import { useState, useRef, useEffect } from 'react';
import type { KeyboardEvent } from 'react';

interface Line { type: 'input' | 'output'; text: string; key: number }

const COMMANDS: Record<string, string[]> = {
  help: [
    'Available commands:',
    '  help       — show this list',
    '  about      — who is mingda',
    '  projects   — list projects',
    '  skills     — tech stack',
    '  contact    — contact info',
    '  neofetch   — system info',
    '  clear      — clear terminal',
  ],
  about: [
    'Mingda Xie (解明达)',
    'Backend Developer · CS Master\'s @ Northeastern University',
    'Shenzhen-bound · Class of 2026',
    '',
    'Runs a personal k3s cluster. Writes Go and Java at 2am.',
    'LeetCode 400+. Pixel art. Stardew Valley. 土屋アンナ.',
    '',
    '"I am the dragon scroll, bitch."',
  ],
  projects: [
    'Projects:',
    '  CampusNest     — Spring Cloud housing platform',
    '  Alfred Bot     — Self-hosted AI agent',
    '  Warden/Bastion — k3s auth + proxy layer',
    '  Collab Platform— Real-time collaborative workspace',
    '  成语填空         — Daily Chinese idiom game',
  ],
  skills: [
    'Tech Stack:',
    '  Languages  : Java, Go, TypeScript, Python',
    '  Frameworks : Spring Cloud, Bun, React',
    '  Infra      : k3s, Nginx, Redis, Docker',
    '  Cloud      : Vultr, Let\'s Encrypt',
    '  Other      : Microservices, WebSocket, LLM APIs',
  ],
  contact: [
    'Contact:',
    '  GitHub : github.com/m1ngdaxie',
    '  Web    : m1ngdaxie.com',
    '  Game   : chengyu.m1ngdaxie.com',
    '  Email  : mingda@m1ngdaxie.com',
  ],
  neofetch: [
    '        .          mingda@doitou-sv',
    '       .:.         ----------------',
    '      .:!:.        OS: MingdaOS 1.0',
    '     .:!!!:.       Host: Vultr VPS',
    '    .::!!!::.      Kernel: Ubuntu 24.04',
    '   .:::!!!:::.     RAM: 4GB',
    '  .::::!!!::::.    Shell: zsh',
    ' .:::::!!!:::::.   Services: Alfred, Chengyu, k3s, VLESS',
    '',
    '  nginx + k3s + let\'s encrypt',
  ],
};

const PROMPT = 'mingda@doitou-sv ~ % ';

let lineCounter = 0; // module-level counter for stable unique keys
function nextKey() { return ++lineCounter; }

export default function Terminal() {
  const [lines, setLines] = useState<Line[]>([
    { type: 'output', text: 'MingdaOS Terminal v1.0', key: nextKey() },
    { type: 'output', text: 'Type "help" to see available commands.', key: nextKey() },
    { type: 'output', text: '', key: nextKey() },
  ]);
  const [input, setInput] = useState('');
  const [history, setHistory] = useState<string[]>([]);
  const [histIdx, setHistIdx] = useState(-1);
  const bottomRef = useRef<HTMLDivElement>(null);
  const inputRef = useRef<HTMLInputElement>(null);

  useEffect(() => {
    bottomRef.current?.scrollIntoView({ behavior: 'smooth' });
  }, [lines]);

  useEffect(() => {
    inputRef.current?.focus();
  }, []);

  function handleSubmit() {
    const cmd = input.trim().toLowerCase();
    const inputLine: Line = { type: 'input', text: PROMPT + input, key: nextKey() };

    if (cmd === 'clear') {
      setLines([]);
    } else if (cmd === '') {
      setLines(prev => [...prev, inputLine, { type: 'output', text: '', key: nextKey() }]);
    } else if (COMMANDS[cmd]) {
      const outputLines: Line[] = COMMANDS[cmd].map(l => ({ type: 'output' as const, text: l, key: nextKey() }));
      outputLines.push({ type: 'output', text: '', key: nextKey() });
      setLines(prev => [...prev, inputLine, ...outputLines]);
    } else {
      setLines(prev => [...prev, inputLine,
        { type: 'output', text: `zsh: command not found: ${cmd}`, key: nextKey() },
        { type: 'output', text: '', key: nextKey() }
      ]);
    }

    if (cmd) setHistory(h => [cmd, ...h].slice(0, 50));
    setHistIdx(-1);
    setInput('');
  }

  function handleKeyDown(e: KeyboardEvent<HTMLInputElement>) {
    if (e.key === 'Enter') {
      handleSubmit();
    } else if (e.key === 'ArrowUp') {
      e.preventDefault();
      const next = Math.min(histIdx + 1, history.length - 1);
      setHistIdx(next);
      if (history[next] !== undefined) setInput(history[next]);
    } else if (e.key === 'ArrowDown') {
      e.preventDefault();
      const next = Math.max(histIdx - 1, -1);
      setHistIdx(next);
      setInput(next === -1 ? '' : history[next]);
    }
  }

  return (
    <div
      style={{
        fontFamily: 'var(--font-mono)',
        fontSize: 13,
        color: '#e2e8f0',
        background: 'transparent',
        padding: '12px 16px',
        height: '100%',
        display: 'flex',
        flexDirection: 'column',
        cursor: 'text',
      }}
      onClick={() => inputRef.current?.focus()}
    >
      <div style={{ flex: 1, overflowY: 'auto' }}>
        {lines.map((line) => (
          <div key={line.key} style={{
            color: line.type === 'input' ? '#00ffff' : '#e2e8f0',
            whiteSpace: 'pre',
            lineHeight: 1.6,
          }}>
            {line.text}
          </div>
        ))}
        <div ref={bottomRef} />
      </div>
      <div style={{ display: 'flex', alignItems: 'center', marginTop: 4 }}>
        <span style={{ color: '#00ffff', whiteSpace: 'nowrap' }}>{PROMPT}</span>
        <input
          ref={inputRef}
          value={input}
          onChange={e => setInput(e.target.value)}
          onKeyDown={handleKeyDown}
          style={{
            flex: 1,
            background: 'transparent',
            border: 'none',
            outline: 'none',
            color: '#e2e8f0',
            fontFamily: 'var(--font-mono)',
            fontSize: 13,
            caretColor: '#00ffff',
          }}
          spellCheck={false}
          autoComplete="off"
        />
      </div>
    </div>
  );
}