Initial implementation of inventree

A small IT asset inventory system built around a nested folder tree,
matching the project brief: Go + html/template + Bootstrap 5 + vanilla JS,
SQLite storage (WAL, FKs, migrations), embedded templates/static assets,
single compiled binary.

- AJAX-driven inventory tree: lazy-loaded folder expansion with per-user
  persisted expand state, drag-and-drop move for folders/assets, safe
  delete-with-relocate-or-cascade confirmation, search with breadcrumbs.
- Assets: CRUD, duplicate, move, auto-generated IT-000001-style IDs,
  CSV import (with optional folder auto-create) and export.
- Admin-defined item types with custom fields (text/long_text/number/date/
  boolean/dropdown/url/ip_address).
- Configurable statuses, session-based auth (bcrypt, secure cookies),
  admin/user roles, user management.
- CLI: serve, version, database migrate, database backup; /healthz;
  graceful shutdown; Dockerfile/docker-compose/systemd unit; Go test suite.

internal/web/tree.go

@@ -0,0 +1,116 @@
+package web
+
+import (
+	"context"
+	"fmt"
+
+	"inventree/internal/assets"
+	"inventree/internal/models"
+)
+
+// treeAssetLimit bounds how many assets are rendered directly inside a
+// single tree node before showing a "N more" placeholder, so a folder with
+// thousands of assets doesn't blow up the tree fragment.
+const treeAssetLimit = 300
+
+// expandedFolderIDs returns the set of folder IDs the given user has
+// persisted as expanded.
+func (a *App) expandedFolderIDs(ctx context.Context, userID int64) (map[int64]bool, error) {
+	rows, err := a.DB.QueryContext(ctx, `SELECT folder_id FROM user_tree_state WHERE user_id = ?`, userID)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	out := map[int64]bool{}
+	for rows.Next() {
+		var id int64
+		if err := rows.Scan(&id); err != nil {
+			return nil, err
+		}
+		out[id] = true
+	}
+	return out, rows.Err()
+}
+
+func (a *App) persistExpand(ctx context.Context, userID, folderID int64) error {
+	_, err := a.DB.ExecContext(ctx,
+		`INSERT INTO user_tree_state (user_id, folder_id) VALUES (?, ?) ON CONFLICT(user_id, folder_id) DO NOTHING`,
+		userID, folderID)
+	return err
+}
+
+func (a *App) persistCollapse(ctx context.Context, userID, folderID int64) error {
+	_, err := a.DB.ExecContext(ctx, `DELETE FROM user_tree_state WHERE user_id = ? AND folder_id = ?`, userID, folderID)
+	return err
+}
+
+func (a *App) persistCollapseAll(ctx context.Context, userID int64) error {
+	_, err := a.DB.ExecContext(ctx, `DELETE FROM user_tree_state WHERE user_id = ?`, userID)
+	return err
+}
+
+// buildTree returns the ordered list of tree nodes (subfolders then assets)
+// directly under parentID. Folders present in the expanded set are
+// recursively expanded inline; others are returned collapsed for the client
+// to lazy-load on demand.
+func (a *App) buildTree(ctx context.Context, parentID *int64, expanded map[int64]bool) ([]models.TreeNode, error) {
+	childFolders, err := a.Folders.Children(ctx, parentID)
+	if err != nil {
+		return nil, err
+	}
+
+	var out []models.TreeNode
+	for _, f := range childFolders {
+		node := models.TreeNode{
+			Type:        "folder",
+			ID:          f.ID,
+			Name:        f.Name,
+			Icon:        f.Icon,
+			ParentID:    f.ParentID,
+			HasChildren: f.FolderCount > 0 || f.AssetCount > 0,
+		}
+		if expanded[f.ID] {
+			node.Expanded = true
+			children, err := a.buildTree(ctx, &f.ID, expanded)
+			if err != nil {
+				return nil, err
+			}
+			node.Children = children
+		}
+		out = append(out, node)
+	}
+
+	assetList, total, err := a.Assets.List(ctx, assets.ListFilter{
+		FolderID: parentID, FolderSet: true, Page: 1, PageSize: treeAssetLimit,
+	})
+	if err != nil {
+		return nil, err
+	}
+	for _, as := range assetList {
+		out = append(out, models.TreeNode{
+			Type:        "asset",
+			ID:          as.ID,
+			Name:        as.Name,
+			Icon:        as.ItemTypeIcon,
+			AssetTag:    as.AssetTag,
+			StatusName:  as.StatusName,
+			StatusColor: as.StatusColor,
+		})
+	}
+	if total > len(assetList) {
+		out = append(out, models.TreeNode{
+			Type: "more",
+			Name: fmt.Sprintf("%d more asset(s) — open this folder to view all", total-len(assetList)),
+		})
+	}
+
+	return out, nil
+}
+
+func fieldValuesForCreate(fields []models.CustomFieldDef) []models.AssetFieldValue {
+	out := make([]models.AssetFieldValue, len(fields))
+	for i, f := range fields {
+		out[i] = models.AssetFieldValue{Def: f, Value: f.DefaultValue}
+	}
+	return out
+}