import type { APIRoute } from 'astro';
import { spawn } from 'child_process';

const SYSTEM_PROMPT = `You are a meditation guide. Generate one short, calming guidance message for a meditation session.

Rules:
- One sentence only, 8-20 words
- Gentle, present-tense, second person ("you")
- No questions, no exclamation marks
- Match the phase: "start" = settling in, "middle" = sustained awareness, "end" = returning
- Never repeat common meditation cliches verbatim
- Vary your language — draw from mindfulness, somatic awareness, nature imagery, gratitude, breath, stillness
- Output only the guidance sentence, nothing else — no quotes, no labels, no extra text`;

const lastCall = new Map<string, number>();

export const POST: APIRoute = async ({ request }) => {
  const body = await request.json() as {
    phase: string;
    progress: number;
    duration: number;
    streak: number;
    sessionCount: number;
    sessionId: string;
  };

  // Rate limiting: 20s minimum between calls per session
  const now = Date.now();
  const last = lastCall.get(body.sessionId) || 0;
  if (now - last < 20_000) {
    return new Response(JSON.stringify({ error: "rate limited" }), {
      status: 429,
      headers: { 'Content-Type': 'application/json' },
    });
  }
  lastCall.set(body.sessionId, now);

  // Prune stale entries
  if (lastCall.size > 1000) {
    const cutoff = now - 3_600_000;
    for (const [k, v] of lastCall) {
      if (v < cutoff) lastCall.delete(k);
    }
  }

  const contextParts = [`Phase: ${body.phase}`, `Progress: ${Math.round(body.progress * 100)}%`];
  if (body.duration) contextParts.push(`Session length: ${body.duration} minutes`);
  if (body.streak > 1) contextParts.push(`User is on a ${body.streak}-day streak`);
  if (body.sessionCount > 1) contextParts.push(`This is their session #${body.sessionCount}`);

  const prompt = `${SYSTEM_PROMPT}\n\n${contextParts.join(". ")}.`;

  return new Promise<Response>((resolve) => {
    const proc = spawn('claude', ['-p', '--model', 'claude-haiku-4-5-20251001'], {
      stdio: ['pipe', 'pipe', 'pipe'],
    });

    let output = '';
    let stderr = '';

    proc.stdout.on('data', (chunk: Buffer) => { output += chunk.toString(); });
    proc.stderr.on('data', (chunk: Buffer) => { stderr += chunk.toString(); });

    proc.on('close', (code) => {
      const text = output.trim().replace(/^["']|["']$/g, '');
      if (code !== 0 || !text) {
        console.error('Meditation guidance error:', stderr || 'empty output');
        resolve(new Response(JSON.stringify({ error: 'generation failed' }), {
          status: 500,
          headers: { 'Content-Type': 'application/json' },
        }));
        return;
      }
      resolve(new Response(JSON.stringify({ guidance: text }), {
        headers: { 'Content-Type': 'application/json' },
      }));
    });

    proc.on('error', (err) => {
      console.error('Failed to spawn claude:', err);
      resolve(new Response(JSON.stringify({ error: 'generation failed' }), {
        status: 500,
        headers: { 'Content-Type': 'application/json' },
      }));
    });

    proc.stdin.write(prompt);
    proc.stdin.end();
  });
};