// functions/api/chat.js
// Cloudflare Pages Function for chat assistant.
//
// ⚠️ PASTE YOUR ANTHROPIC API KEY ON THE LINE BELOW (replace the placeholder text):

const ANTHROPIC_API_KEY = "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";

// ⚠️ Repo MUST stay private. Anyone with read access to this file can use your key.

const corsHeaders = {
  'Access-Control-Allow-Origin': '*',
  'Access-Control-Allow-Methods': 'POST, OPTIONS',
  'Access-Control-Allow-Headers': 'Content-Type',
};

// Simple in-memory rate limiter
const rateLimitStore = new Map();
const RATE_LIMIT_MAX = 30;
const RATE_LIMIT_WINDOW_MS = 60 * 60 * 1000;

function checkRateLimit(ip) {
  const now = Date.now();
  const record = rateLimitStore.get(ip);
  if (!record || now - record.start > RATE_LIMIT_WINDOW_MS) {
    rateLimitStore.set(ip, { count: 1, start: now });
    return { allowed: true };
  }
  if (record.count >= RATE_LIMIT_MAX) {
    const resetIn = Math.ceil((record.start + RATE_LIMIT_WINDOW_MS - now) / 60000);
    return { allowed: false, resetIn };
  }
  record.count++;
  return { allowed: true };
}

export async function onRequest(context) {
  const { request } = context;

  if (request.method === 'OPTIONS') {
    return new Response(null, { status: 204, headers: corsHeaders });
  }

  if (request.method !== 'POST') {
    return new Response(
      JSON.stringify({ error: 'Method not allowed' }),
      { status: 405, headers: { ...corsHeaders, 'Content-Type': 'application/json' } }
    );
  }

  const ip =
    request.headers.get('cf-connecting-ip') ||
    request.headers.get('x-forwarded-for')?.split(',')[0] ||
    'unknown';

  const limit = checkRateLimit(ip);
  if (!limit.allowed) {
    return new Response(
      JSON.stringify({
        error: `Whoa, slow down! You've hit the message limit. Try again in ${limit.resetIn} minute(s).`,
      }),
      { status: 429, headers: { ...corsHeaders, 'Content-Type': 'application/json' } }
    );
  }

  let body;
  try {
    body = await request.json();
  } catch {
    return new Response(
      JSON.stringify({ error: 'Invalid JSON' }),
      { status: 400, headers: { ...corsHeaders, 'Content-Type': 'application/json' } }
    );
  }

  const { messages, system, model, max_tokens } = body;

  if (!Array.isArray(messages) || messages.length === 0) {
    return new Response(
      JSON.stringify({ error: 'Missing messages' }),
      { status: 400, headers: { ...corsHeaders, 'Content-Type': 'application/json' } }
    );
  }

  const trimmedMessages = messages.slice(-20);

  if (!ANTHROPIC_API_KEY || ANTHROPIC_API_KEY === "PASTE_YOUR_KEY_HERE") {
    return new Response(
      JSON.stringify({ error: 'Server not configured. API key not set in chat.js.' }),
      { status: 500, headers: { ...corsHeaders, 'Content-Type': 'application/json' } }
    );
  }

  try {
    const anthropicRes = await fetch('https://api.anthropic.com/v1/messages', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
        'x-api-key': ANTHROPIC_API_KEY,
        'anthropic-version': '2023-06-01',
      },
      body: JSON.stringify({
        model: model || 'claude-haiku-4-5-20251001',
        max_tokens: max_tokens || 1024,
        system: system || 'You are a helpful, friendly AI assistant.',
        messages: trimmedMessages,
      }),
    });

    if (!anthropicRes.ok) {
      const errText = await anthropicRes.text();
      console.error('Anthropic error:', anthropicRes.status, errText);
      return new Response(
        JSON.stringify({ error: `AI service error (${anthropicRes.status})` }),
        { status: anthropicRes.status, headers: { ...corsHeaders, 'Content-Type': 'application/json' } }
      );
    }

    const data = await anthropicRes.json();
    return new Response(JSON.stringify(data), {
      status: 200,
      headers: { ...corsHeaders, 'Content-Type': 'application/json' },
    });
  } catch (err) {
    console.error('Function error:', err);
    return new Response(
      JSON.stringify({ error: 'Internal server error' }),
      { status: 500, headers: { ...corsHeaders, 'Content-Type': 'application/json' } }
    );
  }
}