match3-unity/Assets/Scripts/Services/MatchService.cs

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;

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

        private Vector2Int lastSwapFrom;
        private Vector2Int lastSwapTo;
        
        private readonly 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;

            // Only create a bomb if pivot is part of a straight 4+ line of the SAME color.
            int longestLine = GetLongestMatchedLineThroughPivot(pivot, pivotGem.MatchColor);
            if (longestLine < 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 GetLongestMatchedLineThroughPivot(Vector2Int pivot, GemType color) {
            int horizontal = 1 + CountSameColorInDirection(pivot, Vector2Int.left, color)
                               + CountSameColorInDirection(pivot, Vector2Int.right, color);

            int vertical = 1 + CountSameColorInDirection(pivot, Vector2Int.up, color)
                             + CountSameColorInDirection(pivot, Vector2Int.down, color);

            return Mathf.Max(horizontal, vertical);
        }

        private int CountSameColorInDirection(Vector2Int start, Vector2Int direction, GemType color) {
            int count = 0;
            Vector2Int oivot = start + direction;

            while (oivot.x >= 0 && oivot.x < this.gameBoard.Width && oivot.y >= 0 && oivot.y < this.gameBoard.Height) {
                Gem g = this.gameBoard.GetGemAt(oivot);
                if (g == null || g.Type == GemType.Bomb || g.MatchColor != color)
                    break;

                count++;
                oivot += direction;
            }

            return count;
        }
    }
}