// Gradio Server-mode API client: POST /gradio_api/call/<name> {"data": [...]}
// returns {event_id}; GET /gradio_api/call/<name>/<event_id> streams SSE
// events ("generating" per chunk, "complete" at the end).

async function beginCall(name, data) {
  const res = await fetch(`./gradio_api/call/${name}`, {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ data }),
  });
  if (!res.ok) throw new Error(`API ${name}: HTTP ${res.status}`);
  const { event_id } = await res.json();
  return event_id;
}

// Parse an SSE byte stream and invoke onEvent(type, payload) per event.
async function readSSE(name, eventId, onEvent) {
  const res = await fetch(`./gradio_api/call/${name}/${eventId}`);
  if (!res.ok) throw new Error(`API ${name}: HTTP ${res.status} on stream`);
  const reader = res.body.getReader();
  const decoder = new TextDecoder();
  let buffer = '';
  for (;;) {
    const { done, value } = await reader.read();
    if (done) break;
    buffer += decoder.decode(value, { stream: true });
    let sep;
    while ((sep = buffer.indexOf('\n\n')) !== -1) {
      const block = buffer.slice(0, sep);
      buffer = buffer.slice(sep + 2);
      let type = 'message';
      let dataLine = '';
      for (const line of block.split('\n')) {
        if (line.startsWith('event:')) type = line.slice(6).trim();
        else if (line.startsWith('data:')) dataLine += line.slice(5).trim();
      }
      if (!dataLine) continue;
      let payload = null;
      try { payload = JSON.parse(dataLine); } catch { /* keep null */ }
      onEvent(type, payload);
    }
  }
}

function unwrap(payload) {
  // Endpoints return a single dict; gradio wraps outputs in a list.
  return Array.isArray(payload) ? payload[0] : payload;
}

// One-shot call: resolves with the final (complete) output dict.
export async function call(name, data = []) {
  const eventId = await beginCall(name, data);
  let result = null;
  let errored = null;
  await readSSE(name, eventId, (type, payload) => {
    if (type === 'error') errored = payload || 'server error';
    else result = unwrap(payload);
  });
  if (errored) throw new Error(typeof errored === 'string' ? errored : JSON.stringify(errored));
  return result;
}

// Streaming call: onChunk(dict) per "generating" event; resolves with the
// final dict. Our streaming endpoints tag payloads {type: progress|final}.
export async function stream(name, data, onChunk) {
  const eventId = await beginCall(name, data);
  let result = null;
  let errored = null;
  await readSSE(name, eventId, (type, payload) => {
    if (type === 'error') { errored = payload || 'server error'; return; }
    const value = unwrap(payload);
    if (value == null) return;
    if (type === 'generating') onChunk(value);
    else result = value;
  });
  if (errored) throw new Error(typeof errored === 'string' ? errored : JSON.stringify(errored));
  return result;
}

export async function getJSON(url) {
  const res = await fetch(url);
  if (!res.ok) throw new Error(`GET ${url}: HTTP ${res.status}`);
  return res.json();
}

export async function uploadFile(url, file) {
  const form = new FormData();
  form.append('file', file);
  const res = await fetch(url, { method: 'POST', body: form });
  if (!res.ok) throw new Error(`upload: HTTP ${res.status}`);
  return res.json();
}