import { useState, useRef, useEffect } from 'react'
import type { ChatMessage } from '../types'
import { SourceBadge } from './SourceBadge'

interface ChatPanelProps {
  onSend: (message: string, temperature?: number, maxTokens?: number) => Promise<any>
  loading: boolean
}

function formatNum(n: number): string {
  if (n >= 1_000_000) return `${(n / 1_000_000).toFixed(1)}M`
  if (n >= 1_000) return `${(n / 1_000).toFixed(1)}K`
  return n.toString()
}

export function ChatPanel({ onSend, loading }: ChatPanelProps) {
  const [messages, setMessages] = useState<ChatMessage[]>([])
  const [input, setInput] = useState('')
  const [temperature, setTemperature] = useState(0.0)
  const [showSettings, setShowSettings] = useState(false)
  const scrollRef = useRef<HTMLDivElement>(null)

  useEffect(() => {
    if (scrollRef.current) {
      scrollRef.current.scrollTop = scrollRef.current.scrollHeight
    }
  }, [messages, loading])

  const handleSend = async () => {
    const msg = input.trim()
    if (!msg || loading) return

    const userMsg: ChatMessage = {
      id: `u-${Date.now()}`,
      role: 'user',
      text: msg,
      timestamp: Date.now(),
    }
    setMessages(prev => [...prev, userMsg])
    setInput('')

    try {
      const resp = await onSend(msg, temperature)
      const botMsg: ChatMessage = {
        id: `b-${Date.now()}`,
        role: 'palimpseste',
        text: resp.response,
        confidence: resp.confidence,
        source: resp.source,
        explanation: resp.explanation,
        chain: resp.chain,
        elapsed_ms: resp.elapsed_ms,
        timestamp: Date.now(),
      }
      setMessages(prev => [...prev, botMsg])
    } catch (err) {
      setMessages(prev => [...prev, {
        id: `e-${Date.now()}`,
        role: 'palimpseste',
        text: '⚠️ Connection error. Is the API server running on :3332?',
        source: 'fallback',
        confidence: 0,
        timestamp: Date.now(),
      }])
    }
  }

  const handleKeyDown = (e: React.KeyboardEvent) => {
    if (e.key === 'Enter' && !e.shiftKey) {
      e.preventDefault()
      handleSend()
    }
  }

  const clearChat = () => setMessages([])

  return (
    <div className="flex flex-col h-full glass-card overflow-hidden">
      {/* Header */}
      <div className="flex items-center justify-between px-5 py-3 border-b border-pal-border">
        <div className="flex items-center gap-3">
          <div className="relative">
            <div className="w-2.5 h-2.5 rounded-full bg-pal-green" />
            <div className="absolute inset-0 w-2.5 h-2.5 rounded-full bg-pal-green animate-ping" />
          </div>
          <h2 className="text-sm font-semibold text-pal-text">Cortex Chat</h2>
          <span className="text-xs text-pal-muted">
            {messages.length} message{messages.length !== 1 ? 's' : ''}
          </span>
        </div>
        <div className="flex items-center gap-2">
          <button
            onClick={() => setShowSettings(!showSettings)}
            className="text-pal-muted hover:text-pal-text transition-colors p-1.5 rounded-lg hover:bg-pal-card"
            title="Settings"
          >
            <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2">
              <circle cx="12" cy="12" r="3" />
              <path d="M19.4 15a1.65 1.65 0 0 0 .33 1.82l.06.06a2 2 0 0 1 0 2.83 2 2 0 0 1-2.83 0l-.06-.06a1.65 1.65 0 0 0-1.82-.33 1.65 1.65 0 0 0-1 1.51V21a2 2 0 0 1-4 0v-.09A1.65 1.65 0 0 0 9 19.4a1.65 1.65 0 0 0-1.82.33l-.06.06a2 2 0 0 1-2.83 0 2 2 0 0 1 0-2.83l.06-.06a1.65 1.65 0 0 0 .33-1.82 1.65 1.65 0 0 0-1.51-1H3a2 2 0 0 1 0-4h.09A1.65 1.65 0 0 0 4.6 9a1.65 1.65 0 0 0-.33-1.82l-.06-.06a2 2 0 0 1 0-2.83 2 2 0 0 1 2.83 0l.06.06a1.65 1.65 0 0 0 1.82.33H9a1.65 1.65 0 0 0 1-1.51V3a2 2 0 0 1 4 0v.09a1.65 1.65 0 0 0 1 1.51 1.65 1.65 0 0 0 1.82-.33l.06-.06a2 2 0 0 1 2.83 0 2 2 0 0 1 0 2.83l-.06.06a1.65 1.65 0 0 0-.33 1.82V9a1.65 1.65 0 0 0 1.51 1H21a2 2 0 0 1 0 4h-.09a1.65 1.65 0 0 0-1.51 1z" />
            </svg>
          </button>
          {messages.length > 0 && (
            <button
              onClick={clearChat}
              className="text-pal-muted hover:text-pal-red transition-colors p-1.5 rounded-lg hover:bg-pal-card text-xs"
            >
              Clear
            </button>
          )}
        </div>
      </div>

      {/* Settings drawer */}
      {showSettings && (
        <div className="px-5 py-3 border-b border-pal-border bg-pal-surface/50 animate-slide-up">
          <div className="flex items-center gap-4">
            <label className="text-xs text-pal-muted font-medium whitespace-nowrap">
              Temperature: <span className="text-pal-accent2 font-mono">{temperature.toFixed(2)}</span>
            </label>
            <input
              type="range"
              min="0"
              max="1"
              step="0.05"
              value={temperature}
              onChange={e => setTemperature(parseFloat(e.target.value))}
              className="flex-1 accent-pal-accent"
            />
          </div>
        </div>
      )}

      {/* Messages */}
      <div ref={scrollRef} className="flex-1 overflow-y-auto px-5 py-4 space-y-4">
        {messages.length === 0 && (
          <div className="flex flex-col items-center justify-center h-full text-center gap-4 animate-fade-in">
            <div className="text-5xl animate-float">🧠</div>
            <div>
              <h3 className="text-lg font-bold gradient-text mb-1">PALIMPSESTE</h3>
              <p className="text-sm text-pal-muted max-w-xs">
                A self-referential hypervectorial cortex.<br/>
                No weights. No gradient. No GPU.
              </p>
            </div>
            <div className="flex flex-wrap gap-2 justify-center max-w-md">
              {['hello', 'who are you?', 'what is python?', 'what is the capital of france'].map(q => (
                <button
                  key={q}
                  onClick={() => setInput(q)}
                  className="px-3 py-1.5 text-xs rounded-full glass hover:border-pal-accent/40 transition-all text-pal-muted hover:text-pal-text"
                >
                  {q}
                </button>
              ))}
            </div>
          </div>
        )}

        {messages.map(msg => (
          <div
            key={msg.id}
            className={`flex ${msg.role === 'user' ? 'justify-end' : 'justify-start'} animate-slide-up`}
          >
            <div
              className={`max-w-[80%] rounded-2xl px-4 py-2.5 ${
                msg.role === 'user'
                  ? 'bg-gradient-to-br from-pal-accent/30 to-pal-accent/10 border border-pal-accent/30'
                  : 'glass border border-pal-border'
              }`}
            >
              <p className="text-sm text-pal-text whitespace-pre-wrap break-words">{msg.text}</p>

              {msg.role === 'palimpseste' && msg.source && (
                <div className="mt-2 pt-2 border-t border-pal-border/50 space-y-1.5">
                  <div className="flex items-center justify-between gap-2 flex-wrap">
                    <SourceBadge source={msg.source} confidence={msg.confidence ?? 0} />
                    {msg.elapsed_ms !== undefined && (
                      <span className="text-[10px] text-pal-muted font-mono">
                        {msg.elapsed_ms < 1 ? '<1' : msg.elapsed_ms.toFixed(0)}ms
                      </span>
                    )}
                  </div>
                  {msg.explanation && msg.source !== 'fallback' && (
                    <p className="text-[11px] text-pal-muted leading-relaxed">
                      <span className="text-pal-accent2/70">💡 </span>
                      {msg.explanation.split('\n').map((line, i) => (
                        <span key={i}>{i > 0 && <br/>}{line}</span>
                      ))}
                    </p>
                  )}
                  {msg.chain && msg.chain.success && (
                    <ChainVisualization chain={msg.chain} />
                  )}
                </div>
              )}
            </div>
          </div>
        ))}

        {loading && (
          <div className="flex justify-start animate-fade-in">
            <div className="glass border border-pal-border rounded-2xl px-4 py-3">
              <div className="flex gap-1.5">
                <span className="w-2 h-2 rounded-full bg-pal-accent animate-bounce" style={{ animationDelay: '0ms' }} />
                <span className="w-2 h-2 rounded-full bg-pal-accent animate-bounce" style={{ animationDelay: '150ms' }} />
                <span className="w-2 h-2 rounded-full bg-pal-accent animate-bounce" style={{ animationDelay: '300ms' }} />
              </div>
            </div>
          </div>
        )}
      </div>

      {/* Input */}
      <div className="px-4 py-3 border-t border-pal-border">
        <div className="flex gap-2 items-end">
          <textarea
            value={input}
            onChange={e => setInput(e.target.value)}
            onKeyDown={handleKeyDown}
            placeholder="Ask PALIMPSESTE anything..."
            rows={1}
            className="flex-1 bg-pal-surface border border-pal-border rounded-xl px-4 py-2.5 text-sm text-pal-text placeholder:text-pal-muted focus:outline-none focus:border-pal-accent/50 focus:glow-accent transition-all resize-none max-h-32"
            style={{ minHeight: '42px' }}
          />
          <button
            onClick={handleSend}
            disabled={!input.trim() || loading}
            className="px-4 py-2.5 rounded-xl bg-gradient-to-br from-pal-accent to-pal-accent2 text-white font-semibold text-sm transition-all hover:scale-105 hover:glow-accent disabled:opacity-30 disabled:cursor-not-allowed disabled:hover:scale-100"
          >
            <svg width="18" height="18" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2.5">
              <path d="M22 2L11 13M22 2l-7 20-4-9-9-4 20-7z" />
            </svg>
          </button>
        </div>
      </div>
    </div>
  )
}

function ChainVisualization({ chain }: { chain: NonNullable<ChatMessage['chain']> }) {
  return (
    <div className="mt-2 p-2.5 rounded-lg bg-pal-surface/70 border border-pal-accent/20">
      <div className="text-[10px] text-pal-accent font-semibold mb-1.5 uppercase tracking-wide">
        🔗 Chain ({chain.n_hops} hops)
      </div>
      <div className="space-y-1">
        {chain.steps.map((step, i) => (
          <div key={i} className="flex items-start gap-2 text-[11px]">
            <span className="text-pal-muted font-mono mt-0.5">{i + 1}.</span>
            <div className="flex-1">
              <span className="text-pal-text">{step.sub_question}</span>
              <span className="text-pal-accent2 mx-1">→</span>
              <span className="text-pal-green font-medium">{step.sub_answer}</span>
            </div>
          </div>
        ))}
        <div className="flex items-center gap-2 text-[11px] pt-1 border-t border-pal-border/50">
          <span className="text-pal-muted">Result:</span>
          <span className="text-pal-gold font-semibold">{chain.answer}</span>
        </div>
      </div>
    </div>
  )
}