package sqs

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"log"
	"time"

	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/config"
	"github.com/aws/aws-sdk-go-v2/service/sqs"
	"github.com/aws/aws-sdk-go-v2/service/sqs/types"
)

// Message represents a message from SQS queue
type Message struct {
	ID            string
	Body          string
	ReceiptHandle string
	RawEventID    string
	CorrelationID *string // Optional correlation ID from message attributes
}

// RawEventMessage represents the expected structure of SQS message body
type RawEventMessage struct {
	RawEventID string `json:"raw_event_id"`
	Timestamp  string `json:"timestamp,omitempty"`
	Source     string `json:"source,omitempty"`
}

// Client wraps the AWS SQS client with our specific functionality
// It implements the SQSClient interface
type Client struct {
	sqsClient           *sqs.Client
	queueURL            string
	maxMessages         int32
	waitTimeSeconds     int32
	visibilityTimeout   int32
	region              string
}

// NewClient creates a new SQS client
func NewClient(region, queueURL string, maxMessages, waitTimeSeconds, visibilityTimeout int32) (*Client, error) {
	// Load AWS configuration
	cfg, err := config.LoadDefaultConfig(context.TODO(),
		config.WithRegion(region),
	)
	if err != nil {
		return nil, fmt.Errorf("failed to load AWS config: %w", err)
	}

	// Create SQS client
	sqsClient := sqs.NewFromConfig(cfg)

	return &Client{
		sqsClient:         sqsClient,
		queueURL:          queueURL,
		maxMessages:       maxMessages,
		waitTimeSeconds:   waitTimeSeconds,
		visibilityTimeout: visibilityTimeout,
		region:            region,
	}, nil
}

// ReceiveMessages polls the SQS queue for messages
func (c *Client) ReceiveMessages(ctx context.Context) ([]*Message, error) {
	input := &sqs.ReceiveMessageInput{
		QueueUrl:            &c.queueURL,
		MaxNumberOfMessages: c.maxMessages,
		WaitTimeSeconds:     c.waitTimeSeconds,
		VisibilityTimeout:   c.visibilityTimeout,
		MessageAttributeNames: []string{"All"},
	}

	result, err := c.sqsClient.ReceiveMessage(ctx, input)
	if err != nil {
		return nil, fmt.Errorf("failed to receive messages from SQS: %w", err)
	}

	messages := make([]*Message, 0, len(result.Messages))
	for _, sqsMsg := range result.Messages {
		msg, err := c.parseMessage(sqsMsg)
		if err != nil {
			log.Printf("Error parsing SQS message %s: %v", aws.ToString(sqsMsg.MessageId), err)
			// Continue processing other messages even if one fails to parse
			continue
		}
		messages = append(messages, msg)
	}

	return messages, nil
}

// parseMessage converts an SQS message to our internal Message structure
func (c *Client) parseMessage(sqsMsg types.Message) (*Message, error) {
	if sqsMsg.MessageId == nil {
		return nil, errors.New("message ID is nil")
	}

	if sqsMsg.Body == nil {
		return nil, errors.New("message body is nil")
	}

	if sqsMsg.ReceiptHandle == nil {
		return nil, errors.New("receipt handle is nil")
	}

	// Parse the message body as JSON to extract raw_event_id
	var rawEventMsg RawEventMessage
	if err := json.Unmarshal([]byte(*sqsMsg.Body), &rawEventMsg); err != nil {
		return nil, fmt.Errorf("failed to parse message body as JSON: %w", err)
	}

	if rawEventMsg.RawEventID == "" {
		return nil, errors.New("raw_event_id is missing from message body")
	}

	// Extract correlation_id from message attributes if present
	var correlationID *string
	if sqsMsg.MessageAttributes != nil {
		if attr, ok := sqsMsg.MessageAttributes["correlation_id"]; ok && attr.StringValue != nil {
			correlationID = attr.StringValue
		}
		// Also check for x-correlation-id (alternative naming)
		if correlationID == nil {
			if attr, ok := sqsMsg.MessageAttributes["x-correlation-id"]; ok && attr.StringValue != nil {
				correlationID = attr.StringValue
			}
		}
	}

	return &Message{
		ID:            *sqsMsg.MessageId,
		Body:          *sqsMsg.Body,
		ReceiptHandle: *sqsMsg.ReceiptHandle,
		RawEventID:    rawEventMsg.RawEventID,
		CorrelationID: correlationID,
	}, nil
}

// DeleteMessage removes a message from the queue after successful processing
func (c *Client) DeleteMessage(ctx context.Context, receiptHandle string) error {
	input := &sqs.DeleteMessageInput{
		QueueUrl:      &c.queueURL,
		ReceiptHandle: &receiptHandle,
	}

	_, err := c.sqsClient.DeleteMessage(ctx, input)
	if err != nil {
		return fmt.Errorf("failed to delete message from SQS: %w", err)
	}

	return nil
}

// ChangeMessageVisibility extends the visibility timeout for a message
// This is useful when processing takes longer than expected
func (c *Client) ChangeMessageVisibility(ctx context.Context, receiptHandle string, visibilityTimeout int32) error {
	input := &sqs.ChangeMessageVisibilityInput{
		QueueUrl:          &c.queueURL,
		ReceiptHandle:     &receiptHandle,
		VisibilityTimeout: visibilityTimeout,
	}

	_, err := c.sqsClient.ChangeMessageVisibility(ctx, input)
	if err != nil {
		return fmt.Errorf("failed to change message visibility: %w", err)
	}

	return nil
}

// PollMessages continuously polls for messages and sends them to a channel
func (c *Client) PollMessages(ctx context.Context, messagesChan chan<- *Message, errorsChan chan<- error) {
	log.Printf("Starting SQS polling for queue: %s", c.queueURL)

	ticker := time.NewTicker(1 * time.Second)
	defer ticker.Stop()

	for {
		select {
		case <-ctx.Done():
			log.Println("SQS polling stopped due to context cancellation")
			return
		case <-ticker.C:
			messages, err := c.ReceiveMessages(ctx)
			if err != nil {
				log.Printf("Error receiving messages: %v", err)
				errorsChan <- err
				continue
			}

			if len(messages) > 0 {
				log.Printf("Received %d messages from SQS", len(messages))
			}

			for _, msg := range messages {
				select {
				case messagesChan <- msg:
					log.Printf("Sent message %s to processing channel", msg.ID)
				case <-ctx.Done():
					return
				}
			}
		}
	}
}

// GetQueueAttributes retrieves queue attributes for monitoring
func (c *Client) GetQueueAttributes(ctx context.Context) (map[string]string, error) {
	input := &sqs.GetQueueAttributesInput{
		QueueUrl: &c.queueURL,
		AttributeNames: []types.QueueAttributeName{
			types.QueueAttributeNameApproximateNumberOfMessages,
			types.QueueAttributeNameApproximateNumberOfMessagesNotVisible,
			types.QueueAttributeNameApproximateNumberOfMessagesDelayed,
		},
	}

	result, err := c.sqsClient.GetQueueAttributes(ctx, input)
	if err != nil {
		return nil, fmt.Errorf("failed to get queue attributes: %w", err)
	}

	return result.Attributes, nil
}