package smtp

import (
	"context"
	"strings"
	"testing"
	"time"
)

func TestSendReturnsConfigurationErrorWhenSMTPMissing(t *testing.T) {
	mailer := NewSMTPMailer(SMTPConfig{Host: "", Port: 587, From: "noreply@example.com", Mode: SMTPModeTLS})

	err := mailer.Send(context.Background(), "to@example.com", "subject", "<p>body</p>", "body")
	if err == nil {
		t.Fatal("expected configuration error")
	}
	if !strings.Contains(err.Error(), "smtp is not configured") {
		t.Fatalf("unexpected error: %v", err)
	}
}

func TestSendReturnsDeadlineExceededForExpiredContext(t *testing.T) {
	mailer := NewSMTPMailer(SMTPConfig{Host: "smtp.example.com", Port: 587, From: "noreply@example.com", Mode: SMTPModeTLS})
	ctx, cancel := context.WithDeadline(context.Background(), time.Now().Add(-time.Second))
	defer cancel()

	err := mailer.Send(ctx, "to@example.com", "subject", "<p>body</p>", "body")
	if err == nil {
		t.Fatal("expected context deadline exceeded")
	}
	if err != context.DeadlineExceeded {
		t.Fatalf("expected context deadline exceeded, got %v", err)
	}
}

func TestLoginAuthNextHandlesChallenges(t *testing.T) {
	auth := loginAuth{username: "alice", password: "s3cret"}

	proto, initial, err := auth.Start(nil)
	if err != nil {
		t.Fatalf("unexpected start error: %v", err)
	}
	if proto != "LOGIN" {
		t.Fatalf("expected LOGIN auth proto, got %q", proto)
	}
	if len(initial) != 0 {
		t.Fatalf("expected empty initial response, got %q", string(initial))
	}

	value, err := auth.Next([]byte("Username:"), true)
	if err != nil {
		t.Fatalf("unexpected username challenge error: %v", err)
	}
	if string(value) != "alice" {
		t.Fatalf("expected username response alice, got %q", string(value))
	}

	value, err = auth.Next([]byte("UGFzc3dvcmQ6"), true)
	if err != nil {
		t.Fatalf("unexpected password challenge error: %v", err)
	}
	if string(value) != "s3cret" {
		t.Fatalf("expected password response s3cret, got %q", string(value))
	}
}

func TestLoginAuthNextHandlesTerminalAndUnexpectedChallenge(t *testing.T) {
	auth := loginAuth{username: "alice", password: "s3cret"}

	value, err := auth.Next([]byte("ignored"), false)
	if err != nil {
		t.Fatalf("expected nil error when more=false, got %v", err)
	}
	if value != nil {
		t.Fatalf("expected nil value when more=false, got %q", string(value))
	}

	if _, err := auth.Next([]byte("realm"), true); err == nil {
		t.Fatal("expected error for unexpected login challenge")
	}
}

func TestBuildMIMEMessageContainsMultipartSections(t *testing.T) {
	msg := buildMIMEMessage("from@example.com", "to@example.com", "Subject", "plain body", "<p>html body</p>")

	checks := []string{
		"From: from@example.com",
		"To: to@example.com",
		"Subject: Subject",
		"MIME-Version: 1.0",
		"Content-Type: text/plain; charset=UTF-8",
		"plain body",
		"Content-Type: text/html; charset=UTF-8",
		"<p>html body</p>",
	}
	for _, snippet := range checks {
		if !strings.Contains(msg, snippet) {
			t.Fatalf("expected MIME message to contain %q", snippet)
		}
	}
	if !strings.Contains(msg, "\r\n") {
		t.Fatal("expected CRLF separators in MIME message")
	}

	if !strings.Contains(msg, "Content-Type: multipart/alternative; boundary=mime-boundary-") {
		t.Fatalf("expected random mime boundary header, got %q", msg)
	}
	if !strings.Contains(msg, "--mime-boundary-") {
		t.Fatalf("expected mime boundary delimiters in message, got %q", msg)
	}
}

func TestDialHelpersReturnDeadlineExceededWhenDeadlineHasPassed(t *testing.T) {
	deadline := time.Now().Add(-time.Second)
	ctx := context.Background()

	if _, err := dialPlain(ctx, "smtp.example.com:25", "smtp.example.com", deadline); err != context.DeadlineExceeded {
		t.Fatalf("dialPlain expected context deadline exceeded, got %v", err)
	}
	if _, err := dialSSL(ctx, "smtp.example.com:465", "smtp.example.com", deadline); err != context.DeadlineExceeded {
		t.Fatalf("dialSSL expected context deadline exceeded, got %v", err)
	}
	if _, err := dialStartTLS(ctx, "smtp.example.com:587", "smtp.example.com", deadline); err != context.DeadlineExceeded {
		t.Fatalf("dialStartTLS expected context deadline exceeded, got %v", err)
	}
}