using System.Security.Cryptography;
using System.Text;
using GmRelay.Web.Services;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Primitives;

namespace GmRelay.Bot.Tests.Web;

public sealed class TelegramAuthServiceTests
{
    [Fact]
    public void Verify_ShouldAcceptValidTelegramPayload()
    {
        const string botToken = "test-bot-token";
        var authDate = DateTimeOffset.UtcNow.ToUnixTimeSeconds().ToString();
        var query = CreateQueryCollection(
            botToken,
            new Dictionary<string, string>
            {
                ["auth_date"] = authDate,
                ["first_name"] = "Ada",
                ["id"] = "424242",
                ["last_name"] = "Lovelace",
                ["username"] = "ada"
            });
        var service = new TelegramAuthService(CreateConfiguration(botToken));

        var verified = service.Verify(query, out var telegramId, out var name);

        Assert.True(verified);
        Assert.Equal(424242L, telegramId);
        Assert.Equal("Ada Lovelace", name);
    }

    [Fact]
    public void Verify_ShouldRejectTamperedHash()
    {
        const string botToken = "test-bot-token";
        var values = new Dictionary<string, string>
        {
            ["auth_date"] = DateTimeOffset.UtcNow.ToUnixTimeSeconds().ToString(),
            ["first_name"] = "Ada",
            ["id"] = "424242"
        };
        var query = CreateQueryCollection(botToken, values);
        var invalidQuery = new QueryCollection(new Dictionary<string, StringValues>(query.ToDictionary(
            pair => pair.Key,
            pair => pair.Value))
        {
            ["hash"] = "00"
        });
        var service = new TelegramAuthService(CreateConfiguration(botToken));

        var verified = service.Verify(invalidQuery, out _, out _);

        Assert.False(verified);
    }

    [Fact]
    public void Verify_ShouldRejectExpiredPayload()
    {
        const string botToken = "test-bot-token";
        var expiredAuthDate = DateTimeOffset.UtcNow.AddDays(-2).ToUnixTimeSeconds().ToString();
        var query = CreateQueryCollection(
            botToken,
            new Dictionary<string, string>
            {
                ["auth_date"] = expiredAuthDate,
                ["first_name"] = "Ada",
                ["id"] = "424242"
            });
        var service = new TelegramAuthService(CreateConfiguration(botToken));

        var verified = service.Verify(query, out _, out _);

        Assert.False(verified);
    }

    private static IConfiguration CreateConfiguration(string botToken) =>
        new ConfigurationBuilder()
            .AddInMemoryCollection(new Dictionary<string, string?>
            {
                ["Telegram:BotToken"] = botToken
            })
            .Build();

    private static QueryCollection CreateQueryCollection(string botToken, Dictionary<string, string> values)
    {
        var hash = ComputeTelegramHash(botToken, values);
        var queryValues = values.ToDictionary(
            pair => pair.Key,
            pair => new StringValues(pair.Value));
        queryValues["hash"] = new StringValues(hash);
        return new QueryCollection(queryValues);
    }

    private static string ComputeTelegramHash(string botToken, IReadOnlyDictionary<string, string> values)
    {
        var dataCheckString = string.Join(
            "\n",
            values
                .OrderBy(pair => pair.Key, StringComparer.Ordinal)
                .Select(pair => $"{pair.Key}={pair.Value}"));
        var secretKey = SHA256.HashData(Encoding.UTF8.GetBytes(botToken));
        var hashBytes = HMACSHA256.HashData(secretKey, Encoding.UTF8.GetBytes(dataCheckString));
        return Convert.ToHexString(hashBytes).ToLowerInvariant();
    }
}