package mailer

import (
	"bufio"
	"net"
	"strconv"
	"strings"
	"testing"
)

func TestSendFailsWhenConfigMissing(t *testing.T) {
	t.Setenv("EMAIL_HOST", "")
	t.Setenv("EMAIL_PORT", "")
	t.Setenv("EMAIL_FROM", "")

	if err := Send("user@example.com", "subj", "body"); err == nil {
		t.Fatal("expected error for incomplete email config")
	}
}

func TestSendPlainSMTP(t *testing.T) {
	ln, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatalf("failed to listen: %v", err)
	}
	defer ln.Close()

	done := make(chan error, 1)
	go func() {
		conn, err := ln.Accept()
		if err != nil {
			done <- err
			return
		}
		defer conn.Close()

		r := bufio.NewReader(conn)
		w := bufio.NewWriter(conn)
		write := func(s string) error {
			if _, err := w.WriteString(s); err != nil {
				return err
			}
			return w.Flush()
		}

		if err := write("220 localhost Simple Mail Transfer Service Ready\r\n"); err != nil {
			done <- err
			return
		}

		for {
			line, err := r.ReadString('\n')
			if err != nil {
				done <- err
				return
			}
			cmd := strings.TrimSpace(line)

			switch {
			case strings.HasPrefix(strings.ToUpper(cmd), "EHLO") || strings.HasPrefix(strings.ToUpper(cmd), "HELO"):
				if err := write("250-localhost\r\n250 AUTH PLAIN\r\n"); err != nil {
					done <- err
					return
				}
			case strings.HasPrefix(strings.ToUpper(cmd), "MAIL FROM"):
				if err := write("250 OK\r\n"); err != nil {
					done <- err
					return
				}
			case strings.HasPrefix(strings.ToUpper(cmd), "RCPT TO"):
				if err := write("250 OK\r\n"); err != nil {
					done <- err
					return
				}
			case strings.HasPrefix(strings.ToUpper(cmd), "DATA"):
				if err := write("354 End data with <CR><LF>.<CR><LF>\r\n"); err != nil {
					done <- err
					return
				}
				for {
					d, err := r.ReadString('\n')
					if err != nil {
						done <- err
						return
					}
					if strings.TrimSpace(d) == "." {
						break
					}
				}
				if err := write("250 OK queued\r\n"); err != nil {
					done <- err
					return
				}
			case strings.HasPrefix(strings.ToUpper(cmd), "QUIT"):
				_ = write("221 Bye\r\n")
				done <- nil
				return
			default:
				if err := write("250 OK\r\n"); err != nil {
					done <- err
					return
				}
			}
		}
	}()

	host, portStr, err := net.SplitHostPort(ln.Addr().String())
	if err != nil {
		t.Fatalf("failed to parse listener address: %v", err)
	}
	if _, err := strconv.Atoi(portStr); err != nil {
		t.Fatalf("invalid test smtp port: %v", err)
	}

	t.Setenv("EMAIL_HOST", host)
	t.Setenv("EMAIL_PORT", portStr)
	t.Setenv("EMAIL_FROM", "noreply@example.com")
	t.Setenv("EMAIL_HOST_USER", "")
	t.Setenv("EMAIL_HOST_PASSWORD", "")
	t.Setenv("EMAIL_USE_TLS", "false")
	t.Setenv("EMAIL_USE_SSL", "false")

	if err := Send("user@example.com", "Verify", "Hello"); err != nil {
		t.Fatalf("expected send success, got error: %v", err)
	}

	if err := <-done; err != nil {
		t.Fatalf("smtp server finished with error: %v", err)
	}
}