server/block: Implement the snow layer block

server/block/model/snow.go

@@ -0,0 +1,28 @@
+package model
+
+import (
+	"github.com/df-mc/dragonfly/server/block/cube"
+	"github.com/df-mc/dragonfly/server/world"
+)
+
+// Snow is the model of a snow layer. The height of its bounding box scales with the number of layers the block
+// has, ranging from a single passable layer to a near-full block.
+type Snow struct {
+	// Layers is the number of snow layers the block has, ranging from 1 to 8.
+	Layers int
+}
+
+// BBox returns a flat box whose height scales with the number of layers. A single layer returns no box at all, so
+// that entities walk over it freely as they do in vanilla.
+func (s Snow) BBox(cube.Pos, world.BlockSource) []cube.BBox {
+	if s.Layers <= 1 {
+		return nil
+	}
+	return []cube.BBox{cube.Box(0, 0, 0, 1, float64(s.Layers-1)*0.125, 1)}
+}
+
+// FaceSolid returns true only for the upward face of a full eight-layer block, the only state to which other
+// blocks may be attached.
+func (s Snow) FaceSolid(_ cube.Pos, face cube.Face, _ world.BlockSource) bool {
+	return s.Layers >= 8 && face == cube.FaceUp
+}

server/block/register.go

@@ -108,6 +108,7 @@ func init() {
 	world.RegisterBlock(SmithingTable{})
 	world.RegisterBlock(SmoothBasalt{})
 	world.RegisterBlock(Snow{})
+	registerAll(allSnowLayers())
 	world.RegisterBlock(SoulSand{})
 	world.RegisterBlock(SoulSoil{})
 	world.RegisterBlock(Sponge{Wet: true})
@@ -382,6 +383,7 @@ func init() {
 	world.RegisterItem(Smoker{})
 	world.RegisterItem(SmoothBasalt{})
 	world.RegisterItem(Snow{})
+	world.RegisterItem(SnowLayer{})
 	world.RegisterItem(SoulSand{})
 	world.RegisterItem(SoulSoil{})
 	world.RegisterItem(Sponge{Wet: true})

server/block/snow_layer.go

@@ -0,0 +1,121 @@
+package block
+
+import (
+	"math/rand/v2"
+
+	"github.com/df-mc/dragonfly/server/block/cube"
+	"github.com/df-mc/dragonfly/server/block/model"
+	"github.com/df-mc/dragonfly/server/item"
+	"github.com/df-mc/dragonfly/server/world"
+	"github.com/go-gl/mathgl/mgl64"
+)
+
+// SnowLayer is a thin, partial covering of snow that may be stacked up to eight layers high.
+type SnowLayer struct {
+	transparent
+
+	// Height is the number of snow layers in addition to the bottom one, ranging from 0 (a single layer) to 7
+	// (eight layers, the height of a full block).
+	Height int
+}
+
+// Model ...
+func (s SnowLayer) Model() world.BlockModel {
+	return model.Snow{Layers: s.Height + 1}
+}
+
+// ReplaceableBy returns true if more snow may still be stacked onto the layer, or, for any other block, only when
+// this is a single layer thin enough to be replaced.
+func (s SnowLayer) ReplaceableBy(b world.Block) bool {
+	if _, ok := b.(SnowLayer); ok {
+		return s.Height < 7
+	}
+	return s.Height == 0
+}
+
+// UseOnBlock places a new snow layer or, when used on an existing layer, stacks another layer onto it.
+func (s SnowLayer) UseOnBlock(pos cube.Pos, face cube.Face, _ mgl64.Vec3, tx *world.Tx, user item.User, ctx *item.UseContext) bool {
+	if existing, ok := tx.Block(pos).(SnowLayer); ok && existing.Height < 7 {
+		existing.Height++
+		place(tx, pos, existing, user, ctx)
+		return placed(ctx)
+	}
+
+	pos, _, used := firstReplaceable(tx, pos, face, s)
+	if !used {
+		return false
+	}
+	below := pos.Side(cube.FaceDown)
+	if !tx.Block(below).Model().FaceSolid(below, cube.FaceUp, tx) {
+		// Snow can only rest on top of a block with a solid upward face.
+		return false
+	}
+
+	place(tx, pos, s, user, ctx)
+	return placed(ctx)
+}
+
+// NeighbourUpdateTick breaks the snow layer if the block below it no longer supports it.
+func (s SnowLayer) NeighbourUpdateTick(pos, _ cube.Pos, tx *world.Tx) {
+	below := pos.Side(cube.FaceDown)
+	if !tx.Block(below).Model().FaceSolid(below, cube.FaceUp, tx) {
+		breakBlock(s, pos, tx)
+	}
+}
+
+// RandomTick melts the snow in biomes too warm to sustain it, removing a single layer at a time until it is gone.
+func (s SnowLayer) RandomTick(pos cube.Pos, tx *world.Tx, _ *rand.Rand) {
+	// TODO: also melt when the block light level is 12 or higher, regardless of the biome temperature. The world
+	// does not currently expose the block light level separately from the sky light, which is required to do this
+	// without melting snow in daylight.
+	if tx.Temperature(pos) <= 0.15 {
+		return
+	}
+	if s.Height == 0 {
+		tx.SetBlock(pos, nil, nil)
+		return
+	}
+	s.Height--
+	tx.SetBlock(pos, s, nil)
+}
+
+// BreakInfo ...
+func (s SnowLayer) BreakInfo() BreakInfo {
+	return newBreakInfo(0.1, alwaysHarvestable, shovelEffective, func(t item.Tool, enchantments []item.Enchantment) []item.Stack {
+		layers := s.Height + 1
+		if hasSilkTouch(enchantments) {
+			if layers >= 8 {
+				return []item.Stack{item.NewStack(Snow{}, 1)}
+			}
+			return []item.Stack{item.NewStack(SnowLayer{}, layers)}
+		}
+		switch {
+		case layers <= 3:
+			return []item.Stack{item.NewStack(item.Snowball{}, 1)}
+		case layers <= 5:
+			return []item.Stack{item.NewStack(item.Snowball{}, 2)}
+		case layers <= 7:
+			return []item.Stack{item.NewStack(item.Snowball{}, 3)}
+		default:
+			return []item.Stack{item.NewStack(item.Snowball{}, 4)}
+		}
+	})
+}
+
+// EncodeItem ...
+func (SnowLayer) EncodeItem() (name string, meta int16) {
+	return "minecraft:snow_layer", 0
+}
+
+// EncodeBlock ...
+func (s SnowLayer) EncodeBlock() (string, map[string]any) {
+	return "minecraft:snow_layer", map[string]any{"height": int32(s.Height), "covered_bit": boolByte(false)}
+}
+
+// allSnowLayers ...
+func allSnowLayers() (s []world.Block) {
+	for h := 0; h < 8; h++ {
+		s = append(s, SnowLayer{Height: h})
+	}
+	return
+}