/*
 * Author: Ruthberg
 *
 * Calculates the muzzle velocity shift caused by different barrel lengths
 *
 * Arguments:
 * 0: barrel length - mm
 * 1: muzzle velocity lookup table - m/s <ARRAY>
 * 2: barrel length lookup table - mm <ARRAY>
 * 3: muzzle velocity - m/s <NUMBER>
 *
 * Return Value:
 * 0: muzzle velocity shift - m/s <NUMBER>
 *
 * Return value:
 * None
 */
#include "script_component.hpp"

private ["_barrelLength", "_muzzleVelocityTable", "_barrelLengthTable", "_muzzleVelocity", "_lowerIndex", "_upperIndex", "_barrelLengthRatio", "_muzzleVelocityNew"];
_barrelLength        = _this select 0;
_muzzleVelocityTable = _this select 1;
_barrelLengthTable   = _this select 2;
_muzzleVelocity      = _this select 3;

if (_barrelLength == 0) exitWith { 0 };
if (count _muzzleVelocityTable != count _barrelLengthTable) exitWith { 0 };
if (count _muzzleVelocityTable == 0 || count _barrelLengthTable == 0) exitWith { 0 };
if (count _muzzleVelocityTable == 1) exitWith { (_muzzleVelocityTable select 0) - _muzzleVelocity };

_lowerIndex = 0;
_upperIndex = (count _barrelLengthTable) - 1;

if (_barrelLength <= (_barrelLengthTable select _lowerIndex)) exitWith { (_muzzleVelocityTable select _lowerIndex) - _muzzleVelocity };
if (_barrelLength >= (_barrelLengthTable select _upperIndex)) exitWith { (_muzzleVelocityTable select _upperIndex) - _muzzleVelocity };

for "_i" from 0 to (count _barrelLengthTable) - 1 do {
    if (_barrelLength >= _barrelLengthTable select _i) then {
        _lowerIndex = _i;
    };
};
for "_i" from (count _barrelLengthTable) - 1 to 0 step -1 do {
    if (_barrelLength <= _barrelLengthTable select _i) then {
        _upperIndex = _i;
    };
};

_barrelLengthRatio = 0;
if ((_barrelLengthTable select _upperIndex) - (_barrelLengthTable select _lowerIndex) > 0) then {
    _barrelLengthRatio = ((_barrelLengthTable select _upperIndex) - _barrelLength) / ((_barrelLengthTable select _upperIndex) - (_barrelLengthTable select _lowerIndex));
};

_muzzleVelocityNew = (_muzzleVelocityTable select _lowerIndex) + ((_muzzleVelocityTable select _upperIndex) - (_muzzleVelocityTable select _lowerIndex)) * (1 - _barrelLengthRatio);

_muzzleVelocityNew - _muzzleVelocity