package api

import (
	"context"
	"errors"
	"fmt"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/trace"
	"strings"

	"dev.azure.com/schwarzit/schwarzit.stackit-public/audit-go.git/audit/messaging"
	auditV1 "dev.azure.com/schwarzit/schwarzit.stackit-public/audit-go.git/gen/go/audit/v1"

	"google.golang.org/protobuf/proto"
)

type ContextKey string

const ContextKeyTopic ContextKey = "topic"

var ErrNoTopicNameProvided = errors.New("no topic name provided")
var ErrTopicNameEmpty = errors.New("empty topic name provided")

// DynamicLegacyAuditApi is an implementation of AuditApi to send events to the legacy audit log system
// by setting the topic name explicitly in the context with the key "topic".
//
// Note: The implementation will be deprecated and replaced with the "routableAuditApi" once the new audit log routing is implemented
type DynamicLegacyAuditApi struct {
	messagingApi messaging.Api
	tracer       trace.Tracer
	validator    ProtobufValidator
}

// NewDynamicLegacyAuditApi can be used to initialize the audit log api.
//
// Note: The NewLegacyAuditApi method will be deprecated and replaced with "newRoutableAuditApi" once the new audit log routing is implemented
func NewDynamicLegacyAuditApi(
	messagingApi messaging.Api,
	validator ProtobufValidator,
) (AuditApi, error) {

	if messagingApi == nil {
		return nil, ErrMessagingApiNil
	}

	// Audit api
	var auditApi AuditApi = &DynamicLegacyAuditApi{
		messagingApi: messagingApi,
		tracer:       otel.Tracer("dynamic-legacy-audit-api"),
		validator:    validator,
	}

	return auditApi, nil
}

// Log implements AuditApi.Log
func (a *DynamicLegacyAuditApi) Log(
	ctx context.Context,
	event *auditV1.AuditLogEntry,
	visibility auditV1.Visibility,
	routableIdentifier *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.
// It serializes the event into the byte representation of the legacy audit log system.
func (a *DynamicLegacyAuditApi) ValidateAndSerialize(
	ctx context.Context,
	event *auditV1.AuditLogEntry,
	visibility auditV1.Visibility,
	routableIdentifier *RoutableIdentifier,
) (*CloudEvent, error) {

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

	routableEvent, err := 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(EventTypeDataAccess)) {
		return nil, ErrUnsupportedEventTypeDataAccess
	}

	// Do nothing with the serialized data in the legacy solution
	_, err = proto.Marshal(routableEvent)
	if err != nil {
		return nil, err
	}

	// Convert attributes
	legacyBytes, err := convertAndSerializeIntoLegacyFormat(event, routableEvent)
	if err != nil {
		return nil, err
	}

	traceParent, traceState := TraceParentAndStateFromContext(ctx)

	message := CloudEvent{
		SpecVersion:     "1.0",
		Source:          event.ProtoPayload.ServiceName,
		Id:              event.InsertId,
		Time:            event.ProtoPayload.RequestMetadata.RequestAttributes.Time.AsTime(),
		DataContentType: ContentTypeCloudEventsJson,
		DataType:        DataTypeLegacyAuditEventV1,
		Subject:         event.ProtoPayload.ResourceName,
		Data:            legacyBytes,
		TraceParent:     &traceParent,
		TraceState:      &traceState,
	}
	return &message, nil
}

// Send implements AuditApi.Send
//
// Requires to have the topic name set as key "topic" in the context.
func (a *DynamicLegacyAuditApi) Send(
	ctx context.Context,
	routableIdentifier *RoutableIdentifier,
	cloudEvent *CloudEvent,
) error {

	rawTopicName := ctx.Value(ContextKeyTopic)
	if rawTopicName == nil {
		return ErrNoTopicNameProvided
	}
	topicName := fmt.Sprintf("%s", rawTopicName)
	if topicName == "" {
		return ErrTopicNameEmpty
	}
	if !TopicNamePattern.MatchString(topicName) {
		return fmt.Errorf("invalid topic name: %s - "+
			"expected stackit-platform/t/swz/audit-log/{region}/{version}/{eventSource}/{additionalParts} "+
			"where region is one of [conway, eu01, eu02, sx-stoi01], version is vX.Y, eventSource is the service name "+
			"and additionalParts is a describing string the audit log relates to or 'events'", topicName)
	}

	var topicNameResolver TopicNameResolver = &LegacyTopicNameResolver{topicName: topicName}

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

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