import { GoogleGenerativeAI } from '@google/generative-ai';
import { env } from '$env/dynamic/private';
import {
  RECIPE_EXTRACTION_SYSTEM_PROMPT,
  RECIPE_EXTRACTION_USER_PROMPT,
  GEMINI_RESPONSE_SCHEMA,
  extractionResponseSchema,
  type ExtractionResponse
} from './recipe-extraction-prompt';

export type GeminiErrorCode =
  | 'AI_NOT_CONFIGURED'
  | 'AI_RATE_LIMITED'
  | 'AI_TIMEOUT'
  | 'AI_FAILED';

export class GeminiError extends Error {
  constructor(
    public readonly code: GeminiErrorCode,
    message: string
  ) {
    super(message);
    this.name = 'GeminiError';
  }
}

function getStatus(err: unknown): number | undefined {
  if (err && typeof err === 'object' && 'status' in err) {
    const s = (err as { status?: unknown }).status;
    if (typeof s === 'number') return s;
  }
  return undefined;
}

function getCfg(): { apiKey: string; model: string; timeoutMs: number } {
  const apiKey = env.GEMINI_API_KEY ?? process.env.GEMINI_API_KEY ?? '';
  const model =
    env.GEMINI_MODEL ?? process.env.GEMINI_MODEL ?? 'gemini-2.5-flash';
  const rawTimeout =
    env.GEMINI_TIMEOUT_MS ?? process.env.GEMINI_TIMEOUT_MS ?? '20000';
  const timeoutMs = Number(rawTimeout) || 20000;
  return { apiKey, model, timeoutMs };
}

async function withTimeout<T>(promise: Promise<T>, ms: number): Promise<T> {
  return new Promise((resolve, reject) => {
    const timer = setTimeout(
      () => reject(new GeminiError('AI_TIMEOUT', `Gemini timeout after ${ms} ms`)),
      ms
    );
    promise.then(
      (v) => {
        clearTimeout(timer);
        resolve(v);
      },
      (e) => {
        clearTimeout(timer);
        reject(e);
      }
    );
  });
}

async function callGemini(
  imageBuffer: Buffer,
  mimeType: string,
  appendUserNote?: string
): Promise<ExtractionResponse> {
  const { apiKey, model: modelId, timeoutMs } = getCfg();
  if (!apiKey) {
    throw new GeminiError('AI_NOT_CONFIGURED', 'GEMINI_API_KEY is not set');
  }

  const client = new GoogleGenerativeAI(apiKey);
  const model = client.getGenerativeModel({
    model: modelId,
    systemInstruction: RECIPE_EXTRACTION_SYSTEM_PROMPT,
    generationConfig: {
      temperature: 0.1,
      responseMimeType: 'application/json',
      // eslint-disable-next-line @typescript-eslint/no-explicit-any
      responseSchema: GEMINI_RESPONSE_SCHEMA as any
    }
  });

  const parts: Array<
    { inlineData: { data: string; mimeType: string } } | { text: string }
  > = [
    { inlineData: { data: imageBuffer.toString('base64'), mimeType } },
    { text: RECIPE_EXTRACTION_USER_PROMPT }
  ];
  if (appendUserNote) parts.push({ text: appendUserNote });

  const result = await withTimeout(
    model.generateContent({ contents: [{ role: 'user', parts }] }),
    timeoutMs
  );
  const text = result.response.text();
  let parsed: unknown;
  try {
    parsed = JSON.parse(text);
  } catch {
    throw new GeminiError('AI_FAILED', 'Gemini returned non-JSON output');
  }
  const validated = extractionResponseSchema.safeParse(parsed);
  if (!validated.success) {
    throw new GeminiError(
      'AI_FAILED',
      `Schema validation failed: ${validated.error.message}`
    );
  }
  return validated.data;
}

// Public entry: one retry on recoverable failures (5xx or schema-invalid),
// no retry on 429, AI_TIMEOUT, or config errors.
export async function extractRecipeFromImage(
  imageBuffer: Buffer,
  mimeType: string
): Promise<ExtractionResponse> {
  let firstMsg: string | null = null;
  try {
    return await callGemini(imageBuffer, mimeType);
  } catch (e) {
    if (e instanceof GeminiError && e.code === 'AI_NOT_CONFIGURED') throw e;
    if (e instanceof GeminiError && e.code === 'AI_TIMEOUT') throw e;

    const status = getStatus(e);
    if (status === 429) throw new GeminiError('AI_RATE_LIMITED', 'Gemini rate limit');

    const recoverable =
      (e instanceof GeminiError && e.code === 'AI_FAILED') ||
      (status !== undefined && status >= 500);
    if (!recoverable) {
      throw e instanceof GeminiError
        ? e
        : new GeminiError('AI_FAILED', String(e));
    }

    firstMsg = e instanceof Error ? e.message : String(e);
    console.warn(`[gemini-client] first attempt failed, retrying: ${firstMsg}`);

    await new Promise((r) => setTimeout(r, 500));
    try {
      return await callGemini(
        imageBuffer,
        mimeType,
        'Dein vorheriger Output war ungültig. Bitte antworte ausschließlich mit JSON gemäß Schema.'
      );
    } catch (retryErr) {
      const retryMsg = retryErr instanceof Error ? retryErr.message : String(retryErr);
      if (retryErr instanceof GeminiError) {
        if (retryErr.code === 'AI_FAILED') {
          throw new GeminiError(
            'AI_FAILED',
            `retry failed: ${retryMsg} (first: ${firstMsg})`
          );
        }
        throw retryErr;
      }
      const retryStatus = getStatus(retryErr);
      if (retryStatus === 429)
        throw new GeminiError('AI_RATE_LIMITED', 'Gemini rate limit on retry');
      throw new GeminiError(
        'AI_FAILED',
        `retry failed: ${retryMsg} (first: ${firstMsg})`
      );
    }
  }
}