package reports

import (
	"fmt"
	"strings"
	"testing"
	"time"
)

func TestParseDateRange(t *testing.T) {
	// Use a fixed time for testing
	testTime := time.Date(2024, time.August, 15, 10, 30, 0, 0, time.UTC) // Thursday, August 15, 2024

	tests := []struct {
		name     string
		input    string
		wantErr  bool
		validate func(t *testing.T, dr DateRange)
	}{
		{
			name:    "this week",
			input:   "this week",
			wantErr: false,
			validate: func(t *testing.T, dr DateRange) {
				// Should be Monday Aug 12 to Sunday Aug 18
				expectedStart := time.Date(2024, time.August, 12, 0, 0, 0, 0, time.UTC)
				expectedEnd := time.Date(2024, time.August, 18, 23, 59, 59, 999999999, time.UTC)
				if !dr.Start.Equal(expectedStart) {
					t.Errorf("Start = %v, want %v", dr.Start, expectedStart)
				}
				if !dr.End.Equal(expectedEnd) {
					t.Errorf("End = %v, want %v", dr.End, expectedEnd)
				}
			},
		},
		{
			name:    "this month",
			input:   "this month",
			wantErr: false,
			validate: func(t *testing.T, dr DateRange) {
				// Should be Aug 1 to Aug 31
				expectedStart := time.Date(2024, time.August, 1, 0, 0, 0, 0, time.UTC)
				expectedEnd := time.Date(2024, time.August, 31, 23, 59, 59, 999999999, time.UTC)
				if !dr.Start.Equal(expectedStart) {
					t.Errorf("Start = %v, want %v", dr.Start, expectedStart)
				}
				if !dr.End.Equal(expectedEnd) {
					t.Errorf("End = %v, want %v", dr.End, expectedEnd)
				}
			},
		},
		{
			name:    "month name - current month",
			input:   "august",
			wantErr: false,
			validate: func(t *testing.T, dr DateRange) {
				// Should be August 2024 (current year since we're in August)
				expectedStart := time.Date(2024, time.August, 1, 0, 0, 0, 0, time.UTC)
				expectedEnd := time.Date(2024, time.August, 31, 23, 59, 59, 999999999, time.UTC)
				if !dr.Start.Equal(expectedStart) {
					t.Errorf("Start = %v, want %v", dr.Start, expectedStart)
				}
				if !dr.End.Equal(expectedEnd) {
					t.Errorf("End = %v, want %v", dr.End, expectedEnd)
				}
			},
		},
		{
			name:    "month name - past month this year",
			input:   "july",
			wantErr: false,
			validate: func(t *testing.T, dr DateRange) {
				// Should be July 2024 (current year since July already passed)
				expectedStart := time.Date(2024, time.July, 1, 0, 0, 0, 0, time.UTC)
				expectedEnd := time.Date(2024, time.July, 31, 23, 59, 59, 999999999, time.UTC)
				if !dr.Start.Equal(expectedStart) {
					t.Errorf("Start = %v, want %v", dr.Start, expectedStart)
				}
				if !dr.End.Equal(expectedEnd) {
					t.Errorf("End = %v, want %v", dr.End, expectedEnd)
				}
			},
		},
		{
			name:    "month name - future month last year",
			input:   "december",
			wantErr: false,
			validate: func(t *testing.T, dr DateRange) {
				// Should be December 2023 (last year since December hasn't come yet)
				expectedStart := time.Date(2023, time.December, 1, 0, 0, 0, 0, time.UTC)
				expectedEnd := time.Date(2023, time.December, 31, 23, 59, 59, 999999999, time.UTC)
				if !dr.Start.Equal(expectedStart) {
					t.Errorf("Start = %v, want %v", dr.Start, expectedStart)
				}
				if !dr.End.Equal(expectedEnd) {
					t.Errorf("End = %v, want %v", dr.End, expectedEnd)
				}
			},
		},
		{
			name:    "case insensitive month name",
			input:   "FEBRUARY",
			wantErr: false,
			validate: func(t *testing.T, dr DateRange) {
				// Should be February 2024 (current year since February already passed)
				expectedStart := time.Date(2024, time.February, 1, 0, 0, 0, 0, time.UTC)
				expectedEnd := time.Date(2024, time.February, 29, 23, 59, 59, 999999999, time.UTC) // 2024 is a leap year
				if !dr.Start.Equal(expectedStart) {
					t.Errorf("Start = %v, want %v", dr.Start, expectedStart)
				}
				if !dr.End.Equal(expectedEnd) {
					t.Errorf("End = %v, want %v", dr.End, expectedEnd)
				}
			},
		},
		{
			name:    "short month name",
			input:   "feb",
			wantErr: false,
			validate: func(t *testing.T, dr DateRange) {
				// Should be February 2024
				expectedStart := time.Date(2024, time.February, 1, 0, 0, 0, 0, time.UTC)
				expectedEnd := time.Date(2024, time.February, 29, 23, 59, 59, 999999999, time.UTC) // 2024 is a leap year
				if !dr.Start.Equal(expectedStart) {
					t.Errorf("Start = %v, want %v", dr.Start, expectedStart)
				}
				if !dr.End.Equal(expectedEnd) {
					t.Errorf("End = %v, want %v", dr.End, expectedEnd)
				}
			},
		},
		{
			name:    "month year format",
			input:   "july 2023",
			wantErr: false,
			validate: func(t *testing.T, dr DateRange) {
				// Should be July 2023
				expectedStart := time.Date(2023, time.July, 1, 0, 0, 0, 0, time.UTC)
				expectedEnd := time.Date(2023, time.July, 31, 23, 59, 59, 999999999, time.UTC)
				if !dr.Start.Equal(expectedStart) {
					t.Errorf("Start = %v, want %v", dr.Start, expectedStart)
				}
				if !dr.End.Equal(expectedEnd) {
					t.Errorf("End = %v, want %v", dr.End, expectedEnd)
				}
			},
		},
		{
			name:    "short month year format",
			input:   "feb 2022",
			wantErr: false,
			validate: func(t *testing.T, dr DateRange) {
				// Should be February 2022
				expectedStart := time.Date(2022, time.February, 1, 0, 0, 0, 0, time.UTC)
				expectedEnd := time.Date(2022, time.February, 28, 23, 59, 59, 999999999, time.UTC) // 2022 is not a leap year
				if !dr.Start.Equal(expectedStart) {
					t.Errorf("Start = %v, want %v", dr.Start, expectedStart)
				}
				if !dr.End.Equal(expectedEnd) {
					t.Errorf("End = %v, want %v", dr.End, expectedEnd)
				}
			},
		},
		{
			name:    "case insensitive month year",
			input:   "MARCH 2023",
			wantErr: false,
			validate: func(t *testing.T, dr DateRange) {
				// Should be March 2023
				expectedStart := time.Date(2023, time.March, 1, 0, 0, 0, 0, time.UTC)
				expectedEnd := time.Date(2023, time.March, 31, 23, 59, 59, 999999999, time.UTC)
				if !dr.Start.Equal(expectedStart) {
					t.Errorf("Start = %v, want %v", dr.Start, expectedStart)
				}
				if !dr.End.Equal(expectedEnd) {
					t.Errorf("End = %v, want %v", dr.End, expectedEnd)
				}
			},
		},
		{
			name:    "invalid month name",
			input:   "invalid",
			wantErr: true,
		},
		{
			name:    "invalid month year format",
			input:   "july 23",
			wantErr: true,
		},
		{
			name:    "invalid year",
			input:   "july abcd",
			wantErr: true,
		},
		{
			name:    "since format",
			input:   "since 2024-07-01",
			wantErr: false,
			validate: func(t *testing.T, dr DateRange) {
				// Should start on July 1, 2024 with no end date
				expectedStart := time.Date(2024, time.July, 1, 0, 0, 0, 0, time.UTC)
				if !dr.Start.Equal(expectedStart) {
					t.Errorf("Start = %v, want %v", dr.Start, expectedStart)
				}
				if !dr.End.IsZero() {
					t.Errorf("End = %v, want zero time (no end date)", dr.End)
				}
			},
		},
		{
			name:    "since format case insensitive",
			input:   "SINCE 2024-12-25",
			wantErr: false,
			validate: func(t *testing.T, dr DateRange) {
				// Should start on December 25, 2024 with no end date
				expectedStart := time.Date(2024, time.December, 25, 0, 0, 0, 0, time.UTC)
				if !dr.Start.Equal(expectedStart) {
					t.Errorf("Start = %v, want %v", dr.Start, expectedStart)
				}
				if !dr.End.IsZero() {
					t.Errorf("End = %v, want zero time (no end date)", dr.End)
				}
			},
		},
		{
			name:    "since format invalid date",
			input:   "since 2024-13-01",
			wantErr: true,
		},
		{
			name:    "since format missing date",
			input:   "since",
			wantErr: true,
		},
		{
			name:    "custom date range format",
			input:   "2024-07-01 to 2024-07-31",
			wantErr: false,
			validate: func(t *testing.T, dr DateRange) {
				expectedStart := time.Date(2024, time.July, 1, 0, 0, 0, 0, time.UTC)
				expectedEnd := time.Date(2024, time.July, 31, 23, 59, 59, 999999999, time.UTC)
				if !dr.Start.Equal(expectedStart) {
					t.Errorf("Start = %v, want %v", dr.Start, expectedStart)
				}
				if !dr.End.Equal(expectedEnd) {
					t.Errorf("End = %v, want %v", dr.End, expectedEnd)
				}
			},
		},
		{
			name:    "custom date range - same day",
			input:   "2024-08-15 to 2024-08-15",
			wantErr: false,
			validate: func(t *testing.T, dr DateRange) {
				expectedStart := time.Date(2024, time.August, 15, 0, 0, 0, 0, time.UTC)
				expectedEnd := time.Date(2024, time.August, 15, 23, 59, 59, 999999999, time.UTC)
				if !dr.Start.Equal(expectedStart) {
					t.Errorf("Start = %v, want %v", dr.Start, expectedStart)
				}
				if !dr.End.Equal(expectedEnd) {
					t.Errorf("End = %v, want %v", dr.End, expectedEnd)
				}
			},
		},
		{
			name:    "custom date range - invalid order",
			input:   "2024-08-15 to 2024-08-01",
			wantErr: true,
		},
		{
			name:    "custom date range - invalid format",
			input:   "2024-08-15 through 2024-08-31",
			wantErr: true,
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			// Create a custom ParseDateRange that uses our test time
			testParseFunc := func(dateStr string) (DateRange, error) {
				dateStr = strings.TrimSpace(dateStr)

				// Check for predefined ranges (case-insensitive)
				lowerDateStr := strings.ToLower(dateStr)
				switch lowerDateStr {
				case "last week":
					return getLastWeek(testTime), nil
				case "this week":
					return getThisWeek(testTime), nil
				case "last month":
					return getLastMonth(testTime), nil
				case "this month":
					return getThisMonth(testTime), nil
				}

				// Check for month name patterns (case-insensitive)
				if dateRange, err := parseMonthName(dateStr, testTime); err == nil {
					return dateRange, nil
				}

				// Check for "month year" format
				if dateRange, err := parseMonthYear(dateStr); err == nil {
					return dateRange, nil
				}

				// Check for "since YYYY-MM-DD" format
				if strings.HasPrefix(lowerDateStr, "since ") {
					return parseSinceDateRange(dateStr)
				}

				// Check for custom date range format: "YYYY-MM-DD to YYYY-MM-DD"
				if strings.Contains(dateStr, " to ") {
					return parseCustomDateRange(dateStr)
				}

				return DateRange{}, fmt.Errorf("unsupported date range: %s", dateStr)
			}

			got, err := testParseFunc(tt.input)
			if (err != nil) != tt.wantErr {
				t.Errorf("ParseDateRange() error = %v, wantErr %v", err, tt.wantErr)
				return
			}

			if !tt.wantErr && tt.validate != nil {
				tt.validate(t, got)
			}
		})
	}
}

func TestParseDateRangeDSTTransitions(t *testing.T) {
	// Test date range parsing during DST transitions
	// Use dates around US DST transitions (2nd Sunday in March, 1st Sunday in November)

	tests := []struct {
		name        string
		input       string
		currentTime time.Time
		wantStart   time.Time
		wantEnd     time.Time
		wantErr     bool
	}{
		{
			name:        "this week during spring DST transition",
			input:       "this week",
			currentTime: time.Date(2024, time.March, 10, 12, 0, 0, 0, time.UTC),           // Sunday of DST transition week
			wantStart:   time.Date(2024, time.March, 4, 0, 0, 0, 0, time.UTC),             // Monday of that week
			wantEnd:     time.Date(2024, time.March, 10, 23, 59, 59, 999999999, time.UTC), // Sunday 23:59:59
		},
		{
			name:        "this week during fall DST transition",
			input:       "this week",
			currentTime: time.Date(2024, time.November, 3, 12, 0, 0, 0, time.UTC),           // Sunday of DST transition week
			wantStart:   time.Date(2024, time.October, 28, 0, 0, 0, 0, time.UTC),            // Monday of that week
			wantEnd:     time.Date(2024, time.November, 3, 23, 59, 59, 999999999, time.UTC), // Sunday 23:59:59
		},
		{
			name:        "last week before spring DST",
			input:       "last week",
			currentTime: time.Date(2024, time.March, 11, 12, 0, 0, 0, time.UTC),           // Monday after DST transition
			wantStart:   time.Date(2024, time.March, 4, 0, 0, 0, 0, time.UTC),             // Start of previous week
			wantEnd:     time.Date(2024, time.March, 10, 23, 59, 59, 999999999, time.UTC), // End of previous week
		},
		{
			name:        "this month with DST transition",
			input:       "this month",
			currentTime: time.Date(2024, time.March, 15, 12, 0, 0, 0, time.UTC), // Mid-March after DST
			wantStart:   time.Date(2024, time.March, 1, 0, 0, 0, 0, time.UTC),
			wantEnd:     time.Date(2024, time.March, 31, 23, 59, 59, 999999999, time.UTC),
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			// Create custom parse function with specific time
			testParseFunc := func(dateStr string) (DateRange, error) {
				dateStr = strings.TrimSpace(dateStr)
				lowerDateStr := strings.ToLower(dateStr)

				switch lowerDateStr {
				case "last week":
					return getLastWeek(tt.currentTime), nil
				case "this week":
					return getThisWeek(tt.currentTime), nil
				case "last month":
					return getLastMonth(tt.currentTime), nil
				case "this month":
					return getThisMonth(tt.currentTime), nil
				}

				return DateRange{}, fmt.Errorf("unsupported test case")
			}

			result, err := testParseFunc(tt.input)

			if tt.wantErr {
				if err == nil {
					t.Errorf("Expected error but got none")
				}
				return
			}

			if err != nil {
				t.Errorf("Unexpected error: %v", err)
				return
			}

			if !result.Start.Equal(tt.wantStart) {
				t.Errorf("Start = %v, want %v", result.Start, tt.wantStart)
			}
			if !result.End.Equal(tt.wantEnd) {
				t.Errorf("End = %v, want %v", result.End, tt.wantEnd)
			}
		})
	}
}

func TestParseDateRangeTimezoneEdgeCases(t *testing.T) {
	// Test edge cases around timezone boundaries
	tests := []struct {
		name        string
		input       string
		currentTime time.Time
		wantStart   time.Time
		wantEnd     time.Time
	}{
		{
			name:        "new years boundary - this week",
			input:       "this week",
			currentTime: time.Date(2025, time.January, 1, 12, 0, 0, 0, time.UTC),           // Wednesday New Year's Day
			wantStart:   time.Date(2024, time.December, 30, 0, 0, 0, 0, time.UTC),          // Monday of that week (prev year)
			wantEnd:     time.Date(2025, time.January, 5, 23, 59, 59, 999999999, time.UTC), // Sunday of that week (new year)
		},
		{
			name:        "month boundary - this week",
			input:       "this week",
			currentTime: time.Date(2024, time.August, 1, 12, 0, 0, 0, time.UTC),           // Thursday Aug 1
			wantStart:   time.Date(2024, time.July, 29, 0, 0, 0, 0, time.UTC),             // Monday of that week (prev month)
			wantEnd:     time.Date(2024, time.August, 4, 23, 59, 59, 999999999, time.UTC), // Sunday of that week (current month)
		},
		{
			name:        "leap year february",
			input:       "february",
			currentTime: time.Date(2024, time.August, 15, 10, 30, 0, 0, time.UTC), // 2024 is leap year
			wantStart:   time.Date(2024, time.February, 1, 0, 0, 0, 0, time.UTC),
			wantEnd:     time.Date(2024, time.February, 29, 23, 59, 59, 999999999, time.UTC), // Leap day
		},
		{
			name:        "non-leap year february",
			input:       "february",
			currentTime: time.Date(2023, time.August, 15, 10, 30, 0, 0, time.UTC), // 2023 is not leap year
			wantStart:   time.Date(2023, time.February, 1, 0, 0, 0, 0, time.UTC),
			wantEnd:     time.Date(2023, time.February, 28, 23, 59, 59, 999999999, time.UTC), // No leap day
		},
	}

	for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
			testParseFunc := func(dateStr string) (DateRange, error) {
				dateStr = strings.TrimSpace(dateStr)
				lowerDateStr := strings.ToLower(dateStr)

				switch lowerDateStr {
				case "this week":
					return getThisWeek(tt.currentTime), nil
				case "this month":
					return getThisMonth(tt.currentTime), nil
				}

				// Check for month name patterns
				if dateRange, err := parseMonthName(dateStr, tt.currentTime); err == nil {
					return dateRange, nil
				}

				return DateRange{}, fmt.Errorf("unsupported test case")
			}

			result, err := testParseFunc(tt.input)
			if err != nil {
				t.Errorf("Unexpected error: %v", err)
				return
			}

			if !result.Start.Equal(tt.wantStart) {
				t.Errorf("Start = %v, want %v", result.Start, tt.wantStart)
			}
			if !result.End.Equal(tt.wantEnd) {
				t.Errorf("End = %v, want %v", result.End, tt.wantEnd)
			}
		})
	}
}