package azblob

import (

	"bytes"

	"context"

	"fmt"

	"os"

	"runtime"

	"github.com/Azure/azure-pipeline-go/pipeline"

)

// TelemetryOptions configures the telemetry policy's behavior.

type TelemetryOptions struct {

	// Value is a string prepended to each request's User-Agent and sent to the service.

	// The service records the user-agent in logs for diagnostics and tracking of client requests.

	Value string

}

// NewTelemetryPolicyFactory creates a factory that can create telemetry policy objects

// which add telemetry information to outgoing HTTP requests.

func NewTelemetryPolicyFactory(o TelemetryOptions) pipeline.Factory {

	b := &bytes.Buffer{}

	b.WriteString(o.Value)

	if b.Len() > 0 {

		b.WriteRune(' ')

	}

	fmt.Fprintf(b, "Azure-Storage/%s %s", serviceLibVersion, platformInfo)

	telemetryValue := b.String()

	return pipeline.FactoryFunc(func(next pipeline.Policy, po *pipeline.PolicyOptions) pipeline.PolicyFunc {

		return func(ctx context.Context, request pipeline.Request) (pipeline.Response, error) {

			request.Header.Set("User-Agent", telemetryValue)

			return next.Do(ctx, request)

		}

	})

}

// NOTE: the ONLY function that should write to this variable is this func

var platformInfo = func() string {

	// Azure-Storage/version (runtime; os type and version)”

	// Azure-Storage/1.4.0 (NODE-VERSION v4.5.0; Windows_NT 10.0.14393)'

	operatingSystem := runtime.GOOS // Default OS string

	switch operatingSystem {

	case "windows":

		operatingSystem = os.Getenv("OS") // Get more specific OS information

	case "linux": // accept default OS info

	case "freebsd": //  accept default OS info

	}

	return fmt.Sprintf("(%s; %s)", runtime.Version(), operatingSystem)

}()