using System.IdentityModel.Tokens.Jwt;
using System.Net.Http.Headers;
using System.Security.Claims;
using System.Text;
using Microsoft.IdentityModel.Tokens;

namespace SatelliteProvider.IntegrationTests;

public static class JwtTestHelpers
{
    public const string JwtSecretEnvVar = "JWT_SECRET";
    public const string DefaultSubject = "integration-tests";

    public static string ResolveSecretOrThrow()
    {
        var secret = Environment.GetEnvironmentVariable(JwtSecretEnvVar);
        if (string.IsNullOrWhiteSpace(secret))
        {
            throw new InvalidOperationException(
                $"{JwtSecretEnvVar} is not set in the integration test environment. " +
                "It must match the JWT_SECRET configured for the API container.");
        }

        var byteLength = Encoding.UTF8.GetByteCount(secret);
        if (byteLength < 32)
        {
            throw new InvalidOperationException(
                $"{JwtSecretEnvVar} is {byteLength} bytes; the test runner requires at least 32 bytes to match API validation.");
        }

        return secret;
    }

    public static string MintValidToken(string secret, string subject = DefaultSubject, TimeSpan? lifetime = null, IEnumerable<Claim>? extraClaims = null)
    {
        ArgumentNullException.ThrowIfNull(secret);

        var signingKey = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(secret));
        var credentials = new SigningCredentials(signingKey, SecurityAlgorithms.HmacSha256);

        var now = DateTime.UtcNow;
        var claims = new List<Claim>
        {
            new(JwtRegisteredClaimNames.Sub, subject),
            new(JwtRegisteredClaimNames.Jti, Guid.NewGuid().ToString("N"))
        };
        if (extraClaims is not null)
        {
            claims.AddRange(extraClaims);
        }

        var token = new JwtSecurityToken(
            issuer: null,
            audience: null,
            claims: claims,
            notBefore: now,
            expires: now.Add(lifetime ?? TimeSpan.FromHours(1)),
            signingCredentials: credentials);

        return new JwtSecurityTokenHandler().WriteToken(token);
    }

    public static string MintExpiredToken(string secret, string subject = DefaultSubject)
    {
        return MintValidToken(secret, subject, lifetime: TimeSpan.FromMinutes(-10));
    }

    public static string TamperSignature(string token)
    {
        var parts = token.Split('.');
        if (parts.Length != 3)
        {
            throw new ArgumentException("JWT must have three dot-separated segments.", nameof(token));
        }

        var signature = parts[2];
        var firstChar = signature[0];
        parts[2] = (firstChar == 'A' ? 'B' : 'A') + signature[1..];
        return string.Join('.', parts);
    }

    public static void AttachDefaultAuthorization(HttpClient httpClient, string token)
    {
        httpClient.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", token);
    }
}