package azblob

import (

	"context"

	"errors"

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

)

// NewUniqueRequestIDPolicyFactory creates a UniqueRequestIDPolicyFactory object

// that sets the request's x-ms-client-request-id header if it doesn't already exist.

func NewUniqueRequestIDPolicyFactory() pipeline.Factory {

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

		// This is Policy's Do method:

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

			id := request.Header.Get(xMsClientRequestID)

			if id == "" { // Add a unique request ID if the caller didn't specify one already

				id = newUUID().String()

				request.Header.Set(xMsClientRequestID, id)

			}

			resp, err := next.Do(ctx, request)

			if err == nil && resp != nil {

				val := resp.Response().Header.Values(xMsClientRequestID)

				if len(val) > 0 {

					if val[0] != id {

						err = errors.New("client Request ID from request and response does not match")

					}

				}

			}

			return resp, err

		}

	})

}

const xMsClientRequestID = "x-ms-client-request-id"