using Microsoft.Extensions.Configuration;
using System.Security.Cryptography;
using System.Text;
using Dapper;
using Npgsql;

namespace Registration.Infra.Repositories;

public interface IMemberRepository
{
    Task EnsureCreated();
    Task<bool> GetIsRegistered(string ssn);
    Task<bool> AddRegistration(string ssn);
    Task ClearRegistrations();
}

public class MemberRepository(IConfiguration configuration) : IMemberRepository
{
    private readonly string _connectionString = configuration.GetConnectionString("DefaultConnection")
        ?? throw new InvalidOperationException("Connection string 'DefaultConnection' not found.");

    private readonly string _pepper = configuration["Security:SsnPepper"]
        ?? throw new InvalidOperationException("Security pepper 'SsnPepper' not found.");

    private NpgsqlConnection CreateConnection() => new(_connectionString);

    private string ComputeBlindIndex(string ssn)
    {
        using var hmac = new HMACSHA256(Encoding.UTF8.GetBytes(_pepper));
        var hashedBytes = hmac.ComputeHash(Encoding.UTF8.GetBytes(ssn));
        return Convert.ToBase64String(hashedBytes);
    }

    public async Task EnsureCreated()
    {
        using var connection = CreateConnection();

        var sql = @"
            CREATE TABLE IF NOT EXISTS members (
                id SERIAL PRIMARY KEY,
                ssn_index VARCHAR(255) NOT NULL UNIQUE
            );
            CREATE INDEX IF NOT EXISTS idx_members_ssn_index ON members(ssn_index);
        ";

        await connection.ExecuteAsync(sql);
    }

    public async Task<bool> AddRegistration(string ssn)
    {
        using var connection = CreateConnection();

        var sql = "INSERT INTO members (ssn_index) VALUES (@SsnIndex) ON CONFLICT DO NOTHING";
        var ssnIndex = ComputeBlindIndex(ssn);

        var rows = await connection.ExecuteAsync(sql, new { SsnIndex = ssnIndex });

        return rows > 0;
    }

    public async Task<bool> GetIsRegistered(string ssn)
    {
        using var connection = CreateConnection();

        var ssnIndex = ComputeBlindIndex(ssn);
        var sql = "SELECT EXISTS(SELECT 1 FROM members WHERE ssn_index = @SsnIndex)";

        return await connection.ExecuteScalarAsync<bool>(sql, new { SsnIndex = ssnIndex });
    }

    public async Task ClearRegistrations()
    {
        using var connection = CreateConnection();

        var sql = "DELETE FROM members";
        await connection.ExecuteAsync(sql);
    }
}