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           amqpConn
	dialer         amqpDial
}

// amqpConn is an abstraction of amqp.Conn
type amqpConn interface {
	NewSession(ctx context.Context, opts *amqp.SessionOptions) (amqpSession, error)
	Close() error
	Done() <-chan struct{}
}

type defaultAmqpConn struct {
	conn *amqp.Conn
}

func newDefaultAmqpConn(conn *amqp.Conn) *defaultAmqpConn {
	return &defaultAmqpConn{
		conn: conn,
	}
}

func (d defaultAmqpConn) NewSession(ctx context.Context, opts *amqp.SessionOptions) (amqpSession, error) {
	session, err := d.conn.NewSession(ctx, opts)
	if err != nil {
		return nil, err
	}
	return newDefaultAmqpSession(session), nil
}

func (d defaultAmqpConn) Close() error {
	return d.conn.Close()
}

func (d defaultAmqpConn) Done() <-chan struct{} {
	return d.conn.Done()
}

var _ amqpConn = (*defaultAmqpConn)(nil)

type amqpDial interface {
	Dial(ctx context.Context, addr string, opts *amqp.ConnOptions) (amqpConn, error)
}

type amqpSession interface {
	NewSender(ctx context.Context, target string, opts *amqp.SenderOptions) (amqpSender, error)
	Close(ctx context.Context) error
}

type defaultAmqpSession struct {
	session *amqp.Session
}

func newDefaultAmqpSession(session *amqp.Session) *defaultAmqpSession {
	return &defaultAmqpSession{
		session: session,
	}
}

func (s *defaultAmqpSession) NewSender(ctx context.Context, target string, opts *amqp.SenderOptions) (amqpSender, error) {
	return s.session.NewSender(ctx, target, opts)
}

func (s *defaultAmqpSession) Close(ctx context.Context) error {
	return s.session.Close(ctx)
}

var _ amqpSession = (*defaultAmqpSession)(nil)

type defaultAmqpDialer struct{}

func (d *defaultAmqpDialer) Dial(ctx context.Context, addr string, opts *amqp.ConnOptions) (amqpConn, error) {
	dial, err := amqp.Dial(ctx, addr, opts)
	if err != nil {
		return nil, err
	}
	return newDefaultAmqpConn(dial), nil
}

var _ amqpDial = (*defaultAmqpDialer)(nil)

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

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(err, fmt.Errorf("close session: %w", closeErr))
		}
		return nil, err
	}

	return &AmqpSenderSession{newSession, newSender}, 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() error {
	c.lock.Lock()
	defer c.lock.Unlock()

	subCtx, cancel := context.WithTimeout(context.Background(), connectionTimeoutSeconds*time.Second)
	defer cancel()

	if err := c.internalConnect(subCtx); err != nil {
		return fmt.Errorf("internal connect: %w", err)
	}
	return nil
}

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

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

	if err := c.internalClose(); err != nil {
		return fmt.Errorf("internal close: %w", err)
	}
	return nil
}

func (c *AmqpConnection) internalClose() error {
	if c.conn != nil {
		if err := c.conn.Close(); err != nil {
			return fmt.Errorf("connection close: %w", err)
		}
		c.conn = nil
	}
	return nil
}

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
	}
}