using FlowAPI.Application.Interfaces;
using FlowAPI.Domain.Entities;
using FlowAPI.Infrastructure.Data;
using Microsoft.EntityFrameworkCore;

namespace FlowAPI.Infrastructure.Repositories
{
    public class GraphRepository : GenericRepository<Graph>, IGraphRepository
    {
        public GraphRepository(AppDbContext context) : base(context) { }

        public async Task<IEnumerable<Graph>> GetAllByUserIdAsync(Guid userId)
        {
            return await _dbSet
                .Where(g => g.UserId == userId)
                .Include(g => g.Nodes)
                .Include(g => g.Edges)
                .AsNoTracking()
                .ToListAsync();
        }

        public async Task<Graph?> GetByIdWithDetailsAsync(Guid id)
        {
            return await _dbSet
                .Include(g => g.Nodes)
                .Include(g => g.Edges)
                .FirstOrDefaultAsync(g => g.Id == id);
        }

        public async Task ClearDetailsAsync(Guid id)
        {
            var graph = await _dbSet
                .Include(g => g.Nodes)
                .Include(g => g.Edges)
                .FirstOrDefaultAsync(g => g.Id == id);

            if (graph != null)
            {
                if (graph.Edges.Any())
                {
                    _context.Edges.RemoveRange(graph.Edges);
                }
                if (graph.Nodes.Any())
                {
                    _context.TaskNodes.RemoveRange(graph.Nodes);
                }
                await _context.SaveChangesAsync();
            }
        }

        public async Task<bool> UpsertFullGraphAsync(Guid graphId, IEnumerable<TaskNode> nodes, IEnumerable<Edge> edges)
        {
            var graph = await _dbSet
                .Include(g => g.Nodes)
                .Include(g => g.Edges)
                .FirstOrDefaultAsync(g => g.Id == graphId);

            if (graph == null) return false;

            var existingNodes = graph.Nodes.ToList();
            var incomingNodes = nodes.ToList();
            var existingEdges = graph.Edges.ToList();
            var incomingEdges = edges.ToList();

            // 1. Identify nodes and edges to delete
            var nodesToDelete = existingNodes.Where(e => !incomingNodes.Any(i => i.Id == e.Id)).ToList();
            var deletedNodeIds = nodesToDelete.Select(n => n.Id).ToHashSet();

            var edgesToDelete = existingEdges
                .Where(e => !incomingEdges.Any(i => i.FromNodeId == e.FromNodeId && i.ToNodeId == e.ToNodeId && i.Condition == e.Condition)
                            || deletedNodeIds.Contains(e.FromNodeId)
                            || deletedNodeIds.Contains(e.ToNodeId))
                .ToList();

            // 2. Queue deletes (but don't save yet)
            if (edgesToDelete.Any())
            {
                _context.Edges.RemoveRange(edgesToDelete);
            }

            if (nodesToDelete.Any())
            {
                _context.TaskNodes.RemoveRange(nodesToDelete);
            }

            // 3. Update or Create Nodes
            foreach (var node in incomingNodes)
            {
                var existingNode = existingNodes.FirstOrDefault(e => e.Id == node.Id);
                if (existingNode != null)
                {
                    existingNode.Label = node.Label;
                    existingNode.PosX = node.PosX;
                    existingNode.PosY = node.PosY;
                    existingNode.Type = node.Type;
                    existingNode.Decision = node.Decision;
                    existingNode.State = node.State;
                    existingNode.Description = node.Description;
                    existingNode.Color = node.Color;
                    existingNode.IsPinned = node.IsPinned;
                    existingNode.Width = node.Width;
                    existingNode.Height = node.Height;
                    if (node.Data != null)
                    {
                        existingNode.Data = node.Data;
                    }
                }
                else
                {
                    node.GraphId = graphId;
                    _context.TaskNodes.Add(node);
                }
            }

            var incomingNodeIds = incomingNodes.Select(n => n.Id).ToHashSet();

            // 4. Update or Create Edges
            foreach (var edge in incomingEdges)
            {
                // Only create/update edge if both FromNode and ToNode exist in the incoming nodes list
                if (!incomingNodeIds.Contains(edge.FromNodeId) || !incomingNodeIds.Contains(edge.ToNodeId))
                {
                    continue;
                }

                var existingEdge = existingEdges.FirstOrDefault(e => e.FromNodeId == edge.FromNodeId && e.ToNodeId == edge.ToNodeId && e.Condition == edge.Condition);
                if (existingEdge != null)
                {
                    existingEdge.Condition = edge.Condition;
                }
                else
                {
                    edge.Id = Guid.NewGuid();
                    edge.GraphId = graphId;
                    _context.Edges.Add(edge);
                }
            }

            // 5. Single atomic save to minimize lock duration
            await _context.SaveChangesAsync();
            return true;
        }
    }
}