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(() => {
    // include_external=1 ensures external sires/dams appear for pairing
    fetch('/api/dogs?include_external=1')
      .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)
  }

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

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

  const coiColor = (coi) => {
    if (coi < 0.0625) return 'var(--success)'
    if (coi < 0.125)  return 'var(--warning)'
    return 'var(--danger)'
  }

  const coiLabel = (coi) => {
    if (coi < 0.0625) return 'Low'
    if (coi < 0.125)  return 'Moderate'
    if (coi < 0.25)   return 'High'
    return 'Very High'
  }

  return (
    <div className="container" style={{ paddingTop: '2rem', paddingBottom: '3rem', maxWidth: '720px' }}>
      <div style={{ display: 'flex', alignItems: 'center', gap: '0.75rem', marginBottom: '0.5rem' }}>
        <FlaskConical size={28} style={{ color: 'var(--primary)' }} />
        <h1 style={{ margin: 0 }}>Pairing Simulator</h1>
      </div>
      <p style={{ color: 'var(--text-muted)', marginBottom: '2rem' }}>
        Estimate the Coefficient of Inbreeding (COI) for a hypothetical pairing before breeding.
        Includes both kennel and external dogs.
      </p>

      <div className="card" style={{ marginBottom: '1.5rem' }}>
        <form onSubmit={handleSimulate}>
          <div className="form-grid" style={{ marginBottom: '1rem' }}>
            <div className="form-group">
              <label className="label">Sire (Male) *</label>
              {dogsLoading ? (
                <div className="input" style={{ color: 'var(--text-muted)' }}>Loading dogs...</div>
              ) : (
                <select className="input" value={sireId} onChange={handleSireChange} required>
                  <option value="">Select sire...</option>
                  {males.map(d => (
                    <option key={d.id} value={d.id}>
                      {d.name}{d.is_champion ? ' ✪' : ''}{d.is_external ? ' [Ext]' : ''}
                    </option>
                  ))}
                </select>
              )}
            </div>

            <div className="form-group">
              <label className="label">Dam (Female) *</label>
              {dogsLoading ? (
                <div className="input" style={{ color: 'var(--text-muted)' }}>Loading dogs...</div>
              ) : (
                <select className="input" value={damId} onChange={handleDamChange} required>
                  <option value="">Select dam...</option>
                  {females.map(d => (
                    <option key={d.id} value={d.id}>
                      {d.name}{d.is_champion ? ' ✪' : ''}{d.is_external ? ' [Ext]' : ''}
                    </option>
                  ))}
                </select>
              )}
            </div>
          </div>

          {relationChecking && (
            <div style={{ fontSize: '0.85rem', color: 'var(--text-muted)', marginBottom: '0.75rem' }}>
              Checking relationship...
            </div>
          )}

          {relationWarning && !relationChecking && (
            <div style={{
              display: 'flex', alignItems: 'center', gap: '0.5rem',
              padding: '0.6rem 1rem', marginBottom: '0.75rem',
              background: 'rgba(239,68,68,0.08)', border: '1px solid rgba(239,68,68,0.3)',
              borderRadius: 'var(--radius)', fontSize: '0.875rem', color: 'var(--danger)',
            }}>
              <ShieldAlert size={16} />
              <strong>Related:</strong>&nbsp;{relationWarning}
            </div>
          )}

          <button
            type="submit"
            className="btn btn-primary"
            disabled={loading || dogsLoading || !sireId || !damId}
            style={{ width: '100%' }}
          >
            {loading ? 'Simulating...' : <><GitMerge size={16} style={{ marginRight: '0.4rem' }} />Simulate Pairing</>}
          </button>
        </form>
      </div>

      {error && (
        <div className="card" style={{ borderColor: 'var(--danger)', marginBottom: '1.5rem' }}>
          <div style={{ display: 'flex', alignItems: 'center', gap: '0.5rem', color: 'var(--danger)' }}>
            <XCircle size={18} />
            <strong>Error:</strong> {error}
          </div>
        </div>
      )}

      {result && (
        <div className="card">
          <h2 style={{ fontSize: '1rem', marginBottom: '1.25rem', color: 'var(--text-muted)', textTransform: 'uppercase', letterSpacing: '0.05em' }}>
            Simulation Result
          </h2>

          <div style={{
            display: 'flex', alignItems: 'center', gap: '1rem',
            padding: '1.25rem', marginBottom: '1rem',
            background: 'var(--bg-primary)', borderRadius: 'var(--radius)',
            border: `2px solid ${coiColor(result.coi)}`,
          }}>
            {result.coi < 0.0625
              ? <CheckCircle size={32} style={{ color: coiColor(result.coi), flexShrink: 0 }} />
              : <AlertTriangle size={32} style={{ color: coiColor(result.coi), flexShrink: 0 }} />
            }
            <div>
              <div style={{ fontSize: '2rem', fontWeight: 700, color: coiColor(result.coi), lineHeight: 1 }}>
                {(result.coi * 100).toFixed(2)}%
              </div>
              <div style={{ color: 'var(--text-muted)', fontSize: '0.875rem' }}>
                COI &mdash; <strong style={{ color: coiColor(result.coi) }}>{coiLabel(result.coi)}</strong>
              </div>
            </div>
          </div>

          {result.common_ancestors && result.common_ancestors.length > 0 && (
            <div>
              <h3 style={{ fontSize: '0.875rem', color: 'var(--text-muted)', textTransform: 'uppercase', letterSpacing: '0.05em', marginBottom: '0.5rem' }}>
                Common Ancestors ({result.common_ancestors.length})
              </h3>
              <div style={{ display: 'flex', flexWrap: 'wrap', gap: '0.4rem' }}>
                {result.common_ancestors.map((a, i) => (
                  <span key={i} style={{
                    padding: '0.2rem 0.6rem',
                    background: 'var(--bg-tertiary)',
                    borderRadius: 'var(--radius-sm)',
                    fontSize: '0.8rem',
                    border: '1px solid var(--border)',
                  }}>{a}</span>
                ))}
              </div>
            </div>
          )}

          {result.recommendation && (
            <div style={{
              marginTop: '1rem', padding: '0.75rem 1rem',
              background: result.coi < 0.0625 ? 'rgba(34,197,94,0.08)' : 'rgba(239,68,68,0.08)',
              borderRadius: 'var(--radius)',
              border: `1px solid ${result.coi < 0.0625 ? 'rgba(34,197,94,0.3)' : 'rgba(239,68,68,0.3)'}`,
              fontSize: '0.875rem',
              color: 'var(--text-secondary)',
            }}>
              {result.recommendation}
            </div>
          )}
        </div>
      )}
    </div>
  )
}