package mail

import (
	"os"
	"path/filepath"
	"testing"
)

func loadFixture(t *testing.T, name string) []byte {
	t.Helper()
	b, err := os.ReadFile(filepath.Join("testdata", name))
	if err != nil {
		t.Fatalf("read fixture: %v", err)
	}
	return b
}

func TestParseMessage(t *testing.T) {
	raw := loadFixture(t, "with_attachment.eml")
	m, err := ParseMessage(42, raw)
	if err != nil {
		t.Fatalf("ParseMessage: %v", err)
	}
	if m.Header.UID != 42 {
		t.Fatalf("uid: %d", m.Header.UID)
	}
	if m.Header.Subject != "Your Invoice #5" {
		t.Fatalf("subject: %q", m.Header.Subject)
	}
	if m.Header.From != `"Bob" <bob@trusted.com>` && m.Header.From != "Bob <bob@trusted.com>" {
		t.Fatalf("from: %q", m.Header.From)
	}
	if m.Header.MessageID != "abc123@trusted.com" && m.Header.MessageID != "<abc123@trusted.com>" {
		t.Fatalf("message-id: %q", m.Header.MessageID)
	}
	if want := "Hello, here is your invoice."; !contains(m.BodyText, want) {
		t.Fatalf("body=%q want contains %q", m.BodyText, want)
	}
	if !m.Header.HasAttachments {
		t.Fatal("HasAttachments should be true")
	}
	if len(m.Attachments) != 1 || m.Attachments[0].Name != "invoice.txt" {
		t.Fatalf("attachments: %+v", m.Attachments)
	}
	if !contains(string(m.Attachments[0].Content), "LINE-ITEM 1") {
		t.Fatalf("attachment content: %q", m.Attachments[0].Content)
	}
}

func TestParseHeaderOnly(t *testing.T) {
	raw := loadFixture(t, "with_attachment.eml")
	h, err := ParseHeaderOnly(7, raw)
	if err != nil {
		t.Fatalf("ParseHeaderOnly: %v", err)
	}
	if h.Subject != "Your Invoice #5" || !h.HasAttachments {
		t.Fatalf("header: %+v", h)
	}
}

func TestParseHeaderBytes(t *testing.T) {
	// Header-only bytes (no body), as returned by an IMAP BODY[HEADER] fetch,
	// including an RFC2047-encoded subject to confirm decoding is preserved.
	raw := []byte("From: \"Bob\" <bob@trusted.com>\r\n" +
		"To: me@example.com\r\n" +
		"Subject: =?UTF-8?Q?Caf=C3=A9=20Invoice?=\r\n" +
		"Date: Sat, 20 Jun 2026 10:00:00 +0000\r\n" +
		"Message-ID: <abc123@trusted.com>\r\n" +
		"\r\n")
	h, err := ParseHeaderBytes(9, raw)
	if err != nil {
		t.Fatalf("ParseHeaderBytes: %v", err)
	}
	if h.UID != 9 {
		t.Fatalf("uid: %d", h.UID)
	}
	if h.Subject != "Café Invoice" {
		t.Fatalf("subject not RFC2047-decoded: %q", h.Subject)
	}
	if h.From != `"Bob" <bob@trusted.com>` {
		t.Fatalf("from: %q", h.From)
	}
	if h.MessageID != "abc123@trusted.com" && h.MessageID != "<abc123@trusted.com>" {
		t.Fatalf("message-id: %q", h.MessageID)
	}
	// HasAttachments is left false — the IMAP layer sets it from BODYSTRUCTURE.
	if h.HasAttachments {
		t.Fatal("ParseHeaderBytes must not set HasAttachments")
	}
}

func contains(s, sub string) bool {
	return len(s) >= len(sub) && (func() bool {
		for i := 0; i+len(sub) <= len(s); i++ {
			if s[i:i+len(sub)] == sub {
				return true
			}
		}
		return false
	}())
}