package imapx

import (
	"context"
	"crypto/tls"
	"fmt"
	"time"

	"github.com/emersion/go-imap/v2/imapclient"
)

type Endpoint struct {
	Host    string
	Port    int
	TLSMode string // ssl | starttls | plain
}

func (e Endpoint) addr() string { return fmt.Sprintf("%s:%d", e.Host, e.Port) }

func dialOnce(ep Endpoint) (*imapclient.Client, error) {
	switch ep.TLSMode {
	case "ssl":
		return imapclient.DialTLS(ep.addr(), &imapclient.Options{
			TLSConfig: &tls.Config{ServerName: ep.Host},
		})
	case "starttls":
		return imapclient.DialStartTLS(ep.addr(), &imapclient.Options{
			TLSConfig: &tls.Config{ServerName: ep.Host},
		})
	case "plain":
		return imapclient.DialInsecure(ep.addr(), nil)
	default:
		return nil, fmt.Errorf("unknown tls_mode %q", ep.TLSMode)
	}
}

func Connect(ctx context.Context, ep Endpoint) (*imapclient.Client, error) {
	const attempts = 3
	var lastErr error
	for i := 0; i < attempts; i++ {
		if err := ctx.Err(); err != nil {
			return nil, err
		}
		c, err := dialOnce(ep)
		if err == nil {
			return c, nil
		}
		lastErr = err
		if i < attempts-1 {
			backoff := time.Duration(200*(i+1)) * time.Millisecond
			select {
			case <-ctx.Done():
				return nil, ctx.Err()
			case <-time.After(backoff):
			}
		}
	}
	return nil, lastErr
}

func TestEndpoint(ctx context.Context, ep Endpoint) error {
	c, err := Connect(ctx, ep)
	if err != nil {
		return err
	}
	return c.Logout().Wait()
}