frontend/src/scene/useNpcActorAnimation.ts

import { useFrame } from "@react-three/fiber";
import type { RefObject } from "react";
import type { Group, Mesh } from "three";
import { MathUtils, Vector3 } from "three";

import type { EntitySnapshot } from "../types";
import { angularDistance, dampAngle } from "./characterUtils";
import type { NpcBodyRefs } from "./NpcBody";

type NpcAnimationRefs = NpcBodyRefs & {
  groupRef: RefObject<Group | null>;
  pulseRef: RefObject<Mesh | null>;
};

type NpcActorAnimationOptions = {
  entity: EntitySnapshot;
  isSelected: boolean;
  refs: NpcAnimationRefs;
  target: readonly [number, number, number];
  focusTarget: readonly [number, number, number] | null;
  moveDirection: Vector3;
  animationPhase: number;
  walkBlendRef: RefObject<number>;
  attackBlendRef: RefObject<number>;
};

export function isAttackingIntention(intention: string): boolean {
  return /^attacking\b/.test(intention) || intention.includes("fighting");
}

export function useNpcActorAnimation({
  entity,
  isSelected,
  refs,
  target,
  focusTarget,
  moveDirection,
  animationPhase,
  walkBlendRef,
  attackBlendRef,
}: NpcActorAnimationOptions) {
  useFrame((state, delta) => {
    const time = state.clock.elapsedTime + animationPhase;
    const walkTarget = updatePosition(
      entity,
      refs.groupRef.current,
      target,
      focusTarget,
      moveDirection,
      delta,
    );

    if (refs.pulseRef.current) {
      const pulse = 1 + Math.sin(state.clock.elapsedTime * 4) * 0.08;
      refs.pulseRef.current.scale.setScalar(isSelected ? pulse : 0.001);
    }

    walkBlendRef.current = MathUtils.damp(walkBlendRef.current, walkTarget, 7, delta);
    const attackTarget =
      entity.state.is_alive && isAttackingIntention(entity.state.intention) ? 1 : 0;
    attackBlendRef.current = MathUtils.damp(attackBlendRef.current, attackTarget, 8, delta);
    if (!entity.state.is_alive) {
      animateDeath(refs, delta);
      return;
    }

    animateWalk(refs, time, walkBlendRef.current, delta);
    animateAttack(refs, time, attackBlendRef.current);
  });
}

function updatePosition(
  entity: EntitySnapshot,
  group: Group | null,
  target: readonly [number, number, number],
  focusTarget: readonly [number, number, number] | null,
  moveDirection: Vector3,
  delta: number,
): number {
  if (!group) {
    return 0;
  }

  group.position.y = MathUtils.damp(group.position.y, target[1], 8, delta);
  if (!entity.state.is_alive) {
    return 0;
  }

  const deltaX = target[0] - group.position.x;
  const deltaZ = target[2] - group.position.z;
  const distanceToTarget = Math.hypot(deltaX, deltaZ);
  if (distanceToTarget <= 0.025) {
    group.position.x = target[0];
    group.position.z = target[2];
    faceFocusTarget(group, focusTarget, delta);
    return 0;
  }

  moveDirection.set(deltaX / distanceToTarget, 0, deltaZ / distanceToTarget);
  const desiredRotation = Math.atan2(moveDirection.x, moveDirection.z);
  const rotationDelta = angularDistance(group.rotation.y, desiredRotation);
  const alignment = MathUtils.clamp(1 - rotationDelta / (Math.PI * 0.62), 0, 1);
  const distanceBlend = MathUtils.clamp(distanceToTarget / 0.45, 0, 1);
  const movementBlend = distanceBlend * MathUtils.lerp(0.2, 1, alignment);
  const step = Math.min(distanceToTarget, 1.65 * MathUtils.lerp(0.18, 1, movementBlend) * delta);

  group.position.x += moveDirection.x * step;
  group.position.z += moveDirection.z * step;
  group.rotation.y = dampAngle(group.rotation.y, desiredRotation, 5.5, delta);
  return movementBlend;
}

function faceFocusTarget(
  group: Group,
  focusTarget: readonly [number, number, number] | null,
  delta: number,
) {
  if (!focusTarget) {
    return;
  }
  const deltaX = focusTarget[0] - group.position.x;
  const deltaZ = focusTarget[2] - group.position.z;
  if (Math.hypot(deltaX, deltaZ) <= 0.05) {
    return;
  }
  group.rotation.y = dampAngle(group.rotation.y, Math.atan2(deltaX, deltaZ), 5.5, delta);
}

function animateDeath(refs: NpcAnimationRefs, delta: number) {
  if (refs.characterRef.current) {
    refs.characterRef.current.position.y = MathUtils.damp(
      refs.characterRef.current.position.y,
      0.12,
      5,
      delta,
    );
    refs.characterRef.current.rotation.x = MathUtils.damp(
      refs.characterRef.current.rotation.x,
      Math.PI / 2,
      4,
      delta,
    );
    refs.characterRef.current.rotation.z = MathUtils.damp(
      refs.characterRef.current.rotation.z,
      0.22,
      4,
      delta,
    );
  }

  // Settle the torso and head out of whatever walk/attack pose they were in.
  dampGroupToRest(refs.torsoRef, delta);
  dampGroupToRest(refs.headRef, delta);

  // Limbs collapse into a relaxed, slightly splayed sprawl. Reset every channel
  // (not just rotation.x) so no leftover stride/chop rotation freezes mid-motion.
  dampLimb(refs.leftArmRef, -0.1, -0.4, delta);
  dampLimb(refs.rightArmRef, -0.1, 0.4, delta);
  dampLimb(refs.leftLegRef, 0.08, -0.18, delta);
  dampLimb(refs.rightLegRef, 0.08, 0.18, delta);
}

function dampGroupToRest(ref: RefObject<Group | null>, delta: number) {
  if (!ref.current) {
    return;
  }
  ref.current.rotation.x = MathUtils.damp(ref.current.rotation.x, 0, 5, delta);
  ref.current.rotation.y = MathUtils.damp(ref.current.rotation.y, 0, 5, delta);
  ref.current.rotation.z = MathUtils.damp(ref.current.rotation.z, 0, 5, delta);
}

function dampLimb(
  ref: RefObject<Group | null>,
  xRotation: number,
  zRotation: number,
  delta: number,
) {
  if (ref.current) {
    ref.current.rotation.x = MathUtils.damp(ref.current.rotation.x, xRotation, 5, delta);
    ref.current.rotation.y = MathUtils.damp(ref.current.rotation.y, 0, 5, delta);
    ref.current.rotation.z = MathUtils.damp(ref.current.rotation.z, zRotation, 5, delta);
  }
}

function animateWalk(refs: NpcAnimationRefs, time: number, walkBlend: number, delta: number) {
  const stride = Math.sin(time * 7.2) * walkBlend;
  const counterStride = Math.sin(time * 7.2 + Math.PI) * walkBlend;
  const bob = Math.abs(stride) * 0.055;

  if (refs.characterRef.current) {
    refs.characterRef.current.position.y = bob;
    refs.characterRef.current.rotation.x = MathUtils.damp(
      refs.characterRef.current.rotation.x,
      0,
      8,
      delta,
    );
    refs.characterRef.current.rotation.z = Math.sin(time * 2.1) * 0.035 * walkBlend;
  }
  if (refs.torsoRef.current) {
    refs.torsoRef.current.rotation.x = Math.sin(time * 7.2) * 0.035 * walkBlend;
  }
  if (refs.headRef.current) {
    refs.headRef.current.rotation.y = Math.sin(time * 8.2) * 0.025 * walkBlend;
    refs.headRef.current.rotation.z = Math.sin(time * 3.1) * 0.018 * walkBlend;
  }
  setWalkLimb(refs.leftArmRef, counterStride, -0.16, 0.62, walkBlend);
  setWalkLimb(refs.rightArmRef, stride, 0.16, 0.62, walkBlend);
  setWalkLimb(refs.leftLegRef, stride, 0, 0.48, walkBlend);
  setWalkLimb(refs.rightLegRef, counterStride, 0, 0.48, walkBlend);
}

function animateAttack(refs: NpcAnimationRefs, time: number, attackBlend: number) {
  if (attackBlend <= 0.001) {
    return;
  }

  // Overhead chop with the right arm: raised (~-2.2) down to extended (~-0.7).
  const swing = (Math.sin(time * 10.5) + 1) / 2;
  const chop = -2.2 + swing * 1.5;

  if (refs.rightArmRef.current) {
    refs.rightArmRef.current.rotation.x = MathUtils.lerp(
      refs.rightArmRef.current.rotation.x,
      chop,
      attackBlend,
    );
    refs.rightArmRef.current.rotation.z = MathUtils.lerp(
      refs.rightArmRef.current.rotation.z,
      0.18,
      attackBlend,
    );
  }
  if (refs.leftArmRef.current) {
    refs.leftArmRef.current.rotation.x = MathUtils.lerp(
      refs.leftArmRef.current.rotation.x,
      -0.55,
      attackBlend,
    );
    refs.leftArmRef.current.rotation.z = MathUtils.lerp(
      refs.leftArmRef.current.rotation.z,
      -0.3,
      attackBlend,
    );
  }
  if (refs.torsoRef.current) {
    refs.torsoRef.current.rotation.x = MathUtils.lerp(
      refs.torsoRef.current.rotation.x,
      0.12 - swing * 0.18,
      attackBlend,
    );
    // Walk never writes these channels, so scale by blend to decay back to rest.
    refs.torsoRef.current.rotation.y = (-0.16 + swing * 0.28) * attackBlend;
  }
  if (refs.headRef.current) {
    refs.headRef.current.rotation.x = -0.08 * attackBlend;
  }
}

function setWalkLimb(
  ref: RefObject<Group | null>,
  stride: number,
  zRotation: number,
  scale: number,
  walkBlend: number,
) {
  if (!ref.current) {
    return;
  }
  ref.current.rotation.x = stride * scale;
  ref.current.rotation.z = zRotation * walkBlend;
}