package messaging

import (
	"context"
	"errors"
	"fmt"
	"github.com/Azure/go-amqp"
	"log/slog"
	"sync"
	"time"
)

var ConnectionClosedError = errors.New("amqp connection is closed")

type AmqpConnection struct {
	connectionName string
	lock           sync.RWMutex
	brokerUrl      string
	username       string
	password       string
	conn           *amqp.Conn
}

func NewAmqpConnection(config *AmqpConnectionConfig, connectionName string) *AmqpConnection {
	return &AmqpConnection{
		connectionName: connectionName,
		lock:           sync.RWMutex{},
		brokerUrl:      config.BrokerUrl,
		username:       config.Username,
		password:       config.Password,
	}
}

func (c *AmqpConnection) NewReceiver(ctx context.Context, source string) (*AmqpReceiverSession, error) {
	if c.conn == nil {
		return nil, errors.New("connection is not initialized")
	}

	if c.internalIsClosed() {
		return nil, ConnectionClosedError
	}

	c.lock.RLock()
	defer c.lock.RUnlock()

	// new session
	session, err := c.conn.NewSession(ctx, nil)
	if err != nil {
		return nil, fmt.Errorf("new session: %w", err)
	}

	// new receiver
	receiver, err := session.NewReceiver(ctx, source, nil)
	if err != nil {
		err = fmt.Errorf("new internal receiver: %w", err)

		closeErr := session.Close(ctx)
		if closeErr != nil {
			return nil, errors.Join(fmt.Errorf("close session: %w", err), err)
		}
		return nil, err
	}

	return &AmqpReceiverSession{session, receiver}, nil
}

func (c *AmqpConnection) NewSender(ctx context.Context, topic string) (*AmqpSenderSession, error) {
	if c.conn == nil {
		return nil, errors.New("connection is not initialized")
	}

	if c.internalIsClosed() {
		return nil, ConnectionClosedError
	}

	c.lock.RLock()
	defer c.lock.RUnlock()

	// new session
	newSession, err := c.conn.NewSession(ctx, nil)
	if err != nil {
		return nil, fmt.Errorf("new session: %w", err)
	}

	// new sender
	newSender, err := newSession.NewSender(ctx, topic, nil)
	if err != nil {
		err = fmt.Errorf("new internal sender: %w", err)

		closeErr := newSession.Close(ctx)
		if closeErr != nil {
			return nil, errors.Join(fmt.Errorf("close session: %w", err), err)
		}
		return nil, err
	}

	return &AmqpSenderSession{newSession, newSender}, nil
}

func (c *AmqpConnection) ResetConnectionAndRetryIfErrorWithReturnValue(opName string, fn func(ctx context.Context) (any, error)) (any, error) {
	ctx, cancelFn := context.WithTimeout(context.Background(), 10*time.Second)
	result, err := fn(ctx)
	cancelFn()

	if err != nil {
		slog.Info(fmt.Sprintf("amqp connection: %s", opName), slog.Any("connection", c.connectionName), slog.Any("err", err))
		err := c.ResetConnection(context.Background())
		if err != nil {
			return nil, fmt.Errorf("reset connection: %w", err)
		}

		newCtx, closeFn := context.WithTimeout(context.Background(), 10*time.Second)
		defer closeFn()

		// Retry
		return fn(newCtx)
	}
	return result, nil
}

func (c *AmqpConnection) ResetConnection(ctx context.Context) error {
	c.lock.Lock()
	defer c.lock.Unlock()

	subCtx, cancel := context.WithTimeout(ctx, disconnectionTimeoutSeconds*time.Second)
	err := c.internalClose(subCtx)
	cancel()
	if err != nil {
		slog.Warn("amqp connection: reset: failed to close amqp connection", slog.Any("err", err))
	}

	subCtx, cancel = context.WithTimeout(ctx, connectionTimeoutSeconds*time.Second)
	err = c.internalConnect(subCtx)
	cancel()
	if err != nil {
		slog.Warn("amqp connection: reset: failed to connect to amqp server, retry..", slog.Any("err", err))
		subCtx, cancel = context.WithTimeout(ctx, connectionTimeoutSeconds*time.Second)
		err = c.internalConnect(subCtx)
		cancel()
		if err != nil {
			return fmt.Errorf("connect: %w", err)
		}
	}
	return nil
}

func As[T any](value any, err error) (*T, error) {
	if err != nil {
		return nil, err
	}
	if value == nil {
		return nil, nil
	}
	castedValue, isType := value.(*T)
	if !isType {
		return nil, fmt.Errorf("could not cast value: %T", value)
	}
	return castedValue, nil
}

func (c *AmqpConnection) Connect(ctx context.Context) error {
	c.lock.Lock()
	defer c.lock.Unlock()

	subCtx, cancel := context.WithTimeout(ctx, connectionTimeoutSeconds*time.Second)
	defer cancel()
	return c.internalConnect(subCtx)
}

func (c *AmqpConnection) internalConnect(ctx context.Context) error {
	if c.conn == nil {
		// Set credentials if specified
		auth := amqp.SASLTypeAnonymous()
		if c.username != "" && c.password != "" {
			auth = amqp.SASLTypePlain(c.username, c.password)
		} else {
			slog.Debug("amqp connection: connect: using anonymous messaging")
		}
		options := &amqp.ConnOptions{
			SASLType: auth,
		}

		// Initialize connection
		conn, err := amqp.Dial(ctx, c.brokerUrl, options)
		if err != nil {
			return fmt.Errorf("dial: %w", err)
		}
		c.conn = conn
	}
	return nil
}

func (c *AmqpConnection) Close(ctx context.Context) error {
	c.lock.Lock()
	defer c.lock.Unlock()

	subCtx, cancel := context.WithTimeout(ctx, disconnectionTimeoutSeconds*time.Second)
	defer cancel()

	return c.internalClose(subCtx)
}

func (c *AmqpConnection) internalClose(ctx context.Context) error {
	if c.conn != nil {
		closeErrors := make([]error, 0)
		closeErrors = c.internalCloseConnection(closeErrors)

		// return errors or nil
		if len(closeErrors) > 0 {
			return errors.Join(closeErrors...)
		}
	}
	return nil
}

func (c *AmqpConnection) internalCloseConnection(closeErrors []error) []error {
	err := c.conn.Close()
	if err != nil {
		closeErrors = append(closeErrors, err)
	}
	return closeErrors
}

func (c *AmqpConnection) IsClosed() bool {
	c.lock.RLock()
	defer c.lock.RUnlock()

	return c.internalIsClosed()
}

func (c *AmqpConnection) internalIsClosed() bool {
	if c.conn == nil {
		return true
	}
	select {
	case <-c.conn.Done():
		return true
	default:
		return false
	}
}