package main

import (
	"strconv"
	"testing"
)

func TestGenerateCPFLength(t *testing.T) {
	cpf := generateCPF()
	if len(cpf) != 11 {
		t.Fatalf("expected length 11, got %d: %s", len(cpf), cpf)
	}
}

func TestGenerateCPFCheckDigits(t *testing.T) {
	for range 100 {
		cpf := generateCPF()
		if !isValidCPF(cpf) {
			t.Fatalf("invalid CPF generated: %s", cpf)
		}
	}
}

func TestGenerateCPFAllDigits(t *testing.T) {
	seen := make(map[string]bool)
	for range 1000 {
		cpf := generateCPF()
		if seen[cpf] {
			t.Fatal("duplicate CPF generated")
		}
		seen[cpf] = true
	}
}

func isValidCPF(cpf string) bool {
	if len(cpf) != 11 {
		return false
	}

	digits := make([]int, 11)
	for i, ch := range cpf {
		d, err := strconv.Atoi(string(ch))
		if err != nil {
			return false
		}
		digits[i] = d
	}

	allEqual := true
	for i := 1; i < 11; i++ {
		if digits[i] != digits[0] {
			allEqual = false
			break
		}
	}
	if allEqual {
		return false
	}

	sum := 0
	for i := range 9 {
		sum += digits[i] * (10 - i)
	}
	rem := sum % 11
	var d1 int
	if rem < 2 {
		d1 = 0
	} else {
		d1 = 11 - rem
	}
	if d1 != digits[9] {
		return false
	}

	sum = 0
	for i := range 10 {
		sum += digits[i] * (11 - i)
	}
	rem = sum % 11
	var d2 int
	if rem < 2 {
		d2 = 0
	} else {
		d2 = 11 - rem
	}
	return d2 == digits[10]
}