/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 (
	"errors"
	"fmt"
)

import (
	"github.com/dubbogo/gost/log/logger"

	"go.opentelemetry.io/contrib/propagators/b3"

	"go.opentelemetry.io/otel/propagation"

	"go.opentelemetry.io/otel/sdk/resource"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"

	semconv "go.opentelemetry.io/otel/semconv/v1.7.0"
)

type ExporterConfig struct {
	Exporter         string
	Endpoint         string
	SampleMode       string
	SampleRatio      float64
	Propagator       string
	ServiceNamespace string
	ServiceName      string
	ServiceVersion   string
}

type Exporter interface {
	GetTracerProvider() *sdktrace.TracerProvider
	GetPropagator() propagation.TextMapPropagator
}

type DefaultExporter struct {
	TracerProvider *sdktrace.TracerProvider
	Propagator     propagation.TextMapPropagator
}

func (e *DefaultExporter) GetTracerProvider() *sdktrace.TracerProvider {
	return e.TracerProvider
}

func (e *DefaultExporter) GetPropagator() propagation.TextMapPropagator {
	return e.Propagator
}

// NewExporter is an absolute function with @customFunc to create a spec exporter
func NewExporter(config *ExporterConfig, customFunc func() (sdktrace.SpanExporter, error)) (tracerProvider *sdktrace.TracerProvider, propagator propagation.TextMapPropagator, err error) {
	if config == nil {
		err = errors.New("otel exporter config is nil")
		return
	}

	exporter, err := customFunc()
	if err != nil {
		err = fmt.Errorf("failed to create %s exporter: %v", config.Exporter, err)
		logger.Error(err)
		return
	}

	var samplerOption sdktrace.TracerProviderOption
	switch config.SampleMode {
	case "ratio":
		samplerOption = sdktrace.WithSampler(sdktrace.ParentBased(sdktrace.TraceIDRatioBased(config.SampleRatio)))
	case "always":
		samplerOption = sdktrace.WithSampler(sdktrace.ParentBased(sdktrace.AlwaysSample()))
	case "never":
		samplerOption = sdktrace.WithSampler(sdktrace.ParentBased(sdktrace.NeverSample()))
	default:
		err = fmt.Errorf("otel sample mode %s not supported", config.SampleMode)
		logger.Error(err)
		return
	}

	tracerProvider = sdktrace.NewTracerProvider(
		samplerOption,
		sdktrace.WithBatcher(exporter),
		sdktrace.WithResource(resource.NewSchemaless(
			semconv.ServiceNamespaceKey.String(config.ServiceNamespace),
			semconv.ServiceNameKey.String(config.ServiceName),
			semconv.ServiceVersionKey.String(config.ServiceVersion),
		)),
	)

	switch config.Propagator {
	case "w3c":
		propagator = propagation.NewCompositeTextMapPropagator(propagation.TraceContext{}, propagation.Baggage{})
	case "b3":
		b3Propagator := b3.New(b3.WithInjectEncoding(b3.B3MultipleHeader | b3.B3SingleHeader))
		propagator = propagation.NewCompositeTextMapPropagator(b3Propagator, propagation.Baggage{})
	}

	return tracerProvider, propagator, nil
}