import { FastifyInstance } from 'fastify';
import { readFileSync, writeFileSync, existsSync, mkdirSync } from 'fs';
import { resolve, dirname } from 'path';

const CONFIG_PATH = resolve(process.env.BOOCODE_DATA_DIR || '/opt/boocode/data', 'inference-settings.json');

const DEFAULTS = {
  cache_type_k: 'q4_0',
  cache_reuse: 256,
  spec_type: 'ngram-mod',
  spec_ngram_mod_thsh: 2,
  ctx_checkpoints: 32,
  sleep_idle_seconds: 600,
  metrics_enabled: true,
  slot_save_path: '/tmp/llama-slots',
};

function load(): Record<string, unknown> {
  try {
    if (existsSync(CONFIG_PATH)) {
      return JSON.parse(readFileSync(CONFIG_PATH, 'utf-8'));
    }
  } catch { /* corrupt file */ }
  return { ...DEFAULTS };
}

function save(data: Record<string, unknown>): void {
  const dir = dirname(CONFIG_PATH);
  if (!existsSync(dir)) mkdirSync(dir, { recursive: true });
  writeFileSync(CONFIG_PATH, JSON.stringify(data, null, 2) + '\n');
}

const VALID_CACHE_TYPES = ['f32', 'f16', 'q8_0', 'q4_0'] as const;
const VALID_SPEC_TYPES = ['off', 'ngram-mod', 'draft-simple'] as const;

export function registerInferenceSettingsRoutes(app: FastifyInstance): void {
  app.get('/api/settings/inference', async (_req, _res) => {
    return { ...DEFAULTS, ...load() };
  });

  app.patch<{ Body: Record<string, unknown> }>('/api/settings/inference', async (req, reply) => {
    const current = { ...DEFAULTS, ...load() };
    const merged = { ...current, ...req.body };

    if (merged.cache_type_k && !(VALID_CACHE_TYPES as readonly string[]).includes(merged.cache_type_k as string)) {
      return reply.status(400).send({ error: 'Invalid cache_type_k' });
    }
    if (merged.spec_type && !(VALID_SPEC_TYPES as readonly string[]).includes(merged.spec_type as string)) {
      return reply.status(400).send({ error: 'Invalid spec_type' });
    }

    save(merged);
    return { ...DEFAULTS, ...load() };
  });
}