Unicopia/src/main/java/com/minelittlepony/unicopia/TreeTraverser.java

package com.minelittlepony.unicopia;

import java.util.HashSet;
import java.util.Optional;
import java.util.Set;

import com.minelittlepony.unicopia.util.PosHelper;

import net.minecraft.block.Block;
import net.minecraft.block.BlockState;
import net.minecraft.block.Blocks;
import net.minecraft.block.LeavesBlock;
import net.minecraft.util.math.BlockPos;
import net.minecraft.util.math.Direction;
import net.minecraft.world.World;

public class TreeTraverser {

    public static void removeTree(World w, BlockPos pos) {
        BlockState log = w.getBlockState(pos);

        int size = measureTree(w, log, pos);

        if (size > 0) {
            removeTreePart(w, log, ascendTrunk(new HashSet<BlockPos>(), w, pos, log, 0).get(), 0);
        }
    }

    private static void removeTreePart(World w, BlockState log, BlockPos pos, int level) {
        if (level < 10 && isWoodOrLeaf(w, log, pos)) {
            if (level < 5) {
                w.breakBlock(pos, true);
            } else {
                Block.dropStacks(w.getBlockState(pos), w, pos);
                w.setBlockState(pos, Blocks.AIR.getDefaultState(), 3);
            }

            PosHelper.all(pos, p -> {
                removeTreePart(w, log, p, level + 1);
            }, Direction.UP, Direction.NORTH, Direction.SOUTH, Direction.EAST, Direction.WEST);

        }
    }

    private static Optional<BlockPos> ascendTrunk(Set<BlockPos> done, World w, BlockPos pos, BlockState log, int level) {
        if (level < 3 && !done.contains(pos)) {
            done.add(pos);

            BlockPos.Mutable result = new BlockPos.Mutable(ascendTree(w, log, pos, true));

            PosHelper.all(pos, p -> {
                if (variantAndBlockEquals(w.getBlockState(pos.east()), log)) {
                    ascendTrunk(done, w, pos.east(), log, level + 1).filter(a -> a.getY() > result.getY()).ifPresent(result::set);
                }
            }, Direction.EAST, Direction.WEST, Direction.NORTH, Direction.SOUTH);

            done.add(result.toImmutable());
            return Optional.of(result.toImmutable());
        }
        return Optional.of(pos);
    }

    public static BlockPos ascendTree(World w, BlockState log, BlockPos pos, boolean remove) {
        int breaks = 0;
        BlockState state;
        while (variantAndBlockEquals(w.getBlockState(pos.up()), log)) {
            if (PosHelper.some(pos, p -> isLeaves(w.getBlockState(p), log), Direction.NORTH, Direction.SOUTH, Direction.EAST, Direction.WEST)) {
                break;
            }

            if (remove) {
                if (breaks < 10) {
                    w.breakBlock(pos, true);
                } else {
                    state = w.getBlockState(pos);
                    Block.dropStacks(state, w, pos);
                    w.setBlockState(pos, Blocks.AIR.getDefaultState(), 3);
                }
                breaks++;
            }
            pos = pos.up();
        }
        return pos;
    }

    public static Optional<BlockPos> descendTree(World w, BlockState log, BlockPos pos) {
        return descendTreePart(new HashSet<BlockPos>(), w, log, new BlockPos.Mutable(pos));
    }

    private static Optional<BlockPos> descendTreePart(Set<BlockPos> done, World w, BlockState log, BlockPos.Mutable pos) {
        if (done.contains(pos) || !variantAndBlockEquals(w.getBlockState(pos), log)) {
            return Optional.empty();
        }

        done.add(pos.toImmutable());
        while (variantAndBlockEquals(w.getBlockState(pos.down()), log)) {
            pos.setOffset(Direction.DOWN);
            done.add(pos.toImmutable());
        }

        PosHelper.all(pos.toImmutable(), p -> {
            descendTreePart(done, w, log, new BlockPos.Mutable(p)).filter(a -> a.getY() < pos.getY()).ifPresent(pos::set);
        }, Direction.NORTH, Direction.SOUTH, Direction.EAST, Direction.WEST);

        done.add(pos.toImmutable());
        return Optional.of(pos.toImmutable());
    }

    public static int measureTree(World w, BlockState log, BlockPos pos) {
        Set<BlockPos> logs = new HashSet<>();
        Set<BlockPos> leaves = new HashSet<>();

        countParts(logs, leaves, w, log, pos);

        return logs.size() <= (leaves.size() / 2) ? logs.size() + leaves.size() : 0;
    }

    private static void countParts(Set<BlockPos> logs, Set<BlockPos> leaves, World w, BlockState log, BlockPos pos) {
        if (logs.contains(pos) || leaves.contains(pos)) {
            return;
        }

        BlockState state = w.getBlockState(pos);
        boolean yay = false;

        if (isLeaves(state, log) && !state.get(LeavesBlock.PERSISTENT)) {
            leaves.add(pos);
            yay = true;
        } else if (variantAndBlockEquals(state, log)) {
            logs.add(pos);
            yay = true;
        }

        if (yay) {
            PosHelper.all(pos, p -> {
                countParts(logs, leaves, w, log, p);
            }, Direction.UP, Direction.NORTH, Direction.SOUTH, Direction.EAST, Direction.WEST);
        }
    }

    public static boolean isWoodOrLeaf(World w, BlockState log, BlockPos pos) {
        BlockState state = w.getBlockState(pos);
        return variantAndBlockEquals(state, log) || (isLeaves(state, log) && !state.get(LeavesBlock.PERSISTENT));
    }

    private static boolean isLeaves(BlockState state, BlockState log) {
        return state.getBlock() instanceof LeavesBlock && variantEquals(state, log);
    }

    private static boolean variantAndBlockEquals(BlockState one, BlockState two) {
        return (one.getBlock() == two.getBlock()) && variantEquals(one, two);
    }

    private static boolean variantEquals(BlockState one, BlockState two) {
        return TreeType.get(one).equals(TreeType.get(two));
    }
}