package mail

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

// relay is the least of an SMTP server: it takes one message and keeps it.
func relay(t *testing.T) (addr string, got chan string) {
	t.Helper()
	ln, err := net.Listen("tcp", "127.0.0.1:0")
	if err != nil {
		t.Fatal(err)
	}
	got = make(chan string, 1)
	go func() {
		c, err := ln.Accept()
		if err != nil {
			return
		}
		defer c.Close()
		r := bufio.NewReader(c)
		say := func(s string) { _, _ = c.Write([]byte(s + "\r\n")) }
		say("220 relay ready")
		var data strings.Builder
		inData := false
		for {
			line, err := r.ReadString('\n')
			if err != nil {
				return
			}
			if inData {
				if line == ".\r\n" {
					inData = false
					got <- data.String()
					say("250 kept")
					continue
				}
				data.WriteString(line)
				continue
			}
			switch cmd := strings.ToUpper(strings.TrimSpace(line)); {
			case strings.HasPrefix(cmd, "EHLO"), strings.HasPrefix(cmd, "HELO"):
				say("250 relay")
			case strings.HasPrefix(cmd, "DATA"):
				inData = true
				say("354 go on")
			case strings.HasPrefix(cmd, "QUIT"):
				say("221 bye")
				return
			default:
				say("250 ok")
			}
		}
	}()
	t.Cleanup(func() { _ = ln.Close() })
	return ln.Addr().String(), got
}

func TestAMessageGoesThroughTheRelay(t *testing.T) {
	addr, got := relay(t)
	c := Config{SMTP: addr, From: "llmgw <llmgw@example.com>", BaseURL: "https://llm.example.com"}
	if err := c.Validate(); err != nil {
		t.Fatal(err)
	}
	if err := c.Send(context.Background(), "ayse@example.com", "Set a new password", "Hello,\nthe link."); err != nil {
		t.Fatal(err)
	}
	msg := <-got
	for _, want := range []string{"Subject: Set a new password", "To: ayse@example.com", "Hello,\r\nthe link."} {
		if !strings.Contains(msg, want) {
			t.Errorf("the message lacks %q:\n%s", want, msg)
		}
	}
}

func TestHalfAMailConfigurationIsRefused(t *testing.T) {
	if err := (Config{}).Validate(); err != nil || (Config{}).Enabled() {
		t.Errorf("none: %v", err)
	}
	if err := (Config{SMTP: "smtp.example.com:587"}).Validate(); err == nil {
		t.Error("a relay without a sender was accepted")
	}
	if err := (Config{SMTP: "smtp.example.com:587", From: "a@b.c", BaseURL: "llm.example.com"}).Validate(); err == nil {
		t.Error("a base URL without a scheme was accepted")
	}
	if got := address("llmgw <llmgw@example.com>"); got != "llmgw@example.com" {
		t.Errorf("%q", got)
	}
}