using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Threading.Tasks;
using Microsoft.Extensions.Caching.Memory;

namespace MiniWiki.Data.Users;

public class UsersCachingRepository(UsersDatabaseRepository inner, IMemoryCache cache) : IUsersRepository
{
    public async Task<User?> GetByIdAsync(string id)
    {
        if (cache.TryGetValue(IdKey(id), out User? user)) return user;

        var dbUser = await inner.GetByIdAsync(id);
        CacheUser(dbUser);
        return dbUser;
    }

    public async Task<User[]> GetMultiple(IEnumerable<string> ids)
    {
        ConcurrentBag<User> users = [];
        await Parallel.ForEachAsync(ids, async (id, _) =>
        {
            var user = await GetByIdAsync(id);
            if (user is not null) users.Add(user);
        });

        return [.. users];
    }

    public async Task<User?> GetByEmailAsync(string email)
    {
        if (cache.TryGetValue(EmailKey(email), out User? user)) return user;

        var dbUser = await inner.GetByEmailAsync(email);
        CacheUser(dbUser);
        return dbUser;
    }

    public Task<long> GetUserCount() => inner.GetUserCount();

    public async Task<User> CreateAsync(User user)
    {
        var dbUser = await inner.CreateAsync(user);

        CacheUser(dbUser);
        return dbUser;
    }

    public async Task UpdateAsync(User user)
    {
        await inner.UpdateAsync(user);
        CacheUser(user);
    }

    private void CacheUser(User? user)
    {
        cache.Set(IdKey(user?.Id), user, TimeSpan.FromMinutes(5));
        cache.Set(EmailKey(user?.Email), user, TimeSpan.FromMinutes(5));
    }

    private static string IdKey(string? id) => $"users:id:{id}";
    private static string EmailKey(string? email) => $"users:email:{email}";
}