import { useState, useEffect, useCallback } from 'react'
import { FlaskConical, AlertTriangle, CheckCircle, XCircle, GitMerge, ShieldAlert } from 'lucide-react'

export default function PairingSimulator() {
  const [dogs, setDogs] = useState([])
  const [sireId, setSireId] = useState('')
  const [damId, setDamId] = useState('')
  const [result, setResult] = useState(null)
  const [loading, setLoading] = useState(false)
  const [error, setError] = useState(null)
  const [dogsLoading, setDogsLoading] = useState(true)
  const [relationWarning, setRelationWarning] = useState(null)
  const [relationChecking, setRelationChecking] = useState(false)

  useEffect(() => {
    fetch('/api/dogs')
      .then(r => r.json())
      .then(data => {
        setDogs(Array.isArray(data) ? data : (data.dogs || []))
        setDogsLoading(false)
      })
      .catch(() => setDogsLoading(false))
  }, [])

  // Check for direct relation whenever both sire and dam are selected
  const checkRelation = useCallback(async (sid, did) => {
    if (!sid || !did) {
      setRelationWarning(null)
      return
    }
    setRelationChecking(true)
    try {
      const res = await fetch(`/api/pedigree/relations/${sid}/${did}`)
      const data = await res.json()
      setRelationWarning(data.related ? data.relationship : null)
    } catch {
      setRelationWarning(null)
    } finally {
      setRelationChecking(false)
    }
  }, [])

  function handleSireChange(e) {
    const val = e.target.value
    setSireId(val)
    setResult(null)
    checkRelation(val, damId)
  }

  function handleDamChange(e) {
    const val = e.target.value
    setDamId(val)
    setResult(null)
    checkRelation(sireId, val)
  }

  const males   = dogs.filter(d => d.sex === 'male')
  const females = dogs.filter(d => d.sex === 'female')

  async function handleSimulate(e) {
    e.preventDefault()
    if (!sireId || !damId) return
    setLoading(true)
    setError(null)
    setResult(null)
    try {
      const res = await fetch('/api/pedigree/trial-pairing', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ sire_id: parseInt(sireId), dam_id: parseInt(damId) })
      })
      if (!res.ok) {
        const err = await res.json()
        throw new Error(err.error || 'Failed to calculate')
      }
      setResult(await res.json())
    } catch (err) {
      setError(err.message)
    } finally {
      setLoading(false)
    }
  }

  function RiskBadge({ coi, recommendation }) {
    const isLow  = coi < 5
    const isMed  = coi >= 5 && coi < 10
    const isHigh = coi >= 10
    return (
      <div className={`risk-badge risk-${isLow ? 'low' : isMed ? 'med' : 'high'}`}>
        {isLow  && <CheckCircle size={20} />}
        {isMed  && <AlertTriangle size={20} />}
        {isHigh && <XCircle size={20} />}
        <span>{recommendation}</span>
      </div>
    )
  }

  return (
    <div className="container" style={{ paddingTop: '2rem', paddingBottom: '3rem' }}>
      {/* Header */}
      <div style={{ marginBottom: '2rem' }}>
        <div style={{ display: 'flex', alignItems: 'center', gap: '0.75rem', marginBottom: '0.5rem' }}>
          <div style={{ width: '2.5rem', height: '2.5rem', borderRadius: 'var(--radius)', background: 'rgba(139,92,246,0.2)', display: 'flex', alignItems: 'center', justifyContent: 'center', color: 'var(--accent)' }}>
            <FlaskConical size={20} />
          </div>
          <h1 style={{ fontSize: '1.75rem', margin: 0 }}>Trial Pairing Simulator</h1>
        </div>
        <p style={{ color: 'var(--text-muted)', margin: 0 }}>
          Select a sire and dam to calculate the estimated inbreeding coefficient (COI) and view common ancestors.
        </p>
      </div>

      {/* Selector Card */}
      <div className="card" style={{ marginBottom: '1.5rem', maxWidth: '720px' }}>
        <form onSubmit={handleSimulate}>
          <div className="form-grid" style={{ marginBottom: '1.25rem' }}>
            <div className="form-group" style={{ margin: 0 }}>
              <label className="label">Sire (Male) ♂</label>
              <select
                value={sireId}
                onChange={handleSireChange}
                required
                disabled={dogsLoading}
              >
                <option value="">— Select Sire —</option>
                {males.map(d => (
                  <option key={d.id} value={d.id}>
                    {d.name}{d.breed ? ` · ${d.breed}` : ''}
                  </option>
                ))}
              </select>
              {!dogsLoading && males.length === 0 && (
                <p style={{ color: 'var(--text-muted)', fontSize: '0.8rem', marginTop: '0.4rem' }}>No male dogs registered.</p>
              )}
            </div>

            <div className="form-group" style={{ margin: 0 }}>
              <label className="label">Dam (Female) ♀</label>
              <select
                value={damId}
                onChange={handleDamChange}
                required
                disabled={dogsLoading}
              >
                <option value="">— Select Dam —</option>
                {females.map(d => (
                  <option key={d.id} value={d.id}>
                    {d.name}{d.breed ? ` · ${d.breed}` : ''}
                  </option>
                ))}
              </select>
              {!dogsLoading && females.length === 0 && (
                <p style={{ color: 'var(--text-muted)', fontSize: '0.8rem', marginTop: '0.4rem' }}>No female dogs registered.</p>
              )}
            </div>
          </div>

          {/* Direct-relation warning banner */}
          {relationChecking && (
            <p style={{ fontSize: '0.8125rem', color: 'var(--text-muted)', marginBottom: '1rem' }}>Checking relationship…</p>
          )}
          {!relationChecking && relationWarning && (
            <div style={{
              display: 'flex', alignItems: 'flex-start', gap: '0.6rem',
              background: 'rgba(234,179,8,0.12)', border: '1px solid rgba(234,179,8,0.4)',
              borderRadius: 'var(--radius-sm)', padding: '0.75rem 1rem', marginBottom: '1rem'
            }}>
              <ShieldAlert size={18} style={{ color: '#eab308', flexShrink: 0, marginTop: '0.1rem' }} />
              <div>
                <p style={{ margin: 0, fontWeight: 600, color: '#eab308', fontSize: '0.875rem' }}>Direct Relation Detected</p>
                <p style={{ margin: '0.2rem 0 0', fontSize: '0.8125rem', color: 'var(--text-secondary)' }}>
                  {relationWarning}. COI will reflect the high inbreeding coefficient for this pairing.
                </p>
              </div>
            </div>
          )}

          <button
            type="submit"
            className="btn btn-primary"
            disabled={!sireId || !damId || loading || relationChecking}
            style={{ minWidth: '160px' }}
          >
            {loading ? 'Calculating…' : <><FlaskConical size={16} /> Simulate Pairing</>}
          </button>
        </form>
      </div>

      {/* Error */}
      {error && <div className="error" style={{ maxWidth: '720px' }}>{error}</div>}

      {/* Results */}
      {result && (
        <div style={{ maxWidth: '720px' }}>
          {/* Direct-relation alert in results */}
          {result.directRelation && (
            <div style={{
              display: 'flex', alignItems: 'flex-start', gap: '0.6rem',
              background: 'rgba(239,68,68,0.1)', border: '1px solid rgba(239,68,68,0.35)',
              borderRadius: 'var(--radius-sm)', padding: '0.75rem 1rem', marginBottom: '1.25rem'
            }}>
              <ShieldAlert size={18} style={{ color: 'var(--danger)', flexShrink: 0, marginTop: '0.1rem' }} />
              <div>
                <p style={{ margin: 0, fontWeight: 600, color: 'var(--danger)', fontSize: '0.875rem' }}>Direct Relation — High Inbreeding Risk</p>
                <p style={{ margin: '0.2rem 0 0', fontSize: '0.8125rem', color: 'var(--text-secondary)' }}>{result.directRelation}</p>
              </div>
            </div>
          )}

          {/* COI Summary */}
          <div className="card" style={{ marginBottom: '1.25rem' }}>
            <div style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'flex-start', flexWrap: 'wrap', gap: '1rem' }}>
              <div>
                <p style={{ color: 'var(--text-muted)', fontSize: '0.8125rem', textTransform: 'uppercase', letterSpacing: '0.05em', fontWeight: 500, marginBottom: '0.25rem' }}>Pairing</p>
                <p style={{ fontSize: '1.125rem', fontWeight: 600, margin: 0 }}>
                  <span style={{ color: '#60a5fa' }}>{result.sire.name}</span>
                  <span style={{ color: 'var(--text-muted)', margin: '0 0.5rem' }}>×</span>
                  <span style={{ color: '#f472b6' }}>{result.dam.name}</span>
                </p>
              </div>
              <div style={{ textAlign: 'right' }}>
                <p style={{ color: 'var(--text-muted)', fontSize: '0.8125rem', textTransform: 'uppercase', letterSpacing: '0.05em', fontWeight: 500, marginBottom: '0.25rem' }}>COI</p>
                <p style={{
                  fontSize: '2rem', fontWeight: 700, lineHeight: 1,
                  color: result.coi < 5 ? 'var(--success)' : result.coi < 10 ? 'var(--warning)' : 'var(--danger)'
                }}>
                  {result.coi.toFixed(2)}%
                </p>
              </div>
            </div>

            <div style={{ marginTop: '1.25rem' }}>
              <RiskBadge coi={result.coi} recommendation={result.recommendation} />
            </div>

            <div style={{ marginTop: '1rem', padding: '0.75rem', background: 'var(--bg-tertiary)', borderRadius: 'var(--radius-sm)', fontSize: '0.8125rem', color: 'var(--text-secondary)' }}>
              <strong>COI Guide:</strong> &lt;5% Low risk · 5–10% Moderate risk · &gt;10% High risk
            </div>
          </div>

          {/* Common Ancestors */}
          <div className="card">
            <div style={{ display: 'flex', alignItems: 'center', gap: '0.5rem', marginBottom: '1rem' }}>
              <GitMerge size={18} style={{ color: 'var(--accent)' }} />
              <h3 style={{ margin: 0, fontSize: '1rem' }}>Common Ancestors</h3>
              <span className="badge badge-primary" style={{ marginLeft: 'auto' }}>
                {result.commonAncestors.length} found
              </span>
            </div>

            {result.commonAncestors.length === 0 ? (
              <p style={{ color: 'var(--text-muted)', textAlign: 'center', padding: '1.5rem 0', margin: 0 }}>
                No common ancestors found within 6 generations. This pairing has excellent genetic diversity.
              </p>
            ) : (
              <div style={{ overflowX: 'auto' }}>
                <table style={{ width: '100%', borderCollapse: 'collapse', fontSize: '0.875rem' }}>
                  <thead>
                    <tr style={{ borderBottom: '1px solid var(--border)' }}>
                      <th style={{ textAlign: 'left', padding: '0.625rem 0.75rem', color: 'var(--text-muted)', fontWeight: 500, fontSize: '0.75rem', textTransform: 'uppercase', letterSpacing: '0.05em' }}>Ancestor</th>
                      <th style={{ textAlign: 'center', padding: '0.625rem 0.75rem', color: 'var(--text-muted)', fontWeight: 500, fontSize: '0.75rem', textTransform: 'uppercase', letterSpacing: '0.05em' }}>Sire Gen</th>
                      <th style={{ textAlign: 'center', padding: '0.625rem 0.75rem', color: 'var(--text-muted)', fontWeight: 500, fontSize: '0.75rem', textTransform: 'uppercase', letterSpacing: '0.05em' }}>Dam Gen</th>
                    </tr>
                  </thead>
                  <tbody>
                    {result.commonAncestors.map((anc, i) => (
                      <tr key={i} style={{ borderBottom: '1px solid var(--border)' }}>
                        <td style={{ padding: '0.625rem 0.75rem', fontWeight: 500 }}>{anc.name}</td>
                        <td style={{ padding: '0.625rem 0.75rem', textAlign: 'center' }}>
                          <span className="badge badge-primary">Gen {anc.sireGen}</span>
                        </td>
                        <td style={{ padding: '0.625rem 0.75rem', textAlign: 'center' }}>
                          <span className="badge" style={{ background: 'rgba(244,114,182,0.15)', color: '#f472b6' }}>Gen {anc.damGen}</span>
                        </td>
                      </tr>
                    ))}
                  </tbody>
                </table>
              </div>
            )}
          </div>
        </div>
      )}
    </div>
  )
}