import express from 'express';
import { loadModels } from './models.js';

const router = express.Router();
const REPLICATE_BASE = 'https://api.replicate.com/v1';

function buildInput(model, prompt, systemPrompt, extraParams) {
  const base = { ...model.defaultInput };

  // Inject system prompt if model supports it
  if (model.systemPromptParam && systemPrompt) {
    base[model.systemPromptParam] = systemPrompt;
  }

  // Apply extra params from user
  if (extraParams) {
    Object.assign(base, extraParams);
  }

  base.prompt = prompt;
  return base;
}

async function runPrediction(model, input, token) {
  const url = `${REPLICATE_BASE}/models/${model.owner}/${model.name}/predictions`;

  const response = await fetch(url, {
    method: 'POST',
    headers: {
      'Authorization': `Bearer ${token}`,
      'Content-Type': 'application/json',
      'Prefer': 'wait'
    },
    body: JSON.stringify({ input })
  });

  if (!response.ok) {
    const err = await response.json().catch(() => ({ detail: 'Unknown error' }));
    throw new Error(err.detail || `HTTP ${response.status}`);
  }

  return response.json();
}

function extractOutput(prediction) {
  const { output } = prediction;
  if (!output) return '';
  if (typeof output === 'string') return output;
  if (Array.isArray(output)) return output.join('');
  if (typeof output === 'object') return JSON.stringify(output, null, 2);
  return String(output);
}

// POST /api/chat - single model call
router.post('/', async (req, res) => {
  const token = process.env.REPLICATE_API_TOKEN;
  if (!token) return res.status(400).json({ error: 'REPLICATE_API_TOKEN not configured' });

  const { modelId, prompt, systemPrompt, searchContext, extraParams } = req.body;
  if (!modelId || !prompt) return res.status(400).json({ error: 'modelId and prompt are required' });

  try {
    const models = await loadModels();
    const model = models.find(m => m.id === modelId);
    if (!model) return res.status(404).json({ error: `Model not found: ${modelId}` });

    const finalPrompt = searchContext ? `${searchContext}\n\n${prompt}` : prompt;
    const input = buildInput(model, finalPrompt, systemPrompt, extraParams);

    const prediction = await runPrediction(model, input, token);
    const content = extractOutput(prediction);

    res.json({
      id: prediction.id,
      modelId: model.id,
      modelTag: model.tag,
      modelName: model.displayName,
      content,
      status: prediction.status,
      metrics: prediction.metrics,
      urls: prediction.urls
    });
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

// POST /api/chat/multi - send to multiple models in parallel
router.post('/multi', async (req, res) => {
  const token = process.env.REPLICATE_API_TOKEN;
  if (!token) return res.status(400).json({ error: 'REPLICATE_API_TOKEN not configured' });

  const { modelIds, prompt, systemPrompt, searchContext, extraParams } = req.body;
  if (!modelIds?.length || !prompt) return res.status(400).json({ error: 'modelIds and prompt are required' });

  try {
    const models = await loadModels();

    const tasks = modelIds.map(async (modelId) => {
      const model = models.find(m => m.id === modelId);
      if (!model) return { modelId, error: 'Model not found' };

      try {
        const finalPrompt = searchContext ? `${searchContext}\n\n${prompt}` : prompt;
        const input = buildInput(model, finalPrompt, systemPrompt, extraParams);
        const prediction = await runPrediction(model, input, token);
        const content = extractOutput(prediction);
        return {
          id: prediction.id,
          modelId: model.id,
          modelTag: model.tag,
          modelName: model.displayName,
          content,
          status: prediction.status,
          metrics: prediction.metrics
        };
      } catch (err) {
        return { modelId, modelTag: model.tag, modelName: model.displayName, error: err.message };
      }
    });

    const results = await Promise.all(tasks);
    res.json({ results });
  } catch (err) {
    res.status(500).json({ error: err.message });
  }
});

export { router as chatRouter };