Introduce built-in templates for enhanced configuration options, support JSONC format

internal/templates/templates.go

@@ -0,0 +1,96 @@
+// Package templates provides embedded configuration templates for fence.
+package templates
+
+import (
+	"embed"
+	"encoding/json"
+	"fmt"
+	"path/filepath"
+	"sort"
+	"strings"
+
+	"github.com/Use-Tusk/fence/internal/config"
+	"github.com/tidwall/jsonc"
+)
+
+//go:embed *.json
+var templatesFS embed.FS
+
+// Template represents a named configuration template.
+type Template struct {
+	Name        string
+	Description string
+}
+
+// AvailableTemplates lists all embedded templates with descriptions.
+var templateDescriptions = map[string]string{
+	"default-deny":      "No network allowlist; no write access (most restrictive)",
+	"disable-telemetry": "Block analytics/error reporting (Sentry, Posthog, Statsig, etc.)",
+	"workspace-write":   "Allow writes in the current directory",
+	"npm-install":       "Allow npm registry; allow writes to workspace/node_modules/tmp",
+	"pip-install":       "Allow PyPI; allow writes to workspace/tmp",
+	"local-dev-server":  "Allow binding and localhost outbound; allow writes to workspace/tmp",
+	"git-readonly":      "Blocks destructive commands like git push, rm -rf, etc.",
+	"code":              "Production-ready config for AI coding agents (Claude Code, Codex, Copilot, etc.)",
+}
+
+// List returns all available template names sorted alphabetically.
+func List() []Template {
+	entries, err := templatesFS.ReadDir(".")
+	if err != nil {
+		return nil
+	}
+
+	var templates []Template
+	for _, entry := range entries {
+		if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".json") {
+			continue
+		}
+		name := strings.TrimSuffix(entry.Name(), ".json")
+		desc := templateDescriptions[name]
+		if desc == "" {
+			desc = "No description available"
+		}
+		templates = append(templates, Template{Name: name, Description: desc})
+	}
+
+	sort.Slice(templates, func(i, j int) bool {
+		return templates[i].Name < templates[j].Name
+	})
+
+	return templates
+}
+
+// Load loads a template by name and returns the parsed config.
+func Load(name string) (*config.Config, error) {
+	// Normalize name (remove .json if present)
+	name = strings.TrimSuffix(name, ".json")
+	filename := name + ".json"
+
+	data, err := templatesFS.ReadFile(filename)
+	if err != nil {
+		return nil, fmt.Errorf("template %q not found", name)
+	}
+
+	var cfg config.Config
+	if err := json.Unmarshal(jsonc.ToJSON(data), &cfg); err != nil {
+		return nil, fmt.Errorf("failed to parse template %q: %w", name, err)
+	}
+
+	return &cfg, nil
+}
+
+// Exists checks if a template with the given name exists.
+func Exists(name string) bool {
+	name = strings.TrimSuffix(name, ".json")
+	filename := name + ".json"
+
+	_, err := templatesFS.ReadFile(filename)
+	return err == nil
+}
+
+// GetPath returns the embedded path for a template (for display purposes).
+func GetPath(name string) string {
+	name = strings.TrimSuffix(name, ".json")
+	return filepath.Join("internal/templates", name+".json")
+}