import { selectEmbeddingPrecision } from '../model-precision.js';

/**
 * Format-neutral runtime boundary.
 *
 * An ONNX or GGUF implementation must satisfy the same adapter contract. The
 * product UI intentionally has no dependency on either runtime.
 */
class Runtime extends EventTarget {
  adapter = null;
  status = 'idle';
  backend = 'Engine not selected';
  webgpu = null;
  embeddingPrecision = null;

  emit(type, detail) {
    this.dispatchEvent(new CustomEvent(type, { detail }));
  }

  log(level, message, detail = '') {
    if (level !== 'error' && level !== 'warn') return;
    console[level](`[LFM edge runtime] ${message}`, detail || '');
  }

  async probe() {
    if (!globalThis.isSecureContext) throw new Error('WebGPU requires HTTPS or localhost.');
    if (!navigator.gpu) throw new Error('WebGPU is unavailable in this browser.');
    const adapter = await navigator.gpu.requestAdapter({ powerPreference: 'high-performance' });
    if (!adapter) throw new Error('The browser did not return a WebGPU adapter.');
    const info = adapter.info || {};
    this.webgpu = {
      adapter,
      name: info.description || info.device || info.architecture || 'WebGPU adapter',
      vendor: info.vendor || 'Not exposed',
      architecture: info.architecture || 'Not exposed',
      features: [...adapter.features].sort(),
      limits: adapter.limits,
    };
    return this.webgpu;
  }

  async load() {
    if (this.status === 'loading') return;
    this.status = 'loading';
    this.emit('status', { status: this.status, backend: this.backend });
    try {
      await this.probe();
      const baseManifest = await fetch('/model-manifest.json', { cache: 'no-store' }).then(response => response.json());
      const selection = selectEmbeddingPrecision(baseManifest, this.webgpu.features);
      const manifest = selection.manifest;
      this.embeddingPrecision = selection.precision;
      this.emit('status', { status: this.status, backend: this.backend });
      const loaders = {
        'onnx-transformers': () => import('../engines/onnx-transformers-engine.js'),
      };
      const loadEngine = loaders[manifest.engine?.adapter];
      if (!loadEngine) throw new Error(`Unknown or unselected inference adapter: ${manifest.engine?.adapter || 'none'}.`);
      const module = await loadEngine();
      this.adapter = await module.createEngine({ manifest, telemetry: event => this.log(event.level, event.message, event.detail) });
      await this.adapter.load(progress => this.emit('progress', progress));
      this.backend = this.adapter.backend;
      this.status = 'ready';
    } catch (error) {
      this.status = 'error';
      this.log('error', 'Engine load stopped', error.message);
      throw error;
    } finally {
      this.emit('status', { status: this.status, backend: this.backend });
    }
  }

  /** Returns { text, toolCalls, finishReason } for every inference adapter. */
  async generate(messages, options) {
    if (!this.adapter || this.status !== 'ready') throw new Error('No inference engine is configured.');
    this.status = 'generating';
    this.emit('status', { status: this.status, backend: this.backend });
    try {
      return await this.adapter.generate(messages, options);
    } finally {
      this.status = 'ready';
      this.emit('status', { status: this.status, backend: this.backend });
    }
  }

  async clearCache() {
    const result = this.adapter?.clearCache ? await this.adapter.clearCache() : { cleared: false, entriesDeleted: 0 };
    const cleared = typeof result === 'object' ? result.cleared : Boolean(result);
    return cleared;
  }

  async cacheInfo() {
    if (this.adapter?.cacheInfo) return this.adapter.cacheInfo();
    if (globalThis.caches) {
      const cacheNames = await caches.keys();
      const modelCacheNames = cacheNames.filter(name => name === 'liquid-lfm-models-v4');
      let used = 0;
      for (const cacheName of modelCacheNames) {
        const cache = await caches.open(cacheName);
        for (const request of await cache.keys()) {
          const response = await cache.match(request);
          used += Number(response?.headers.get('content-length') || 0);
        }
      }
      const estimate = await navigator.storage?.estimate?.();
      return { used, available: estimate?.quota || 0 };
    }
    const estimate = await navigator.storage?.estimate?.();
    return { used: 0, available: estimate?.quota || 0 };
  }

  clearConversationCache() {
    this.adapter?.clearConversationCache?.();
  }
}

export const runtime = new Runtime();