extends Control
## TestHarness - Standalone runtime rig viewer / IK playground (Phase 9).
##
## Loads .stk files via StickmanFactory, spawns a master_rig.tscn instance into
## a SubViewport, and provides a debug overlay (skeleton bones + IK handles)
## plus interactive IK-handle dragging. NOT wired into the editor — run
## standalone via F6 on res://scenes/test_harness.tscn.

# ---------------------------------------------------------------------------
# Constants
# ---------------------------------------------------------------------------

const MIN_ZOOM: float = 0.1
const MAX_ZOOM: float = 5.0
const ZOOM_STEP: float = 1.10

const HANDLE_HIT_RADIUS_PX: float = 12.0   # screen-space grab radius
const HANDLE_DRAW_RADIUS_PX: float = 6.0   # screen-space marker radius
const JOINT_DOT_RADIUS_PX: float = 4.0     # screen-space bone-joint dot radius
const BONE_LINE_WIDTH_PX: float = 2.0      # screen-space bone line width

const BONE_COLOR_LEFT := Color(0.35, 0.70, 1.00)
const BONE_COLOR_RIGHT := Color(1.00, 0.50, 0.20)
const BONE_COLOR_CENTRAL := Color(1.00, 1.00, 1.00)
const HANDLE_COLOR_HAND := Color(0.00, 1.00, 0.00)   # green
const HANDLE_COLOR_FOOT := Color(0.00, 0.50, 1.00)   # blue
const HANDLE_COLOR_HEAD := Color(1.00, 1.00, 0.00)   # yellow
const HANDLE_COLOR_TORSO := Color(1.00, 0.00, 1.00)  # magenta

const SKELETON_PATH := "Skeleton2D"

## Quick-load buttons: [label, res:// path].
const QUICK_LOADS: Array = [
	["Break", "res://stickmen/break.stk"],
	["Basic", "res://stickmen/basic.stk"],
	["Test",  "res://stickmen/test.stk"],
]

## IK handle node paths (relative to rig root), keyed by handle name.
## The four limb targets drive TwoBoneIK; "Head" is the LookAt aim point and
## "Torso" is the hip anchor (dragging it translates the whole rig via its
## RemoteTransform2D — no target-following logic).
const IK_HANDLE_PATHS: Dictionary = {
	"Left_Hand":  "IK_Targets/Left_Hand",
	"Right_Hand": "IK_Targets/Right_Hand",
	"Left_Leg":   "IK_Targets/Left_Leg",
	"Right_Leg":  "IK_Targets/Right_Leg",
	"Head":       "IK_Targets/Head",
	"Torso":      "IK_Targets/Torso",
}

## Leaf bone → IK target node path (relative to rig root), keyed by bone name.
## Used by the bone overlay to draw the forearm/shin segments out to their
## wrist/ankle targets. The Head leaf is NOT listed here — its IK target is a
## LookAt aim point, so it draws along its own bone direction instead (see
## _draw_bones' leaf fallback).
const LEAF_BONE_IK_PATHS: Dictionary = {
	"LeftLowerArm":  "IK_Targets/Left_Hand",
	"RightLowerArm": "IK_Targets/Right_Hand",
	"LeftLowerLeg":  "IK_Targets/Left_Leg",
	"RightLowerLeg": "IK_Targets/Right_Leg",
}

# ---------------------------------------------------------------------------
# Runtime-built node references
# ---------------------------------------------------------------------------

var _viewport_container: SubViewportContainer
var _viewport: SubViewport
var _world: Node2D
var _camera: Camera2D
var _debug_overlay: Node2D
var _status_label: Label
var _file_dialog: FileDialog

# ---------------------------------------------------------------------------
# State
# ---------------------------------------------------------------------------

var _rig: Node2D = null
var _skeleton: Skeleton2D = null
var _ik_handles: Dictionary = {}   # { String : Marker2D }

var _show_bones: bool = true
var _show_ik: bool = true

var _is_panning: bool = false
var _pan_last: Vector2 = Vector2.ZERO
var _dragging_handle: Marker2D = null

# ---------------------------------------------------------------------------
# Lifecycle
# ---------------------------------------------------------------------------

func _ready() -> void:
	_build_ui()
	_viewport_container.resized.connect(_on_viewport_container_resized)
	call_deferred("_on_viewport_container_resized")


func _input(event: InputEvent) -> void:
	if _file_dialog != null and _file_dialog.visible:
		return

	if event is InputEventMouseButton:
		_handle_mouse_button(event as InputEventMouseButton)
	elif event is InputEventMouseMotion:
		_handle_mouse_motion(event as InputEventMouseMotion)

# ---------------------------------------------------------------------------
# UI construction
# ---------------------------------------------------------------------------

func _build_ui() -> void:
	# Dark background behind the transparent SubViewport.
	var bg := ColorRect.new()
	bg.color = Color(0.10, 0.10, 0.10, 1.0)
	bg.set_anchors_and_offsets_preset(Control.PRESET_FULL_RECT)
	add_child(bg)

	# Top UI bar.
	var top_bar := PanelContainer.new()
	top_bar.set_anchors_and_offsets_preset(Control.PRESET_TOP_WIDE)
	top_bar.offset_bottom = 40.0
	add_child(top_bar)

	var hbox := HBoxContainer.new()
	hbox.add_theme_constant_override("separation", 8)
	top_bar.add_child(hbox)

	var open_btn := Button.new()
	open_btn.text = "Open .stk…"
	open_btn.pressed.connect(_on_open_pressed)
	hbox.add_child(open_btn)

	for entry: Array in QUICK_LOADS:
		var btn := Button.new()
		btn.text = str(entry[0])
		btn.pressed.connect(_on_quick_load.bind(str(entry[1])))
		hbox.add_child(btn)

	var bones_cb := CheckBox.new()
	bones_cb.text = "Show Bones"
	bones_cb.button_pressed = true
	bones_cb.toggled.connect(_on_show_bones_toggled)
	hbox.add_child(bones_cb)

	var ik_cb := CheckBox.new()
	ik_cb.text = "Show IK Handles"
	ik_cb.button_pressed = true
	ik_cb.toggled.connect(_on_show_ik_toggled)
	hbox.add_child(ik_cb)

	_status_label = Label.new()
	_status_label.text = "No file loaded"
	_status_label.size_flags_horizontal = Control.SIZE_EXPAND_FILL
	_status_label.horizontal_alignment = HORIZONTAL_ALIGNMENT_RIGHT
	_status_label.vertical_alignment = VERTICAL_ALIGNMENT_CENTER
	_status_label.text_overrun_behavior = TextServer.OVERRUN_TRIM_ELLIPSIS
	hbox.add_child(_status_label)

	# Viewport area (fills everything below the top bar).
	_viewport_container = SubViewportContainer.new()
	_viewport_container.set_anchors_and_offsets_preset(Control.PRESET_FULL_RECT)
	_viewport_container.offset_top = 40.0
	_viewport_container.mouse_filter = Control.MOUSE_FILTER_STOP
	add_child(_viewport_container)

	_viewport = SubViewport.new()
	_viewport.transparent_bg = true
	_viewport_container.add_child(_viewport)

	_world = Node2D.new()
	_world.name = "World"
	_viewport.add_child(_world)

	_camera = Camera2D.new()
	_camera.enabled = true
	_world.add_child(_camera)
	_camera.make_current()

	_debug_overlay = Node2D.new()
	_debug_overlay.name = "DebugOverlay"
	_debug_overlay.draw.connect(_on_debug_overlay_draw)
	_world.add_child(_debug_overlay)

	# File dialog for "Open .stk…".
	_file_dialog = FileDialog.new()
	_file_dialog.title = "Open .stk"
	_file_dialog.access = FileDialog.ACCESS_FILESYSTEM
	_file_dialog.file_mode = FileDialog.FILE_MODE_OPEN_FILE
	_file_dialog.filters = PackedStringArray(["*.stk ; Stickman Files"])
	_file_dialog.file_selected.connect(_on_file_selected)
	add_child(_file_dialog)


func _on_viewport_container_resized() -> void:
	var size := _viewport_container.size
	if size.x < 1.0 or size.y < 1.0:
		return
	_viewport.size = Vector2i(size)

# ---------------------------------------------------------------------------
# Input handling
# ---------------------------------------------------------------------------

func _handle_mouse_button(mb: InputEventMouseButton) -> void:
	if not _is_over_viewport(mb.position):
		return

	if mb.button_index == MOUSE_BUTTON_MIDDLE:
		if mb.pressed:
			_is_panning = true
			_pan_last = mb.position
		else:
			_is_panning = false
		return

	if mb.button_index == MOUSE_BUTTON_WHEEL_UP and mb.pressed:
		_apply_zoom(mb.position, ZOOM_STEP)
		return
	if mb.button_index == MOUSE_BUTTON_WHEEL_DOWN and mb.pressed:
		_apply_zoom(mb.position, 1.0 / ZOOM_STEP)
		return

	if mb.button_index == MOUSE_BUTTON_LEFT:
		if mb.pressed:
			_dragging_handle = _hit_test_handle(_viewport_to_world(mb.position))
		else:
			_dragging_handle = null


func _handle_mouse_motion(mm: InputEventMouseMotion) -> void:
	if _is_panning:
		var delta := mm.position - _pan_last
		_pan_last = mm.position
		_camera.position -= delta / _camera.zoom
		_debug_overlay.queue_redraw()
		return

	if _dragging_handle != null and is_instance_valid(_dragging_handle):
		_dragging_handle.global_position = _viewport_to_world(mm.position)
		_debug_overlay.queue_redraw()


func _is_over_viewport(screen_pos: Vector2) -> bool:
	return _viewport_container.get_global_rect().has_point(screen_pos)


func _viewport_to_world(screen_pos: Vector2) -> Vector2:
	var local := screen_pos - _viewport_container.global_position
	return (local - _viewport.size * 0.5) / _camera.zoom + _camera.position


func _apply_zoom(screen_pos: Vector2, factor: float) -> void:
	var world_before := _viewport_to_world(screen_pos)
	var new_zoom := clampf(_camera.zoom.x * factor, MIN_ZOOM, MAX_ZOOM)
	_camera.zoom = Vector2(new_zoom, new_zoom)
	var world_after := _viewport_to_world(screen_pos)
	_camera.position += world_before - world_after
	_debug_overlay.queue_redraw()


func _hit_test_handle(world_pos: Vector2) -> Marker2D:
	var hit_radius := HANDLE_HIT_RADIUS_PX / _camera.zoom.x
	var best: Marker2D = null
	var best_dist := hit_radius
	for handle_name: String in _ik_handles:
		var handle := _ik_handles[handle_name] as Marker2D
		if handle == null or not is_instance_valid(handle):
			continue
		var dist := world_pos.distance_to(handle.global_position)
		if dist <= best_dist:
			best = handle
			best_dist = dist
	return best

# ---------------------------------------------------------------------------
# Debug overlay drawing
# ---------------------------------------------------------------------------

func _on_debug_overlay_draw() -> void:
	if _show_bones:
		_draw_bones()
	if _show_ik:
		_draw_ik_handles()


func _draw_bones() -> void:
	if _skeleton == null or not is_instance_valid(_skeleton):
		return
	var zoom := _camera.zoom.x
	var line_w := BONE_LINE_WIDTH_PX / zoom
	var dot_r := JOINT_DOT_RADIUS_PX / zoom

	for i: int in _skeleton.get_bone_count():
		var bone := _skeleton.get_bone(i)
		if bone == null:
			continue
		var color := _bone_color(bone.name)
		var origin := bone.global_position
		_debug_overlay.draw_circle(origin, dot_r, color)

		# Collect the bone's Bone2D children (true bone segments, including the
		# nested lower bones).
		var bone_children: Array[Bone2D] = []
		for child in bone.get_children():
			if child is Bone2D:
				bone_children.append(child as Bone2D)

		if bone_children.is_empty():
			# Leaf bone — draw out to its IK target (forearm/shin), falling
			# back to the bone's own direction (bone_angle + rotation) when
			# there is no target (e.g. the Head, whose target is a LookAt aim
			# point, not a joint).
			var target := _leaf_bone_target(bone)
			if target != null:
				_debug_overlay.draw_line(origin, target.global_position, color, line_w)
			else:
				var fallback := origin + Vector2(bone.get_length(), 0.0).rotated(deg_to_rad(bone.bone_angle)).rotated(bone.global_rotation)
				_debug_overlay.draw_line(origin, fallback, color, line_w)
		else:
			for child_bone in bone_children:
				_debug_overlay.draw_line(origin, child_bone.global_position, color, line_w)


func _leaf_bone_target(bone: Bone2D) -> Node2D:
	if not LEAF_BONE_IK_PATHS.has(bone.name):
		return null
	if _rig == null or not is_instance_valid(_rig):
		return null
	return _rig.get_node_or_null(NodePath(str(LEAF_BONE_IK_PATHS[bone.name]))) as Node2D


func _draw_ik_handles() -> void:
	var zoom := _camera.zoom.x
	var r := HANDLE_DRAW_RADIUS_PX / zoom
	var outline_w := 1.5 / zoom

	for handle_name: String in _ik_handles:
		var handle := _ik_handles[handle_name] as Marker2D
		if handle == null or not is_instance_valid(handle):
			continue
		var color := _handle_color(handle_name)
		var pos := handle.global_position
		_debug_overlay.draw_circle(pos, r, color)
		_debug_overlay.draw_arc(pos, r, 0.0, TAU, 24, Color(1.0, 1.0, 1.0, 0.8), outline_w)

	# Head aim line — visual aid showing what the head bone is aiming at.
	var head_handle: Marker2D = _ik_handles.get("Head", null) as Marker2D
	if head_handle != null and is_instance_valid(head_handle) \
			and _skeleton != null and is_instance_valid(_skeleton):
		var head_bone := _skeleton.get_node_or_null(NodePath("Torso/Head")) as Bone2D
		if head_bone != null and is_instance_valid(head_bone):
			_debug_overlay.draw_line(
				head_bone.global_position,
				head_handle.global_position,
				Color(1.0, 1.0, 0.0, 0.5),
				1.5 / zoom
			)


func _handle_color(handle_name: String) -> Color:
	match handle_name:
		"Head":
			return HANDLE_COLOR_HEAD
		"Torso":
			return HANDLE_COLOR_TORSO
		_:
			return HANDLE_COLOR_HAND if handle_name.ends_with("Hand") else HANDLE_COLOR_FOOT


func _bone_color(bone_name: String) -> Color:
	if bone_name.begins_with("Left"):
		return BONE_COLOR_LEFT
	if bone_name.begins_with("Right"):
		return BONE_COLOR_RIGHT
	return BONE_COLOR_CENTRAL

# ---------------------------------------------------------------------------
# Spawn / swap
# ---------------------------------------------------------------------------

func _on_open_pressed() -> void:
	_file_dialog.popup_centered_ratio(0.6)


func _on_quick_load(path: String) -> void:
	_load_and_spawn(path)


func _on_file_selected(path: String) -> void:
	_load_and_spawn(path)


func _load_and_spawn(path: String) -> void:
	_free_current_rig()

	var rig := StickmanFactory.spawn(path)
	if rig == null:
		_status_label.text = "Error: failed to load " + path.get_file()
		return

	_rig = rig
	_world.add_child(_rig)
	_world.move_child(_rig, 0)   # keep the rig behind the debug overlay

	_resolve_rig_nodes()
	_ensure_modification_stack_enabled()

	_status_label.text = path.get_file()
	_recenter_camera()
	_debug_overlay.queue_redraw()


func _free_current_rig() -> void:
	if _rig != null and is_instance_valid(_rig):
		_rig.queue_free()
	_rig = null
	_skeleton = null
	_ik_handles.clear()
	_dragging_handle = null


func _resolve_rig_nodes() -> void:
	_skeleton = _rig.get_node_or_null(NodePath(SKELETON_PATH)) as Skeleton2D
	if _skeleton == null:
		push_warning("TestHarness: missing '%s' node in rig." % SKELETON_PATH)

	_ik_handles.clear()
	for handle_name: String in IK_HANDLE_PATHS:
		var handle := _rig.get_node_or_null(NodePath(IK_HANDLE_PATHS[handle_name])) as Marker2D
		if handle != null:
			_ik_handles[handle_name] = handle
		else:
			push_warning("TestHarness: missing IK handle '%s'." % IK_HANDLE_PATHS[handle_name])


func _ensure_modification_stack_enabled() -> void:
	if _skeleton == null:
		return
	var stack: SkeletonModificationStack2D = _skeleton.modification_stack
	if stack != null:
		stack.enabled = true
	else:
		push_warning("TestHarness: Skeleton2D has no modification_stack assigned.")


func _recenter_camera() -> void:
	if _rig == null:
		return
	# The rig root sits at the hips; nudge the camera up so the whole figure is
	# roughly centered in the viewport.
	_camera.position = _rig.global_position + Vector2(0.0, -50.0)
	_camera.zoom = Vector2.ONE
	_debug_overlay.queue_redraw()

# ---------------------------------------------------------------------------
# Checkbox handlers
# ---------------------------------------------------------------------------

func _on_show_bones_toggled(pressed: bool) -> void:
	_show_bones = pressed
	_debug_overlay.queue_redraw()


func _on_show_ik_toggled(pressed: bool) -> void:
	_show_ik = pressed
	_debug_overlay.queue_redraw()