using AuthApi.Models;
using AuthApi.Services;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc;
using MongoDB.Driver;
using MongoDB.Bson;
using System.IdentityModel.Tokens.Jwt;
using System.Net.Mail;
using System.Security.Claims;
using System.Text.RegularExpressions;
using System.Net.Http.Json;

namespace AuthApi.Controllers;

[ApiController]
[Route("api/[controller]")]
public class AuthController : ControllerBase
{
    private readonly UserService _users;
    private readonly IConfiguration _cfg;
    private readonly BlacklistService _blacklist;
    private readonly IHttpClientFactory _httpClients;
    private readonly JwtTokenService _tokens;

    public AuthController(UserService users, IConfiguration cfg, BlacklistService blacklist,
        IHttpClientFactory httpClients, JwtTokenService tokens)
    {
        _users = users; _cfg = cfg; _blacklist = blacklist; _httpClients = httpClients; _tokens = tokens;
    }

    [HttpPost("register")]
    public async Task<IActionResult> Register([FromBody] RegisterRequest req)
    {
        var username = req.Username?.Trim() ?? "";
        var password = req.Password ?? "";
        var email = req.Email?.Trim() ?? "";

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

        if (await _users.GetByUsernameAsync(username) != null)
            return Conflict("Username already exists");

        var hash = BCrypt.Net.BCrypt.HashPassword(password);
        var user = new User { Username = username, PasswordHash = hash, Role = "USER", Email = email, CreatedUtc = DateTime.UtcNow };
        try
        {
            await _users.CreateAsync(user);
        }
        catch (MongoWriteException ex) when (ex.WriteError.Category == ServerErrorCategory.DuplicateKey)
        {
            return Conflict("Username already exists");
        }
        return Ok("User created");
    }

    [HttpPost("login")]
    public async Task<IActionResult> Login([FromBody] LoginRequest req)
    {
        var candidates = await _users.GetByLoginCandidatesAsync(req.Username);
        var user = candidates.FirstOrDefault(candidate => BCrypt.Net.BCrypt.Verify(req.Password, candidate.PasswordHash));
        if (user == null)
            return Unauthorized();

        var (accessToken, jti, expUtc) = _tokens.Generate(user);
        user.RefreshToken = Guid.NewGuid().ToString("N");
        user.RefreshTokenExpiry = DateTime.UtcNow.AddDays(7);
        await _users.UpdateAsync(user);

        return Ok(new { accessToken, refreshToken = user.RefreshToken, user.Username, user.Role, jti, exp = expUtc });
    }

    [HttpPost("refresh")]
    public async Task<IActionResult> Refresh([FromBody] RefreshRequest req)
    {
        var user = await _users.GetByUsernameAsync(req.Username);
        if (user == null || user.RefreshToken != req.RefreshToken || user.RefreshTokenExpiry < DateTime.UtcNow)
            return Unauthorized("Invalid or expired refresh token");

        var (accessToken, _, expUtc) = _tokens.Generate(user);
        return Ok(new { accessToken, exp = expUtc });
    }

    [HttpPost("logout")]
    [Authorize(Roles = "USER,SUPER")]
    public async Task<IActionResult> Logout()
    {
        var token = HttpContext.Request.Headers["Authorization"].FirstOrDefault()?.Replace("Bearer ", "");
        if (string.IsNullOrWhiteSpace(token)) return BadRequest("Token missing");
        var jwt = new JwtSecurityTokenHandler().ReadJwtToken(token);
        await _blacklist.AddToBlacklistAsync(jwt.Id, jwt.ValidTo);
        return Ok("Logged out.");
    }

    [HttpGet("me")]
    [Authorize(Roles = "USER,SUPER")]
    public async Task<IActionResult> Me()
    {
        var user = await CurrentUserAsync();
        return user is null ? Unauthorized() : Ok(ProfileResponse(user));
    }

    [HttpPatch("me")]
    [Authorize(Roles = "USER,SUPER")]
    public async Task<IActionResult> UpdateProfile([FromBody] UpdateProfileRequest req)
    {
        var user = await CurrentUserAsync();
        if (user is null) return Unauthorized();
        var displayName = req.DisplayName?.Trim();
        var email = req.Email?.Trim().ToLowerInvariant();
        if (!string.IsNullOrEmpty(displayName) && displayName.Length > 80)
            return BadRequest("Display name must be 80 characters or fewer.");
        if (!string.IsNullOrEmpty(email) && !ValidEmail(email))
            return BadRequest("A valid email address is required.");
        if (!string.IsNullOrEmpty(email))
        {
            var existing = await _users.GetByEmailAsync(email);
            if (existing is not null && existing.Id != user.Id) return Conflict("Email address is already in use.");
        }
        user.DisplayName = string.IsNullOrEmpty(displayName) ? null : displayName;
        user.Email = string.IsNullOrEmpty(email) ? null : email;
        user.CreatedUtc ??= CreationDate(user);
        await _users.UpdateAsync(user);
        return Ok(ProfileResponse(user));
    }

    [HttpPost("me/change-password")]
    [Authorize(Roles = "USER,SUPER")]
    public async Task<IActionResult> ChangePassword([FromBody] ChangePasswordRequest req)
    {
        var user = await CurrentUserAsync();
        if (user is null) return Unauthorized();
        if (!BCrypt.Net.BCrypt.Verify(req.CurrentPassword, user.PasswordHash)) return BadRequest("Current password is incorrect.");
        if (req.NewPassword.Length < 8) return BadRequest("Password must be at least 8 characters.");
        user.PasswordHash = BCrypt.Net.BCrypt.HashPassword(req.NewPassword);
        user.RefreshToken = null;
        user.RefreshTokenExpiry = null;
        await _users.UpdateAsync(user);
        await RevokeCurrentTokenAsync();
        return NoContent();
    }

    [HttpDelete("me")]
    [Authorize(Roles = "USER,SUPER")]
    public async Task<IActionResult> DeleteAccount([FromBody] DeleteAccountRequest req)
    {
        var user = await CurrentUserAsync();
        if (user is null) return Unauthorized();
        if (req.Confirmation != "DELETE") return BadRequest("Type DELETE to confirm permanent deletion.");
        if (!BCrypt.Net.BCrypt.Verify(req.Password, user.PasswordHash)) return BadRequest("Password is incorrect.");

        var baseUrl = _cfg["QuestionsApi:BaseUrl"]?.TrimEnd('/');
        var secret = _cfg["InternalPurge:Secret"];
        if (string.IsNullOrWhiteSpace(baseUrl) || string.IsNullOrWhiteSpace(secret))
            return StatusCode(503, "Account deletion is temporarily unavailable.");
        var client = _httpClients.CreateClient();
        client.Timeout = TimeSpan.FromSeconds(30);
        using var purge = new HttpRequestMessage(HttpMethod.Delete, $"{baseUrl}/api/profile/internal/users/{Uri.EscapeDataString(user.Id)}");
        purge.Headers.Add("X-MedMind-Internal-Key", secret);
        using var response = await client.SendAsync(purge);
        if (!response.IsSuccessStatusCode)
            return StatusCode(503, "Study data could not be removed. The account was not deleted; please try again.");

        await RevokeCurrentTokenAsync();
        await _users.DeleteAsync(user.Id);
        return NoContent();
    }

    [HttpPost("role")]
    [Authorize(Roles = "SUPER")]
    public async Task<IActionResult> ChangeUserRole([FromBody] ChangeRoleRequest req)
    {
        if (req.NewRole is not ("USER" or "SUPER")) return BadRequest("Role must be 'USER' or 'SUPER'");
        var user = await _users.GetByUsernameAsync(req.Username);
        if (user is null) return NotFound("User not found");
        user.Role = req.NewRole;
        await _users.UpdateAsync(user);
        return Ok($"{req.Username}'s role updated to {req.NewRole}");
    }

    [HttpGet("users")]
    [Authorize(Roles = "SUPER")]
    public async Task<IActionResult> GetAllUsers() => Ok(await _users.GetAllAsync());

    private async Task<User?> CurrentUserAsync()
    {
        var id = User.FindFirstValue(ClaimTypes.NameIdentifier);
        return string.IsNullOrWhiteSpace(id) ? null : await _users.GetByIdAsync(id);
    }

    private static bool ValidEmail(string email)
    {
        var domain = email.Split('@').LastOrDefault() ?? "";
        return MailAddress.TryCreate(email, out _) && domain.Contains('.');
    }

    private static DateTime CreationDate(User user)
    {
        return ObjectId.TryParse(user.Id, out var id) ? id.CreationTime : DateTime.UtcNow;
    }

    private static object ProfileResponse(User user) => new
    {
        userId = user.Id,
        user.Username,
        user.DisplayName,
        user.Email,
        user.Role,
        createdUtc = user.CreatedUtc ?? CreationDate(user)
    };

    private async Task RevokeCurrentTokenAsync()
    {
        var token = HttpContext.Request.Headers.Authorization.FirstOrDefault()?.Replace("Bearer ", "");
        if (string.IsNullOrWhiteSpace(token)) return;
        var jwt = new JwtSecurityTokenHandler().ReadJwtToken(token);
        await _blacklist.AddToBlacklistAsync(jwt.Id, jwt.ValidTo);
    }
}