package redriver

import (
	"context"
	"encoding/json"
	"fmt"
	"io"
	"strconv"

	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/service/sqs"
	"github.com/aws/aws-sdk-go-v2/service/sqs/types"
	"github.com/fgm/izidic"

	"code.osinet.fr/fgm/sqs_demo/services"
)

const (
	// MessageSystemAttributeNameDeadLetterQueueSourceArn is an undocumented
	// types.Message attribute, used by the SQS console to support redrive.
	MessageSystemAttributeNameDeadLetterQueueSourceArn types.MessageSystemAttributeName = "DeadLetterQueueSourceArn"
)

type ItemsKeys struct {
	MessageID     string
	ReceiptHandle string
}

// Redriver is a redrive-oriented facade in front of the sqs.Client API.
type Redriver interface {
	ListQueues(ctx context.Context, prefix string) (QueueUrls []string, err error)
	GetDLQ(ctx context.Context, qName string) (QueueUrls string, err error)
	GetQueueInfo(ctx context.Context, qName string) (*QueueInfo, error)
	GetQueueItems(ctx context.Context, qName string) ([]Message, error)
	DeleteItems(ctx context.Context, qName string, itemsIDs []ItemsKeys) error
	Purge(ctx context.Context, qName string) error
	RedriveItems(ctx context.Context, qName string, itemIDs []ItemsKeys) error
}

type redriver struct {
	Wait int32

	io.Writer
	*sqs.Client
}

func (r *redriver) ListQueues(ctx context.Context, prefix string) (QueueUrls []string, err error) {
	lqi := &sqs.ListQueuesInput{
		MaxResults:      aws.Int32(1000),
		NextToken:       nil,
		QueueNamePrefix: aws.String(prefix),
	}
	lqo, err := r.Client.ListQueues(ctx, lqi)
	if err != nil {
		return nil, fmt.Errorf("listing queues: %w", err)
	}
	return lqo.QueueUrls, nil
}

func (*redriver) parseQueueInfoRedriveAllowPolicy(qName string, qao sqs.GetQueueAttributesOutput) (qrap *QueueInfoAttributesRedriveAllowPolicy, err error) {
	srap, ok := qao.Attributes[string(types.QueueAttributeNameRedriveAllowPolicy)]
	if !ok || srap == "" {
		return nil, nil
	}
	qrap = &QueueInfoAttributesRedriveAllowPolicy{}
	if err = json.Unmarshal([]byte(srap), qrap); err != nil {
		return nil, fmt.Errorf(
			"failed parsing redrive policy for queue %q %w", qName, err)
	}
	return qrap, nil
}

func (*redriver) parseQueueInfoRedrivePolicy(qName string, qao sqs.GetQueueAttributesOutput) (qrp *QueueInfoAttributesRedrivePolicy, err error) {
	srp, ok := qao.Attributes[string(types.QueueAttributeNameRedrivePolicy)]
	if !ok || srp == "" {
		return nil, nil
	}
	qrp = &QueueInfoAttributesRedrivePolicy{}
	if err = json.Unmarshal([]byte(srp), qrp); err != nil {
		return qrp, fmt.Errorf(
			"failed parsing redrive policy for queue %q %w", qName, err)
	}
	if _, err = URLFromARNString(qrp.DeadLetterTargetARN); err != nil {
		return qrp, fmt.Errorf(
			"failed converting queue %q ARN to URL: %w", qName, err)
	}
	return qrp, nil
}

func (r *redriver) GetDLQ(ctx context.Context, qName string) (QueueUrl string, err error) {
	qui := &sqs.GetQueueUrlInput{QueueName: &qName}
	qu, err := r.GetQueueUrl(ctx, qui)
	if err != nil {
		return "", fmt.Errorf("failed getting URL for queue %q: %w", qName, err)
	}
	qai := &sqs.GetQueueAttributesInput{
		QueueUrl:       qu.QueueUrl,
		AttributeNames: []types.QueueAttributeName{types.QueueAttributeNameRedrivePolicy},
	}
	qao, err := r.Client.GetQueueAttributes(ctx, qai)
	if err != nil {
		return "", fmt.Errorf("failed getting DLQ for queue %q: %w", qName, err)
	}
	if qao == nil {
		return "", fmt.Errorf("redrive policy for queue %q is empty", qName)
	}
	qrp, err := r.parseQueueInfoRedrivePolicy(qName, *qao)
	if err != nil {
		return "", fmt.Errorf("failed parsing redrive policy for queue %q: %w", qName, err)
	}
	if qrp == nil {
		return "", nil // Queue has no DLQ: this is not an error
	}
	qURL, _ := URLFromARNString(qrp.DeadLetterTargetARN) // Already checked in parseQueueInfoRedrivePolicy
	return qURL, nil
}

func (r *redriver) GetQueueInfo(ctx context.Context, qName string) (*QueueInfo, error) {
	qui := &sqs.GetQueueUrlInput{QueueName: &qName}
	qu, err := r.GetQueueUrl(ctx, qui)
	if err != nil {
		return nil, fmt.Errorf("failed getting URL for queue %q: %w", qName, err)
	}
	if qu.QueueUrl == nil {
		return nil, fmt.Errorf("URL for queue %q is empty", qName)
	}

	qai := &sqs.GetQueueAttributesInput{
		QueueUrl:       qu.QueueUrl,
		AttributeNames: []types.QueueAttributeName{types.QueueAttributeNameAll},
	}
	qao, err := r.Client.GetQueueAttributes(ctx, qai)
	if err != nil {
		return nil, fmt.Errorf("failed getting all attributes for queue %q: %w", qName, err)
	}
	if qao == nil {
		return nil, fmt.Errorf("no attributes returned for queue %q", qName)
	}
	qi, err := r.parseQueueInfoAttributes(qName, qu, qao)
	if err != nil {
		return nil, err
	}
	return qi, err
}

func (r *redriver) parseQueueInfoAttributes(qName string, qu *sqs.GetQueueUrlOutput, qao *sqs.GetQueueAttributesOutput) (*QueueInfo, error) {
	var (
		qi                               *QueueInfo
		errCount                         int
		anom, anomd, anomnv              int64
		created, changed                 int64 // timestamps
		delay, max, retention, vto, wait int64
	)
	u := *qu.QueueUrl
	a, err := ARNFromURL(u)
	if err != nil {
		return nil, fmt.Errorf("ARN for queue %q cannot be parsed from URL %q: %w", qName, u, err)
	}

	for _, field := range []struct {
		name  types.QueueAttributeName
		value *int64
		sDef  string
		def   int64
	}{
		{types.QueueAttributeNameApproximateNumberOfMessages, &anom, "-1", -1},
		{types.QueueAttributeNameApproximateNumberOfMessagesDelayed, &anomd, "-1", -1},
		{types.QueueAttributeNameApproximateNumberOfMessagesNotVisible, &anomnv, "-1", -1},
		{types.QueueAttributeNameCreatedTimestamp, &created, "0", 0},
		{types.QueueAttributeNameDelaySeconds, &delay, "-1", -1},
		{types.QueueAttributeNameLastModifiedTimestamp, &changed, "0", 0},
		{types.QueueAttributeNameMaximumMessageSize, &max, "262144", 1 << (8 + 10)},          // 256ko
		{types.QueueAttributeNameMessageRetentionPeriod, &max, "1209600", 14 * 24 * 60 * 60}, // 2 weeks
		{types.QueueAttributeNameReceiveMessageWaitTimeSeconds, &wait, "0", 0},               // short polling
		{types.QueueAttributeNameVisibilityTimeout, &vto, "0", 0},                            // short polling
	} {
		s, ok := qao.Attributes[string(field.name)]
		if !ok {
			errCount++
			s = field.sDef
		}
		n, err := strconv.Atoi(s)
		if err != nil {
			errCount++
		}
		*field.value = int64(n)
	}
	qrp, err := r.parseQueueInfoRedrivePolicy(qName, *qao)
	if err != nil {
		return nil, fmt.Errorf("failed parsing redrive policy for queue %q: %w", qName, err)
	}
	qrap, err := r.parseQueueInfoRedriveAllowPolicy(qName, *qao)
	if err != nil {
		return nil, fmt.Errorf("failed parsing redrive allow policy for queue %q: %w", qName, err)
	}
	qi = &QueueInfo{
		Name: qName,
		Url:  u,
		Attributes: &QueueInfoAttributes{
			ApproximateNumberOfMessages:           anom,
			ApproximateNumberOfMessagesDelayed:    anomd,
			ApproximateNumberOfMessagesNotVisible: anomnv,
			CreatedTimestamp:                      created,
			DelaySeconds:                          delay,
			LastModifiedTimestamp:                 changed,
			MaximumMessageSize:                    max,
			MessageRetentionPeriod:                retention,
			QueueARN:                              a.String(),
			ReceiveMessageWaitTimeSeconds:         wait,
			VisibilityTimeout:                     vto,
			RedrivePolicy:                         qrp,
			RedriveAllowPolicy:                    qrap,
		},
	}
	return qi, nil
}

func (*redriver) parseReceivedAttributes(msg types.Message) (*SystemMessageAttributes, error) {
	var (
		afrt, arc, sent int64
		errCount        int
		err             error
	)
	for _, field := range []struct {
		name  types.MessageSystemAttributeName
		value *int64
		sDef  string
		def   int64
	}{
		{types.MessageSystemAttributeNameApproximateFirstReceiveTimestamp, &afrt, "0", 0},
		{types.MessageSystemAttributeNameApproximateReceiveCount, &arc, "0", 0},
		{types.MessageSystemAttributeNameSentTimestamp, &sent, "0", 0},
	} {
		s, ok := msg.Attributes[string(field.name)]
		if !ok {
			errCount++
			s = field.sDef
		}
		n, err := strconv.Atoi(s)
		if err != nil {
			errCount++
		}
		*field.value = int64(n)
	}
	ma := SystemMessageAttributes{
		ApproximateFirstReceiveTimestamp: afrt,
		ApproximateReceiveCount:          arc,
		DeadLetterQueueSourceARN:         msg.Attributes[string(MessageSystemAttributeNameDeadLetterQueueSourceArn)],
		SenderId:                         msg.Attributes[string(types.MessageSystemAttributeNameSenderId)],
		SentTimestamp:                    sent,
	}
	if errCount > 0 {
		err = fmt.Errorf("encounted %d errors parsing system message attributes", errCount)
		return nil, err
	}
	return &ma, nil
}

func (r *redriver) GetQueueItems(ctx context.Context, qName string) ([]Message, error) {
	qui := &sqs.GetQueueUrlInput{QueueName: &qName}
	qu, err := r.GetQueueUrl(ctx, qui)
	if err != nil {
		return nil, fmt.Errorf("failed getting URL for queue %q: %w", qName, err)
	}
	if qu.QueueUrl == nil {
		return nil, fmt.Errorf("URL for queue %q is empty", qName)
	}
	rmi := sqs.ReceiveMessageInput{
		QueueUrl:              qu.QueueUrl,
		AttributeNames:        []types.QueueAttributeName{types.QueueAttributeNameAll},
		MaxNumberOfMessages:   10,
		MessageAttributeNames: []string{".*"},
		VisibilityTimeout:     0,
		WaitTimeSeconds:       r.Wait,
	}
	rmo, err := r.Client.ReceiveMessage(ctx, &rmi)
	ms := make([]Message, 0, len(rmo.Messages))
	for _, m := range rmo.Messages {
		ma, err := r.parseReceivedAttributes(m)
		if err != nil {
			return nil, err
		}
		for _, field := range []struct {
			name  string
			value any
		}{
			{"body", m.Body},
			{"md5 of body", m.MD5OfBody},
			{"md5 of message attributes", m.MD5OfMessageAttributes},
			{"message ID", m.MessageId},
			{"receipt handle", m.ReceiptHandle},
		} {
			if field.value == nil {
				return nil, fmt.Errorf("missing field %s on message", field.name)
			}
		}
		j, err := JSONableFromMessageAttributeValues(m.MessageAttributes)
		if err != nil {
			return nil, fmt.Errorf("failed decoding message boby: %w", err)
		}
		m := Message{
			Attributes:             ma,
			Body:                   *m.Body,
			Md5OfBody:              *m.MD5OfBody,
			Md5OfMessageAttributes: *m.MD5OfMessageAttributes,
			MessageAttributes:      j,
			MessageId:              *m.MessageId,
			ReceiptHandle:          *m.ReceiptHandle,
		}
		ms = append(ms, m)
	}
	return ms, err
}

func (r *redriver) DeleteItems(ctx context.Context, qName string, itemsIDs []ItemsKeys) error {
	// TODO implement me
	panic("implement me")
}

func (r *redriver) Purge(ctx context.Context, qName string) error {
	// TODO implement me
	panic("implement me")
}

func (r *redriver) RedriveItems(ctx context.Context, qName string, itemIDs []ItemsKeys) error {
	// TODO implement me
	panic("implement me")
}

func RedriverService(dic *izidic.Container) (any, error) {
	cli := dic.MustService(services.SvcClient).(*sqs.Client)
	w := dic.MustParam(services.PWriter).(io.Writer)
	wait := int32(dic.MustParam(services.PWait).(int))
	return &redriver{
		Wait: wait,

		Writer: w,
		Client: cli,
	}, nil
}