import type { NextApiRequest, NextApiResponse } from "next";
import { VALID_MODELS, validateModel, validateApiKey } from "../../lib/config";
import { getCachedGeneration, setCachedGeneration } from "../../lib/cache";
import type { GenerateRequestBody } from "../../lib/types";

export default async function handler(req: NextApiRequest, res: NextApiResponse) {
  res.setHeader("Content-Type", "application/json");

  if (req.method !== "POST") {
    return res.status(405).json({ error: "Method not allowed" });
  }

  const hfApiKey = process.env.HF_API_KEY;
  if (!validateApiKey(hfApiKey)) {
    return res.status(500).json({ error: "Invalid or missing Hugging Face API key" });
  }

  const model = VALID_MODELS.ACE_STEP;
  if (!validateModel(model)) {
    return res.status(500).json({ error: "Invalid model configuration" });
  }

  let body: GenerateRequestBody;
  try {
    body = req.body as GenerateRequestBody;
  } catch {
    return res.status(400).json({ error: "Invalid JSON body" });
  }

  const {
    stylePrompt,
    lyricPrompt = "",
    voice = "Random",
    durationSeconds,
  } = body;

  if (!stylePrompt || typeof stylePrompt !== "string") {
    return res.status(400).json({ error: "stylePrompt is required" });
  }

  const duration =
    typeof durationSeconds === "number"
      ? Math.min(240, Math.max(30, durationSeconds))
      : Math.floor(Math.random() * (240 - 30 + 1)) + 30;

  const cacheKey = JSON.stringify({ stylePrompt, lyricPrompt, voice, duration });
  const cached = getCachedGeneration(cacheKey);
  if (cached) {
    return res.status(200).json({ cached: true, ...cached });
  }

  try {
    const payload = {
      inputs: {
        text: `${stylePrompt}\n${lyricPrompt}`,
        voice,
        duration,
      },
    };

    const hfUrl = `https://api-inference.huggingface.co/models/${encodeURIComponent(model)}`;

    const response = await fetch(hfUrl, {
      method: "POST",
      headers: {
        Authorization: `Bearer ${hfApiKey}`,
        "Content-Type": "application/json",
        Accept: "application/json",
      },
      body: JSON.stringify(payload),
    });

    if (!response.ok) {
      const errText = await response.text().catch(() => "");
      return res.status(response.status).json({
        error: "Model request failed",
        details: errText || response.statusText,
      });
    }

    const result = await response.json();

    const data = {
      cached: false,
      model,
      duration,
      voice,
      result,
    };

    setCachedGeneration(cacheKey, data);

    return res.status(200).json(data);
  } catch (e: any) {
    return res.status(500).json({
      error: "Unexpected error during generation",
      details: e?.message ?? "Unknown error",
    });
  }
}