Add fertilization plan merge workflow

frontend/src/app/fertilizer/page.tsx

@@ -2,7 +2,7 @@
 
 import { useEffect, useState } from 'react';
 import { useRouter } from 'next/navigation';
-import { FileDown, NotebookText, Pencil, Plus, Sprout, Trash2, Truck } from 'lucide-react';
+import { FileDown, GitMerge, NotebookText, Pencil, Plus, Sprout, Trash2, Truck, X } from 'lucide-react';
 
 import Navbar from '@/components/Navbar';
 import { api } from '@/lib/api';
@@ -36,6 +36,14 @@ export default function FertilizerPage() {
   const [plans, setPlans] = useState<FertilizationPlan[]>([]);
   const [loading, setLoading] = useState(true);
   const [error, setError] = useState<string | null>(null);
+  const [mergeSourcePlan, setMergeSourcePlan] = useState<FertilizationPlan | null>(null);
+  const [mergeTargets, setMergeTargets] = useState<
+    { id: number; name: string; field_count: number; planned_total_bags: string; is_confirmed: boolean }[]
+  >([]);
+  const [mergeTargetId, setMergeTargetId] = useState<number | ''>('');
+  const [mergeLoading, setMergeLoading] = useState(false);
+  const [mergeSubmitting, setMergeSubmitting] = useState(false);
+  const [mergeError, setMergeError] = useState<string | null>(null);
 
   useEffect(() => {
     localStorage.setItem('fertilizerYear', String(year));
@@ -83,6 +91,68 @@ export default function FertilizerPage() {
     }
   };
 
+  const openMergeDialog = async (plan: FertilizationPlan) => {
+    setMergeSourcePlan(plan);
+    setMergeTargets([]);
+    setMergeTargetId('');
+    setMergeError(null);
+    setMergeLoading(true);
+    try {
+      const res = await api.get(`/fertilizer/plans/${plan.id}/merge_targets/`);
+      setMergeTargets(res.data);
+    } catch (e) {
+      console.error(e);
+      setMergeError('マージ先候補の読み込みに失敗しました。');
+    } finally {
+      setMergeLoading(false);
+    }
+  };
+
+  const closeMergeDialog = () => {
+    if (mergeSubmitting) return;
+    setMergeSourcePlan(null);
+    setMergeTargets([]);
+    setMergeTargetId('');
+    setMergeError(null);
+    setMergeLoading(false);
+  };
+
+  const handleMerge = async () => {
+    if (!mergeSourcePlan || !mergeTargetId) {
+      setMergeError('マージ先の施肥計画を選択してください。');
+      return;
+    }
+    setMergeSubmitting(true);
+    setMergeError(null);
+    try {
+      await api.post(`/fertilizer/plans/${mergeSourcePlan.id}/merge_into/`, {
+        target_plan_id: mergeTargetId,
+      });
+      closeMergeDialog();
+      await fetchPlans();
+    } catch (e: unknown) {
+      const err = e as {
+        response?: {
+          data?: {
+            error?: string;
+            conflicts?: { field_name: string; fertilizer_name: string }[];
+          };
+        };
+      };
+      const conflicts = err.response?.data?.conflicts ?? [];
+      if (conflicts.length > 0) {
+        const details = conflicts
+          .map((conflict) => `${conflict.field_name} × ${conflict.fertilizer_name}`)
+          .join('、');
+        setMergeError(`${err.response?.data?.error ?? '競合があるためマージできません。'} ${details}`);
+      } else {
+        setMergeError(err.response?.data?.error ?? 'マージに失敗しました。');
+      }
+    } finally {
+      setMergeSubmitting(false);
+    }
+  };
+
   const years = Array.from({ length: 5 }, (_, i) => currentYear + 1 - i);
 
   return (
@@ -208,6 +278,16 @@ export default function FertilizerPage() {
                           <Pencil className="h-3.5 w-3.5" />
                           編集
                         </button>
+                        {plan.is_variety_change_plan && (
+                          <button
+                            onClick={() => openMergeDialog(plan)}
+                            className="flex items-center gap-1 rounded border border-emerald-300 px-2.5 py-1.5 text-xs text-emerald-700 hover:bg-emerald-50"
+                            title="既存計画へマージ"
+                          >
+                            <GitMerge className="h-3.5 w-3.5" />
+                            マージ
+                          </button>
+                        )}
                         <button
                           onClick={() => handleDelete(plan.id, plan.name)}
                           className="flex items-center gap-1 rounded border border-red-300 px-2.5 py-1.5 text-xs text-red-600 hover:bg-red-50"
@@ -225,6 +305,85 @@ export default function FertilizerPage() {
           </div>
         )}
       </div>
+
+      {mergeSourcePlan && (
+        <div className="fixed inset-0 z-50 flex items-center justify-center bg-black/40 p-4">
+          <div className="w-full max-w-xl rounded-lg bg-white shadow-xl">
+            <div className="flex items-center justify-between border-b px-5 py-4">
+              <div>
+                <h2 className="text-lg font-semibold text-gray-800">既存計画へマージ</h2>
+                <p className="mt-1 text-sm text-gray-500">{mergeSourcePlan.name}</p>
+              </div>
+              <button onClick={closeMergeDialog} className="text-gray-400 hover:text-gray-600">
+                <X className="h-5 w-5" />
+              </button>
+            </div>
+
+            <div className="space-y-4 px-5 py-4">
+              <p className="text-sm text-gray-600">
+                同年度・同品種の既存施肥計画へ統合します。競合する圃場 × 肥料がある場合はマージせず停止します。
+              </p>
+
+              {mergeError && (
+                <div className="rounded-lg border border-red-300 bg-red-50 px-4 py-3 text-sm text-red-700">
+                  {mergeError}
+                </div>
+              )}
+
+              {mergeLoading ? (
+                <p className="text-sm text-gray-500">候補を読み込み中...</p>
+              ) : mergeTargets.length === 0 ? (
+                <p className="text-sm text-gray-500">マージ可能な施肥計画がありません。</p>
+              ) : (
+                <div className="space-y-2">
+                  {mergeTargets.map((target) => (
+                    <label
+                      key={target.id}
+                      className={`flex cursor-pointer items-start gap-3 rounded-lg border px-4 py-3 ${
+                        target.is_confirmed ? 'border-gray-200 bg-gray-50 text-gray-400' : 'border-gray-300'
+                      }`}
+                    >
+                      <input
+                        type="radio"
+                        name="merge-target"
+                        value={target.id}
+                        checked={mergeTargetId === target.id}
+                        onChange={() => setMergeTargetId(target.id)}
+                        disabled={target.is_confirmed}
+                        className="mt-1"
+                      />
+                      <div className="min-w-0 flex-1">
+                        <div className="font-medium text-gray-800">{target.name}</div>
+                        <div className="mt-1 text-xs text-gray-500">
+                          {target.field_count}筆 / 計画 {target.planned_total_bags}袋
+                          {target.is_confirmed ? ' / 散布確定済みのため選択不可' : ''}
+                        </div>
+                      </div>
+                    </label>
+                  ))}
+                </div>
+              )}
+            </div>
+
+            <div className="flex items-center justify-end gap-3 border-t px-5 py-4">
+              <button
+                onClick={closeMergeDialog}
+                disabled={mergeSubmitting}
+                className="rounded-lg border border-gray-300 px-4 py-2 text-sm text-gray-700 hover:bg-gray-100 disabled:opacity-50"
+              >
+                キャンセル
+              </button>
+              <button
+                onClick={handleMerge}
+                disabled={mergeSubmitting || mergeLoading || !mergeTargetId}
+                className="rounded-lg bg-emerald-600 px-4 py-2 text-sm text-white hover:bg-emerald-700 disabled:opacity-50"
+              >
+                {mergeSubmitting ? 'マージ中...' : 'マージ実行'}
+              </button>
+            </div>
+          </div>
+        </div>
+      )}
     </div>
   );
 }

frontend/src/types/index.ts

@@ -176,6 +176,7 @@ export interface FertilizationPlan {
   spread_status: 'unspread' | 'partial' | 'completed' | 'over_applied';
   is_confirmed: boolean;
   confirmed_at: string | null;
+  is_variety_change_plan: boolean;
   created_at: string;
   updated_at: string;
 }