package block

import (
	"math/rand/v2"
	"time"

	"github.com/df-mc/dragonfly/server/block/cube"
	"github.com/df-mc/dragonfly/server/block/customblock"
	"github.com/df-mc/dragonfly/server/item"
	"github.com/df-mc/dragonfly/server/world"
	"github.com/df-mc/dragonfly/server/world/sound"
	"github.com/go-gl/mathgl/mgl64"
)

// Activatable represents a block that may be activated by a viewer of the world. When activated, the block
// will execute some specific logic.
type Activatable interface {
	// Activate activates the block at a specific block position. The face clicked is passed, as well as the
	// world in which the block was activated and the viewer that activated it.
	// Activate returns a bool indicating if activating the block was used successfully.
	Activate(pos cube.Pos, clickedFace cube.Face, tx *world.Tx, u item.User, ctx *item.UseContext) bool
}

// Pickable represents a block that may give a different item then the block itself when picked.
type Pickable interface {
	// Pick returns the item that is picked when the block is picked.
	Pick() item.Stack
}

// Punchable represents a block that may be punched by a viewer of the world. When punched, the block
// will execute some specific logic.
type Punchable interface {
	// Punch punches the block at a specific block position. The face clicked is passed, as well as the
	// world in which the block was punched and the viewer that punched it.
	Punch(pos cube.Pos, clickedFace cube.Face, tx *world.Tx, u item.User)
}

// LightEmitter represents a block that emits light when placed. Blocks such as torches or lanterns implement
// this interface.
type LightEmitter interface {
	// LightEmissionLevel returns the light emission level of the block, a number from 0-15 where 15 is the
	// brightest and 0 means it doesn't emit light at all.
	LightEmissionLevel() uint8
}

// LightDiffuser represents a block that diffuses light. This means that a specific amount of light levels
// will be subtracted when light passes through the block.
// Blocks that do not implement LightDiffuser will be assumed to be solid: Light will not be able to pass
// through these blocks.
type LightDiffuser interface {
	// LightDiffusionLevel returns the amount of light levels that is subtracted when light passes through
	// this block. Some blocks, such as leaves, have this behaviour. A diffusion level of 15 means that all
	// light will be completely blocked when it passes through the block.
	LightDiffusionLevel() uint8
}

// RedstoneWireStepDowner represents a block with custom behaviour for redstone wire providing power when travelling
// down it.
type RedstoneWireStepDowner interface {
	// CanRedstoneWireStepDown returns whether redstone wire may provide power while travelling down the block at
	// pos from the wire position passed.
	CanRedstoneWireStepDown(pos, from cube.Pos, tx *world.Tx) bool
}

// Replaceable represents a block that may be replaced by another block automatically. An example is grass,
// which may be replaced by clicking it with another block.
type Replaceable interface {
	// ReplaceableBy returns a bool which indicates if the block is replaceableWith by another block.
	ReplaceableBy(b world.Block) bool
}

// EntityLander represents a block that reacts to an entity landing on it after falling.
type EntityLander interface {
	// EntityLand is called when an entity lands on the block.
	EntityLand(pos cube.Pos, tx *world.Tx, e world.Entity, distance *float64)
}

// EntityInsider represents a block that reacts to an entity going inside its 1x1x1 axis
// aligned bounding box.
type EntityInsider interface {
	// EntityInside is called when an entity goes inside the block's 1x1x1 axis aligned bounding box.
	EntityInside(pos cube.Pos, tx *world.Tx, e world.Entity)
}

// EntityStepper represents a block that reacts to an entity standing on top of it.
type EntityStepper interface {
	// EntityStepOn is called every tick while an entity is standing on the top face of the block.
	EntityStepOn(pos cube.Pos, tx *world.Tx, e world.Entity)
}

// ProjectileHitter represents a block that handles being hit by a projectile.
type ProjectileHitter interface {
	// ProjectileHit is called when a projectile hits the block.
	ProjectileHit(pos cube.Pos, tx *world.Tx, e world.Entity, face cube.Face)
}

// Frictional represents a block that may have a custom friction value. Friction is used for entity drag when the
// entity is on ground. If a block does not implement this interface, it should be assumed that its friction is 0.6.
type Frictional interface {
	// Friction returns the block's friction value.
	Friction() float64
}

// Permutable represents a custom block that can have more permutations than its default state.
type Permutable interface {
	// States returns a map of all the different properties for the block. The key is the property name, and the value
	// is a slice of all the possible values for that property. It is important that a block is registered in dragonfly
	// for each of the possible combinations of properties and values.
	States() map[string][]any
	// Permutations returns a slice of all the different permutations for the block. Multiple permutations can be
	// applied at once if their conditions are met.
	Permutations() []customblock.Permutation
}

// unknownFace is a face that is used for certain block items. This should not be exposed in the API.
var unknownFace = cube.Face(len(cube.Faces()))

// unknownDirection is a direction that is used for certain block items. This should not be exposed in the API.
var unknownDirection = cube.Direction(len(cube.Directions()))

func calculateFace(user item.User, placePos cube.Pos) cube.Face {
	userPos := user.Position()
	pos := cube.PosFromVec3(userPos)
	if abs(pos[0]-placePos[0]) < 2 && abs(pos[2]-placePos[2]) < 2 {
		y := userPos[1]
		if eyed, ok := user.(interface{ EyeHeight() float64 }); ok {
			y += eyed.EyeHeight()
		}

		if y-float64(placePos[1]) > 2.0 {
			return cube.FaceUp
		} else if float64(placePos[1])-y > 0.0 {
			return cube.FaceDown
		}
	}
	return user.Rotation().Direction().Opposite().Face()
}

func abs(x int) int {
	if x > 0 {
		return x
	}
	return -x
}

// replaceableWith checks if the block at the position passed is replaceable with the block passed.
func replaceableWith(tx *world.Tx, pos cube.Pos, with world.Block) bool {
	if pos.OutOfBounds(tx.Range()) {
		return false
	}
	b := tx.Block(pos)
	if replaceable, ok := b.(Replaceable); ok {
		if !replaceable.ReplaceableBy(with) || b == with {
			return false
		}
		if liquid, ok := tx.Liquid(pos); ok {
			replaceable, ok := liquid.(Replaceable)
			return ok && replaceable.ReplaceableBy(with)
		}
		return true
	}
	return false
}

// firstReplaceable finds the first replaceable block position eligible to have a block placed on it after
// clicking on the position and face passed.
// If none can be found, the bool returned is false.
func firstReplaceable(tx *world.Tx, pos cube.Pos, face cube.Face, with world.Block) (cube.Pos, cube.Face, bool) {
	if replaceableWith(tx, pos, with) {
		// A replaceableWith block was clicked, so we can replace it. This will then be assumed to be placed on
		// the top face. (Torches, for example, will get attached to the floor when clicking tall grass.)
		return pos, cube.FaceUp, true
	}
	side := pos.Side(face)
	if replaceableWith(tx, side, with) {
		return side, face, true
	}
	return pos, face, false
}

// place places the block passed at the position passed. If the user implements the block.Placer interface, it
// will use its PlaceBlock method. If not, the block is placed without interaction from the user.
func place(tx *world.Tx, pos cube.Pos, b world.Block, user item.User, ctx *item.UseContext) {
	if placer, ok := user.(Placer); ok {
		placer.PlaceBlock(pos, b, ctx)
		return
	}
	tx.SetBlock(pos, b, nil)
	tx.PlaySound(pos.Vec3(), sound.BlockPlace{Block: b})
}

// horizontalDirection returns the horizontal direction of the given direction. This is a legacy type still used in
// various blocks.
func horizontalDirection(d cube.Direction) cube.Direction {
	switch d {
	case cube.South:
		return cube.North
	case cube.West:
		return cube.South
	case cube.North:
		return cube.West
	case cube.East:
		return cube.East
	}
	panic("invalid direction")
}

// placed checks if an item was placed with the use context passed.
func placed(ctx *item.UseContext) bool {
	return ctx.CountSub > 0
}

// boolByte returns 1 if the bool passed is true, or 0 if it is false.
func boolByte(b bool) uint8 {
	if b {
		return 1
	}
	return 0
}

// replaceable is a struct that may be embedded to make a block replaceable by any other block.
type replaceable struct{}

// ReplaceableBy ...
func (replaceable) ReplaceableBy(world.Block) bool {
	return true
}

// transparent is a struct that may be embedded to make a block transparent to light. Light will be able to
// pass through this block freely.
type transparent struct{}

// LightDiffusionLevel ...
func (transparent) LightDiffusionLevel() uint8 {
	return 0
}

// gravityAffected is a struct that may be embedded for blocks affected by gravity.
type gravityAffected struct{}

// Solidifies ...
func (g gravityAffected) Solidifies(cube.Pos, *world.Tx) bool {
	return false
}

// fall spawns a falling block entity at the given position.
func (g gravityAffected) fall(b world.Block, pos cube.Pos, tx *world.Tx) {
	if replaceableWith(tx, pos.Side(cube.FaceDown), b) {
		tx.SetBlock(pos, nil, nil)
		opts := world.EntitySpawnOpts{Position: pos.Vec3Centre()}
		tx.AddEntity(tx.World().EntityRegistry().Config().FallingBlock(opts, b))
	}
}

// Flammable is an interface for blocks that can catch on fire.
type Flammable interface {
	// FlammabilityInfo returns information about a block's behaviour involving fire.
	FlammabilityInfo() FlammabilityInfo
}

// FlammabilityInfo contains values related to block behaviours involving fire.
type FlammabilityInfo struct {
	// Encouragement is the chance a block will catch on fire during attempted fire spread.
	Encouragement int
	// Flammability is the chance a block will burn away during a fire block tick.
	Flammability int
	// LavaFlammable returns whether it can catch on fire from lava.
	LavaFlammable bool
}

// newFlammabilityInfo creates a FlammabilityInfo struct with the properties passed.
func newFlammabilityInfo(encouragement, flammability int, lavaFlammable bool) FlammabilityInfo {
	return FlammabilityInfo{
		Encouragement: encouragement,
		Flammability:  flammability,
		LavaFlammable: lavaFlammable,
	}
}

// livingEntity ...
type livingEntity interface {
	// Hurt hurts the entity for a given amount of damage. The source passed represents the cause of the
	// damage, for example damage.SourceEntityAttack if the entity is attacked by another entity.
	// If the final damage exceeds the health that the entity currently has, the entity is killed.
	// Hurt returns the final amount of damage dealt to the Living entity and returns whether the Living entity
	// was vulnerable to the damage at all.
	Hurt(damage float64, src world.DamageSource) (n float64, vulnerable bool)
}

// flammableEntity ...
type flammableEntity interface {
	// OnFireDuration returns duration of fire in ticks.
	OnFireDuration() time.Duration
	// SetOnFire sets the entity on fire for the specified duration.
	SetOnFire(duration time.Duration)
	// Extinguish extinguishes the entity.
	Extinguish()
}

// dropItem ...
func dropItem(tx *world.Tx, it item.Stack, pos mgl64.Vec3) {
	create := tx.World().EntityRegistry().Config().Item
	opts := world.EntitySpawnOpts{Position: pos, Velocity: mgl64.Vec3{rand.Float64()*0.2 - 0.1, 0.2, rand.Float64()*0.2 - 0.1}}
	tx.AddEntity(create(opts, it))
}

// bass is a struct that may be embedded for blocks that create a bass sound.
type bass struct{}

// Instrument ...
func (bass) Instrument() sound.Instrument {
	return sound.Bass()
}

// snare is a struct that may be embedded for blocks that create a snare drum sound.
type snare struct{}

// Instrument ...
func (snare) Instrument() sound.Instrument {
	return sound.Snare()
}

// clicksAndSticks is a struct that may be embedded for blocks that create a clicks and sticks sound.
type clicksAndSticks struct{}

// Instrument ...
func (clicksAndSticks) Instrument() sound.Instrument {
	return sound.ClicksAndSticks()
}

// bassDrum is a struct that may be embedded for blocks that create a bass drum sound.
type bassDrum struct{}

// Instrument ...
func (bassDrum) Instrument() sound.Instrument {
	return sound.BassDrum()
}

// flute is a struct that may be embedded for blocks that create a flute sound.
type flute struct{}

// Instrument ...
func (flute) Instrument() sound.Instrument {
	return sound.Flute()
}

// newSmeltInfo returns a new SmeltInfo with the given values.
func newSmeltInfo(product item.Stack, experience float64) item.SmeltInfo {
	return item.SmeltInfo{
		Product:    product,
		Experience: experience,
	}
}

// newFoodSmeltInfo returns a new SmeltInfo with the given values that allows smelting in a smelter.
func newFoodSmeltInfo(product item.Stack, experience float64) item.SmeltInfo {
	return item.SmeltInfo{
		Product:    product,
		Experience: experience,
		Food:       true,
	}
}

// newOreSmeltInfo returns a new SmeltInfo with the given values that allows smelting in a blast furnace.
func newOreSmeltInfo(product item.Stack, experience float64) item.SmeltInfo {
	return item.SmeltInfo{
		Product:    product,
		Experience: experience,
		Ores:       true,
	}
}

// newFuelInfo returns a new FuelInfo with the given values.
func newFuelInfo(duration time.Duration) item.FuelInfo {
	return item.FuelInfo{Duration: duration}
}