using System.Security.Cryptography;
using System.Text;

namespace Hutopy.Infrastructure.Security;

// If we need to add special characters we can alternate between 2 pools.
public static class PasswordGenerator
{
    private const string LowerLetters = "abcdefghijklmnopqrstuvwxyz";
    private const string UpperLetters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    private const string Numbers = "0123456789";
    private const string SpecialCharacters = "!@#$%^&*()_+-=[];',./`~{}|:\"<>?";

    private static readonly Random Random = new();

    public static string Next(
        int length = 15,
        bool requireNumber = true,
        bool requireLowercase = true,
        bool requireCapital = true,
        bool requireSpecialCharacter = true)
    {
        // Create pools based on the requirements
        var characterPool = new StringBuilder();

        if (requireNumber)
            characterPool.Append(LowerLetters);
        
        if (requireCapital)
            characterPool.Append(UpperLetters);

        if (requireNumber)
            characterPool.Append(Numbers);

        if (requireSpecialCharacter)
            characterPool.Append(SpecialCharacters);

        // Ensure that the length is within the specified bounds
        var password = new char[length];

        // Ensure at least one character from each required category is included
        int index = 0;
        
        if (requireLowercase)
            password[index++] = LowerLetters[Random.Next(LowerLetters.Length)];
        
        if (requireCapital)
            password[index++] = UpperLetters[Random.Next(UpperLetters.Length)];
        
        if (requireNumber)
            password[index++] = Numbers[Random.Next(Numbers.Length)];
        
        if (requireSpecialCharacter)
            password[index++] = SpecialCharacters[Random.Next(SpecialCharacters.Length)];
        
        // Fill the rest with the password
        for (int i = index; i < length; i++)
        {
            password[i] = characterPool[RandomNumberGenerator.GetInt32(characterPool.Length)];
        }

        // Shuffle the password to randomize the placement of the required characters
        Shuffle(password);
        return new string(password);
    }

    private static void Shuffle(
        char[] array)
    {
        for (int i = array.Length - 1; i > 0; i--)
        {
            int j = Random.Next(i + 1);
            (array[i], array[j]) = (array[j], array[i]); // Swap elements
        }
    }
}