using FlowAPI.Application.DTOs.Graph;
using FlowAPI.Application.Interfaces;
using FlowAPI.Domain.Entities;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.Json;
using System.Threading.Tasks;

namespace FlowAPI.Application.Services
{
    public class GraphService : IGraphService
    {
        private readonly IGraphRepository _repo;
        private readonly ITaskNodeRepository _nodeRepo;
        private readonly IEdgeRepository _edgeRepo;
        private readonly IAchievementService _achievementService;
        private readonly ISharedGraphRepository _sharedGraphRepo;
        private readonly IUserRepository _userRepo;
        private readonly ICustomTemplateRepository _customTemplateRepo;

        public GraphService(
            IGraphRepository repo, 
            ITaskNodeRepository nodeRepo, 
            IEdgeRepository edgeRepo, 
            IAchievementService achievementService,
            ISharedGraphRepository sharedGraphRepo,
            IUserRepository userRepo,
            ICustomTemplateRepository customTemplateRepo)
        {
            _repo = repo;
            _nodeRepo = nodeRepo;
            _edgeRepo = edgeRepo;
            _achievementService = achievementService;
            _sharedGraphRepo = sharedGraphRepo;
            _userRepo = userRepo;
            _customTemplateRepo = customTemplateRepo;
        }

        public async Task<IEnumerable<GraphResponseDto>> GetAllByUserIdAsync(Guid userId)
        {
            // Owned graphs
            var ownedGraphs = await _repo.GetAllByUserIdAsync(userId);
            var ownedDtos = ownedGraphs.Select(g => 
            {
                var dto = MapToDto(g);
                dto.IsShared = false;
                dto.Permission = "Owner";
                return dto;
            }).ToList();

            // Shared graphs
            var sharedShares = await _sharedGraphRepo.GetSharedGraphsByUserIdAsync(userId);

            var sharedDtos = sharedShares.Select(s => 
            {
                var dto = MapToDto(s.Graph);
                dto.IsShared = true;
                dto.Permission = s.Permission;
                return dto;
            }).ToList();

            return ownedDtos.Concat(sharedDtos);
        }

        public async Task<GraphResponseDto?> GetByIdAsync(Guid id, Guid currentUserId)
        {
            var graph = await _repo.GetByIdAsync(id);
            if (graph is null) return null;

            if (graph.UserId == currentUserId)
            {
                var dto = MapToDto(graph);
                dto.IsShared = false;
                dto.Permission = "Owner";
                return dto;
            }

            var shared = await _sharedGraphRepo.GetShareAsync(id, currentUserId);
            if (shared is not null)
            {
                var dto = MapToDto(graph);
                dto.IsShared = true;
                dto.Permission = shared.Permission;
                return dto;
            }

            return null;
        }

        public async Task<FullGraphResponseDto?> GetFullByIdAsync(Guid id, Guid currentUserId)
        {
            var graph = await _repo.GetByIdWithDetailsAsync(id);
            if (graph is null) return null;

            string permission = "Owner";
            bool isShared = false;

            if (graph.UserId != currentUserId)
            {
                var shared = await _sharedGraphRepo.GetShareAsync(id, currentUserId);
                if (shared is null) return null;
                permission = shared.Permission;
                isShared = true;
            }

            return new FullGraphResponseDto
            {
                Id = graph.Id,
                UserId = graph.UserId,
                Title = graph.Title,
                Description = graph.Description,
                CreatedAt = graph.CreatedAt,
                IsShared = isShared,
                Permission = permission,
                Nodes = graph.Nodes.Select(n => 
                {
                    bool hasLarge = n.Data != null && n.Data.Length > 2000;
                    return new NodeDto
                    {
                        Id = n.Id,
                        Label = n.Label,
                        PosX = n.PosX,
                        PosY = n.PosY,
                        Type = n.Type,
                        State = (int)n.State,
                        Decision = n.Decision,
                        Description = n.Description,
                        Color = n.Color,
                        IsPinned = n.IsPinned,
                        Width = n.Width,
                        Height = n.Height,
                        Data = hasLarge ? null : n.Data,
                        HasLargeData = hasLarge
                    };
                }).ToList(),
                Edges = graph.Edges.Select(e => new EdgeDto
                {
                    Id = e.Id,
                    FromNodeId = e.FromNodeId,
                    ToNodeId = e.ToNodeId,
                    Condition = e.Condition.ToString()
                }).ToList()
            };
        }

        public async Task<GraphResponseDto> CreateAsync(CreateGraphDto dto, Guid currentUserId)
        {
            var user = await _userRepo.GetByIdAsync(currentUserId);
            if (user == null) throw new Exception("User not found.");

            var tier = user.SubscriptionTier?.Trim();
            bool isFree = string.IsNullOrEmpty(tier) || tier == "Free";

            if (isFree)
            {
                var ownedGraphsCount = (await _repo.GetAllByUserIdAsync(currentUserId)).Count();
                if (ownedGraphsCount >= 3)
                {
                    throw new InvalidOperationException("Free tier is limited to 3 canvases.");
                }
            }

            var graph = new Graph
            {
                Id = Guid.NewGuid(),
                UserId = currentUserId, // Secure: always force authenticated user ID
                Title = dto.Title,
                Description = dto.Description,
                CreatedAt = DateTime.UtcNow
            };

            if (!string.IsNullOrEmpty(dto.TemplateKey))
            {
                // Try to load system template first
                var (nodes, edges) = TemplateLibrary.GetTemplateContent(dto.TemplateKey, graph.Id);
                
                // If not found in system templates, check custom templates in DB
                if (nodes.Count == 0 && Guid.TryParse(dto.TemplateKey, out var customTemplateId))
                {
                    var customTemplate = await _customTemplateRepo.GetByIdAsync(customTemplateId);
                    if (customTemplate != null && (customTemplate.UserId == currentUserId || user.SubscriptionTier == "Ultra"))
                    {
                        try
                        {
                            var data = JsonSerializer.Deserialize<CustomTemplateContentDto>(customTemplate.ContentJson);
                            if (data != null)
                            {
                                var idMapping = new Dictionary<Guid, Guid>();
                                foreach (var nodeDto in data.Nodes)
                                {
                                    var newId = Guid.NewGuid();
                                    idMapping[nodeDto.Id] = newId;
                                    var node = new TaskNode
                                    {
                                        Id = newId,
                                        GraphId = graph.Id,
                                        Label = nodeDto.Label,
                                        PosX = nodeDto.PosX,
                                        PosY = nodeDto.PosY,
                                        Type = nodeDto.Type,
                                        State = FlowAPI.Domain.Enums.NodeState.Pending,
                                        CreatedAt = DateTime.UtcNow,
                                        Description = nodeDto.Description,
                                        Color = nodeDto.Color,
                                        IsPinned = nodeDto.IsPinned,
                                        Width = nodeDto.Width,
                                        Height = nodeDto.Height,
                                        Data = nodeDto.Data,
                                        Decision = nodeDto.Decision
                                    };
                                    nodes.Add(node);
                                }
                                foreach (var edgeDto in data.Edges)
                                {
                                    if (idMapping.TryGetValue(edgeDto.FromNodeId, out var fromId) &&
                                        idMapping.TryGetValue(edgeDto.ToNodeId, out var toId))
                                    {
                                        edges.Add(new Edge
                                        {
                                            Id = Guid.NewGuid(),
                                            GraphId = graph.Id,
                                            FromNodeId = fromId,
                                            ToNodeId = toId,
                                            Condition = edgeDto.Condition
                                        });
                                    }
                                }
                            }
                        }
                        catch (Exception ex)
                        {
                            System.Console.WriteLine($"[GraphService] Failed to load custom template: {ex.Message}");
                        }
                    }
                }

                if (nodes.Count > 0)
                {
                    graph.Nodes = nodes;
                    graph.Edges = edges;
                    if (string.IsNullOrEmpty(dto.Description) || dto.Description == "New strategy path...")
                    {
                        graph.Description = $"Побудовано за шаблоном";
                    }
                }
            }

            var created = await _repo.CreateAsync(graph);
            
            await _achievementService.ProcessEventAsync(currentUserId, "GraphCreated");

            if (graph.Nodes.Count > 0)
            {
                await _achievementService.ProcessEventAsync(currentUserId, "NodeCreated", graph.Nodes.Count);
            }
            if (graph.Edges.Count > 0)
            {
                await _achievementService.ProcessEventAsync(currentUserId, "EdgeCreated", graph.Edges.Count);
            }
            
            var result = MapToDto(created);
            result.IsShared = false;
            result.Permission = "Owner";
            return result;
        }

        public async Task<GraphResponseDto?> UpdateAsync(Guid id, UpdateGraphDto dto, Guid currentUserId)
        {
            var graph = await _repo.GetByIdAsync(id);
            if (graph is null) return null;

            // Secure: only allowed for owner or edit shared users
            if (graph.UserId != currentUserId)
            {
                var shared = await _sharedGraphRepo.GetShareAsync(id, currentUserId);
                if (shared is null || shared.Permission != "Edit") return null;
            }

            if (dto.Title is not null) graph.Title = dto.Title;
            if (dto.Description is not null) graph.Description = dto.Description;

            var updated = await _repo.UpdateAsync(graph);
            var result = MapToDto(updated);
            if (graph.UserId != currentUserId)
            {
                result.IsShared = true;
                result.Permission = "Edit";
            }
            return result;
        }

        public async Task<bool> DeleteAsync(Guid id, Guid currentUserId)
        {
            var graph = await _repo.GetByIdAsync(id);
            if (graph == null) return false;

            // Secure: only owner can delete the graph
            if (graph.UserId != currentUserId) return false;
            
            var deleted = await _repo.DeleteAsync(id);
            if (deleted)
            {
                await _achievementService.ProcessEventAsync(graph.UserId, "GraphDeleted");
            }
            return deleted;
        }

        public async Task<bool> SaveFullGraphAsync(Guid id, FullGraphResponseDto dto, Guid currentUserId)
        {
            var graph = await _repo.GetByIdWithDetailsAsync(id);
            if (graph is null) return false;

            var user = await _userRepo.GetByIdAsync(currentUserId);
            if (user == null) throw new Exception("User not found.");

            var tier = user.SubscriptionTier?.Trim();
            bool isFree = string.IsNullOrEmpty(tier) || tier == "Free";

            if (isFree)
            {
                if (dto.Nodes.Count > 200)
                {
                    throw new InvalidOperationException("Free tier is limited to 200 nodes per canvas.");
                }
            }

            // Secure: only allowed for owner or shared users with Edit permission
            if (graph.UserId != currentUserId)
            {
                var shared = await _sharedGraphRepo.GetShareAsync(id, currentUserId);
                if (shared is null || shared.Permission != "Edit") return false;
            }

            // Map DTOs to Domain Entities
            var mappedNodes = dto.Nodes.Select(nodeDto => new TaskNode
            {
                Id = nodeDto.Id == Guid.Empty ? Guid.NewGuid() : nodeDto.Id,
                GraphId = id,
                Label = nodeDto.Label,
                PosX = nodeDto.PosX,
                PosY = nodeDto.PosY,
                Type = nodeDto.Type,
                Decision = nodeDto.Decision,
                State = (FlowAPI.Domain.Enums.NodeState)nodeDto.State,
                Description = nodeDto.Description,
                Color = nodeDto.Color,
                IsPinned = nodeDto.IsPinned,
                Width = nodeDto.Width,
                Height = nodeDto.Height,
                Data = nodeDto.Data
            }).ToList();

            var mappedEdges = dto.Edges.Select(edgeDto => new Edge
            {
                Id = edgeDto.Id == Guid.Empty ? Guid.NewGuid() : edgeDto.Id,
                GraphId = id,
                FromNodeId = edgeDto.FromNodeId,
                ToNodeId = edgeDto.ToNodeId,
                Condition = edgeDto.Condition ?? "True"
            }).ToList();

            // Calculate deltas for achievements
            var oldNodes = graph.Nodes ?? new List<TaskNode>();
            var oldEdges = graph.Edges ?? new List<Edge>();

            int newlyCreatedNodes = mappedNodes.Count(n => !oldNodes.Any(o => o.Id == n.Id));
            int newlyCreatedEdges = mappedEdges.Count(e => !oldEdges.Any(o => o.Id == e.Id));
            
            int newlyCompletedNodes = mappedNodes.Count(n => 
                n.State == FlowAPI.Domain.Enums.NodeState.Done && 
                (!oldNodes.Any(o => o.Id == n.Id) || oldNodes.First(o => o.Id == n.Id).State != FlowAPI.Domain.Enums.NodeState.Done)
            );

            // Perform robust Upsert
            var success = await _repo.UpsertFullGraphAsync(id, mappedNodes, mappedEdges);
            if (!success) return false;

            // Trigger Achievements based on deltas
            if (newlyCreatedNodes > 0) await _achievementService.ProcessEventAsync(graph.UserId, "NodeCreated", newlyCreatedNodes);
            if (newlyCreatedEdges > 0) await _achievementService.ProcessEventAsync(graph.UserId, "EdgeCreated", newlyCreatedEdges);
            if (newlyCompletedNodes > 0) await _achievementService.ProcessEventAsync(graph.UserId, "TaskCompleted", newlyCompletedNodes);

            return true;
        }

        public async Task<GraphResponseDto?> ShareGraphAsync(Guid graphId, Guid ownerId, ShareGraphRequestDto dto)
        {
            var graph = await _repo.GetByIdAsync(graphId);
            if (graph is null || graph.UserId != ownerId) return null;

            var owner = await _userRepo.GetByIdAsync(ownerId);
            if (owner == null) throw new Exception("Owner user not found.");

            var targetUser = await _userRepo.GetByEmailAsync(dto.Email.ToLower().Trim());
            if (targetUser is null || targetUser.Id == ownerId) return null;

            var existing = await _sharedGraphRepo.GetShareAsync(graphId, targetUser.Id);
            if (existing is not null)
            {
                existing.Permission = dto.Permission;
                await _sharedGraphRepo.UpdateAsync(existing);
            }
            else
            {
                // Enforce sharing tier limits based on owner's tier
                var shares = await _sharedGraphRepo.GetSharesForGraphAsync(graphId);
                int currentSharedCount = shares?.Count() ?? 0;

                var ownerTier = owner.SubscriptionTier?.Trim();
                bool ownerIsFree = string.IsNullOrEmpty(ownerTier) || ownerTier == "Free";

                if (ownerIsFree && currentSharedCount >= 1)
                {
                    throw new InvalidOperationException("Free tier is limited to 2 people on a board (1 guest).");
                }
                else if (ownerTier == "Pro" && currentSharedCount >= 9)
                {
                    throw new InvalidOperationException("Pro tier is limited to 10 people on a board (9 guests).");
                }

                var share = new SharedGraph
                {
                    Id = Guid.NewGuid(),
                    GraphId = graphId,
                    SharedWithUserId = targetUser.Id,
                    Permission = dto.Permission,
                    CreatedAt = DateTime.UtcNow
                };
                await _sharedGraphRepo.CreateAsync(share);
            }

            var res = MapToDto(graph);
            res.IsShared = true;
            res.Permission = dto.Permission;
            return res;
        }

        public async Task<IEnumerable<SharedUserResponseDto>> GetSharedUsersAsync(Guid graphId, Guid ownerId)
        {
            var graph = await _repo.GetByIdAsync(graphId);
            if (graph is null) return Enumerable.Empty<SharedUserResponseDto>();

            // Allow access to shares list if caller is the owner or a guest with access
            if (graph.UserId != ownerId)
            {
                var shareAccess = await _sharedGraphRepo.GetShareAsync(graphId, ownerId);
                if (shareAccess is null) return Enumerable.Empty<SharedUserResponseDto>();
            }

            var result = new List<SharedUserResponseDto>();

            // Get owner details
            var owner = await _userRepo.GetByIdAsync(graph.UserId);
            if (owner is not null)
            {
                result.Add(new SharedUserResponseDto
                {
                    Id = Guid.Empty,
                    SharedWithUserId = owner.Id,
                    Email = owner.Email,
                    DisplayName = owner.DisplayName,
                    Permission = "Owner"
                });
            }

            // Get shared users
            var shares = await _sharedGraphRepo.GetSharesForGraphAsync(graphId);
            if (shares is not null)
            {
                result.AddRange(shares.Select(s => new SharedUserResponseDto
                {
                    Id = s.Id,
                    SharedWithUserId = s.SharedWithUserId,
                    Email = s.SharedWithUser?.Email ?? string.Empty,
                    DisplayName = s.SharedWithUser?.DisplayName ?? string.Empty,
                    Permission = s.Permission
                }));
            }

            return result;
        }

        public async Task<bool> RevokeShareAsync(Guid graphId, Guid ownerId, Guid shareId)
        {
            var graph = await _repo.GetByIdAsync(graphId);
            if (graph is null || graph.UserId != ownerId) return false;

            var share = await _sharedGraphRepo.GetByIdAsync(shareId);
            if (share is null || share.GraphId != graphId) return false;

            return await _sharedGraphRepo.DeleteAsync(shareId);
        }

        private static GraphResponseDto MapToDto(Graph graph) => new()
        {
            Id = graph.Id,
            UserId = graph.UserId,
            Title = graph.Title,
            Description = graph.Description,
            CreatedAt = graph.CreatedAt
        };

        public async Task<CustomTemplate> SaveAsTemplateAsync(Guid graphId, Guid userId, string title, string description)
        {
            var user = await _userRepo.GetByIdAsync(userId);
            if (user == null) throw new Exception("User not found.");

            if (user.SubscriptionTier != "Ultra")
            {
                throw new InvalidOperationException("Creating custom templates is an Ultra tier feature.");
            }

            var graph = await _repo.GetByIdWithDetailsAsync(graphId);
            if (graph == null || graph.UserId != userId)
            {
                throw new Exception("Graph not found or you are not the owner.");
            }

            // Map nodes and edges to DTOs for serialization
            var nodes = graph.Nodes.Select(n => new NodeDto
            {
                Id = n.Id,
                Label = n.Label,
                PosX = n.PosX,
                PosY = n.PosY,
                Type = n.Type,
                State = (int)n.State,
                Decision = n.Decision,
                Description = n.Description,
                Color = n.Color,
                IsPinned = n.IsPinned,
                Width = n.Width,
                Height = n.Height,
                Data = n.Data
            }).ToList();

            var edges = graph.Edges.Select(e => new EdgeDto
            {
                Id = e.Id,
                FromNodeId = e.FromNodeId,
                ToNodeId = e.ToNodeId,
                Condition = e.Condition
            }).ToList();

            var contentJson = JsonSerializer.Serialize(new CustomTemplateContentDto
            {
                Nodes = nodes,
                Edges = edges
            });

            var template = new CustomTemplate
            {
                Id = Guid.NewGuid(),
                UserId = userId,
                Title = title,
                Description = description,
                Category = "Custom",
                Icon = "BookOpen",
                ContentJson = contentJson,
                CreatedAt = DateTime.UtcNow
            };

            return await _customTemplateRepo.CreateAsync(template);
        }

        public async Task<IEnumerable<CustomTemplate>> GetCustomTemplatesAsync(Guid userId)
        {
            return await _customTemplateRepo.GetByUserIdAsync(userId);
        }

        private class CustomTemplateContentDto
        {
            public List<NodeDto> Nodes { get; set; } = new();
            public List<EdgeDto> Edges { get; set; } = new();
        }
    }
}