feat: AI 辅助修改行程（自然语言调整 + 单活动替代推荐）

- 新增 refinePlan / suggestAlternativeItems 到 ai.ts
- 新增 POST /api/blindbox/plan/refine（整体行程调整）
- 新增 POST /api/blindbox/plan/suggest-item（单活动 AI 替代 + POI 搜索）
- BlindboxPlan 底部新增自然语言输入框（方案 A）
- 编辑 modal 内新增 AI 推荐替代方案卡片（方案 B）
- export searchPois 供 suggest-item 路由复用

src/app/api/blindbox/plan/refine/route.ts

@@ -0,0 +1,14 @@
+import { NextResponse } from "next/server";
+import { apiHandler, ApiError, requireUserId } from "@/lib/api";
+import { refinePlan } from "@/lib/ai";
+
+export const POST = apiHandler(async (req) => {
+  const { userId, instruction, days } = await req.json();
+  requireUserId(userId);
+  if (!instruction?.trim()) throw new ApiError("指令不能为空", 400);
+  if (!Array.isArray(days) || days.length === 0) throw new ApiError("days 无效", 400);
+
+  const newDays = await refinePlan(days, instruction);
+  if (!newDays) throw new ApiError("AI 调整失败，请重试", 500);
+  return NextResponse.json({ days: newDays });
+});

src/app/api/blindbox/plan/suggest-item/route.ts

@@ -0,0 +1,49 @@
+import { NextResponse } from "next/server";
+import { apiHandler, ApiError } from "@/lib/api";
+import { suggestAlternativeItems } from "@/lib/ai";
+import { searchPois } from "@/lib/blindboxPlanGen";
+
+export const POST = apiHandler(async (req) => {
+  const { activity, time, location } = await req.json();
+  if (!activity) throw new ApiError("activity 不能为空", 400);
+
+  const alts = await suggestAlternativeItems(activity, time ?? "");
+  if (!alts) throw new ApiError("AI 推荐失败，请重试", 500);
+
+  // Parse location "lng,lat"
+  let anchorLat = 31.23, anchorLng = 121.47; // default Shanghai
+  if (location) {
+    const [lng, lat] = location.split(",").map(Number);
+    if (!isNaN(lat) && !isNaN(lng)) { anchorLat = lat; anchorLng = lng; }
+  }
+
+  // Parallel POI search with per-item fallback
+  const results = await Promise.all(
+    alts.map(async (alt) => {
+      try {
+        const pois = await searchPois(alt.searchQuery, "place", anchorLat, anchorLng);
+        const top = pois[0];
+        if (top) {
+          return {
+            activity: alt.activity,
+            poi: top.name,
+            address: top.address,
+            lat: top.lat,
+            lng: top.lng,
+            reason: alt.reason,
+          };
+        }
+      } catch { /* ignore, use fallback */ }
+      return {
+        activity: alt.activity,
+        poi: alt.searchQuery,
+        address: "",
+        lat: 0,
+        lng: 0,
+        reason: alt.reason,
+      };
+    }),
+  );
+
+  return NextResponse.json({ suggestions: results });
+});

src/app/blindbox/[code]/page.tsx

@@ -627,6 +627,24 @@ export default function BlindboxRoomPage() {
     }
   }, [planId, profile, planDays, planAccepted, toast]);
 
+  const handleRefine = useCallback(async (instruction: string) => {
+    if (!profile || !planDays.length) return;
+    const prevDays = planDays;
+    try {
+      const res = await fetch("/api/blindbox/plan/refine", {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ userId: profile.id, instruction, days: planDays }),
+      });
+      if (!res.ok) throw new Error((await res.json().catch(() => ({}))).error || "AI 调整失败");
+      const data = await res.json();
+      await handlePlanDaysChange(data.days);
+    } catch (e) {
+      setPlanDays(prevDays);
+      toast.show(e instanceof Error ? e.message : "AI 调整失败");
+    }
+  }, [profile, planDays, handlePlanDaysChange, toast]);
+
   /** Non-creator: leave room (remove membership). Creator: delete room (after confirm). */
   const handleLeaveOrDelete = async () => {
     if (!confirmLeave) {
@@ -1112,6 +1130,7 @@ export default function BlindboxRoomPage() {
                   accepted={planAccepted}
                   regenerating={generating}
                   onDaysChange={handlePlanDaysChange}
+                  onRefine={handleRefine}
                   location={room.lng != null && room.lat != null ? `${room.lng},${room.lat}` : undefined}
                   onAccept={async () => {
                     setPlanAccepted(true);

src/components/BlindboxPlan.tsx

@@ -38,6 +38,15 @@ import Button from "@/components/Button";
 import Modal from "@/components/Modal";
 import type { WeekendPlanData, PlanItem } from "@/types";
 
+interface AltSuggestion {
+  activity: string;
+  poi: string;
+  address: string;
+  lat: number;
+  lng: number;
+  reason: string;
+}
+
 interface BlindboxPlanProps {
   days: WeekendPlanData[];
   onAccept: () => void;
@@ -49,6 +58,7 @@ interface BlindboxPlanProps {
   onDaysChange?: (newDays: WeekendPlanData[]) => void;
   /** "lng,lat" 格式，用于 POI 搜索附近优先 */
   location?: string;
+  onRefine?: (instruction: string) => Promise<void>;
 }
 
 function guessCategory(activity: string): string | null {
@@ -265,6 +275,7 @@ export default function BlindboxPlan({
   regenerating,
   onDaysChange,
   location,
+  onRefine,
 }: BlindboxPlanProps) {
   const [dayIndex, setDayIndex] = useState(0);
   const scrollRef = useRef<HTMLDivElement>(null);
@@ -275,6 +286,10 @@ export default function BlindboxPlan({
 
   const [editingItem, setEditingItem] = useState<{ dayIndex: number; itemIndex: number } | null>(null);
   const [draft, setDraft] = useState<PlanItem | null>(null);
+  const [refineInput, setRefineInput] = useState("");
+  const [refining, setRefining] = useState(false);
+  const [suggestingAlt, setSuggestingAlt] = useState(false);
+  const [altSuggestions, setAltSuggestions] = useState<AltSuggestion[]>([]);
 
   useEffect(() => {
     scrollRef.current?.scrollTo({ top: 0, behavior: "smooth" });
@@ -314,6 +329,7 @@ export default function BlindboxPlan({
     onDaysChange(newDays);
     setEditingItem(null);
     setDraft(null);
+    setAltSuggestions([]);
   }
 
   // Cross-day move: immediately call onDaysChange
@@ -338,6 +354,34 @@ export default function BlindboxPlan({
     setDraft(null);
   }
 
+  async function handleRefine() {
+    if (!refineInput.trim() || refining || !onRefine) return;
+    setRefining(true);
+    try {
+      await onRefine(refineInput.trim());
+      setRefineInput("");
+    } finally {
+      setRefining(false);
+    }
+  }
+
+  async function handleSuggestAlt() {
+    if (!draft || suggestingAlt) return;
+    setSuggestingAlt(true);
+    try {
+      const res = await fetch("/api/blindbox/plan/suggest-item", {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ activity: draft.activity, time: draft.time, location }),
+      });
+      if (!res.ok) return;
+      const data = await res.json();
+      setAltSuggestions(data.suggestions ?? []);
+    } finally {
+      setSuggestingAlt(false);
+    }
+  }
+
   if (!currentDay) return null;
 
   return (
@@ -446,6 +490,27 @@ export default function BlindboxPlan({
 
       {/* Fixed bottom bar — actions + day navigation */}
       <div className="shrink-0 border-t border-border/40 bg-background/80 pt-3 pb-[max(0.75rem,env(safe-area-inset-bottom))] backdrop-blur-lg">
+        {/* Refine input (Plan A) */}
+        {onRefine && (
+          <div className="mx-auto flex max-w-sm items-center gap-2 px-4 pb-2">
+            <input
+              value={refineInput}
+              onChange={(e) => setRefineInput(e.target.value)}
+              onKeyDown={(e) => { if (e.key === "Enter") handleRefine(); }}
+              placeholder="告诉 AI 你想怎么改..."
+              disabled={refining}
+              className="h-9 flex-1 rounded-xl bg-surface px-3 text-sm outline-none ring-1 ring-border focus:ring-purple-600 disabled:opacity-50"
+            />
+            <button
+              onClick={handleRefine}
+              disabled={!refineInput.trim() || refining}
+              className="flex h-9 w-9 items-center justify-center rounded-xl bg-purple-600/15 text-purple-400 disabled:opacity-30"
+            >
+              {refining ? <Loader2 size={15} className="animate-spin" /> : <Sparkles size={15} />}
+            </button>
+          </div>
+        )}
+
         {/* Day navigation */}
         {days.length > 1 && (
           <div className="mx-auto mb-2.5 flex max-w-sm items-center justify-center gap-2 px-4">
@@ -513,13 +578,13 @@ export default function BlindboxPlan({
       </div>
 
       {/* Edit item modal */}
-      <Modal open={!!editingItem && !!draft} onClose={() => { setEditingItem(null); setDraft(null); }} variant="sheet">
+      <Modal open={!!editingItem && !!draft} onClose={() => { setEditingItem(null); setDraft(null); setAltSuggestions([]); }} variant="sheet">
         {draft && editingItem && (
           <div className="flex flex-col gap-4">
             <div className="flex items-center justify-between">
               <h3 className="text-sm font-bold text-heading">编辑活动</h3>
               <button
-                onClick={() => { setEditingItem(null); setDraft(null); }}
+                onClick={() => { setEditingItem(null); setDraft(null); setAltSuggestions([]); }}
                 className="text-muted active:text-foreground"
               >
                 <X size={16} />
@@ -568,6 +633,38 @@ export default function BlindboxPlan({
                 onSelect={(s) => setDraft({ ...draft, poi: s.name, address: s.address, lat: s.lat, lng: s.lng })}
               />
 
+              {/* AI 推荐替代 (Plan B) */}
+              {altSuggestions.length === 0 ? (
+                <button
+                  onClick={handleSuggestAlt}
+                  disabled={suggestingAlt}
+                  className="flex items-center gap-1.5 self-start text-xs font-medium text-purple-400/70 active:text-purple-400 disabled:opacity-40"
+                >
+                  {suggestingAlt
+                    ? <><Loader2 size={12} className="animate-spin" /> 正在推荐...</>
+                    : <><Sparkles size={12} /> AI 推荐替代方案</>}
+                </button>
+              ) : (
+                <div className="flex flex-col gap-1.5">
+                  <span className="text-[11px] font-medium text-muted">选一个替代方案</span>
+                  {altSuggestions.map((alt, i) => (
+                    <button
+                      key={i}
+                      onClick={() => {
+                        setDraft({ ...draft, ...alt });
+                        setAltSuggestions([]);
+                      }}
+                      className="rounded-lg bg-elevated px-3 py-2 text-left ring-1 ring-border active:ring-purple-500"
+                    >
+                      <p className="text-xs font-bold text-heading">{alt.activity}</p>
+                      <p className="truncate text-[10px] text-muted">{alt.poi}</p>
+                      <p className="text-[10px] text-dim italic">{alt.reason}</p>
+                    </button>
+                  ))}
+                  <button onClick={() => setAltSuggestions([])} className="self-start text-[10px] text-dim">取消</button>
+                </div>
+              )}
+
               {days.length > 1 && (
                 <label className="flex flex-col gap-1">
                   <span className="text-[11px] font-medium text-muted">移动到其他天</span>

src/lib/ai.ts

@@ -230,6 +230,107 @@ ${Object.entries(ctx.candidates)
   }
 }
 
+// ---------------------------------------------------------------------------
+// refinePlan: adjust an existing plan based on a natural-language instruction
+// ---------------------------------------------------------------------------
+
+const REFINE_PLAN_SYSTEM_PROMPT = `你是一个周末行程调整助手。根据用户指令修改现有行程。规则：
+1. 只改用户明确要求的部分，其余原样保留
+2. 时间安排合理，活动间留交通时间
+3. 若需新增活动，poi/address 可留空字符串，lat/lng 填 0
+4. 严格按输入的 JSON 结构输出完整 days 数组`;
+
+export async function refinePlan(
+  days: import("@/types").WeekendPlanData[],
+  instruction: string,
+): Promise<import("@/types").WeekendPlanData[] | null> {
+  try {
+    const client = getClient();
+    const response = await client.chat.completions.create({
+      model: "deepseek-chat",
+      messages: [
+        { role: "system", content: REFINE_PLAN_SYSTEM_PROMPT },
+        {
+          role: "user",
+          content: `当前行程：\n${JSON.stringify(days)}\n\n用户指令：${instruction}`,
+        },
+      ],
+      response_format: { type: "json_object" },
+      temperature: 0.5,
+      max_tokens: 2000,
+    });
+
+    const text = response.choices[0]?.message?.content;
+    if (!text) return null;
+
+    const parsed = JSON.parse(text);
+    const result = parsed.days ?? parsed;
+    if (!Array.isArray(result) || result.length === 0) return null;
+    if (!result.every((d: unknown) => {
+      if (typeof d !== "object" || d === null) return false;
+      const day = d as Record<string, unknown>;
+      return typeof day.date === "string" && Array.isArray(day.items);
+    })) return null;
+
+    return result as import("@/types").WeekendPlanData[];
+  } catch {
+    return null;
+  }
+}
+
+// ---------------------------------------------------------------------------
+// suggestAlternativeItems: recommend 3 alternatives for a single activity
+// ---------------------------------------------------------------------------
+
+const SUGGEST_ALT_SYSTEM_PROMPT = `你是一个周末活动推荐助手。根据当前活动推荐 3 个类似但不同的替代方案，用于替换行程中的该活动。
+
+每个替代方案需要包含：
+- activity: 活动描述（5-15字，口语化）
+- searchQuery: 高德地图搜索关键词
+- reason: 推荐理由（一句话）
+
+只返回 JSON：{ "alternatives": [{ "activity", "searchQuery", "reason" }] }`;
+
+export async function suggestAlternativeItems(
+  activity: string,
+  time: string,
+): Promise<Array<{ activity: string; searchQuery: string; reason: string }> | null> {
+  try {
+    const client = getClient();
+    const response = await client.chat.completions.create({
+      model: "deepseek-chat",
+      messages: [
+        { role: "system", content: SUGGEST_ALT_SYSTEM_PROMPT },
+        {
+          role: "user",
+          content: `当前活动：${activity}${time ? `（时间：${time}）` : ""}`,
+        },
+      ],
+      response_format: { type: "json_object" },
+      temperature: 0.8,
+      max_tokens: 400,
+    });
+
+    const text = response.choices[0]?.message?.content;
+    if (!text) return null;
+
+    const parsed = JSON.parse(text);
+    if (!Array.isArray(parsed.alternatives)) return null;
+
+    return parsed.alternatives
+      .filter(
+        (a: unknown) =>
+          typeof a === "object" &&
+          a !== null &&
+          typeof (a as Record<string, unknown>).activity === "string" &&
+          typeof (a as Record<string, unknown>).searchQuery === "string",
+      )
+      .slice(0, 3) as Array<{ activity: string; searchQuery: string; reason: string }>;
+  } catch {
+    return null;
+  }
+}
+
 // ---------------------------------------------------------------------------
 // Generic tool-calling agent loop
 // ---------------------------------------------------------------------------

src/lib/blindboxPlanGen.ts

@@ -114,7 +114,7 @@ function selectIdeasForSlots(ideas: TaggedIdea[], availableHours: number): Tagge
 // POI search (shared by both paths)
 // ---------------------------------------------------------------------------
 
-async function searchPois(
+export async function searchPois(
   query: string,
   searchType: string,
   anchorLat: number,