import { useState, useRef, useEffect } from 'react'
import { Send, ChevronDown, ChevronRight } from 'lucide-react'
import { api } from '../api'
import type { AppSettings, ChatResponse, CausalChain } from '../types'

interface Props {
  documentId: string
  settings: AppSettings
}

interface Message {
  role: 'user' | 'assistant'
  content: string
  response?: ChatResponse
}

function ChainCard({ chain, index }: { chain: CausalChain; index: number }) {
  const [open, setOpen] = useState(index === 0)

  return (
    <div style={{
      border: '1px solid var(--border)', borderRadius: 'var(--radius)',
      marginBottom: 8, overflow: 'hidden',
    }}>
      <button
        onClick={() => setOpen(!open)}
        style={{
          width: '100%', display: 'flex', alignItems: 'center', gap: 8,
          padding: '8px 12px', background: 'var(--bg3)', border: 'none',
          color: 'var(--text)', cursor: 'pointer', textAlign: 'left', fontSize: 12,
        }}
      >
        {open ? <ChevronDown size={14} /> : <ChevronRight size={14} />}
        <span style={{ fontWeight: 600, color: chain.score > 0.6 ? 'var(--success)' : 'var(--muted)' }}>
          Score: {chain.score.toFixed(2)}
        </span>
        <span style={{
          fontSize: 11, padding: '1px 6px', borderRadius: 99,
          background: chain.direction === 'backward' ? 'rgba(239,68,68,0.15)' : 'rgba(96,165,250,0.15)',
          color: chain.direction === 'backward' ? '#f87171' : '#60a5fa',
        }}>
          {chain.direction}
        </span>
        <span style={{ color: 'var(--muted)', flex: 1, overflow: 'hidden', textOverflow: 'ellipsis', whiteSpace: 'nowrap' }}>
          {chain.path.join(' → ')}
        </span>
      </button>

      {open && (
        <div style={{ padding: 12, fontSize: 12 }}>
          <div style={{ marginBottom: 10, fontFamily: 'monospace', color: 'var(--accent2)', wordBreak: 'break-word' }}>
            {chain.path.map((node, i) => (
              <span key={i}>
                <span style={{ padding: '2px 6px', background: 'rgba(99,102,241,0.15)', borderRadius: 4 }}>{node}</span>
                {i < chain.path.length - 1 && <span style={{ color: 'var(--muted)', margin: '0 4px' }}>→</span>}
              </span>
            ))}
          </div>
          {chain.edges.map((edge, i) => (
            <div key={i} style={{
              borderLeft: '2px solid var(--border)', paddingLeft: 10, marginBottom: 8,
            }}>
              <div style={{ marginBottom: 2 }}>
                <span style={{ color: '#f87171' }}>{edge.cause}</span>
                <span style={{ margin: '0 6px' }}>
                  <span className={`badge ${edge.relation}`}>{edge.relation}</span>
                </span>
                <span style={{ color: '#60a5fa' }}>{edge.effect}</span>
                <span style={{ color: 'var(--muted)', marginLeft: 8 }}>[{edge.confidence.toFixed(2)}]</span>
              </div>
              {edge.evidence && (
                <div style={{ color: 'var(--muted)', fontStyle: 'italic', fontSize: 11 }}>
                  "{edge.evidence}"
                </div>
              )}
            </div>
          ))}
        </div>
      )}
    </div>
  )
}

export function ChatPanel({ documentId, settings }: Props) {
  const [messages, setMessages] = useState<Message[]>([])
  const [input, setInput] = useState('')
  const [loading, setLoading] = useState(false)
  const [error, setError] = useState<string | null>(null)
  const bottomRef = useRef<HTMLDivElement>(null)

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

  const send = async () => {
    const msg = input.trim()
    if (!msg || loading) return
    setInput('')
    setError(null)
    setMessages(prev => [...prev, { role: 'user', content: msg }])
    setLoading(true)
    try {
      const res = await api.chat(documentId, msg, settings)
      setMessages(prev => [...prev, { role: 'assistant', content: res.answer, response: res }])
    } catch (e: any) {
      setError(String(e.message))
    } finally {
      setLoading(false)
    }
  }

  const SAMPLES = [
    'Why did quarterly revenue decrease?',
    'What caused inventory shortages?',
    'What are the downstream effects of port congestion?',
  ]

  return (
    <div style={{ display: 'flex', flexDirection: 'column', height: '100%', maxWidth: 900 }}>
      {messages.length === 0 && (
        <div style={{ marginBottom: 16 }}>
          <div className="label" style={{ marginBottom: 8 }}>Sample Questions</div>
          <div style={{ display: 'flex', gap: 8, flexWrap: 'wrap' }}>
            {SAMPLES.map(q => (
              <button key={q} className="btn-secondary" style={{ fontSize: 12 }} onClick={() => setInput(q)}>
                {q}
              </button>
            ))}
          </div>
        </div>
      )}

      <div style={{ flex: 1, overflowY: 'auto', display: 'flex', flexDirection: 'column', gap: 16, marginBottom: 16 }}>
        {messages.map((m, i) => (
          <div key={i}>
            {m.role === 'user' ? (
              <div style={{
                background: 'var(--accent)', borderRadius: 'var(--radius)',
                padding: '10px 14px', alignSelf: 'flex-end', fontSize: 14,
                maxWidth: '70%', marginLeft: 'auto',
              }}>
                {m.content}
              </div>
            ) : (
              <div>
                <div className="card" style={{ marginBottom: 12, fontSize: 14, lineHeight: 1.6 }}>
                  {m.content}
                </div>
                {m.response && m.response.chains.length > 0 && (
                  <div>
                    <div className="label" style={{ marginBottom: 8 }}>
                      Retrieved Causal Chains ({m.response.chains.length})
                    </div>
                    {m.response.chains.map((chain, ci) => (
                      <ChainCard key={ci} chain={chain} index={ci} />
                    ))}
                  </div>
                )}
              </div>
            )}
          </div>
        ))}
        {loading && (
          <div style={{ display: 'flex', alignItems: 'center', gap: 8, color: 'var(--muted)', fontSize: 13 }}>
            <span className="spinner" style={{ width: 16, height: 16 }} />
            Retrieving causal chains...
          </div>
        )}
        {error && <div className="error-msg">{error}</div>}
        <div ref={bottomRef} />
      </div>

      <div style={{ display: 'flex', gap: 8 }}>
        <input
          type="text"
          placeholder="Ask about causal relationships..."
          value={input}
          onChange={e => setInput(e.target.value)}
          onKeyDown={e => e.key === 'Enter' && send()}
          disabled={loading}
          style={{ flex: 1 }}
        />
        <button className="btn-primary" onClick={send} disabled={loading || !input.trim()}>
          <Send size={16} />
        </button>
      </div>
    </div>
  )
}