def (#12)

Reviewed-on: #12

factory.go

@@ -0,0 +1,98 @@
+package config
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"sync/atomic"
+)
+
+func WrapFactory(fn Factory, prov Provider) *WrapProvider {
+	return &WrapProvider{
+		factory: func(ctx context.Context) (Provider, error) {
+			return fn(ctx, prov)
+		},
+		mu:       sync.Mutex{},
+		done:     0,
+		provider: nil,
+	}
+}
+
+type WrapProvider struct {
+	mu       sync.Mutex
+	done     uint32
+	provider Provider
+	factory  func(ctx context.Context) (Provider, error)
+}
+
+func (p *WrapProvider) Watch(ctx context.Context, callback WatchCallback, path ...string) error {
+	if err := p.init(ctx); err != nil {
+		return fmt.Errorf("init read:%w", err)
+	}
+
+	watch, ok := p.provider.(WatchProvider)
+	if !ok {
+		return nil
+	}
+
+	if err := watch.Watch(ctx, callback, path...); err != nil {
+		return fmt.Errorf("factory provider: %w", err)
+	}
+
+	return nil
+}
+
+func (p *WrapProvider) Value(ctx context.Context, path ...string) (Value, error) {
+	if err := p.init(ctx); err != nil {
+		return nil, fmt.Errorf("init read:%w", err)
+	}
+
+	variable, err := p.provider.Value(ctx, path...)
+	if err != nil {
+		return nil, fmt.Errorf("factory provider: %w", err)
+	}
+
+	return variable, nil
+}
+
+func (p *WrapProvider) Name() string {
+	if err := p.init(context.Background()); err != nil {
+		return fmt.Sprintf("%T", p.provider)
+	}
+
+	return p.provider.Name()
+}
+
+func (p *WrapProvider) Bind(ctx context.Context, data Variables) error {
+	if err := p.init(ctx); err != nil {
+		return fmt.Errorf("init bind: %w", err)
+	}
+
+	prov, ok := p.provider.(BindProvider)
+	if !ok {
+		return nil
+	}
+
+	if perr := prov.Bind(ctx, data); perr != nil {
+		return fmt.Errorf("init bind provider: %w", perr)
+	}
+
+	return nil
+}
+
+func (p *WrapProvider) init(ctx context.Context) error {
+	if atomic.LoadUint32(&p.done) == 0 {
+		if !p.mu.TryLock() {
+			return fmt.Errorf("%w", ErrInitFactory)
+		}
+		defer atomic.StoreUint32(&p.done, 1)
+		defer p.mu.Unlock()
+
+		var err error
+		if p.provider, err = p.factory(ctx); err != nil {
+			return fmt.Errorf("init provider factory:%w", err)
+		}
+	}
+
+	return nil
+}