using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using Fab2ApprovalSystem.Models;

using Microsoft.Extensions.Caching.Memory;
using Microsoft.Extensions.Logging;

namespace Fab2ApprovalSystem.Services;

public interface IUserService {
    Task<IEnumerable<User>> GetAllActiveUsers();
    Task<User> GetUserByLoginId(string loginId);
    Task<User> GetUserByUserId(int userId);
    Task<IEnumerable<int>> GetApproverUserIdsBySubRoleCategoryItem(string item);
}

public class UserService : IUserService {
    private readonly ILogger<UserService> _logger;
    private readonly IDalService _dalService;
    private readonly IMemoryCache _cache;

    public UserService(ILogger<UserService> logger, IDalService dalService, IMemoryCache cache) {
        _logger = logger ??
            throw new ArgumentNullException("ILogger not injected");
        _dalService = dalService ??
            throw new ArgumentNullException("IDalService not injected");
        _cache = cache ??
            throw new ArgumentNullException("IMemoryCache not injected");
    }

    public async Task<IEnumerable<User>> GetAllActiveUsers() {
        try {
            _logger.LogInformation("Attempting to get all active users");

            IEnumerable<User>? allActiveUsers = _cache.Get<IEnumerable<User>>("allActiveUsers");

            if (allActiveUsers is null) {
                string sql = "select * from Users where IsActive = 1";

                allActiveUsers = (await _dalService.QueryAsync<User>(sql)).ToList();

                _cache.Set("allActiveUsers", allActiveUsers, DateTimeOffset.Now.AddHours(1));
            }

            if (allActiveUsers is null || allActiveUsers.Count() == 0) {
                throw new Exception("No users found");
            }

            return allActiveUsers;
        } catch (Exception ex) {
            string errMsg = $"An exception occurred when attempting to get all users. Exception: {ex.Message}";
            _logger.LogError(errMsg);
            throw;
        }
    }

    public async Task<User> GetUserByLoginId(string loginId) {
        try {
            _logger.LogInformation("Attempting to get user by LoginId");

            if (string.IsNullOrWhiteSpace(loginId))
                throw new ArgumentException("LoginId cannot be null or empty");

            User? user = _cache.Get<User>($"userByLoginId{loginId}");

            user ??= _cache.Get<IEnumerable<User>>("allActiveUsers")?.FirstOrDefault(u => u.LoginID == loginId);

            if (user is null) {
                string sql = $"select * from Users where LoginID = '{loginId}';";

                user = (await _dalService.QueryAsync<User>(sql)).FirstOrDefault();

                _cache.Set($"userByLoginId{loginId}", user, DateTimeOffset.Now.AddHours(1));
            }

            if (user is null) throw new Exception($"No user found with LoginID {loginId}");

            return user;
        } catch (Exception ex) {
            string errMsg = $"An exception occurred when attempting to get user for LoginID {loginId}. Exception: {ex.Message}";
            _logger.LogError(errMsg);
            throw;
        }
    }

    public async Task<User> GetUserByUserId(int userId) {
        try {
            _logger.LogInformation("Attempting to get user by user ID");

            if (userId <= 0) throw new ArgumentException($"{userId} is not a valid user ID");

            User? user = _cache.Get<User>($"userByUserId{userId}");

            user ??= _cache.Get<IEnumerable<User>>("allActiveUsers")?.FirstOrDefault(u => u.UserID == userId);

            if (user is null) {
                string sql = $"select * from Users where UserID = '{userId}';";

                user = (await _dalService.QueryAsync<User>(sql)).FirstOrDefault();

                _cache.Set($"userByUserId{userId}", user, DateTimeOffset.Now.AddHours(1));
            }

            if (user is null) throw new Exception($"No user found with UserID {userId}");

            return user;
        } catch (Exception ex) {
            string errMsg = $"An exception occurred when attempting to get user for UserID {userId}. Exception: {ex.Message}";
            _logger.LogError(errMsg);
            throw;
        }
    }

    public async Task<IEnumerable<int>> GetApproverUserIdsBySubRoleCategoryItem(string item) {
        try {
            _logger.LogInformation("Attempting to get approver user IDs");

            if (string.IsNullOrWhiteSpace(item)) throw new ArgumentException("SubRoleCategoryItem cannot be null or empty");

            IEnumerable<int>? userIds = _cache.Get<IEnumerable<int>>($"approverUserIdsBySubRollCategory{item}");

            if (userIds is null) {
                StringBuilder queryBuilder = new();
                queryBuilder.Append("select us.UserID ");
                queryBuilder.Append("from SubRole as sr ");
                queryBuilder.Append("join UserSubRole as us on sr.SubRoleID=us.SubRoleID ");
                queryBuilder.Append("join SubRoleCategory as sc on sr.SubRoleCategoryID=sc.SubRoleCategoryID ");
                queryBuilder.Append($"where sc.SubRoleCategoryItem='{item}'");

                userIds = (await _dalService.QueryAsync<int>(queryBuilder.ToString())).ToList();

                _cache.Set($"approverUserIdsBySubRollCategory{item}", userIds, DateTimeOffset.Now.AddHours(1));
            }

            if (userIds is null || userIds.Count() == 0) {
                throw new Exception($"No users found for SubRoleCategoryItem {item}");
            }

            return userIds;
        } catch (Exception ex) {
            string errMsg = $"An exception occurred when attempting to get approver user IDs. Exception: {ex.Message}";
            _logger.LogError(errMsg);
            throw;
        }
    }
}