using System.Text;
using System.Text.Json;
using SharepointToolbox.Web.Core.Models;

namespace SharepointToolbox.Web.Infrastructure.Persistence;

public class UserRepository
{
    private readonly string _filePath;
    private readonly SemaphoreSlim _writeLock = new(1, 1);
    private static readonly JsonSerializerOptions _opts = new()
    {
        WriteIndented = true,
        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
        PropertyNameCaseInsensitive = true
    };

    public UserRepository(string filePath) { _filePath = filePath; }

    public async Task<IReadOnlyList<AppUser>> LoadAsync()
    {
        if (!File.Exists(_filePath)) return Array.Empty<AppUser>();
        var json = await File.ReadAllTextAsync(_filePath, Encoding.UTF8);
        var root = JsonSerializer.Deserialize<UsersRoot>(json, _opts);
        return (IReadOnlyList<AppUser>?)root?.Users ?? Array.Empty<AppUser>();
    }

    public async Task<AppUser?> FindByEmailAsync(string email)
    {
        var users = await LoadAsync();
        return users.FirstOrDefault(u => u.Email.Equals(email, StringComparison.OrdinalIgnoreCase));
    }

    public async Task SaveAsync(IReadOnlyList<AppUser> users)
    {
        await _writeLock.WaitAsync();
        try
        {
            var root = new UsersRoot { Users = users.ToList() };
            var json = JsonSerializer.Serialize(root, _opts);
            var tmpPath = _filePath + ".tmp";
            var dir = Path.GetDirectoryName(_filePath);
            if (!string.IsNullOrEmpty(dir)) Directory.CreateDirectory(dir);
            await File.WriteAllTextAsync(tmpPath, json, Encoding.UTF8);
            File.Move(tmpPath, _filePath, overwrite: true);
        }
        finally { _writeLock.Release(); }
    }

    public async Task UpsertAsync(AppUser user)
    {
        await _writeLock.WaitAsync();
        try
        {
            var users = (await LoadInternal()).ToList();
            var idx = users.FindIndex(u => u.Id == user.Id);
            if (idx >= 0) users[idx] = user;
            else users.Add(user);
            await SaveInternal(users);
        }
        finally { _writeLock.Release(); }
    }

    public async Task DeleteAsync(string userId)
    {
        await _writeLock.WaitAsync();
        try
        {
            var users = (await LoadInternal()).ToList();
            users.RemoveAll(u => u.Id == userId);
            await SaveInternal(users);
        }
        finally { _writeLock.Release(); }
    }

    private async Task<IReadOnlyList<AppUser>> LoadInternal()
    {
        if (!File.Exists(_filePath)) return Array.Empty<AppUser>();
        var json = await File.ReadAllTextAsync(_filePath, Encoding.UTF8);
        var root = JsonSerializer.Deserialize<UsersRoot>(json, _opts);
        return (IReadOnlyList<AppUser>?)root?.Users ?? Array.Empty<AppUser>();
    }

    private async Task SaveInternal(List<AppUser> users)
    {
        var root = new UsersRoot { Users = users };
        var json = JsonSerializer.Serialize(root, _opts);
        var tmpPath = _filePath + ".tmp";
        var dir = Path.GetDirectoryName(_filePath);
        if (!string.IsNullOrEmpty(dir)) Directory.CreateDirectory(dir);
        await File.WriteAllTextAsync(tmpPath, json, Encoding.UTF8);
        File.Move(tmpPath, _filePath, overwrite: true);
    }

    private sealed class UsersRoot { public List<AppUser> Users { get; set; } = new(); }
}