using Unity.Mathematics;

namespace ProjectM.Simulation
{
    /// <summary>
    /// Pure, deterministic cone hit-test for the MC-4 melee cleave. Shares the EXACT range + bearing predicate with
    /// <see cref="AutoTarget"/> (planar XZ distance gate + <c>dot(bearing, facing) &gt;= cos(halfAngle)</c>) but as a
    /// per-candidate boolean, so the cleave can collect ALL enemies in the cone — <see cref="AutoTarget.Resolve"/> is a
    /// single-winner reducer and cannot be reused for collect-all (MC-4 review REUSE-1). Burst-safe, allocation-free,
    /// no wall-clock / no randomness; intended to run server-side inside the predicted <c>MeleeComboSystem</c>.
    /// </summary>
    public static class MeleeConeMath
    {
        /// <summary>
        /// True iff <paramref name="targetPos"/> lies within <paramref name="range"/> (planar XZ) of
        /// <paramref name="from"/> AND its bearing from <paramref name="from"/> is within the cone half-angle of
        /// <paramref name="facingDir"/> (<paramref name="cosHalfAngle"/> = cos(halfAngle)). A coincident
        /// (zero-distance) target is excluded (undefined bearing). <paramref name="facingDir"/> must be
        /// caller-normalized; a zero-length facing or a non-positive range returns false.
        /// </summary>
        public static bool InCone(float3 from, float2 facingDir, float range, float cosHalfAngle, float3 targetPos)
        {
            if (range <= 0f || math.lengthsq(facingDir) < 1e-6f)
                return false;

            float3 offset = targetPos - from;
            float2 planar = new float2(offset.x, offset.z);
            float distSq = math.lengthsq(planar);

            if (distSq < 1e-6f)
                return false;                 // coincident -> undefined bearing
            if (distSq > range * range)
                return false;                 // out of range

            float2 bearing = planar * math.rsqrt(distSq); // normalized planar bearing
            return math.dot(bearing, facingDir) >= cosHalfAngle;
        }
    }
}