wrote library.

main.go

@@ -0,0 +1,124 @@
+package component
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"slices"
+	"strings"
+)
+
+type componentKey int
+
+const storageKey componentKey = iota
+
+type Component interface {
+	Module() string
+	Path() []string
+	PathString() string
+}
+
+type component struct {
+	module string
+	path   []string
+}
+
+func (c component) Module() string     { return c.module }
+func (c component) Path() []string     { return slices.Clone(c.path) }
+func (c component) PathString() string { return strings.Join(c.path, ".") }
+
+func insert(ctx context.Context, module string, name string, path []string) context.Context {
+	return context.WithValue(ctx, storageKey, component{
+		module: module,
+		path:   append(path, name),
+	})
+}
+
+func Get(ctx context.Context) (Component, bool) {
+	t, ok := ctx.Value(storageKey).(component)
+	return t, ok
+}
+
+func MustStart(ctx context.Context, module string, name string) context.Context {
+	if ctx == nil {
+		panic("context is nil")
+	}
+	if module == "" {
+		panic("module cannot be empty")
+	}
+	if name == "" {
+		panic("name cannot be empty")
+	}
+	return insert(ctx, module, name, []string{})
+}
+
+func MustNext(ctx context.Context, name string) context.Context {
+	if ctx == nil {
+		panic("context is nil")
+	}
+
+	c, ok := Get(ctx)
+	if !ok {
+		panic("missing parent component")
+	}
+
+	if name == "" {
+		panic("name cannot be empty")
+	}
+
+	return insert(ctx, c.Module(), name, c.Path())
+}
+
+func Start(ctx context.Context, module string, name string) (context.Context, error) {
+	if ctx == nil {
+		return nil, fmt.Errorf("context is nil")
+	}
+	if module == "" {
+		return nil, fmt.Errorf("module cannot be empty")
+	}
+	if name == "" {
+		return nil, fmt.Errorf("name cannot be empty")
+	}
+	return insert(ctx, module, name, []string{}), nil
+}
+
+func Next(ctx context.Context, name string) (context.Context, error) {
+	if ctx == nil {
+		return nil, fmt.Errorf("context is nil")
+	}
+
+	c, ok := Get(ctx)
+	if !ok {
+		return nil, fmt.Errorf("missing parent component")
+	}
+
+	if name == "" {
+		return nil, fmt.Errorf("name cannot be empty")
+	}
+
+	return insert(ctx, c.Module(), name, c.Path()), nil
+}
+
+func GetFields(ctx context.Context) (map[string]string, bool) {
+	c, ok := Get(ctx)
+	if !ok {
+		return nil, false
+	}
+
+	return map[string]string{
+		"module": c.Module(),
+		"path":   c.PathString(),
+	}, true
+}
+
+func Attrs(ctx context.Context) ([]slog.Attr, bool) {
+	fields, ok := GetFields(ctx)
+	if !ok {
+		return nil, false
+	}
+
+	return []slog.Attr{
+		slog.String("module", fields["module"]),
+		slog.String("path", fields["path"]),
+	}, true
+}