package timeext

import (
	"math"
	"testing"
	"time"
)

func TestYearDifferenceWithSameYearAndDay(t *testing.T) {
	t1 := time.Date(2020, 1, 1, 0, 0, 0, 0, time.UTC)
	t2 := time.Date(2020, 1, 1, 0, 0, 0, 0, time.UTC)
	expected := 0.0
	result := YearDifference(t1, t2, time.UTC)
	if !epsilonEquals(result, expected) {
		t.Errorf("Expected %v, got %v", expected, result)
	}
}

func TestYearDifferenceWithOneYearApart(t *testing.T) {
	t1 := time.Date(2021, 1, 1, 0, 0, 0, 0, time.UTC)
	t2 := time.Date(2020, 1, 1, 0, 0, 0, 0, time.UTC)
	expected := 1.0
	result := YearDifference(t1, t2, time.UTC)
	if !epsilonEquals(result, expected) {
		t.Errorf("Expected %v, got %v", expected, result)
	}
}

func TestYearDifferenceWithDifferentMonths(t *testing.T) {
	t1 := time.Date(2020, 6, 1, 0, 0, 0, 0, time.UTC)
	t2 := time.Date(2020, 1, 1, 0, 0, 0, 0, time.UTC)
	expected := 0.4166666666666667 // Approximation of 5/12 months
	result := YearDifference(t1, t2, time.UTC)
	if !epsilonEquals(result, expected) {
		t.Errorf("Expected %v, got %v", expected, result)
	}
}

func TestYearDifferenceAcrossYears(t *testing.T) {
	t1 := time.Date(2021, 1, 1, 0, 0, 0, 0, time.UTC)
	t2 := time.Date(2020, 6, 1, 0, 0, 0, 0, time.UTC)
	expected := 0.5833333333333334 // Approximation of 7/12 months
	result := YearDifference(t1, t2, time.UTC)
	if !epsilonEquals(result, expected) {
		t.Errorf("Expected %v, got %v", expected, result)
	}
}

func TestYearDifferenceWithTimezone(t *testing.T) {
	tz, _ := time.LoadLocation("America/New_York")
	t1 := time.Date(2021, 1, 1, 0, 0, 0, 0, tz)
	t2 := time.Date(2020, 6, 1, 0, 0, 0, 0, tz)
	expected := 0.5833333333333334 // Same as UTC but ensuring timezone is considered
	result := YearDifference(t1, t2, tz)
	if !epsilonEquals(result, expected) {
		t.Errorf("Expected %v, got %v", expected, result)
	}
}

func TestYearDifferenceWithNegativeDifference(t *testing.T) {
	t1 := time.Date(2020, 1, 1, 0, 0, 0, 0, TimezoneBerlin)
	t2 := time.Date(2021, 1, 1, 0, 0, 0, 0, TimezoneBerlin)
	expected := -1.0
	result := YearDifference(t1, t2, TimezoneBerlin)
	if !epsilonEquals(result, expected) {
		t.Errorf("Expected %v, got %v", expected, result)
	}
}

func TestYearDifferenceWithNegativeDifference2(t *testing.T) {
	t1 := time.Date(2020, 7, 1, 0, 0, 0, 0, TimezoneBerlin)
	t2 := time.Date(2021, 7, 1, 0, 0, 0, 0, TimezoneBerlin)
	expected := -1.0
	result := YearDifference(t1, t2, TimezoneBerlin)
	if !epsilonEquals(result, expected) {
		t.Errorf("Expected %v, got %v", expected, result)
	}
}

func epsilonEquals(a, b float64) bool {
	epsilon := 0.01
	return math.Abs(a-b) < epsilon
}

func TestMonthDifferenceSameDate(t *testing.T) {
	t1 := time.Date(2022, 1, 1, 0, 0, 0, 0, time.UTC)
	t2 := time.Date(2022, 1, 1, 0, 0, 0, 0, time.UTC)
	expected := 0.0
	result := MonthDifference(t2, t1)
	if !epsilonEquals(result, expected) {
		t.Errorf("Expected %v, got %v", expected, result)
	}
}

func TestMonthDifferenceSameMonth(t *testing.T) {
	t1 := time.Date(2022, 1, 1, 0, 0, 0, 0, time.UTC)
	t2 := time.Date(2022, 1, 31, 0, 0, 0, 0, time.UTC)
	expected := 0.967741935483871 // Approximation of 30/31 days
	result := MonthDifference(t2, t1)
	if !epsilonEquals(result, expected) {
		t.Errorf("Expected %v, got %v", expected, result)
	}
}

func TestMonthDifferenceDifferentMonthsSameYear(t *testing.T) {
	t1 := time.Date(2022, 1, 1, 0, 0, 0, 0, time.UTC)
	t2 := time.Date(2022, 3, 1, 0, 0, 0, 0, time.UTC)
	expected := 2.0
	result := MonthDifference(t2, t1)
	if !epsilonEquals(result, expected) {
		t.Errorf("Expected %v, got %v", expected, result)
	}
}

func TestMonthDifferenceDifferentYears(t *testing.T) {
	t1 := time.Date(2021, 12, 1, 0, 0, 0, 0, time.UTC)
	t2 := time.Date(2022, 2, 1, 0, 0, 0, 0, time.UTC)
	expected := 2.0
	result := MonthDifference(t2, t1)
	if !epsilonEquals(result, expected) {
		t.Errorf("Expected %v, got %v", expected, result)
	}
}

func TestMonthDifferenceT1BeforeT2(t *testing.T) {
	t1 := time.Date(2022, 1, 1, 0, 0, 0, 0, time.UTC)
	t2 := time.Date(2022, 6, 1, 0, 0, 0, 0, time.UTC)
	expected := 5.0
	result := MonthDifference(t2, t1)
	if !epsilonEquals(result, expected) {
		t.Errorf("Expected %v, got %v", expected, result)
	}
}

func TestMonthDifferenceT1AfterT2(t *testing.T) {
	t1 := time.Date(2022, 6, 1, 0, 0, 0, 0, time.UTC)
	t2 := time.Date(2022, 1, 1, 0, 0, 0, 0, time.UTC)
	expected := -5.0
	result := MonthDifference(t2, t1)
	if !epsilonEquals(result, expected) {
		t.Errorf("Expected %v, got %v", expected, result)
	}
}