feat(backend): add mod manager service for scanning workshop/local mods

backend/internal/services/mod_manager.go

@@ -0,0 +1,120 @@
+package services
+
+import (
+	"os"
+	"path/filepath"
+)
+
+type ModInfo struct {
+	ID       string   `json:"id"`
+	Name     string   `json:"name"`
+	Source   string   `json:"source"`
+	Path     string   `json:"path"`
+	Size     int64    `json:"size"`
+	InUse    bool     `json:"in_use"`
+	Modlists []string `json:"modlists"`
+}
+
+func ListWorkshopMods(serverfileDir string) []ModInfo {
+	workshopDir := filepath.Join(serverfileDir, "steamapps", "workshop", "content", workshopAppID)
+	entries, err := os.ReadDir(workshopDir)
+	if err != nil {
+		return nil
+	}
+
+	var mods []ModInfo
+	for _, e := range entries {
+		if !e.IsDir() {
+			continue
+		}
+		id := e.Name()
+		p := filepath.Join(workshopDir, id)
+		size := dirSize(p)
+		mods = append(mods, ModInfo{
+			ID:     id,
+			Name:   "",
+			Source: "workshop",
+			Path:   p,
+			Size:   size,
+		})
+	}
+	return mods
+}
+
+func ListLocalMods(modsDir string) []ModInfo {
+	entries, err := os.ReadDir(modsDir)
+	if err != nil {
+		return nil
+	}
+
+	var mods []ModInfo
+	for _, e := range entries {
+		if !e.IsDir() {
+			continue
+		}
+		name := e.Name()
+		p := filepath.Join(modsDir, name)
+		size := dirSize(p)
+		displayName := name
+		if len(name) > 0 && name[0] == '@' {
+			displayName = name[1:]
+		}
+		mods = append(mods, ModInfo{
+			ID:   displayName,
+			Name: name,
+			Source: "local",
+			Path:   p,
+			Size:   size,
+		})
+	}
+	return mods
+}
+
+func BuildUsageMap(modlists *ModlistManager) (usedWorkshop map[string][]string, usedLocal map[string][]string) {
+	usedWorkshop = make(map[string][]string)
+	usedLocal = make(map[string][]string)
+
+	lists, err := modlists.List()
+	if err != nil {
+		return
+	}
+
+	for _, li := range lists {
+		ml, err := modlists.Get(li.ID)
+		if err != nil {
+			continue
+		}
+		for _, m := range ml.Mods {
+			if m.ID != "" {
+				usedWorkshop[m.ID] = append(usedWorkshop[m.ID], ml.Name)
+			}
+			if m.Name != "" {
+				nameWithAt := "@" + m.Name
+				usedLocal[m.Name] = append(usedLocal[m.Name], ml.Name)
+				usedLocal[nameWithAt] = append(usedLocal[nameWithAt], ml.Name)
+			}
+		}
+	}
+	return
+}
+
+func RemoveMod(path string) error {
+	return os.RemoveAll(path)
+}
+
+func dirSize(path string) int64 {
+	var size int64
+	filepath.WalkDir(path, func(_ string, d os.DirEntry, err error) error {
+		if err != nil {
+			return nil
+		}
+		if !d.IsDir() {
+			fi, err := d.Info()
+			if err == nil {
+				size += fi.Size()
+			}
+		}
+		return nil
+	})
+	return size
+}