import { useState, useRef, useCallback } from 'react';
import { useTranslation } from 'react-i18next';
import { PaperAirplaneIcon, StopCircleIcon, CurrencyDollarIcon } from '@heroicons/react/24/outline';

interface AgentStep {
  step_number: number;
  thought: string;
  action: string | null;
  action_input: Record<string, unknown> | null;
  observation: string | null;
  cost_usd: number;
}

interface AgentChatProps {
  agentId: string;
  agentName: string;
}

export function AgentChat({ agentId, agentName }: AgentChatProps) {
  const { t } = useTranslation();
  const [messages, setMessages] = useState<string[]>([]);
  const [input, setInput] = useState('');
  const [steps, setSteps] = useState<AgentStep[]>([]);
  const [isRunning, setIsRunning] = useState(false);
  const [totalCost, setTotalCost] = useState(0);
  const [extendedTrace, setExtendedTrace] = useState(false);
  const [dryRun, setDryRun] = useState(false);
  const eventSourceRef = useRef<EventSource | null>(null);

  const handleSend = useCallback(() => {
    if (!input.trim() || isRunning) return;
    const userMsg = input.trim();
    setMessages((prev) => [...prev, `User: ${userMsg}`]);
    setInput('');
    setIsRunning(true);
    setSteps([]);
    setTotalCost(0);

    const url = `/api/v1/agents/${agentId}/stream?message=${encodeURIComponent(userMsg)}&trace_mode=${extendedTrace ? 'extended' : 'standard'}&dry_run=${dryRun}`;
    const eventSource = new EventSource(url);
    eventSourceRef.current = eventSource;

    eventSource.addEventListener('step', (e) => {
      const step = JSON.parse(e.data) as AgentStep;
      setSteps((prev) => [...prev, step]);
      setTotalCost((prev) => prev + (step.cost_usd || 0));
    });

    eventSource.addEventListener('status', (e) => {
      const data = JSON.parse(e.data);
      if (data.status === 'running') {
        setMessages((prev) => [...prev, `Step ${data.step}: ${data.action || 'Thinking...'}`]);
      }
    });

    eventSource.addEventListener('done', (e) => {
      const data = JSON.parse(e.data);
      setMessages((prev) => [...prev, `Agent: ${data.final_content}`]);
      setIsRunning(false);
      eventSource.close();
    });

    eventSource.addEventListener('error', (e) => {
      try {
        const data = JSON.parse(e.data);
        setMessages((prev) => [...prev, `Error: ${data.error}`]);
      } catch {
        setMessages((prev) => [...prev, 'Error: Connection lost']);
      }
      setIsRunning(false);
      eventSource.close();
    });
  }, [input, isRunning, agentId, extendedTrace, dryRun]);

  const handleStop = useCallback(() => {
    eventSourceRef.current?.close();
    setIsRunning(false);
    setMessages((prev) => [...prev, 'Agent run stopped by user']);
  }, []);

  return (
    <div className="flex flex-col h-full bg-white dark:bg-gray-900">
      <div className="flex items-center justify-between p-4 border-b border-gray-200 dark:border-gray-700">
        <h2 className="text-lg font-semibold text-gray-900 dark:text-white">{agentName}</h2>
        <div className="flex items-center gap-4">
          <label className="flex items-center gap-2 text-sm text-gray-600 dark:text-gray-400">
            <input type="checkbox" checked={extendedTrace} onChange={(e) => setExtendedTrace(e.target.checked)} className="rounded" aria-label={t('agents.extendedTrace')} />
            {t('agents.extendedTrace')}
          </label>
          <label className="flex items-center gap-2 text-sm text-gray-600 dark:text-gray-400">
            <input type="checkbox" checked={dryRun} onChange={(e) => setDryRun(e.target.checked)} className="rounded" aria-label={t('agents.dryRun')} />
            {t('agents.dryRun')}
          </label>
          {totalCost > 0 && (
            <span className="flex items-center gap-1 text-sm text-gray-600 dark:text-gray-400">
              <CurrencyDollarIcon className="w-4 h-4" />
              {totalCost.toFixed(6)}
            </span>
          )}
        </div>
      </div>

      <div className="flex-1 overflow-y-auto p-4 space-y-3">
        {messages.map((msg, i) => (
          <div key={i} className={`p-3 rounded-lg ${msg.startsWith('User:') ? 'bg-primary-50 dark:bg-primary-900/20' : msg.startsWith('Error:') ? 'bg-red-50 dark:bg-red-900/20' : 'bg-gray-50 dark:bg-gray-800'}`}>
            <p className="text-sm text-gray-900 dark:text-gray-100">{msg}</p>
          </div>
        ))}
        {extendedTrace && steps.map((step) => (
          <div key={step.step_number} className="p-3 rounded-lg border border-gray-200 dark:border-gray-700">
            <div className="flex items-center justify-between mb-2">
              <span className="text-xs font-medium text-gray-500">Step {step.step_number}</span>
              <span className="text-xs text-gray-400">${step.cost_usd.toFixed(6)}</span>
            </div>
            {step.thought && <p className="text-sm text-gray-700 dark:text-gray-300 mb-1"><strong>Thought:</strong> {step.thought}</p>}
            {step.action && <p className="text-sm text-primary-600 dark:text-primary-400 mb-1"><strong>Action:</strong> {step.action}</p>}
            {step.observation && <p className="text-sm text-gray-600 dark:text-gray-400"><strong>Observation:</strong> {step.observation}</p>}
          </div>
        ))}
      </div>

      <div className="p-4 border-t border-gray-200 dark:border-gray-700">
        <div className="flex items-center gap-2">
          <input
            type="text"
            value={input}
            onChange={(e) => setInput(e.target.value)}
            onKeyDown={(e) => e.key === 'Enter' && handleSend()}
            placeholder={t('agents.typeMessage')}
            disabled={isRunning}
            className="flex-1 px-4 py-2 rounded-lg border border-gray-300 dark:border-gray-600 bg-white dark:bg-gray-800 text-gray-900 dark:text-white focus:ring-2 focus:ring-primary-500"
            aria-label={t('agents.messageInput')}
          />
          {isRunning ? (
            <button onClick={handleStop} className="p-2 rounded-lg bg-red-500 text-white hover:bg-red-600 min-h-[44px] min-w-[44px]" aria-label={t('agents.stop')}>
              <StopCircleIcon className="w-5 h-5" />
            </button>
          ) : (
            <button onClick={handleSend} disabled={!input.trim()} className="p-2 rounded-lg bg-primary-600 text-white hover:bg-primary-700 disabled:opacity-50 min-h-[44px] min-w-[44px]" aria-label={t('agents.send')}>
              <PaperAirplaneIcon className="w-5 h-5" />
            </button>
          )}
        </div>
      </div>
    </div>
  );
}