "no-store", headers: { ...authHeaders(), ...localeHeader() } });
  } catch {
    throw new ApiError(t("api.unreachableShort"), "network");
  }
  const body = (await response.json().catch(() => null)) as (Partial<Health> & { error?: string; kind?: string }) | null;
  if (!response.ok) {
    throw new ApiError(
      body?.error ?? t("api.healthFailed", { status: response.status }),
      body?.kind ?? "http",
    );
  }
  // Guard against anything that isn't a health payload (e.g. a proxy error
  // page) so consumers can rely on the shape.
  if (!body || typeof body !== "object" || !body.vision || !body.text) {
    throw new ApiError(t("api.healthUnexpected"), "bad_response");
  }
  return body as Health;
}

export type KeyCheck =
  | { result: "valid" }
  | { result: "invalid"; message: string }
  | { result: "offline"; message: string };

/**
 * Checks a *draft* key before it is saved anywhere, by asking our own
 * `/api/health` route (which performs a real one-token chat probe against
 * Ollama — model listings alone prove nothing). The key travels in the
 * request header for this single call and is never stored server-side.
 */
export async function verifyOllamaKey(apiKey: string): Promise<KeyCheck> {
  let response: Response;
  try {
    response = await fetch("/api/health", {
      cache: "no-store",
      headers: { [API_KEY_HEADER]: apiKey, ...localeHeader() },
    });
  } catch {
    return {
      result: "offline",
      message: t("api.unreachable"),
    };
  }

  const body = (await response.json().catch(() => null)) as Health | null;
  if (!response.ok || !body) {
    return {
      result: "offline",
      message: t("api.serverUnexpected"),
    };
  }

  if (body.keyAccepted === false) {
    return {
      result: "invalid",
      message:
        body.error ?? t("api.keyRejected"),
    };
  }
  if (body.keyAccepted === true) return { result: "valid" };

  if (!body.reachable) {
    return {
      result: "offline",
      message:
        body.error ?? t("api.ollamaUnreachable"),
    };
  }

  // Reachable, but the probe was inconclusive (usually a model-availability
  // matter rather than a bad key). Let the user in — Settings shows details.
  return { result: "valid" };
}