package api

import (
	"context"
	"errors"
	"fmt"
	"strings"

	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/trace"
	"google.golang.org/protobuf/proto"

	auditV1 "dev.azure.com/schwarzit/schwarzit.stackit-public/audit-go.git/gen/go/audit/v1"
	internalAuditApi "dev.azure.com/schwarzit/schwarzit.stackit-public/audit-go.git/internal/audit/api"
	pkgAuditCommon "dev.azure.com/schwarzit/schwarzit.stackit-public/audit-go.git/pkg/audit/common"
	pkgMessagingApi "dev.azure.com/schwarzit/schwarzit.stackit-public/audit-go.git/pkg/messaging/api"
)

// routableTopicNameResolver implements TopicNameResolver.
// Resolves topic names by concatenating topic type prefixes with routing identifiers.
type routableTopicNameResolver struct {
	folderTopicPrefix       string
	organizationTopicPrefix string
	projectTopicPrefix      string
	// If no identifier is provided for routing, it will be routed to a system topic
	systemTopicName string
}

// Resolve implements TopicNameResolver.Resolve.
func (r *routableTopicNameResolver) Resolve(routableIdentifier *pkgAuditCommon.RoutableIdentifier) (string, error) {

	if routableIdentifier == nil {
		return "", pkgAuditCommon.ErrObjectIdentifierNil
	}

	switch routableIdentifier.Type {
	case pkgAuditCommon.ObjectTypeOrganization:
		return fmt.Sprintf("topic://%s/%s", r.organizationTopicPrefix, routableIdentifier.Identifier), nil
	case pkgAuditCommon.ObjectTypeProject:
		return fmt.Sprintf("topic://%s/%s", r.projectTopicPrefix, routableIdentifier.Identifier), nil
	case pkgAuditCommon.ObjectTypeFolder:
		return fmt.Sprintf("topic://%s/%s", r.folderTopicPrefix, routableIdentifier.Identifier), nil
	case pkgAuditCommon.ObjectTypeSystem:
		return r.systemTopicName, nil
	default:
		return "", pkgAuditCommon.ErrUnsupportedObjectIdentifierType
	}
}

// topicNameConfig provides topic name information required for the topic name resolution.
type topicNameConfig struct {
	FolderTopicPrefix       string
	OrganizationTopicPrefix string
	ProjectTopicPrefix      string
	SystemTopicName         string
}

// routableAuditApi is an implementation of AuditApi.
// Warning: It is only there for local (compatibility) testing.
// DO NOT USE IT!
type routableAuditApi struct {
	messagingApi      pkgMessagingApi.Api
	topicNameResolver pkgAuditCommon.TopicNameResolver
	tracer            trace.Tracer
	validator         pkgAuditCommon.ProtobufValidator
}

// NewRoutableAuditApi can be used to initialize the audit log api.
func newRoutableAuditApi(
	messagingApi pkgMessagingApi.Api,
	topicNameConfig topicNameConfig,
	validator pkgAuditCommon.ProtobufValidator,
) (pkgAuditCommon.AuditApi, error) {

	if messagingApi == nil {
		return nil, errors.New("messaging api nil")
	}

	// Topic resolver
	if topicNameConfig.FolderTopicPrefix == "" {
		return nil, errors.New("folder topic prefix is required")
	}
	if topicNameConfig.OrganizationTopicPrefix == "" {
		return nil, errors.New("organization topic prefix is required")
	}
	if topicNameConfig.ProjectTopicPrefix == "" {
		return nil, errors.New("project topic prefix is required")
	}
	if topicNameConfig.SystemTopicName == "" {
		return nil, errors.New("system topic name is required")
	}

	var topicNameResolver pkgAuditCommon.TopicNameResolver = &routableTopicNameResolver{
		folderTopicPrefix:       topicNameConfig.FolderTopicPrefix,
		organizationTopicPrefix: topicNameConfig.OrganizationTopicPrefix,
		projectTopicPrefix:      topicNameConfig.ProjectTopicPrefix,
		systemTopicName:         topicNameConfig.SystemTopicName,
	}

	// Audit api
	var auditApi pkgAuditCommon.AuditApi = &routableAuditApi{
		messagingApi:      messagingApi,
		topicNameResolver: topicNameResolver,
		tracer:            otel.Tracer("routable-audit-api"),
		validator:         validator,
	}

	return auditApi, nil
}

// Log implements AuditApi.Log
func (a *routableAuditApi) Log(
	ctx context.Context,
	event *auditV1.AuditLogEntry,
	visibility auditV1.Visibility,
	routableIdentifier *pkgAuditCommon.RoutableIdentifier,
) error {

	cloudEvent, err := a.ValidateAndSerialize(ctx, event, visibility, routableIdentifier)
	if err != nil {
		return err
	}

	return a.Send(ctx, routableIdentifier, cloudEvent)
}

// ValidateAndSerialize implements AuditApi.ValidateAndSerialize
func (a *routableAuditApi) ValidateAndSerialize(
	ctx context.Context,
	event *auditV1.AuditLogEntry,
	visibility auditV1.Visibility,
	routableIdentifier *pkgAuditCommon.RoutableIdentifier,
) (*pkgAuditCommon.CloudEvent, error) {

	ctx, span := a.tracer.Start(ctx, "validate-and-serialize")
	defer span.End()

	routableEvent, err := internalAuditApi.ValidateAndSerializePartially(
		a.validator,
		event,
		visibility,
		routableIdentifier)

	if err != nil {
		return nil, err
	}

	// Reject event type data-access as the downstream services
	// cannot handle it at the moment
	if strings.HasSuffix(event.LogName, string(pkgAuditCommon.EventTypeDataAccess)) {
		return nil, pkgAuditCommon.ErrUnsupportedEventTypeDataAccess
	}

	routableEventBytes, err := proto.Marshal(routableEvent)
	if err != nil {
		return nil, err
	}

	traceParent, traceState := internalAuditApi.TraceParentAndStateFromContext(ctx)

	message := pkgAuditCommon.CloudEvent{
		SpecVersion:     "1.0",
		Source:          event.ProtoPayload.ServiceName,
		Id:              event.InsertId,
		Time:            event.ProtoPayload.RequestMetadata.RequestAttributes.Time.AsTime(),
		DataContentType: pkgAuditCommon.ContentTypeCloudEventsProtobuf,
		DataType:        fmt.Sprintf("%v", routableEvent.ProtoReflect().Descriptor().FullName()),
		Subject:         event.ProtoPayload.ResourceName,
		Data:            routableEventBytes,
		TraceParent:     &traceParent,
		TraceState:      &traceState,
	}

	return &message, nil
}

// Send implements AuditApi.Send
func (a *routableAuditApi) Send(
	ctx context.Context,
	routableIdentifier *pkgAuditCommon.RoutableIdentifier,
	cloudEvent *pkgAuditCommon.CloudEvent,
) error {

	if cloudEvent != nil && cloudEvent.TraceParent != nil && cloudEvent.TraceState != nil {
		ctx = internalAuditApi.AddTraceParentAndStateToContext(ctx, *cloudEvent.TraceParent, *cloudEvent.TraceState)
	}
	ctx, span := a.tracer.Start(ctx, "send")
	defer span.End()

	return internalAuditApi.Send(a.topicNameResolver, a.messagingApi, ctx, routableIdentifier, cloudEvent)
}