fix(#1197): useStep3Preview增加预览生成逻辑（mock），预留后端接口位置

apps/web/src/pages/generate/hooks/useStep3Preview.ts

@@ -1,8 +1,9 @@
 /**
  * Step 3 生成预览 Hook
- * 封装预览信息的计算逻辑
+ * 封装预览信息计算 + 预览生成逻辑
+ * TODO: 后端预览接口对齐后，替换 mock 逻辑为真实 API 调用
  */
-import { useMemo } from "react"
+import { useState, useCallback, useMemo } from "react"
 import type { EditingTemplate } from "@/api/editing-planner"
 
 interface UseStep3PreviewProps {
@@ -15,6 +16,22 @@ interface UseStep3PreviewProps {
   videoRatio: string
 }
 
+export type PreviewStatus = "idle" | "generating" | "ready" | "error"
+
+/** 预览生成结果 */
+export interface PreviewResult {
+  /** 预计片段数 */
+  clipCount: number
+  /** 预计转场数 */
+  transitionCount: number
+  /** 素材使用率 */
+  materialUsage: number
+  /** 预览视频URL（后端接口出来后填充） */
+  previewVideoUrl: string | null
+  /** 生成耗时（秒） */
+  generateDuration: number
+}
+
 export function useStep3Preview({
   templates,
   selectedTemplate,
@@ -36,11 +53,70 @@ export function useStep3Preview({
     return `${selectedMaterials.length} 个素材`
   }, [materialMode, selectedMaterials.length, smartSelectedIds.length])
 
+  const materialTotal = materialMode === "auto" ? smartSelectedIds.length : selectedMaterials.length
+
+  /* ── 预览生成状态 ── */
+  const [previewStatus, setPreviewStatus] = useState<PreviewStatus>("idle")
+  const [previewResult, setPreviewResult] = useState<PreviewResult | null>(null)
+  const [previewError, setPreviewError] = useState<string>("")
+
+  /**
+   * 生成预览
+   * TODO: 后端 /generation-preview 接口对齐后替换此处 mock 逻辑
+   * 预计接口：POST /generate-preview
+   * 入参：template_id, material_ids, duration, video_ratio, style
+   * 出参：preview_id, status, clip_count, preview_video_url
+   */
+  const generatePreview = useCallback(async () => {
+    if (!selectedTemplate) return
+    if (materialTotal === 0) return
+
+    setPreviewStatus("generating")
+    setPreviewError("")
+
+    try {
+      // TODO: 替换为真实后端接口调用
+      // const res = await generatePreviewAPI({ templateId: selectedTemplate, ... })
+      await new Promise((resolve) => setTimeout(resolve, 1500))
+
+      // Mock 结果
+      const estimatedClips = Math.max(3, Math.min(materialTotal * 2, 20))
+      const result: PreviewResult = {
+        clipCount: estimatedClips,
+        transitionCount: estimatedClips - 1,
+        materialUsage: Math.min(100, Math.round((materialTotal / Math.max(estimatedClips, 1)) * 100)),
+        previewVideoUrl: null, // 后端接口出来后填充
+        generateDuration: 1.5,
+      }
+
+      setPreviewResult(result)
+      setPreviewStatus("ready")
+    } catch (e) {
+      setPreviewError(e instanceof Error ? e.message : "预览生成失败")
+      setPreviewStatus("error")
+    }
+  }, [selectedTemplate, materialTotal])
+
+  /** 重新生成预览 */
+  const regeneratePreview = useCallback(() => {
+    generatePreview()
+  }, [generatePreview])
+
+  /** 是否可以下一步（预览已生成） */
+  const canProceed = previewStatus === "ready"
+
   return {
     templateName,
     materialCount,
     duration,
     videoRatio,
+    // 预览生成状态
+    previewStatus,
+    previewResult,
+    previewError,
+    canProceed,
+    generatePreview,
+    regeneratePreview,
   }
 }