using System.Collections.Generic;
using System.Linq;
using Enums;
using Models.Interfaces;
using Services.Interfaces;
using Structs;
using UnityEngine;

namespace Services {
    public class MatchService : IMatchService {
        private List<Gem> currentMatches = new List<Gem>();
        public List<Gem> CurrentMatches => this.currentMatches;

        public List<BombSpawnRequest> pendingBombSpawns = new List<BombSpawnRequest>();
        public IReadOnlyList<BombSpawnRequest> PendingBombSpawns => this.pendingBombSpawns;

        private Vector2Int lastSwapFrom;
        private Vector2Int lastSwapTo;
        
        private IGameBoard gameBoard;

        public MatchService(IGameBoard gameBoard) {
            this.gameBoard = gameBoard;
        }

        public void SetLastSwap(Vector2Int from, Vector2Int to) {
            this.lastSwapFrom = from;
            this.lastSwapTo = to;
        }

        public void ClearPendingBombs() {
            this.pendingBombSpawns.Clear();
        }
        
        public bool MatchesAt(Vector2Int positionToCheck, GemType gemTypeToCheck) {
            Gem[,] gems = this.gameBoard.GemsGrid;

            // We don't prevent spawning bombs via this rule (and bombs shouldn't be treated as a normal color here).
            if (gemTypeToCheck == GemType.Bomb)
                return false;

            // Check horizontal: would placing gemTypeToCheck at positionToCheck create XXX with 2-left?
            if (positionToCheck.x > 1) {
                Gem left1 = gems[positionToCheck.x - 1, positionToCheck.y];
                Gem left2 = gems[positionToCheck.x - 2, positionToCheck.y];

                if (left1 != null && left2 != null &&
                    left1.MatchColor == gemTypeToCheck &&
                    left2.MatchColor == gemTypeToCheck)
                    return true;
            }

            // Check vertical: would placing gemTypeToCheck at positionToCheck create XXX with 2-down?
            if (positionToCheck.y > 1) {
                Gem down1 = gems[positionToCheck.x, positionToCheck.y - 1];
                Gem down2 = gems[positionToCheck.x, positionToCheck.y - 2];

                if (down1 != null && down2 != null &&
                    down1.MatchColor == gemTypeToCheck &&
                    down2.MatchColor == gemTypeToCheck)
                    return true;
            }

            return false;
        }

        public void FindAllMatches() {
            this.currentMatches.Clear();
            this.pendingBombSpawns.Clear();

            for (int x = 0; x < this.gameBoard.Width; x++)
                for (int y = 0; y < this.gameBoard.Height; y++) {
                    Gem currentGem = this.gameBoard.GemsGrid[x, y];
                    if (currentGem == null)
                        continue;

                    if (x > 0 && x < this.gameBoard.Width - 1) {
                        Gem leftGem = this.gameBoard.GemsGrid[x - 1, y];
                        Gem rightGem = this.gameBoard.GemsGrid[x + 1, y];
                        if (leftGem != null && rightGem != null) {
                            if (leftGem.MatchColor == currentGem.MatchColor && rightGem.MatchColor == currentGem.MatchColor) {
                                this.currentMatches.Add(currentGem);
                                this.currentMatches.Add(leftGem);
                                this.currentMatches.Add(rightGem);
                            }
                        }
                    }

                    if (y > 0 && y < this.gameBoard.Height - 1) {
                        Gem aboveGem = this.gameBoard.GemsGrid[x, y - 1];
                        Gem bellowGem = this.gameBoard.GemsGrid[x, y + 1];
                        if (aboveGem != null && bellowGem != null) {
                            if (aboveGem.MatchColor == currentGem.MatchColor && bellowGem.MatchColor == currentGem.MatchColor) {
                                this.currentMatches.Add(currentGem);
                                this.currentMatches.Add(aboveGem);
                                this.currentMatches.Add(bellowGem);
                            }
                        }
                    }
                }

            if (this.currentMatches.Count > 0)
                this.currentMatches = this.currentMatches.Distinct().ToList();

            DetectBombSpawnFromLastSwap();
        }

        private void DetectBombSpawnFromLastSwap() {
            Vector2Int from = this.lastSwapFrom;
            Vector2Int to = this.lastSwapTo;

            TryCreateBombSpawnAt(from);
            TryCreateBombSpawnAt(to);
        }
        
        private void TryCreateBombSpawnAt(Vector2Int pivot) {
            Gem pivotGem = this.gameBoard.GetGemAt(pivot);
            if (pivotGem == null)
                return;

            // If it's already a bomb, don't create another.
            if (pivotGem.Type == GemType.Bomb)
                return;

            if (this.currentMatches.All(g => g.Position != pivot))
                return;

            // If the matched group that includes this pivot has 4+ connected gems, spawn a bomb.
            int groupSize = GetMatchedGroupSize(pivot);
            if (groupSize < 4)
                return;

            // Prevent duplicates for the same cell.
            if (this.pendingBombSpawns.Any(b => b.Position == pivot))
                return;

            this.pendingBombSpawns.Add(new BombSpawnRequest(pivot, pivotGem.MatchColor));
        }

        private int GetMatchedGroupSize(Vector2Int pivot) {
            Gem pivotGem = this.gameBoard.GetGemAt(pivot);
            if (pivotGem == null)
                return 0;

            GemType color = pivotGem.MatchColor;

            HashSet<Vector2Int> matchedPositions = new HashSet<Vector2Int>(
                this.currentMatches
                    .Where(g => g != null && g.MatchColor == color)
                    .Select(g => g.Position)
            );

            if (!matchedPositions.Contains(pivot))
                return 0;

            Queue<Vector2Int> queue = new Queue<Vector2Int>();
            HashSet<Vector2Int> visited = new HashSet<Vector2Int>();

            queue.Enqueue(pivot);
            visited.Add(pivot);

            Vector2Int[] directions = {
                Vector2Int.left,
                Vector2Int.right,
                Vector2Int.up,
                Vector2Int.down
            };

            while (queue.Count > 0) {
                Vector2Int currentPivot = queue.Dequeue();

                for (int i = 0; i < directions.Length; i++) {
                    Vector2Int n = currentPivot + directions[i];
                    if (visited.Contains(n))
                        continue;

                    if (!matchedPositions.Contains(n))
                        continue;

                    visited.Add(n);
                    queue.Enqueue(n);
                }
            }

            return visited.Count;
        }
    }
}