package pages

import (
	"testing"
	"time"

	"tasksquire/timewarrior"
)

func TestInsertGaps(t *testing.T) {
	tests := []struct {
		name          string
		intervals     timewarrior.Intervals
		expectedCount int
		expectedGaps  int
		description   string
	}{
		{
			name:          "empty intervals",
			intervals:     timewarrior.Intervals{},
			expectedCount: 0,
			expectedGaps:  0,
			description:   "Should return empty list for empty input",
		},
		{
			name: "single interval",
			intervals: timewarrior.Intervals{
				{
					ID:    1,
					Start: time.Now().Add(-1 * time.Hour).UTC().Format("20060102T150405Z"),
					End:   time.Now().UTC().Format("20060102T150405Z"),
					Tags:  []string{"test"},
				},
			},
			expectedCount: 1,
			expectedGaps:  0,
			description:   "Should return single interval without gaps",
		},
		{
			name: "two intervals with gap (reverse chronological)",
			intervals: timewarrior.Intervals{
				{
					ID:    1,
					Start: time.Now().Add(-1 * time.Hour).UTC().Format("20060102T150405Z"),
					End:   time.Now().UTC().Format("20060102T150405Z"),
					Tags:  []string{"test2"},
				},
				{
					ID:    2,
					Start: time.Now().Add(-3 * time.Hour).UTC().Format("20060102T150405Z"),
					End:   time.Now().Add(-2 * time.Hour).UTC().Format("20060102T150405Z"),
					Tags:  []string{"test1"},
				},
			},
			expectedCount: 3,
			expectedGaps:  1,
			description:   "Should insert one gap between two intervals (newest first order)",
		},
		{
			name: "three intervals with two gaps (reverse chronological)",
			intervals: timewarrior.Intervals{
				{
					ID:    1,
					Start: time.Now().Add(-1 * time.Hour).UTC().Format("20060102T150405Z"),
					End:   time.Now().UTC().Format("20060102T150405Z"),
					Tags:  []string{"test3"},
				},
				{
					ID:    2,
					Start: time.Now().Add(-3 * time.Hour).UTC().Format("20060102T150405Z"),
					End:   time.Now().Add(-2 * time.Hour).UTC().Format("20060102T150405Z"),
					Tags:  []string{"test2"},
				},
				{
					ID:    3,
					Start: time.Now().Add(-5 * time.Hour).UTC().Format("20060102T150405Z"),
					End:   time.Now().Add(-4 * time.Hour).UTC().Format("20060102T150405Z"),
					Tags:  []string{"test1"},
				},
			},
			expectedCount: 5,
			expectedGaps:  2,
			description:   "Should insert two gaps between three intervals (newest first order)",
		},
		{
			name: "consecutive intervals with no gap (reverse chronological)",
			intervals: timewarrior.Intervals{
				{
					ID:    1,
					Start: time.Now().Add(-1 * time.Hour).UTC().Format("20060102T150405Z"),
					End:   time.Now().UTC().Format("20060102T150405Z"),
					Tags:  []string{"test2"},
				},
				{
					ID:    2,
					Start: time.Now().Add(-2 * time.Hour).UTC().Format("20060102T150405Z"),
					End:   time.Now().Add(-1 * time.Hour).UTC().Format("20060102T150405Z"),
					Tags:  []string{"test1"},
				},
			},
			expectedCount: 2,
			expectedGaps:  0,
			description:   "Should not insert gap when intervals are consecutive (newest first order)",
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			result := insertGaps(tt.intervals)

			if len(result) != tt.expectedCount {
				t.Errorf("insertGaps() returned %d intervals, expected %d. %s",
					len(result), tt.expectedCount, tt.description)
			}

			gapCount := 0
			for _, interval := range result {
				if interval.IsGap {
					gapCount++
				}
			}

			if gapCount != tt.expectedGaps {
				t.Errorf("insertGaps() created %d gaps, expected %d. %s",
					gapCount, tt.expectedGaps, tt.description)
			}

			// Verify gaps are properly interleaved with intervals
			for i := 0; i < len(result)-1; i++ {
				if result[i].IsGap && result[i+1].IsGap {
					t.Errorf("insertGaps() created consecutive gap rows at indices %d and %d", i, i+1)
				}
			}

			// Verify first and last items are never gaps
			if len(result) > 0 {
				if result[0].IsGap {
					t.Errorf("insertGaps() created gap as first item")
				}
				if result[len(result)-1].IsGap {
					t.Errorf("insertGaps() created gap as last item")
				}
			}
		})
	}
}