using Microsoft.AspNetCore.Mvc;
using Hasher;
using Models;
using System.IdentityModel.Tokens.Jwt;
using System.Security.Claims;
using System.Text;
using Microsoft.IdentityModel.Tokens;


namespace backend.Controllers
{
    [Route("api/auth")]
    [ApiController]
    public class AuthorizationController : ControllerBase
    {
        private readonly IConfiguration _config;
        private readonly ILogger _logger;
        private readonly PortfolioPortalDbContext _dbContext;

        public AuthorizationController(IConfiguration config, ILogger<AuthorizationController> logger, PortfolioPortalDbContext dbContext)
        {
            _config = config;
            _logger = logger;
            _dbContext = dbContext;
        }

        /// <summary>
        /// Processes a user login request by checking the provided email and password against the database,
        /// generating a JWT if successful, and setting the appropriate cookies in the response.
        /// </summary>
        /// <param name="requestBody">The login details submitted in the request body.</param>
        /// <returns>An ActionResult indicating the success or failure of the login attempt.</returns>
        [HttpPost]
        public async Task<ActionResult> ProcessLogin(LoginDetails requestBody)
        {
            // Log the request (password is censored)
            _logger.LogDebug($"Login request with body: {requestBody.ToString()}");
            User? user;
           
            // Check for a user with that email in the database
            user = _dbContext.Users.FirstOrDefault(u => u.Email.ToLower() == requestBody.email.ToLower());
            if (user != null)
            {   
                _logger.LogDebug($"Found user: {user}");
                // Make sure the user is enabled
                if (!user.IsEnabled) 
                {   _logger.LogWarning($"Disabled user {user.Username} attempted to log in.");
                    return Unauthorized("Account disabled.");
                }
        
                // Check the password against the hash from the database
                if (Argon2dHasher.VerifyArgon2Hash(requestBody.password, user.PasswordHash))
                {
                    _logger.LogDebug($"{user.Username} successfully authenticated!");
                    // Reset the users failed attempts to 0
                    Task attemptResetTask = ResetFailedAttempts(user);
                    // Get the user authorizations
                    List<AuthWithLevel> auths = GetUserAuths(user);
                    if (auths.Count == 0) { 
                        _logger.LogWarning($"{user.Username} has no authorization levels!");
                        return Unauthorized("No authorizations.");
                    }

                    // Generate a random string for fingerprinting, hashed used in JWT
                    string[] fingerprintSet = FingerPrinter.GetFingerprintSet();
                    string fingerprint = fingerprintSet[0];
                    string hashedFp = fingerprintSet[1];

                    int authExpiryMinutes = Convert.ToInt32(_config["JwtSettings:expiryTime"]);
                    DateTime authExpiration = DateTime.Now.AddMinutes(authExpiryMinutes);

                    string jwToken = GenerateJwt(user.UserId, auths,requestBody.clientVerificationKey,hashedFp, authExpiration);
                    // Add the JWT to the reponse cookies
                    SetHardenedCookie(HttpContext, "Authorization", jwToken, authExpiration);
                    SetHardenedCookie(HttpContext, "UserFingerprint", fingerprint, authExpiration);
                    _logger.LogDebug($"{user.Username} authorized with {Response.Cookies}");
                    _logger.LogInformation($"Authorized {user} with token {jwToken}");
                    await attemptResetTask;
                    return Ok($"Successfuly authorized! Session is valid for {authExpiryMinutes} minutes.");                  
                }
                // Password did not match records
                // Record the failed attempt
                bool accountLocked = RecordFailedAttempt(user);
                if (accountLocked)
                {
                    return Unauthorized("Account disabled.");
                }
                return Unauthorized("Incorrect username or password!");

            }
            // No User found | It's best not to distinguish between invalid pw and unknown un for security reasons
            return Unauthorized("Incorrect username or password!");
        }

        /// <summary>
        /// Generates a JSON Web Token (JWT) for the specified user and authorizations using the provided client key, fingerprint hash, and expiry date.
        /// </summary>
        /// <param name="userId">The ID of the user for whom the JWT is being generated.</param>
        /// <param name="authorizations">The list of authorizations for the user.</param>
        /// <param name="clientKey">The client key for verifying header signatures.</param>
        /// <param name="fingerprintHash">The hashed fingerprint for user identification.</param>
        /// <param name="expiry">The expiry date for the JWT.</param>
        /// <returns>The generated JWT.</returns>
        private string GenerateJwt(int userId, List<AuthWithLevel> authorizations, string clientKey, string fingerprintHash, DateTime expiry) 
        {
            // Create a new list of claims for the JWT
            List<Claim> claimsList = new List<Claim>
            {
                // Add the user ID, client key, and fingerprint hash as claims
                new Claim(JwtRegisteredClaimNames.Sub, userId.ToString()),
                new Claim("ClientPublicKey", clientKey),
                new Claim("Fingerprint", fingerprintHash)
            };

            // Add authorization claims for each authorization in the list
            foreach (var auth in authorizations)
            {
                claimsList.Add(new Claim("Auth", auth.AuthLevel.AuthLevel));
            }

            // Convert the claims list to an array
            var claims = claimsList.ToArray();

            // Get the secret key from the app configuration and create signing credentials
            var key = new SymmetricSecurityKey(Encoding.UTF8.GetBytes(_config["JwtSettings:SecretKey"]));
            var creds = new SigningCredentials(key, SecurityAlgorithms.HmacSha256);

            // Create a new JWT with the specified issuer, audience, claims, expiry, and signing credentials
            var token = new JwtSecurityToken(
                issuer: _config["JwtSettings:issuer"],
                audience: _config["JwtSettings:audience"],
                claims: claims,
                expires: expiry,
                signingCredentials: creds);

            // Write the JWT to a string and log it for debugging purposes
            string jwToken = new JwtSecurityTokenHandler().WriteToken(token);
            _logger.LogDebug($"New JWT created for {userId}\n{jwToken}");
            return jwToken;
        }


        /// <summary>
        /// Resets the failed attempt count for the specified user to zero in the database.
        /// </summary>
        /// <param name="user">The user whose failed attempt count is being reset.</param>
        private async Task ResetFailedAttempts(User user)
        {        
            // Set the user's failed attempt count to zero
            user.FailedAttempts = 0;
            // Save changes to the database asynchronously
            await _dbContext.SaveChangesAsync();
            
        }


        /// <summary>
        /// Retrieves the authorization levels for the specified user from the database.
        /// </summary>
        /// <param name="user">The user whose authorization levels are being retrieved.</param>
        /// <returns>A list of AuthWithLevel objects representing the user's authorization levels.</returns>
        private List<AuthWithLevel> GetUserAuths(User user)
        {
            List<AuthWithLevel> authsWithLevels;

            // Reset the user's failed attempt count to zero
            user.FailedAttempts = 0;

            // Save changes to the database
            _dbContext.SaveChanges();

            // Retrieve the authorization levels for the specified user from the database
            authsWithLevels = (from auth in _dbContext.Auths
                join level in _dbContext.AuthLevels on auth.AuthLevelId equals level.AuthLevelsId into authLevelGroup
                from authLevel in authLevelGroup.DefaultIfEmpty()
                where auth.UserId == user.UserId
                //FIXME Just take the AuthLevel
                select new AuthWithLevel
                {
                    Auth = auth,
                    AuthLevel = authLevel
                }).ToList();


            // Log a message indicating the user's authorization levels
            _logger.LogDebug($"{user.Username} auths: {authsWithLevels}");
        
            // Return a list of Auth objects representing the user's authorization levels
            return authsWithLevels;
        }


        /// <summary>
        /// Records a failed login attempt for the specified user, and updates the user's failed attempt count and account lock status if necessary.
        /// </summary>
        /// <param name="user">The user whose login attempt failed.</param>
        /// <returns>A boolean value indicating whether the user's account is currently enabled.</returns>
        private bool RecordFailedAttempt(User user)
        {          
            // Increment the user's failed attempt count
            user.FailedAttempts += 1;

            // Log a message indicating that the user's login attempt failed, and how many failed attempts they have made so far
            _logger.LogInformation($"{user.Username} failed authentication! ({user.FailedAttempts}/5)");

            // If the user has made too many failed attempts, lock their account
            if (user.FailedAttempts > 4)
            {
                _logger.LogWarning($"{user.Username} has had their account locked for too many failed attempts!");
                user.IsEnabled = false;
            }

            // Save changes to the database
            _dbContext.SaveChanges();
            
            // Return a boolean value indicating whether the user's account is currently enabled
            return user.IsEnabled;
        }

        /// <summary>
        /// Sets a hardened cookie in the HTTP response with the given cookie name, value, and expiry time.
        /// </summary>
        /// <param name="httpContext">The HttpContext object for the current request.</param>
        /// <param name="cookieName">The name of the cookie.</param>
        /// <param name="cookieValue">The value of the cookie.</param>
        /// <param name="expiry">The expiry time of the cookie.</param>
        private void SetHardenedCookie(HttpContext httpContext, string cookieName, string cookieValue, DateTime expiry)
        {
            // Set the cookie options
            var cookieOptions = new CookieOptions
            {
                HttpOnly = true,            // The cookie cannot be accessed by JavaScript
                Secure = true,              // The cookie can only be sent over HTTPS
                SameSite = SameSiteMode.Strict, // The cookie can only be sent to the same domain that sent it
                Expires = expiry,           // The cookie expires at the given time (see appsettings.json)
                IsEssential = true          // The cookie is essential for the operation of the application (prevents browesers from blocking)
            };

            // Add the "__Secure-" prefix to the cookie name to indicate that it is a hardened cookie
            cookieName = "__Secure-" + cookieName;

            // Append the cookie to the HTTP response
            httpContext.Response.Cookies.Append(cookieName, cookieValue, cookieOptions);
        }
    }
}
//TODO: Consider separating the database access code into a separate repository class to follow the Repository pattern. 
//This would help you decouple the controller from the data access layer, making the code more maintainable and testable.