package caldav

import (
	"context"
	"fmt"
	"io"
	"log/slog"
	"path/filepath"
	"strings"
	"testing"

	ical "github.com/emersion/go-ical"
	"github.com/yourusername/caldav-server/internal/auth"
	"github.com/yourusername/caldav-server/internal/config"
	"github.com/yourusername/caldav-server/internal/db"
	"github.com/yourusername/caldav-server/internal/store"
)

func newTestBackend(t *testing.T) (*Backend, *db.DB) {
	t.Helper()
	dir := t.TempDir()

	st, err := store.NewStore(filepath.Join(dir, "data"))
	if err != nil {
		t.Fatalf("NewStore: %v", err)
	}
	dbase, err := db.Open(filepath.Join(dir, "test.db"))
	if err != nil {
		t.Fatalf("db.Open: %v", err)
	}
	t.Cleanup(func() { dbase.Close() })

	cfg := &config.Config{
		Users: map[string]config.UserConfig{
			"alice": {Calendars: []string{"work"}},
			"bob":   {Calendars: []string{"personal"}},
		},
	}
	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
	return NewBackend(cfg, st, dbase, logger), dbase
}

func ctxFor(username string) context.Context {
	return auth.NewContext(context.Background(), &auth.Principal{Username: username})
}

// minimalEvent returns a minimal, valid VCALENDAR/VEVENT for use in tests.
func minimalEvent() *ical.Calendar {
	const raw = "BEGIN:VCALENDAR\r\n" +
		"VERSION:2.0\r\n" +
		"PRODID:-//nidus//test//EN\r\n" +
		"BEGIN:VEVENT\r\n" +
		"UID:event1@nidus.test\r\n" +
		"DTSTAMP:20240101T000000Z\r\n" +
		"DTSTART:20240101T100000Z\r\n" +
		"SUMMARY:Test Event\r\n" +
		"END:VEVENT\r\n" +
		"END:VCALENDAR\r\n"
	cal, err := ical.NewDecoder(strings.NewReader(raw)).Decode()
	if err != nil {
		panic(fmt.Sprintf("minimalEvent: %v", err))
	}
	return cal
}

func TestListCalendarsIncludesSharedCalendar(t *testing.T) {
	b, dbase := newTestBackend(t)

	if err := dbase.ShareCalendar("alice", "work", "bob", db.PermRead); err != nil {
		t.Fatalf("ShareCalendar: %v", err)
	}
	// The shared calendar must exist on disk for it to be listed; normally
	// this happens when alice's own ListCalendars runs and ensures it.
	if _, err := b.ListCalendars(ctxFor("alice")); err != nil {
		t.Fatalf("ListCalendars(alice): %v", err)
	}

	cals, err := b.ListCalendars(ctxFor("bob"))
	if err != nil {
		t.Fatalf("ListCalendars: %v", err)
	}

	var found bool
	wantName := sharedCalendarName("alice", "work")
	for _, c := range cals {
		if c.Name == wantName {
			found = true
		}
	}
	if !found {
		t.Errorf("shared calendar %q not found in ListCalendars result: %+v", wantName, cals)
	}
}

func TestSharedCalendarReadOnlyRejectsWrite(t *testing.T) {
	b, dbase := newTestBackend(t)

	if err := dbase.ShareCalendar("alice", "work", "bob", db.PermRead); err != nil {
		t.Fatalf("ShareCalendar: %v", err)
	}

	localName := sharedCalendarName("alice", "work")
	objPath := calObjectPath(localName, "event1.ics")

	_, err := b.PutCalendarObject(ctxFor("bob"), objPath, minimalEvent(), nil)
	if err == nil {
		t.Fatal("expected error writing to read-only shared calendar, got nil")
	}
}

func TestSharedCalendarWriteAllowed(t *testing.T) {
	b, dbase := newTestBackend(t)

	if err := dbase.ShareCalendar("alice", "work", "bob", db.PermWrite); err != nil {
		t.Fatalf("ShareCalendar: %v", err)
	}

	localName := sharedCalendarName("alice", "work")
	objPath := calObjectPath(localName, "event1.ics")

	if _, err := b.PutCalendarObject(ctxFor("bob"), objPath, minimalEvent(), nil); err != nil {
		t.Fatalf("PutCalendarObject with write share: %v", err)
	}

	// The object should now be visible under alice's own calendar too,
	// since it's stored in her namespace.
	obj, err := b.GetCalendarObject(ctxFor("alice"), calObjectPath("work", "event1.ics"), nil)
	if err != nil {
		t.Fatalf("GetCalendarObject as owner: %v", err)
	}
	if obj == nil {
		t.Fatal("expected non-nil object")
	}
}

func TestUnauthorizedUserCannotAccessUnsharedCalendar(t *testing.T) {
	b, _ := newTestBackend(t)

	localName := sharedCalendarName("alice", "work")
	_, err := b.GetCalendar(ctxFor("bob"), calHomePath()+localName+"/")
	if err == nil {
		t.Fatal("expected error accessing unshared calendar, got nil")
	}
}