using FlowAPI.Application.DTOs;
using FlowAPI.Application.Interfaces;
using FlowAPI.Domain.Entities;
using FlowAPI.Domain.Enums;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace FlowAPI.Application.Services
{
    public class AchievementService : IAchievementService
    {
        private readonly IAchievementRepository _achievementRepo;
        private readonly IUserAchievementRepository _userAchievementRepo;
        private readonly IUserRepository _userRepo;

        public AchievementService(IAchievementRepository achievementRepo, IUserAchievementRepository userAchievementRepo, IUserRepository userRepo)
        {
            _achievementRepo = achievementRepo;
            _userAchievementRepo = userAchievementRepo;
            _userRepo = userRepo;
        }

        public async Task<IEnumerable<UserAchievementDto>> GetUserAchievementsAsync(Guid userId)
        {
            var allAchievements = await _achievementRepo.GetAllAsync();
            var userAchievements = await _userAchievementRepo.GetByUserIdAsync(userId);
            
            var user = await _userRepo.GetByIdAsync(userId);
            var isAvatarUploaded = user != null && !string.IsNullOrEmpty(user.AvatarUrl);

            var result = new List<UserAchievementDto>();

            foreach (var achievement in allAchievements)
            {
                var userRecord = userAchievements.FirstOrDefault(ua => ua.AchievementId == achievement.Id);
                
                // Retroactively unlock Self Portrait if user already has an avatar set but no record or locked record in DB
                if (achievement.Title == "Self Portrait" && isAvatarUploaded)
                {
                    if (userRecord == null)
                    {
                        var newUa = new UserAchievement
                        {
                            UserId = userId,
                            AchievementId = achievement.Id,
                            CurrentValue = 1,
                            IsUnlocked = true,
                            UnlockedAt = DateTime.UtcNow
                        };
                        userRecord = await _userAchievementRepo.CreateAsync(newUa);
                    }
                    else if (!userRecord.IsUnlocked)
                    {
                        userRecord.CurrentValue = 1;
                        userRecord.IsUnlocked = true;
                        userRecord.UnlockedAt = DateTime.UtcNow;
                        userRecord = await _userAchievementRepo.UpdateAsync(userRecord);
                    }
                }

                result.Add(new UserAchievementDto
                {
                    Id = userRecord?.Id ?? Guid.Empty,
                    AchievementId = achievement.Id,
                    CurrentValue = userRecord?.CurrentValue ?? 0,
                    IsUnlocked = userRecord?.IsUnlocked ?? false,
                    UnlockedAt = userRecord?.UnlockedAt,
                    Achievement = new AchievementDto
                    {
                        Id = achievement.Id,
                        Title = achievement.Title,
                        Description = achievement.Description,
                        IconUrl = achievement.IconUrl,
                        Category = achievement.Category,
                        Type = achievement.Type,
                        TargetValue = achievement.TargetValue,
                        RewardPoints = achievement.RewardPoints
                    }
                });
            }

            return result;
        }

        public async Task ProcessEventAsync(Guid userId, string eventName, int amount = 1)
        {
            // 1. Find achievements triggered by this event
            var triggeredAchievements = await _achievementRepo.GetByTriggerEventAsync(eventName);

            if (!triggeredAchievements.Any()) return;

            // 2. Fetch user's current progress for these achievements
            var achievementIds = triggeredAchievements.Select(a => a.Id).ToList();
            var userAchievements = await _userAchievementRepo.GetByUserAndAchievementIdsAsync(userId, achievementIds);

            foreach (var achievement in triggeredAchievements)
            {
                var ua = userAchievements.FirstOrDefault(u => u.AchievementId == achievement.Id);

                // If user doesn't have a tracking record yet, create it
                if (ua == null)
                {
                    ua = new UserAchievement
                    {
                        UserId = userId,
                        AchievementId = achievement.Id,
                        CurrentValue = 0,
                        IsUnlocked = false
                    };
                    ua = await _userAchievementRepo.CreateAsync(ua);
                }

                // Skip if already unlocked
                if (ua.IsUnlocked) continue;

                // Update progress
                if (achievement.Type == AchievementType.Accumulative || achievement.Type == AchievementType.SingleAction)
                {
                    ua.CurrentValue += amount;
                }

                // Check for unlock
                if (ua.CurrentValue >= achievement.TargetValue)
                {
                    ua.CurrentValue = achievement.TargetValue;
                    ua.IsUnlocked = true;
                    ua.UnlockedAt = DateTime.UtcNow;
                }

                await _userAchievementRepo.UpdateAsync(ua);
            }
        }

        public async Task SeedAchievementsAsync()
        {
            var seedData = new List<Achievement>
            {
                new Achievement { Title = "Blank Canvas", Description = "Create your first project (Graph).", Category = "Projects", Type = AchievementType.SingleAction, TargetValue = 1, RewardPoints = 10, TriggerEventName = "GraphCreated" },
                new Achievement { Title = "Connecting the Dots", Description = "Create 10 connections (Edges) between tasks.", Category = "Tasks", Type = AchievementType.Accumulative, TargetValue = 10, RewardPoints = 50, TriggerEventName = "EdgeCreated" },
                new Achievement { Title = "Sketch Master", Description = "Create 100 task nodes overall.", Category = "Tasks", Type = AchievementType.Accumulative, TargetValue = 100, RewardPoints = 100, TriggerEventName = "NodeCreated" },
                new Achievement { Title = "Daily Doodler", Description = "Track habits 7 times.", Category = "Habits", Type = AchievementType.Accumulative, TargetValue = 7, RewardPoints = 70, TriggerEventName = "HabitTracked" },
                new Achievement { Title = "Decision Maker", Description = "Complete 50 tasks.", Category = "Tasks", Type = AchievementType.Accumulative, TargetValue = 50, RewardPoints = 50, TriggerEventName = "TaskCompleted" },
                new Achievement { Title = "Clear Desk", Description = "Delete 5 projects.", Category = "System", Type = AchievementType.Accumulative, TargetValue = 5, RewardPoints = 20, TriggerEventName = "GraphDeleted" },
                new Achievement { Title = "First Milestone", Description = "Complete your first task.", Category = "Tasks", Type = AchievementType.SingleAction, TargetValue = 1, RewardPoints = 15, TriggerEventName = "TaskCompleted" },
                new Achievement { Title = "Self Portrait", Description = "Upload your profile avatar.", Category = "System", Type = AchievementType.SingleAction, TargetValue = 1, RewardPoints = 15, TriggerEventName = "AvatarUploaded" }
            };

            var existing = await _achievementRepo.GetByTitlesAsync(seedData.Select(s => s.Title));
            var existingTitles = existing.Select(e => e.Title).ToList();

            var toAdd = seedData.Where(s => !existingTitles.Contains(s.Title)).ToList();

            if (toAdd.Any())
            {
                await _achievementRepo.AddRangeAsync(toAdd);
            }
        }
    }
}