// AgentStreamEventRouter — 统一的 agent 流式事件状态机
// 供 Page AI sidebar runtime 和 document editor adapter runtime 共用
//
// 事件状态：
//   init              — 建立 request_id 绑定
//   loading           — message_delta / tool_call_delta → 增量更新
//   stream_event      — tool-started / tool-finished / agent_state
//   finished          — 正常终止
//   interrupted       — 中断（等待审批/恢复）
//   error             — 错误终止
//   approval_required — 等待用户确认

export const AGENT_EVENT_STATES = {
  INIT: 'init',
  LOADING: 'loading',
  STREAM_EVENT: 'stream_event',
  FINISHED: 'finished',
  INTERRUPTED: 'interrupted',
  ERROR: 'error',
  APPROVAL_REQUIRED: 'approval_required',
};

export const TERMINAL_STATES = new Set([
  AGENT_EVENT_STATES.FINISHED,
  AGENT_EVENT_STATES.INTERRUPTED,
  AGENT_EVENT_STATES.ERROR,
]);

export function isTerminalState(status) {
  return TERMINAL_STATES.has(status);
}

// 解析 SSE 帧为 eventName + payloadText
export function parseSSEFrames(buffer, lastBoundary) {
  var frames = buffer.split('\n\n');
  var remaining = frames.pop() || '';
  var events = [];
  frames.forEach(function(frame) {
    var eventName = '';
    var dataLines = [];
    frame.split('\n').forEach(function(line) {
      if (line.startsWith('event:')) eventName = line.slice(6).trim();
      if (line.startsWith('data:')) dataLines.push(line.slice(5).trim());
    });
    var payloadText = dataLines.join('\n');
    if (!eventName && payloadText) {
      try {
        var parsed = JSON.parse(payloadText);
        eventName = parsed && parsed.event ? String(parsed.event) : '';
      } catch (_) {}
    }
    if (eventName) events.push({ eventName: eventName, payloadText: payloadText });
  });
  return { events: events, remaining: remaining };
}

// 从 SSE 流读取事件
export async function readSSEStream(response, onFrame) {
  if (!response.body || typeof response.body.getReader !== 'function') return;
  var reader = response.body.getReader();
  var decoder = new TextDecoder();
  var buffer = '';
  while (true) {
    var chunk = await reader.read();
    if (chunk.done) break;
    buffer += decoder.decode(chunk.value, { stream: true });
    var result = parseSSEFrames(buffer, '');
    buffer = result.remaining;
    result.events.forEach(function(evt) {
      onFrame(evt.eventName, evt.payloadText);
    });
  }
}

// 创建标准事件路由器
// handlers: { onInit, onDelta, onToolCall, onToolResult, onAgentState, onTerminal, onApprovalRequired }
export function createAgentStreamRouter(handlers) {
  var h = handlers || {};

  return function routeEvent(eventName, payloadText) {
    var payload = null;
    try { payload = JSON.parse(payloadText || 'null'); } catch (_) {}

    var status = (payload && payload.status) || eventName;

    switch (status) {
      case AGENT_EVENT_STATES.INIT:
        if (h.onInit) h.onInit(payload);
        break;

      case AGENT_EVENT_STATES.LOADING:
        if (h.onDelta) h.onDelta(payload);
        if (h.onToolCall) {
          var toolChunks = (payload && payload.tool_call_chunks) || (payload && payload.msg && payload.msg.tool_call_chunks);
          if (toolChunks && toolChunks.length) h.onToolCall(payload);
        }
        break;

      case AGENT_EVENT_STATES.STREAM_EVENT:
        if (payload && payload.event === 'tool-finished') {
          if (h.onToolResult) h.onToolResult(payload);
        } else if (payload && payload.event === 'tool-started') {
          // tool start — 可选处理
        } else if (payload && payload.agent_state) {
          if (h.onAgentState) h.onAgentState(payload.agent_state);
        }
        break;

      case AGENT_EVENT_STATES.FINISHED:
      case AGENT_EVENT_STATES.INTERRUPTED:
      case AGENT_EVENT_STATES.ERROR:
        if (h.onTerminal) h.onTerminal(status, payload);
        break;

      case AGENT_EVENT_STATES.APPROVAL_REQUIRED:
        if (h.onApprovalRequired) h.onApprovalRequired(payload);
        break;

      default:
        // 未知状态：尝试作为 loading 处理
        if (payload && (payload.text || payload.delta || payload.content)) {
          if (h.onDelta) h.onDelta(payload);
        }
        break;
    }
  };
}