/**
 * lib/api.ts — API client for the RAG backend.
 */

const API_BASE = process.env.NEXT_PUBLIC_API_URL || 'http://localhost:8000';

export interface SearchResult {
  document_id: string;
  chunk_id: string;
  title: string;
  path: string;
  content: string;
  score: number;
  tags: string[];
  highlight?: string;
}

export interface SearchResponse {
  results: SearchResult[];
  total: number;
  query_time_ms: number;
}

export interface Document {
  id: string;
  path: string;
  title: string;
  content: string;
  frontmatter: Record<string, unknown>;
  tags: string[];
  aliases: string[];
  word_count: number | null;
  created_at: string;
  updated_at: string;
  indexed_at: string | null;
}

export interface StatsResponse {
  total_documents: number;
  total_chunks: number;
  total_relations: number;
  total_tags: number;
  last_indexed: string | null;
  embedding_model: string;
  chat_model: string;
}

export interface TagCount {
  tag: string;
  count: number;
}

export interface GraphData {
  nodes: { id: string; title: string; path: string; tags: string[]; word_count: number | null }[];
  edges: { source: string; target: string; relation_type: string; label: string | null }[];
}

export async function search(query: string, tags?: string[], limit = 10): Promise<SearchResponse> {
  const res = await fetch(`${API_BASE}/api/v1/search`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ query, tags, limit, hybrid: true }),
  });
  if (!res.ok) throw new Error(`Search failed: ${res.status}`);
  return res.json();
}

export async function getDocument(id: string): Promise<Document> {
  const res = await fetch(`${API_BASE}/api/v1/document/${id}`);
  if (!res.ok) throw new Error(`Document not found: ${res.status}`);
  return res.json();
}

export async function getStats(): Promise<StatsResponse> {
  const res = await fetch(`${API_BASE}/api/v1/stats`);
  if (!res.ok) throw new Error('Stats fetch failed');
  return res.json();
}

export async function getTags(): Promise<TagCount[]> {
  const res = await fetch(`${API_BASE}/api/v1/tags`);
  if (!res.ok) throw new Error('Tags fetch failed');
  return res.json();
}

export async function getGraph(limit = 150): Promise<GraphData> {
  const res = await fetch(`${API_BASE}/api/v1/graph?limit=${limit}`);
  if (!res.ok) throw new Error('Graph fetch failed');
  return res.json();
}

export function streamChat(
  message: string,
  contextLimit = 5,
  onToken: (token: string) => void,
  onSources: (sources: { title: string; path: string; score: number }[]) => void,
  onDone: () => void,
): () => void {
  const controller = new AbortController();

  (async () => {
    try {
      const res = await fetch(`${API_BASE}/api/v1/chat`, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ message, context_limit: contextLimit, stream: true }),
        signal: controller.signal,
      });

      if (!res.ok || !res.body) return;
      const reader = res.body.getReader();
      const decoder = new TextDecoder();
      let buffer = '';

      while (true) {
        const { done, value } = await reader.read();
        if (done) break;
        buffer += decoder.decode(value, { stream: true });
        const lines = buffer.split('\n');
        buffer = lines.pop() ?? '';

        for (const line of lines) {
          if (!line.startsWith('data: ')) continue;
          try {
            const data = JSON.parse(line.slice(6));
            if (data.type === 'token') onToken(data.token);
            else if (data.type === 'sources') onSources(data.sources);
            else if (data.type === 'done') onDone();
          } catch {}
        }
      }
    } catch (err: unknown) {
      if ((err as Error)?.name !== 'AbortError') console.error('Stream error:', err);
    }
  })();

  return () => controller.abort();
}