fix(frontend): block/warn direct parent-offspring selections in PairingSimulator

client/src/pages/PairingSimulator.jsx

@@ -1,5 +1,5 @@
-import { useState, useEffect } from 'react'
-import { FlaskConical, AlertTriangle, CheckCircle, XCircle, GitMerge } from 'lucide-react'
+import { useState, useEffect, useCallback } from 'react'
+import { FlaskConical, AlertTriangle, CheckCircle, XCircle, GitMerge, ShieldAlert } from 'lucide-react'
 
 export default function PairingSimulator() {
   const [dogs, setDogs] = useState([])
@@ -9,6 +9,8 @@ export default function PairingSimulator() {
   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')
@@ -20,6 +22,38 @@ export default function PairingSimulator() {
       .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')
 
@@ -84,7 +118,7 @@ export default function PairingSimulator() {
               <label className="label">Sire (Male) ♂</label>
               <select
                 value={sireId}
-                onChange={e => setSireId(e.target.value)}
+                onChange={handleSireChange}
                 required
                 disabled={dogsLoading}
               >
@@ -104,7 +138,7 @@ export default function PairingSimulator() {
               <label className="label">Dam (Female) ♀</label>
               <select
                 value={damId}
-                onChange={e => setDamId(e.target.value)}
+                onChange={handleDamChange}
                 required
                 disabled={dogsLoading}
               >
@@ -121,10 +155,30 @@ export default function PairingSimulator() {
             </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}
+            disabled={!sireId || !damId || loading || relationChecking}
             style={{ minWidth: '160px' }}
           >
             {loading ? 'Calculating…' : <><FlaskConical size={16} /> Simulate Pairing</>}
@@ -138,6 +192,21 @@ export default function PairingSimulator() {
       {/* 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' }}>
@@ -152,9 +221,7 @@ export default function PairingSimulator() {
               <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,
+                  fontSize: '2rem', fontWeight: 700, lineHeight: 1,
                   color: result.coi < 5 ? 'var(--success)' : result.coi < 10 ? 'var(--warning)' : 'var(--danger)'
                 }}>
                   {result.coi.toFixed(2)}%
@@ -183,7 +250,7 @@ export default function PairingSimulator() {
 
             {result.commonAncestors.length === 0 ? (
               <p style={{ color: 'var(--text-muted)', textAlign: 'center', padding: '1.5rem 0', margin: 0 }}>
-                No common ancestors found within 5 generations. This pairing has excellent genetic diversity.
+                No common ancestors found within 6 generations. This pairing has excellent genetic diversity.
               </p>
             ) : (
               <div style={{ overflowX: 'auto' }}>