using Isopoh.Cryptography.Argon2;
using Microsoft.EntityFrameworkCore;
using Mizuki.Database;
using Mizuki.Database.Models;

namespace Mizuki.Services;

/// <summary>
/// The user service.
/// </summary>
/// <param name="dbContext">The Mizuki database context.</param>
public class UserService(
    MizukiDbContext dbContext)
{
    /// <summary>
    /// Check if a user with the given username exists.
    /// </summary>
    /// <param name="username">The username.</param>
    /// <returns>Whether they exist.</returns>
    public async Task<bool> UsernameTaken(
        string username)
    {
        return await dbContext.Users
            .AnyAsync(u => u.Username == username);
    }
    
    /// <summary>
    /// Gets a user with the given username.
    /// </summary>
    /// <param name="username">The username.</param>
    /// <returns>The user model.</returns>
    public async Task<User> GetUserForUsername(
        string username)
    {
        return await dbContext.Users
            .FirstAsync(u => u.Username == username);
    }

    /// <summary>
    /// Check if the password is valid for the given user.
    /// </summary>
    /// <param name="username">The user's name.</param>
    /// <param name="password">The password.</param>
    /// <returns>Whether it's valid.</returns>
    public async Task<bool> CheckPasswordForUser(
        string username,
        string password)
    {
        var user = await dbContext.Users
            .FirstOrDefaultAsync(u => u.Username == username);

        if (user is null)
            return false;

        return Argon2.Verify(user.PasswordHash, password);
    }

    /// <summary>
    /// Creates a user with the given username and password.
    /// </summary>
    /// <param name="username">The username.</param>
    /// <param name="password">The password.</param>
    /// <returns>Whether the user was created.</returns>
    public async Task<User?> CreateUser(
        string username,
        string password)
    {
        if (await UsernameTaken(username))
            return null;
        
        var hash = Argon2.Hash(password);
        var userModel = new User
        {
            Id = Guid.NewGuid(),
            Username = username,
            PasswordHash = hash
        };

        await dbContext.Users.AddAsync(userModel);
        await dbContext.SaveChangesAsync();
        return userModel;
    }

    /// <summary>
    /// Updates the password for a given user.
    /// </summary>
    /// <param name="user">The user.</param>
    /// <param name="newPassword">The new password.</param>
    public async Task UpdatePasswordFor(
        User user,
        string newPassword)
    {
        user.PasswordHash = Argon2.Hash(newPassword);
        dbContext.Users.Update(user);

        await dbContext.SaveChangesAsync();
    }
}