package cart

import (
	"testing"
)

func TestNordicTaxProvider_Name(t *testing.T) {
	p := NewNordicTaxProvider("SE")
	if got := p.Name(); got != "nordic" {
		t.Errorf("Name() = %q, want %q", got, "nordic")
	}
}

func TestNordicTaxProvider_ComputeTax(t *testing.T) {
	tests := []struct {
		total   int64
		taxRate int
		want    int64
		desc    string
	}{
		{0, 25, 0, "zero total"},
		{1250, 25, 250, "25 % VAT on 1250"},
		{1000, 20, 166, "20 % VAT on 1000"},
		{1200, 25, 240, "25 % VAT on 1200"},
		{25000, 25, 5000, "25 % VAT on 25000"},
		{100, 10, 9, "10 % VAT on 100"},
		{100, 100, 50, "100 % VAT on 100"},
		{100, 0, 0, "zero-rate"},
		{100, -1, 0, "negative rate -> zero"},
	}
	for _, tt := range tests {
		p := NewNordicTaxProvider("SE")
		got := p.ComputeTax(tt.total, tt.taxRate)
		if got != tt.want {
			t.Errorf("ComputeTax(%d, %d) [%s] = %d; want %d", tt.total, tt.taxRate, tt.desc, got, tt.want)
		}
	}
}

func TestNordicTaxProvider_DefaultTaxRate(t *testing.T) {
	tests := []struct {
		country string
		want    int
		desc    string
	}{
		{"SE", 25, "Sweden"},
		{"NO", 25, "Norway"},
		{"DK", 25, "Denmark"},
		{"FI", 25, "Finland"},
		{"", 25, "empty -> default SE"},
		{"DE", 25, "unknown -> fallback SE"},
	}
	for _, tt := range tests {
		p := NewNordicTaxProvider("SE")
		got := p.DefaultTaxRate(tt.country)
		if got != tt.want {
			t.Errorf("DefaultTaxRate(%q) [%s] = %d; want %d", tt.country, tt.desc, got, tt.want)
		}
	}
}

func TestStaticTaxProvider_ComputeTax(t *testing.T) {
	p := NewStaticTaxProvider()
	tests := []struct {
		total   int64
		taxRate int
		want    int64
	}{
		{1250, 25, 250},
		{25000, 25, 5000},
		{1000, 20, 166},
		{0, 25, 0},
	}
	for _, tt := range tests {
		got := p.ComputeTax(tt.total, tt.taxRate)
		if got != tt.want {
			t.Errorf("ComputeTax(%d, %d) = %d; want %d", tt.total, tt.taxRate, got, tt.want)
		}
	}
}

func TestStaticTaxProvider_DefaultTaxRate(t *testing.T) {
	p := NewStaticTaxProvider()
	if got := p.DefaultTaxRate("SE"); got != 0 {
		t.Errorf("StaticTaxProvider.DefaultTaxRate(\"SE\") = %d; want 0", got)
	}
}

func TestComputeTax(t *testing.T) {
	tests := []struct {
		total   int64
		taxRate int
		want    int64
		desc    string
	}{
		{1250, 25, 250, "canonical: 25 %"},
		{25000, 25, 5000, "25k with 25 %% -> 5k tax"},
		{0, 25, 0, "zero total"},
	}
	for _, tt := range tests {
		got := ComputeTax(tt.total, tt.taxRate)
		if got != tt.want {
			t.Errorf("ComputeTax(%d, %d) [%s] = %d; want %d", tt.total, tt.taxRate, tt.desc, got, tt.want)
		}
	}
}

func TestTaxProviderImplementsInterface(t *testing.T) {
	var p TaxProvider = NewNordicTaxProvider("SE")
	_ = p
	p2 := NewStaticTaxProvider()
	_ = p2
}