using AuthApi.Models;
using AuthApi.Services;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.RateLimiting;
using MongoDB.Driver;
using System.Net.Mail;
using System.Security.Cryptography;
using System.Text.RegularExpressions;

namespace AuthApi.Controllers;

[ApiController]
[Route("api/Auth/steam")]
public class SteamAuthController : ControllerBase
{
    private readonly UserService _users;
    private readonly SteamAuthTransactionService _transactions;
    private readonly SteamOpenIdService _openId;
    private readonly JwtTokenService _tokens;
    private readonly IConfiguration _cfg;
    private readonly ILogger<SteamAuthController> _logger;

    public SteamAuthController(UserService users, SteamAuthTransactionService transactions,
        SteamOpenIdService openId, JwtTokenService tokens, IConfiguration cfg,
        ILogger<SteamAuthController> logger)
    {
        _users = users;
        _transactions = transactions;
        _openId = openId;
        _tokens = tokens;
        _cfg = cfg;
        _logger = logger;
    }

    [HttpPost("start")]
    [EnableRateLimiting("steam-start")]
    public async Task<IActionResult> Start()
    {
        var realm = ConfiguredRealm();
        var transactionId = Base64Url(RandomNumberGenerator.GetBytes(32));
        var lifetime = Math.Clamp(_cfg.GetValue("Steam:TransactionTtlMinutes", 5), 2, 15);
        var expiresUtc = DateTime.UtcNow.AddMinutes(lifetime);
        await _transactions.CreateAsync(new SteamAuthTransaction
        {
            Id = transactionId,
            CreatedUtc = DateTime.UtcNow,
            ExpiresUtc = expiresUtc
        });
        var returnUrl = ReturnUrl(transactionId);
        return Ok(new
        {
            transactionId,
            authUrl = SteamOpenIdService.BuildAuthenticationUrl(realm, returnUrl),
            expiresUtc
        });
    }

    [HttpGet("callback")]
    [EnableRateLimiting("steam-complete")]
    public async Task<IActionResult> Callback([FromQuery] string transactionId, CancellationToken cancellationToken)
    {
        var transaction = await ActiveTransactionAsync(transactionId);
        if (transaction is null || transaction.Status != "pending")
            return CallbackPage(false, "This Steam sign-in request has expired. Return to RanaZe and try again.");

        var steamId = await _openId.VerifyCallbackAsync(Request.Query, ReturnUrl(transactionId), cancellationToken);
        if (steamId is null)
        {
            _logger.LogWarning("Steam OpenID verification failed");
            return CallbackPage(false, "Steam could not verify this sign-in. Return to RanaZe and try again.");
        }

        var user = await _users.GetBySteamIdAsync(steamId);
        var status = user is null ? "requires_account" : "complete";
        var changed = await _transactions.MarkVerifiedAsync(transactionId, steamId, status, user?.Id);
        if (!changed)
            return CallbackPage(false, "This Steam sign-in request has already been used.");
        if (user is not null)
        {
            user.RefreshToken = NewRefreshToken();
            user.RefreshTokenExpiry = DateTime.UtcNow.AddDays(7);
            await _users.UpdateAsync(user);
        }
        return CallbackPage(true, "Steam verified your identity. You can return to RanaZe.");
    }

    [HttpGet("status/{transactionId}")]
    [EnableRateLimiting("steam-poll")]
    public async Task<IActionResult> Status(string transactionId)
    {
        Response.Headers.CacheControl = "no-store";
        var transaction = await ActiveTransactionAsync(transactionId);
        if (transaction is null)
            return NotFound(new { message = "Steam sign-in expired." });
        if (transaction.Status != "complete")
            return Ok(new { status = transaction.Status });
        if (string.IsNullOrWhiteSpace(transaction.UserId))
            return Conflict(new { message = "Steam sign-in is incomplete." });

        var user = await _users.GetByIdAsync(transaction.UserId);
        if (user is null || user.SteamId != transaction.SteamId)
            return Conflict(new { message = "Steam account link is no longer valid." });
        if (string.IsNullOrWhiteSpace(user.RefreshToken) || user.RefreshTokenExpiry <= DateTime.UtcNow)
        {
            user.RefreshToken = NewRefreshToken();
            user.RefreshTokenExpiry = DateTime.UtcNow.AddDays(7);
            await _users.UpdateAsync(user);
        }
        var (accessToken, jti, exp) = _tokens.Generate(user);
        return Ok(new
        {
            status = "complete",
            accessToken,
            refreshToken = user.RefreshToken,
            user.Username,
            user.Role,
            jti,
            exp
        });
    }

    [HttpPost("complete")]
    [EnableRateLimiting("steam-complete")]
    public async Task<IActionResult> Complete([FromBody] CompleteSteamRequest request)
    {
        var transaction = await ActiveTransactionAsync(request.TransactionId);
        if (transaction?.Status == "complete")
            return Ok(new { status = "complete" });
        if (transaction is null || transaction.Status != "requires_account" || string.IsNullOrWhiteSpace(transaction.SteamId))
            return BadRequest(new { message = "Steam sign-in is not ready or has expired." });

        User? user;
        var createdUser = false;
        if (request.Action == "create")
        {
            var validation = ValidateNewAccount(request);
            if (validation is not null)
                return BadRequest(new { message = validation });
            if (await _users.GetByUsernameAsync(request.Username.Trim()) is not null)
                return Conflict(new { message = "Username already exists." });
            user = new User
            {
                Username = request.Username.Trim(),
                Email = request.Email!.Trim().ToLowerInvariant(),
                PasswordHash = BCrypt.Net.BCrypt.HashPassword(request.Password),
                Role = "USER",
                CreatedUtc = DateTime.UtcNow,
                SteamId = transaction.SteamId,
                RefreshToken = NewRefreshToken(),
                RefreshTokenExpiry = DateTime.UtcNow.AddDays(7)
            };
            try
            {
                await _users.CreateAsync(user);
                createdUser = true;
            }
            catch (MongoWriteException ex) when (ex.WriteError.Category == ServerErrorCategory.DuplicateKey)
            {
                return Conflict(new { message = "That username or Steam account is already connected." });
            }
        }
        else if (request.Action == "link")
        {
            var candidates = await _users.GetByLoginCandidatesAsync(request.Username);
            user = candidates.FirstOrDefault(candidate => BCrypt.Net.BCrypt.Verify(request.Password, candidate.PasswordHash));
            if (user is null)
                return Unauthorized(new { message = "The account credentials are incorrect." });
            if (!string.IsNullOrWhiteSpace(user.SteamId) && user.SteamId != transaction.SteamId)
                return Conflict(new { message = "That RanaZe account is already connected to another Steam account." });
            try
            {
                var linked = await _users.TryLinkSteamAsync(user.Id, transaction.SteamId,
                    NewRefreshToken(), DateTime.UtcNow.AddDays(7));
                if (!linked)
                    return Conflict(new { message = "That account could not be connected to Steam." });
            }
            catch (MongoWriteException ex) when (ex.WriteError.Category == ServerErrorCategory.DuplicateKey)
            {
                return Conflict(new { message = "That Steam account is already connected." });
            }
        }
        else
        {
            return BadRequest(new { message = "Action must be create or link." });
        }

        if (!await _transactions.MarkCompleteAsync(request.TransactionId, transaction.SteamId, user.Id))
        {
            if (createdUser)
                await _users.DeleteAsync(user.Id);
            return Conflict(new { message = "This Steam sign-in was already completed." });
        }
        return Ok(new { status = "complete" });
    }

    private async Task<SteamAuthTransaction?> ActiveTransactionAsync(string id)
    {
        if (string.IsNullOrWhiteSpace(id) || id.Length > 128)
            return null;
        var transaction = await _transactions.GetAsync(id);
        return transaction is not null && transaction.ExpiresUtc > DateTime.UtcNow ? transaction : null;
    }

    private string ConfiguredRealm() =>
        (_cfg["Steam:Realm"] ?? "https://pauth.ranaze.com").TrimEnd('/');

    private string ReturnUrl(string transactionId)
    {
        var callback = _cfg["Steam:ReturnUrl"] ?? $"{ConfiguredRealm()}/api/Auth/steam/callback";
        return $"{callback}?transactionId={Uri.EscapeDataString(transactionId)}";
    }

    private ContentResult CallbackPage(bool success, string message)
    {
        Response.Headers.CacheControl = "no-store";
        Response.Headers.ContentSecurityPolicy = "default-src 'none'; style-src 'unsafe-inline'; script-src 'unsafe-inline'";
        Response.Headers.XFrameOptions = "DENY";
        Response.Headers["Referrer-Policy"] = "no-referrer";
        var color = success ? "#22c55e" : "#ef4444";
        var html = $$"""
            <!doctype html><html><head><meta charset="utf-8"><meta name="viewport" content="width=device-width">
            <title>RanaZe Steam sign-in</title><style>body{font-family:system-ui;background:#081324;color:#f8fafc;display:grid;place-items:center;min-height:100vh;margin:0}.card{max-width:34rem;padding:2rem;border:1px solid #33415d;border-radius:8px}h1{color:{{color}};font-size:1.4rem}</style></head>
            <body><main class="card"><h1>{{(success ? "Steam sign-in complete" : "Steam sign-in failed")}}</h1><p>{{System.Net.WebUtility.HtmlEncode(message)}}</p></main>
            <script>if(window.opener){setTimeout(()=>window.close(),1200);}</script></body></html>
            """;
        return Content(html, "text/html; charset=utf-8");
    }

    private static string? ValidateNewAccount(CompleteSteamRequest request)
    {
        var username = request.Username.Trim();
        var email = request.Email?.Trim() ?? "";
        if (!Regex.IsMatch(username, "^[A-Za-z0-9_]{3,24}$"))
            return "Username must be 3-24 characters using only letters, numbers, or underscores.";
        if (request.Password.Length < 8)
            return "Password must be at least 8 characters.";
        var domain = email.Split('@').LastOrDefault() ?? "";
        if (!MailAddress.TryCreate(email, out _) || !domain.Contains('.'))
            return "A valid email address is required.";
        return null;
    }

    private static string NewRefreshToken() => Convert.ToHexString(RandomNumberGenerator.GetBytes(32)).ToLowerInvariant();
    private static string Base64Url(byte[] bytes) => Convert.ToBase64String(bytes).TrimEnd('=').Replace('+', '-').Replace('/', '_');
}