package tracing

import (
	"git.dev.m-and-m.ovh/mderasse/gocommon/tracing/exporter/jaeger"
	"git.dev.m-and-m.ovh/mderasse/gocommon/tracing/exporter/zipkin"
	"github.com/juju/errors"

	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/sdk/resource"

	sdktrace "go.opentelemetry.io/otel/sdk/trace"
	semconv "go.opentelemetry.io/otel/semconv/v1.12.0"
)

// Init will try to initialize tracing by trying to retrieve config from multiple source.
func Init() (*sdktrace.TracerProvider, error) {

	// loading configuration
	c, err := loadConfig()
	if err != nil {
		return nil, errors.Trace(err)
	}

	return initFromSource(c)
}

// InitFromCustomVaultSecret will initialize tracing with a vault secret.
func InitFromCustomVaultSecret(secret string) (*sdktrace.TracerProvider, error) {

	c, err := loadConfigFromVault(secret)
	if err != nil {
		return nil, errors.Trace(err)
	}

	return initFromSource(c)
}

// InitFromCustomFile will initialize tracing with a config file.
func InitFromCustomFile(path string) (*sdktrace.TracerProvider, error) {

	c, err := loadConfigFromFile(path)
	if err != nil {
		return nil, errors.Trace(err)
	}

	return initFromSource(c)
}

func initFromSource(c *ConfigStruct) (*sdktrace.TracerProvider, error) {
	err := c.applyEnv()
	if err != nil {
		return nil, errors.Trace(err)
	}

	return InitFromCustomConfig(c)
}

// InitFromCustomConfig will initialize tracing from a gaven config.
func InitFromCustomConfig(c *ConfigStruct) (*sdktrace.TracerProvider, error) {

	err := c.IsValid()
	if err != nil {
		return nil, errors.Trace(err)
	}

	// if disabled, never sample
	if !c.Enabled {
		return sdktrace.NewTracerProvider(
			sdktrace.WithSampler(sdktrace.NeverSample()),
		), nil
	}

	attributes := []attribute.KeyValue{
		semconv.ServiceNameKey.String(c.ServiceName),
	}

	if c.ServiceVersion != "" {
		attributes = append(
			attributes,
			semconv.ServiceVersionKey.String(c.ServiceVersion),
		)
	}

	if c.ServiceInstanceID != "" {
		attributes = append(
			attributes,
			semconv.ServiceInstanceIDKey.String(c.ServiceInstanceID),
		)
	}

	for k, v := range c.Attributes {
		attributes = append(
			attributes,
			attribute.String(k, v),
		)
	}

	// Ensure default SDK resources and the required service name are set.
	r, err := resource.Merge(
		resource.Default(),
		resource.NewWithAttributes(
			semconv.SchemaURL,
			attributes...,
		),
	)
	if err != nil {
		return nil, errors.Trace(err)
	}

	// Get the exporter
	var exporter sdktrace.SpanExporter

	switch c.Exporter {
	case ExporterName_JAEGER:
		exporter, err = jaeger.NewExporter(c.JaegerConfig)
		if err != nil {
			return nil, errors.Trace(err)
		}
	case ExporterName_ZIPKIN:
		exporter, err = zipkin.NewExporter(c.ZipkinConfig)
		if err != nil {
			return nil, errors.Trace(err)
		}
	default:
		return nil, errors.BadRequestf("Exporter is not handled.")
	}

	return sdktrace.NewTracerProvider(
		sdktrace.WithResource(r),
		sdktrace.WithBatcher(exporter),
	), nil
}