using System;
using System.Collections.Generic;
using System.IO;
using Newtonsoft.Json;

namespace UserPermissionTest_CS_WinForms
{
    public class JsonUserRepository : IUserRepository
    {
        private const string UsersFile = "users.json";
        private const string PermissionsFile = "permissions.json";

        public List<User> LoadUsers()
        {
            if (!File.Exists(UsersFile))
            {
                var defaults = GetDefaultUsers();
                SaveUsers(defaults);
                return defaults;
            }

            try
            {
                string json = File.ReadAllText(UsersFile);
                var users = JsonConvert.DeserializeObject<List<User>>(json);
                if (users == null) return GetDefaultUsers();

                // Dynamic Migration: If any loaded user has a plain text password, hash it and re-save
                bool modified = false;
                foreach (var user in users)
                {
                    if (user.Password.Length != 64 || !IsHexString(user.Password))
                    {
                        user.Password = PasswordHasher.HashPassword(user.Password);
                        modified = true;
                    }
                }

                if (modified)
                {
                    SaveUsers(users);
                }

                return users;
            }
            catch (Exception ex)
            {
                Console.WriteLine("Error reading users JSON, falling back to defaults: " + ex.Message);
                return GetDefaultUsers();
            }
        }

        private bool IsHexString(string str)
        {
            if (string.IsNullOrEmpty(str)) return false;
            foreach (char c in str)
            {
                if (!((c >= '0' && c <= '9') || (c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F')))
                    return false;
            }
            return true;
        }

        public void SaveUsers(List<User> users)
        {
            try
            {
                string json = JsonConvert.SerializeObject(users, Formatting.Indented);
                File.WriteAllText(UsersFile, json);
            }
            catch (Exception ex)
            {
                Console.WriteLine("Error writing users JSON: " + ex.Message);
            }
        }

        public List<string> LoadPermissions()
        {
            if (!File.Exists(PermissionsFile))
            {
                var defaults = GetDefaultPermissions();
                SavePermissions(defaults);
                return defaults;
            }

            try
            {
                string json = File.ReadAllText(PermissionsFile);
                var permissions = JsonConvert.DeserializeObject<List<string>>(json);
                return permissions ?? GetDefaultPermissions();
            }
            catch (Exception ex)
            {
                Console.WriteLine("Error reading permissions JSON, falling back to defaults: " + ex.Message);
                return GetDefaultPermissions();
            }
        }

        public void SavePermissions(List<string> permissions)
        {
            try
            {
                string json = JsonConvert.SerializeObject(permissions, Formatting.Indented);
                File.WriteAllText(PermissionsFile, json);
            }
            catch (Exception ex)
            {
                Console.WriteLine("Error writing permissions JSON: " + ex.Message);
            }
        }

        private List<User> GetDefaultUsers()
        {
            return new List<User>
            {
                new User
                {
                    Username = "admin",
                    FullName = "System Administrator",
                    Password = PasswordHasher.HashPassword("admin"),
                    Permissions = GetDefaultPermissions()
                },
                new User
                {
                    Username = "user",
                    FullName = "Standard User",
                    Password = PasswordHasher.HashPassword("user"),
                    Permissions = new List<string> { "View Dashboard" }
                }
            };
        }

        private List<string> GetDefaultPermissions()
        {
            return new List<string>
            {
                "View Dashboard",
                "Edit Settings",
                "Manage Users",
                "Full Control",
                "Delete Transactions"
            };
        }
    }
}