修复了一点bug，然后增加了图层拆分更多的功能

backend/internal/httpapi/layer_compositions.go

@@ -0,0 +1,124 @@
+package httpapi
+
+import (
+	"errors"
+	"net/http"
+	"strings"
+
+	"git.nianxx.cn/wangxuming/NianAIGC/backend/internal/jobs"
+	"git.nianxx.cn/wangxuming/NianAIGC/backend/internal/layercompositions"
+)
+
+type LayerCompositionsConfig struct {
+	MaxJSONBytes int64
+}
+
+type layerCompositionsHandler struct {
+	platform     *PlatformAuthorizer
+	jobs         *jobs.Service
+	compositions *layercompositions.Service
+	maxJSONBytes int64
+}
+
+func NewLayerCompositionsHandler(platform *PlatformAuthorizer, jobService *jobs.Service, compositions *layercompositions.Service, config LayerCompositionsConfig) (http.Handler, error) {
+	if platform == nil || jobService == nil || compositions == nil {
+		return nil, errors.New("layer composition HTTP dependencies are not configured")
+	}
+	if config.MaxJSONBytes <= 0 {
+		config.MaxJSONBytes = 1 << 20
+	}
+	return &layerCompositionsHandler{platform: platform, jobs: jobService, compositions: compositions, maxJSONBytes: config.MaxJSONBytes}, nil
+}
+
+func (handler *layerCompositionsHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	jobID, matched := matchLayerCompositionRoute(r.URL.Path)
+	if !matched {
+		http.NotFound(w, r)
+		return
+	}
+	if r.Method == http.MethodOptions {
+		w.Header().Set("Allow", "GET, PUT")
+		w.WriteHeader(http.StatusNoContent)
+		return
+	}
+	if r.Method != http.MethodGet && r.Method != http.MethodPut {
+		w.Header().Set("Allow", "GET, PUT")
+		w.WriteHeader(http.StatusMethodNotAllowed)
+		return
+	}
+	session, err := handler.platform.Authorize(r, PlatformApp)
+	if err != nil {
+		writeLayerCompositionError(w, err)
+		return
+	}
+	job, err := handler.jobs.Get(r.Context(), jobs.Scope{OwnerID: session.User.ID}, jobID)
+	if err != nil || job.Capability != "image.generate" {
+		writeJSON(w, http.StatusNotFound, map[string]string{"error": "图层任务不存在"})
+		return
+	}
+	if r.Method == http.MethodGet {
+		composition, found, err := handler.compositions.Get(r.Context(), session.User.ID, jobID)
+		if err != nil {
+			writeLayerCompositionError(w, err)
+			return
+		}
+		if !found {
+			writeJSON(w, http.StatusOK, map[string]any{"composition": nil})
+			return
+		}
+		writeJSON(w, http.StatusOK, map[string]any{"composition": composition})
+		return
+	}
+	input := struct {
+		Version     int64                     `json:"version"`
+		BaseAssetID string                    `json:"baseAssetId"`
+		BaseVisible bool                      `json:"baseVisible"`
+		Layers      []layercompositions.Layer `json:"layers"`
+	}{}
+	if !decodeJobJSON(w, r, handler.maxJSONBytes, &input, false) {
+		return
+	}
+	if !containsString(job.OutputAssetIDs, input.BaseAssetID) {
+		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "底图必须来自当前图层拆分任务"})
+		return
+	}
+	saved, err := handler.compositions.Save(r.Context(), session.User.ID, jobID, input.Version, layercompositions.Composition{
+		BaseAssetID: input.BaseAssetID,
+		BaseVisible: input.BaseVisible,
+		Layers:      input.Layers,
+	})
+	if err != nil {
+		writeLayerCompositionError(w, err)
+		return
+	}
+	writeJSON(w, http.StatusOK, map[string]any{"composition": saved})
+}
+
+func matchLayerCompositionRoute(path string) (string, bool) {
+	const prefix = "/api/layer-compositions/"
+	if !strings.HasPrefix(path, prefix) {
+		return "", false
+	}
+	jobID := strings.TrimPrefix(path, prefix)
+	return jobID, jobID != "" && !strings.Contains(jobID, "/")
+}
+
+func writeLayerCompositionError(w http.ResponseWriter, err error) {
+	switch {
+	case errors.Is(err, layercompositions.ErrConflict):
+		writeJSON(w, http.StatusConflict, map[string]string{"error": "图层工程已在其他页面更新，请重试"})
+	case errors.Is(err, layercompositions.ErrInvalid), errors.Is(err, layercompositions.ErrAssetNotFound):
+		writeJSON(w, http.StatusBadRequest, map[string]string{"error": err.Error()})
+	default:
+		writeJobError(w, err, false)
+	}
+}
+
+func containsString(values []string, wanted string) bool {
+	for _, value := range values {
+		if value == wanted {
+			return true
+		}
+	}
+	return false
+}