// Copyright 2019, OpenTelemetry Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package trace

import (
	"context"

	"github.com/open-telemetry/opentelemetry-go/api/core"
	"github.com/open-telemetry/opentelemetry-go/api/scope"
)

type noopTracer struct {
	resources core.EventID
}

var _ Tracer = (*noopTracer)(nil)

var t = &noopTracer{}

// ScopeID returns an empty instance of ScopeID
func (t *noopTracer) ScopeID() core.ScopeID {
	return t.resources.Scope()
}

// WithResources does nothing and returns noop implementation of Tracer.
func (t *noopTracer) WithResources(attributes ...core.KeyValue) Tracer {
	return t
}

// WithComponent does nothing and returns noop implementation of Tracer.
func (g *noopTracer) WithComponent(name string) Tracer {
	return g
}

// WithService does nothing and returns noop implementation of Tracer.
func (g *noopTracer) WithService(name string) Tracer {
	return g
}

// WithSpan wraps around execution of func with noop span.
func (t *noopTracer) WithSpan(ctx context.Context, name string, body func(context.Context) error) error {
	ctx, span := t.Start(ctx, name)
	defer span.Finish()

	if err := body(ctx); err != nil {
		return err
	}
	return nil
}

// Start starts a noop span.
func (t *noopTracer) Start(ctx context.Context, name string, opts ...SpanOption) (context.Context, Span) {
	span := &noopSpan{}
	return scope.SetActive(ctx, span), span
}

// Inject does nothing.
func (t *noopTracer) Inject(ctx context.Context, span Span, injector Injector) {
}

var _ Injector = (*noopTracer)(nil)