# 3D adapter for the ported game render (docs/PORT-PLAN.md 2V2-e): every frame it turns the draw calls
# CPythonApplication::RenderGame issued through CStateManager (Metin2PythonHost.render3d_draws, recorded
# by the platform IDirect3DDevice8) into meshes under a camera.
#
# The draws carry 40250's own D3D matrices. CGraphicBase::SetPerspective builds a right-handed
# projection (D3DXMatrixPerspectiveFovRH), so 40250's view space already is Godot's camera space
# (x right, y up, looking down -z): each mesh gets world * view as its transform and the Camera3D stays
# at the origin with the fov/near/far read back from the projection. No axis conversion is involved.
# D3D's default front face (clockwise on screen, D3DCULL_CCW culls the rest) is also Godot's.
#
# PORT: until the map is ported, CMapManager has no environment data (LoadMap → SetEnvironmentData),
# so CPythonBackground::SetCharacterDirLight sets no light and D3DRS_AMBIENT stays 0: D3D would draw
# every lit mesh black. Such draws (lighting on, no light, no ambient, no emissive) are shown unshaded,
# texture only, and counted in unlit_stand_in_count. Delete this with the environment port.
extends Node3D

const UiAssets = preload("res://ui/ui_assets.gd")

# D3DCULL / D3DBLEND / D3DCMPFUNC values used below (D3D8Types.h).
const D3DCULL_NONE := 1
const D3DCULL_CW := 2
const D3DBLEND_ONE := 2
const D3DBLEND_SRCALPHA := 5
const D3DBLEND_INVSRCALPHA := 6

var camera: Camera3D
var light: DirectionalLight3D
var environment: WorldEnvironment
var _meshes: Array[MeshInstance3D] = []
# Materials keyed by texture and state, so an unchanged draw keeps its material from frame to frame.
var _materials := {}

# The draws the last update_frame() showed (for tests and reports).
var draw_count := 0
# How many of them used the no-environment stand-in (see the note at the top).
var unlit_stand_in_count := 0

func _ready() -> void:
	camera = Camera3D.new()
	camera.name = "GameCamera"
	camera.keep_aspect = Camera3D.KEEP_HEIGHT
	camera.current = true
	add_child(camera)
	# 40250's directional light (CPythonBackground::SetCharacterDirLight) arrives with the draws in
	# world space; it is placed in camera space each frame like the meshes.
	light = DirectionalLight3D.new()
	light.name = "Light0"
	light.visible = false
	add_child(light)
	environment = WorldEnvironment.new()
	environment.environment = Environment.new()
	environment.environment.background_mode = Environment.BG_COLOR
	environment.environment.background_color = Color.BLACK
	environment.environment.ambient_light_source = Environment.AMBIENT_SOURCE_COLOR
	environment.environment.ambient_light_color = Color.BLACK
	environment.environment.tonemap_mode = Environment.TONE_MAPPER_LINEAR
	add_child(environment)

func _process(_delta: float) -> void:
	if Metin2PythonHost.is_running():
		update_frame()

# D3D row-vector matrix (v' = v * M) as a Godot Transform3D (v' = T * v): the rows of M are the basis
# columns, row 3 is the origin.
static func d3d_transform(m: PackedFloat32Array) -> Transform3D:
	return Transform3D(Basis(Vector3(m[0], m[1], m[2]), Vector3(m[4], m[5], m[6]), Vector3(m[8], m[9], m[10])),
			Vector3(m[12], m[13], m[14]))

static func multiply(a: PackedFloat32Array, b: PackedFloat32Array) -> PackedFloat32Array:
	var out := PackedFloat32Array()
	out.resize(16)
	for r in 4:
		for c in 4:
			var sum := 0.0
			for k in 4:
				sum += a[r * 4 + k] * b[k * 4 + c]
			out[r * 4 + c] = sum
	return out

func update_frame() -> void:
	var draws: Array = Metin2PythonHost.render3d_draws()
	var shown := 0
	var stand_ins := 0
	var camera_set := false
	var light_set := false
	for draw in draws:
		# XYZRHW (screen-space) draws belong to the 2D pass; lines are debug geometry.
		if draw["pretransformed"] or draw["lines"] or draw["indices"].is_empty():
			continue
		var proj: PackedFloat32Array = draw["proj"]
		# _34 == -1: a perspective projection (the game pass). Ortho draws are UI-space.
		if proj[11] != -1.0:
			continue
		if not camera_set:
			_apply_projection(proj)
			camera_set = true
		var view: PackedFloat32Array = draw["view"]
		if not light_set and draw["light0"]:
			_apply_light(draw, view)
			light_set = true
		if _environment_missing(draw):
			stand_ins += 1
		var instance := _mesh_instance(shown)
		instance.transform = d3d_transform(multiply(draw["world"], view))
		instance.mesh = _build_mesh(draw)
		instance.visible = true
		shown += 1
	for i in range(shown, _meshes.size()):
		_meshes[i].visible = false
		_meshes[i].mesh = null
	if not light_set:
		light.visible = false
	draw_count = shown
	unlit_stand_in_count = stand_ins

func _apply_projection(proj: PackedFloat32Array) -> void:
	# D3DXMatrixPerspectiveFovRH: _22 = cot(fovy / 2), _33 = zf / (zn - zf), _43 = zn * zf / (zn - zf).
	camera.fov = rad_to_deg(2.0 * atan(1.0 / proj[5]))
	camera.near = proj[14] / proj[10]
	camera.far = proj[14] / (proj[10] + 1.0)

func _apply_light(draw: Dictionary, view: PackedFloat32Array) -> void:
	var view_basis := d3d_transform(view).basis
	var direction: Vector3 = view_basis * draw["light0_direction"]
	if direction.length_squared() < 1e-8:
		light.visible = false
		return
	light.visible = true
	# DirectionalLight3D shines along its -Z.
	light.transform = Transform3D(Basis.looking_at(direction.normalized(),
			Vector3.UP if absf(direction.normalized().y) < 0.99 else Vector3.RIGHT), Vector3.ZERO)
	var diffuse: Color = draw["light0_diffuse"]
	light.light_color = Color(diffuse.r, diffuse.g, diffuse.b)
	light.light_energy = 1.0
	# D3D lighting: ambient = D3DRS_AMBIENT + light ambient, both times the material ambient.
	var ambient: Color = draw["ambient"]
	var light_ambient: Color = draw["light0_ambient"]
	environment.environment.ambient_light_color = Color(minf(ambient.r + light_ambient.r, 1.0),
			minf(ambient.g + light_ambient.g, 1.0), minf(ambient.b + light_ambient.b, 1.0))

static func _environment_missing(draw: Dictionary) -> bool:
	var ambient: Color = draw["ambient"]
	var emissive: Color = draw["material_emissive"]
	return draw["lighting"] and not draw["light0"] and ambient.r + ambient.g + ambient.b == 0.0 \
			and emissive.r + emissive.g + emissive.b == 0.0

func _mesh_instance(index: int) -> MeshInstance3D:
	while _meshes.size() <= index:
		var instance := MeshInstance3D.new()
		instance.name = "Draw%d" % _meshes.size()
		instance.cast_shadow = GeometryInstance3D.SHADOW_CASTING_SETTING_OFF
		add_child(instance)
		_meshes.append(instance)
	return _meshes[index]

func _build_mesh(draw: Dictionary) -> ArrayMesh:
	var arrays := []
	arrays.resize(Mesh.ARRAY_MAX)
	arrays[Mesh.ARRAY_VERTEX] = draw["positions"]
	if draw.has("normals"):
		arrays[Mesh.ARRAY_NORMAL] = draw["normals"]
	if draw.has("uv0"):
		arrays[Mesh.ARRAY_TEX_UV] = draw["uv0"]
	if draw.has("diffuse"):
		arrays[Mesh.ARRAY_COLOR] = draw["diffuse"]
	arrays[Mesh.ARRAY_INDEX] = draw["indices"]
	var mesh := ArrayMesh.new()
	mesh.add_surface_from_arrays(Mesh.PRIMITIVE_TRIANGLES, arrays)
	mesh.surface_set_material(0, _material(draw))
	return mesh

func _material(draw: Dictionary) -> StandardMaterial3D:
	var lit: bool = draw["lighting"] and not _environment_missing(draw)
	# alpha_blend / alpha_test / lit are bools: %d needs them as ints.
	var key := "%s|%d|%d|%d|%d|%d|%d|%d|%s|%s" % [draw["texture0"], int(draw["alpha_blend"]), draw["src_blend"],
			draw["dest_blend"], int(draw["alpha_test"]), draw["alpha_ref"], draw["cull_mode"], int(lit),
			draw["material_diffuse"], draw["material_emissive"]]
	if _materials.has(key):
		return _materials[key]
	var material := StandardMaterial3D.new()
	var texture_name: String = draw["texture0"]
	if not texture_name.is_empty():
		# The ported client reads its models from 40250's packs; the texture must come from there too.
		material.albedo_texture = UiAssets.load_pack_tex(texture_name)
	material.albedo_color = draw["material_diffuse"] if lit else Color.WHITE
	material.emission_enabled = lit and draw["material_emissive"] != Color(0, 0, 0, 0)
	if material.emission_enabled:
		material.emission = draw["material_emissive"]
	material.shading_mode = BaseMaterial3D.SHADING_MODE_PER_VERTEX if lit \
			else BaseMaterial3D.SHADING_MODE_UNSHADED
	material.specular_mode = BaseMaterial3D.SPECULAR_DISABLED
	material.roughness = 1.0
	material.vertex_color_use_as_albedo = draw.has("diffuse")
	match int(draw["cull_mode"]):
		D3DCULL_NONE:
			material.cull_mode = BaseMaterial3D.CULL_DISABLED
		D3DCULL_CW:
			material.cull_mode = BaseMaterial3D.CULL_FRONT
		_:
			material.cull_mode = BaseMaterial3D.CULL_BACK
	if draw["alpha_blend"]:
		material.transparency = BaseMaterial3D.TRANSPARENCY_ALPHA
		if int(draw["dest_blend"]) == D3DBLEND_ONE:
			material.blend_mode = BaseMaterial3D.BLEND_MODE_ADD
	elif draw["alpha_test"]:
		material.transparency = BaseMaterial3D.TRANSPARENCY_ALPHA_SCISSOR
		material.alpha_scissor_threshold = float(draw["alpha_ref"]) / 255.0
	_materials[key] = material
	return material