package handlers

import (
	"testing"
	"time"

	"task-dashboard/internal/models"
)

func multiDayEvent(startISO, endISO string) models.TimelineItem {
	start, _ := time.Parse(time.RFC3339, startISO)
	end, _ := time.Parse(time.RFC3339, endISO)
	return models.TimelineItem{
		ID:      "evt-1",
		Title:   "Offsite",
		Type:    models.TimelineItemTypeEvent,
		Time:    start,
		EndTime: &end,
	}
}

func TestIsMultiDayEvent_SameDayTimedEvent_False(t *testing.T) {
	item := multiDayEvent("2026-07-13T10:00:00Z", "2026-07-13T11:00:00Z")
	if isMultiDayEvent(item) {
		t.Error("expected same-day timed event to not be multi-day")
	}
}

func TestIsMultiDayEvent_SpansMultipleDays_True(t *testing.T) {
	item := multiDayEvent("2026-07-13T17:35:00Z", "2026-07-30T22:30:00Z")
	if !isMultiDayEvent(item) {
		t.Error("expected event spanning multiple days to be multi-day")
	}
}

func TestIsMultiDayEvent_NonEventType_AlwaysFalse(t *testing.T) {
	start, _ := time.Parse(time.RFC3339, "2026-07-13T10:00:00Z")
	end, _ := time.Parse(time.RFC3339, "2026-07-30T22:30:00Z")
	item := models.TimelineItem{ID: "t1", Type: models.TimelineItemTypeTask, Time: start, EndTime: &end}
	if isMultiDayEvent(item) {
		t.Error("expected non-event type to never be considered multi-day, regardless of span")
	}
}

func TestIsMultiDayEvent_NoEndTime_False(t *testing.T) {
	start, _ := time.Parse(time.RFC3339, "2026-07-13T10:00:00Z")
	item := models.TimelineItem{ID: "e1", Type: models.TimelineItemTypeEvent, Time: start}
	if isMultiDayEvent(item) {
		t.Error("expected event with nil EndTime to not be multi-day")
	}
}

func TestMultiDayVariant_StartDay_ReturnsStarts(t *testing.T) {
	item := multiDayEvent("2026-07-13T17:35:00Z", "2026-07-30T22:30:00Z")
	renderDay, _ := time.Parse(time.RFC3339, "2026-07-13T00:00:00Z")
	if got := multiDayVariant(item, renderDay); got != "starts" {
		t.Errorf("variant = %q, want %q", got, "starts")
	}
}

func TestMultiDayVariant_EndDay_ReturnsEnds(t *testing.T) {
	item := multiDayEvent("2026-07-13T17:35:00Z", "2026-07-30T22:30:00Z")
	renderDay, _ := time.Parse(time.RFC3339, "2026-07-30T00:00:00Z")
	if got := multiDayVariant(item, renderDay); got != "ends" {
		t.Errorf("variant = %q, want %q", got, "ends")
	}
}

func TestMultiDayVariant_MiddleDay_ReturnsSpans(t *testing.T) {
	item := multiDayEvent("2026-07-13T17:35:00Z", "2026-07-30T22:30:00Z")
	renderDay, _ := time.Parse(time.RFC3339, "2026-07-20T00:00:00Z")
	if got := multiDayVariant(item, renderDay); got != "spans" {
		t.Errorf("variant = %q, want %q", got, "spans")
	}
}

func TestMultiDayVariant_DayOutsideSpan_ReturnsEmpty(t *testing.T) {
	item := multiDayEvent("2026-07-13T17:35:00Z", "2026-07-30T22:30:00Z")
	renderDay, _ := time.Parse(time.RFC3339, "2026-08-01T00:00:00Z")
	if got := multiDayVariant(item, renderDay); got != "" {
		t.Errorf("variant = %q, want empty", got)
	}
}

func TestIsMultiDayEvent_SingleDayAllDayEvent_False(t *testing.T) {
	// Exclusive end-date convention: a single-day all-day event on July 13
	// has Start=Jul13 00:00, End=Jul14 00:00 (one day past its own day).
	start, _ := time.Parse(time.RFC3339, "2026-07-13T00:00:00Z")
	end, _ := time.Parse(time.RFC3339, "2026-07-14T00:00:00Z")
	item := models.TimelineItem{
		ID: "allday-1", Type: models.TimelineItemTypeEvent,
		Time: start, EndTime: &end, IsAllDay: true,
	}
	if isMultiDayEvent(item) {
		t.Error("expected a single-day all-day event (exclusive end-date) to not be multi-day")
	}
}

func TestIsMultiDayEvent_MultiDayAllDayEvent_True(t *testing.T) {
	// A 3-day all-day event (Jul 13, 14, 15) has End=Jul16 00:00 (exclusive).
	start, _ := time.Parse(time.RFC3339, "2026-07-13T00:00:00Z")
	end, _ := time.Parse(time.RFC3339, "2026-07-16T00:00:00Z")
	item := models.TimelineItem{
		ID: "allday-2", Type: models.TimelineItemTypeEvent,
		Time: start, EndTime: &end, IsAllDay: true,
	}
	if !isMultiDayEvent(item) {
		t.Error("expected a 3-day all-day event to be multi-day")
	}
}

func TestMultiDayVariant_MultiDayAllDayEvent_LastRealDayIsEnds(t *testing.T) {
	// The 3-day all-day event above (Jul 13-15 inclusive, End=Jul16 exclusive)
	// must report "ends" on Jul 15 (its real last day), not Jul 16.
	start, _ := time.Parse(time.RFC3339, "2026-07-13T00:00:00Z")
	end, _ := time.Parse(time.RFC3339, "2026-07-16T00:00:00Z")
	item := models.TimelineItem{
		ID: "allday-2", Type: models.TimelineItemTypeEvent,
		Time: start, EndTime: &end, IsAllDay: true,
	}
	renderDay, _ := time.Parse(time.RFC3339, "2026-07-15T00:00:00Z")
	if got := multiDayVariant(item, renderDay); got != "ends" {
		t.Errorf("variant on last real day = %q, want %q", got, "ends")
	}
	exclusiveEndDay, _ := time.Parse(time.RFC3339, "2026-07-16T00:00:00Z")
	if got := multiDayVariant(item, exclusiveEndDay); got != "" {
		t.Errorf("variant on the exclusive (non-real) end day = %q, want empty", got)
	}
}