package server

import (
	"iter"
	"git.citrons.xyz/metronode/classic"
)

type blockType int16

const (
	walkThrough = classic.WalkThrough
	swimThrough = classic.SwimThrough
	solid = classic.Solid
	partiallySlippery = classic.PartiallySlippery
	fullySlippery = classic.FullySlippery
	water = classic.Water
	lava = classic.Lava
	rope = classic.Rope
)
type blockSolidity byte

const (
	noSound = classic.NoSound
	woodSound = classic.WoodSound
	gravelSound = classic.GravelSound
	grassSound = classic.GrassSound
	stoneSound = classic.StoneSound
	metalSound = classic.MetalSound
	glassSound = classic.GlassSound
	woolSound = classic.WoolSound
	sandSound = classic.SandSound
	snowSound = classic.SnowSound
)
type blockSound byte

const (
	opaque = classic.Opaque
	transparentGlass = classic.TransparentGlass
	transparentLeaves = classic.TransparentLeaves
	translucent = classic.Translucent
	invisible = classic.Invisible
)
type blockOpacity byte

const (
	cubeShape = iota
	spriteShape
	cuboidShape
)
type blockShape byte

type textureId int
const fillTextures = -1

type blockDef struct {
	Name string
	Solidity blockSolidity
	MovementSpeed byte
	Textures [6]textureId
	TransmitsLight bool
	WalkSound blockSound
	FullBright bool
	Shape blockShape
	Min [3]byte
	Max [3]byte
	Opacity blockOpacity
	FogDensity byte
	FogColor [3]byte
	Variants map[any]blockType
}

type rotateVariant int
type slabMaterial struct{}
type slabVariant bool

func markVariants(variants map[any]blockType) {
	for _, block := range variants {
		def := blockDefinitions[block]
		if def.Variants == nil {
			def.Variants = make(map[any]blockType)
			blockDefinitions[block] = def
		}
		for variation, block := range variants {
			def.Variants[variation] = block
		}
	}
}

func assertNoDef(block blockType) {
	if _, ok := blockDefinitions[block]; ok {
		panic("variant would override existing block")
	}
}

var rotationNames = []string {"-N", "-E", "-S", "-W"}
func makeRotations(block blockType) {
	oldDef := blockDefinitions[block]
	variants := make(map[any]blockType)
	for i := 0; i < 4; i++ {
		newBlock := block + blockType(i)
		if i != 0 {
			assertNoDef(newBlock)
		}
		newDef := oldDef
		for j := 0; j < 4; j++ {
			k := (j + i) % 4
			newDef.Textures[j + 1] = oldDef.Textures[k + 1]
		}
		var minX, minZ, maxX, maxZ byte
		switch i {
		case 1:
			minX = oldDef.Min[2]
			minZ = 16 - oldDef.Min[0]
			maxX = oldDef.Max[2]
			maxZ = 16 - oldDef.Max[0]
		case 2:
			minX = 16 - oldDef.Min[0]
			minZ = 16 - oldDef.Min[2]
			maxX = 16 - oldDef.Max[0]
			maxZ = 16 - oldDef.Max[2]
		case 3:
			minX = oldDef.Min[2]
			minZ = 16 - oldDef.Min[0]
			maxX = oldDef.Max[2]
			maxZ = 16 - oldDef.Max[0]
		}
		newDef.Min = [3]byte {byte(minX), oldDef.Min[1], byte(minZ)}
		newDef.Max = [3]byte {byte(maxX), oldDef.Max[1], byte(maxZ)}
		newDef.Name = newDef.Name + rotationNames[i]
		variants[rotateVariant(i)] = newBlock
		blockDefinitions[newBlock] = newDef
	}
	markVariants(variants)
}

func makeSlabs(material blockType, slab blockType, name string) {
	materialDef := blockDefinitions[material]
	variants := make(map[any]blockType)
	variants[slabMaterial{}] = material

	if name == "" {
		name = materialDef.Name + " Slab"
	}

	bottomSlab := materialDef
	bottomSlab.Name = name + "-D"
	bottomSlab.Shape = cuboidShape
	bottomSlab.Min = [3]byte {0, 0, 0}
	bottomSlab.Max = [3]byte {16, 8, 16}
	switch material {
	default:
		assertNoDef(slab)
		variants[slabVariant(false)] = slab
		blockDefinitions[slab] = bottomSlab
	case blockDoubleSlab:
		variants[slabVariant(false)] = blockSlab
		blockDefinitions[blockSlab] = bottomSlab
		slab--
	case blockCobblestone:
		variants[slabVariant(false)] = blockCobblestoneSlab
		blockDefinitions[blockCobblestoneSlab] = bottomSlab
		slab--
	}
	topSlab := materialDef
	topSlab.Name = name + "-U"
	topSlab.Shape = cuboidShape
	topSlab.Min = [3]byte {0, 8, 0}
	topSlab.Max = [3]byte {16, 16, 16}
	assertNoDef(slab + 1)
	variants[slabVariant(true)] = slab + 1
	blockDefinitions[slab + 1] = topSlab

	markVariants(variants)
}

func getBlockDefPackets() iter.Seq[classic.Packet] {
	return func(yield func(classic.Packet) bool) {
		for id, def := range blockDefinitions { 
			var packet classic.Packet
			var (
				transmitsLight byte
				fullBright byte
			)
			if def.TransmitsLight {
				transmitsLight = 1
			}
			if def.FullBright {
				fullBright = 1
			}
			if def.Shape != spriteShape {
				var (i int; texture textureId)
				for i, texture = range def.Textures {
					if texture == fillTextures {
						break
					}
				}
				if texture == fillTextures {
					for i = i; i < len(def.Textures); i++ {
						def.Textures[i] = def.Textures[i - 1]
					}
				}
				if def.Shape == cubeShape {
					def.Min = [3]byte {0, 0, 0}
					def.Max = [3]byte {16, 16, 16}
				}
				packet = &classic.DefineBlockExt {
					BlockId: byte(id),
					Name: classic.PadString(def.Name),
					Solidity: byte(def.Solidity),
					MovementSpeed: def.MovementSpeed,
					TopTextureId: byte(def.Textures[0]),
					LeftTextureId: byte(def.Textures[4]),
					RightTextureId: byte(def.Textures[2]),
					FrontTextureId: byte(def.Textures[3]),
					BackTextureId: byte(def.Textures[1]),
					BottomTextureId: byte(def.Textures[5]),
					TransmitsLight: transmitsLight,
					WalkSound: byte(def.WalkSound),
					FullBright: fullBright,
					Min: def.Min,
					Max: def.Max,
					BlockDraw: byte(def.Opacity),
					FogDensity: def.FogDensity,
					FogColor: def.FogColor,
				}
			} else {
				packet = &classic.DefineBlock {
					BlockId: byte(id),
					Name: classic.PadString(def.Name),
					Solidity: byte(def.Solidity),
					MovementSpeed: def.MovementSpeed,
					SideTextureId: byte(def.Textures[1]),
					TransmitsLight: transmitsLight,
					WalkSound: byte(def.WalkSound),
					FullBright: fullBright,
					Shape: 0,
					BlockDraw: byte(def.Opacity),
					FogDensity: def.FogDensity,
					FogColor: def.FogColor,
				}
			}
			if !yield(packet) {
				return
			}
		}
	}
}