settled-reach/client/scripts/sandbox/locomotion_anim.gd

class_name LocomotionAnim
extends RefCounted
## T-1088 gait state machine (design §6) — proto-production.
## Slaves animation to the rig's motion channel: clip selection keys off render
## velocity (never input), transitions are edge-triggered crossfades, and playback
## rate is cadence-synced so foot fall matches actual ground speed (§6.2).
##
## Wiring (sandbox root, design §14 group C):
##   var anim := LocomotionAnim.new()
##   anim.setup(player_rig, character_visual)   # after both exist in-tree
##   anim.update(delta)                          # each frame, after the rig moved
## Teleports: setup() auto-connects the rig's `teleported` signal to notify_teleport()
## when the signal exists; otherwise call notify_teleport() alongside the rig snap.
##
## The rig ref is duck-typed against the §4.0 contract getters — `stance: String`,
## `is_moving: bool`, `current_speed: float` (m/s, constant per leg) — so the machine
## needs no rig class and a test stub drives it headless. The visual ref is duck-typed
## against the §6.3 additive CharacterVisual API: play_animation(name, blend_time)
## and get_animation_player().
##
## Clip strings live ONLY in SandboxConstants.GAIT_CLIP (§6.1) — never here.

## Q-063 seam (footstep audio): emitted once per edge-triggered gait change with the
## clip now playing (the clip identifies stance + motion; Idle clips = no footsteps).
## Clip phase for footstep timing is available via CharacterVisual.get_animation_player().
signal gait_changed(clip: StringName)

## §6.3 pre-flagged caveat (the SKIP_PHASE_SEEK flag): in Godot 4.6, seek() during a
## custom_blend crossfade may cancel the blend (unverified against the live scene).
## If gait<->gait transitions visibly pop instead of crossfading, set this true to
## drop the phase-preserving seek — the 0.15 s blend masks the leg-beat resync
## acceptably (tune-by-eye; record the outcome on T-1088 per design §11.9).
var skip_phase_seek: bool = false

var _rig = null  # duck-typed rig (locomotion_rig.gd): stance / is_moving / current_speed
var _visual = null  # duck-typed CharacterVisual: play_animation() / get_animation_player()
var _current_clip: StringName = &""  # empty = nothing played yet (first play hard-cuts)
var _current_moving: bool = false


## Pure gait table lookup (§6.1). Unknown stances warn and fall back to the Walk row
## (mirrors GameState.player_stance's wire default).
static func gait(stance: String, is_moving: bool) -> StringName:
	if not SandboxConstants.GAIT_CLIP.has(stance):
		push_warning("LocomotionAnim: unknown stance '%s' — defaulting to Walk" % stance)
		stance = "Walk"
	var row: Dictionary = SandboxConstants.GAIT_CLIP[stance]
	return StringName(row["moving"]) if is_moving else StringName(row["idle"])


## Pure blend-table selection (§6.3). Any transition into or out of a Crouch_* clip
## takes the crouch blend; otherwise the idle/gait edge decides.
static func blend_for(
	from_clip: StringName, to_clip: StringName, from_moving: bool, to_moving: bool
) -> float:
	var blends: Dictionary = SandboxConstants.BLEND
	if String(from_clip).begins_with("Crouch") or String(to_clip).begins_with("Crouch"):
		return float(blends["crouch"])
	if not from_moving and to_moving:
		return float(blends["idle_to_gait"])
	if from_moving and not to_moving:
		return float(blends["gait_to_idle"])
	return float(blends["gait_to_gait"])


## The clip currently driven (empty StringName until the first play) — surfaced by
## the sandbox root for the DebugHud "clip" readout.
func get_current_clip() -> StringName:
	return _current_clip


## Store the rig + visual refs. Auto-connects the rig's `teleported(pos_m)` signal
## (if it exposes one) to the hard reset.
func setup(rig, visual) -> void:
	_rig = rig
	_visual = visual
	if rig != null and rig.has_signal("teleported"):
		rig.teleported.connect(_on_rig_teleported)


# Signal adapter — locomotion_rig.gd emits teleported(pos_m: Vector3); the anim
# reset doesn't need the position, only the rig's post-snap state.
func _on_rig_teleported(_pos_m: Vector3) -> void:
	notify_teleport()


## Per-frame drive — call after the rig's own interpolation for the frame.
func update(_delta: float) -> void:
	if _rig == null or _visual == null:
		return
	_apply_state(_rig.stance, _rig.is_moving, _rig.current_speed)


## Teleport hard reset (§6.3): a cross-map jump must not smear — replay the correct
## clip for the rig's post-snap state with the 0.0 teleport blend, rewound to phase 0.
func notify_teleport() -> void:
	if _rig == null or _visual == null:
		return
	var moving: bool = _rig.is_moving
	var clip := gait(_rig.stance, moving)
	var changed := clip != _current_clip
	_visual.play_animation(clip, float(SandboxConstants.BLEND["teleport"]))
	var player = _visual.get_animation_player()
	if player != null:
		# play() on the already-current clip does not rewind — force the hard reset.
		player.seek(0.0, false)
	_current_clip = clip
	_current_moving = moving
	_update_speed_scale(clip, moving, _rig.current_speed)
	if changed:
		gait_changed.emit(clip)


# State application, separated from the rig read so tests drive it directly.
func _apply_state(stance: String, moving: bool, speed: float) -> void:
	var clip := gait(stance, moving)
	if clip != _current_clip:
		_transition_to(clip, moving)
	_update_speed_scale(clip, moving, speed)


# Edge-triggered transition (§6.3): fires only on clip change, so loops never
# restart mid-cycle (a stance toggle between Walk/Careful/Sprint idle keeps the
# shared Idle clip untouched).
func _transition_to(clip: StringName, moving: bool) -> void:
	var first_play := _current_clip == &""
	var blend := -1.0  # first-ever play: hard cut (the character just appeared)
	if not first_play:
		blend = blend_for(_current_clip, clip, _current_moving, moving)
	# gait<->gait phase preservation (§6.3): capture the leg beat before switching,
	# then re-seek into the new clip so feet keep their rhythm across the blend.
	var phase := -1.0
	if not first_play and _current_moving and moving and not skip_phase_seek:
		phase = _capture_phase()
	_visual.play_animation(clip, blend)
	if phase >= 0.0:
		_seek_phase(clip, phase)
	_current_clip = clip
	_current_moving = moving
	gait_changed.emit(clip)


# Cadence sync (§6.2): while moving, speed_scale = clamp(speed / NATIVE_MPS[clip],
# 0.6, 1.8). Rig speed is constant per leg (dist/interval, §4.1), so the scale is
# constant per leg — no within-step wobble; catch-up bursts push it up so feet chase
# instead of skating. Idle clips always run at 1.0.
func _update_speed_scale(clip: StringName, moving: bool, speed: float) -> void:
	var player = _visual.get_animation_player()
	if player == null:
		return
	if not moving:
		player.speed_scale = 1.0
		return
	var native: float = SandboxConstants.NATIVE_MPS.get(String(clip), 0.0)
	if native <= 0.0:
		player.speed_scale = 1.0  # moving clip missing from NATIVE_MPS — table drift
		return
	var limits: Vector2 = SandboxConstants.SPEED_SCALE_CLAMP
	player.speed_scale = clampf(speed / native, limits.x, limits.y)


# Normalized phase [0,1) of the currently playing clip, or -1.0 when unavailable.
func _capture_phase() -> float:
	var player = _visual.get_animation_player()
	if player == null or String(player.current_animation).is_empty():
		return -1.0
	var length: float = player.current_animation_length
	if length <= 0.0:
		return -1.0
	return fposmod(player.current_animation_position, length) / length


# Seek the new clip to the preserved phase without flushing the pose (update=false)
# so the crossfade started by play() keeps blending. See skip_phase_seek caveat.
func _seek_phase(clip: StringName, phase: float) -> void:
	var player = _visual.get_animation_player()
	if player == null:
		return
	var anim: Animation = player.get_animation(clip)
	if anim == null:
		return
	player.seek(phase * anim.length, false)