/*
 * CSB Zombie Knockback
 * Copyright (C) 2026 counter-strike-boost.com
 *
 * Pushes a zombie backwards when it is shot. On Ham_TakeDamage the plugin adds
 * a velocity vector along the attacker's aim, scaled by the damage, the weapon
 * and the zombie's speed. This is the core "feel" plugin of any zombie server.
 *
 * Inspired by the knockback found in the classic Zombie Plague mod. This is an
 * independent GPL re-implementation; no original code is reused. It has no hard
 * dependency on a specific zombie mod: a zombie is simply any player on the team
 * chosen by csb_kb_zombie_team.
 *
 * This program is free software: you can redistribute it and/or modify it under
 * the terms of the GNU General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later
 * version. See <https://www.gnu.org/licenses/> for details.
 */

#include <amxmodx>
#include <fakemeta>
#include <hamsandwich>

new const PLUGIN[] = "CSB Zombie Knockback"
new const VERSION[] = "1.0.0"
new const AUTHOR[]  = "counter-strike-boost.com"

new g_pEnabled, g_pPower, g_pZombieTeam, g_pAirMul, g_pMaxSpeed

/* per-weapon multipliers, indexed by CSW_* id (0..30) */
new Float:g_fWeaponMul[31]

public plugin_init()
{
    register_plugin(PLUGIN, VERSION, AUTHOR)

    g_pEnabled    = register_cvar("csb_kb_enabled", "1")
    g_pPower      = register_cvar("csb_kb_power", "6.0")
    g_pZombieTeam = register_cvar("csb_kb_zombie_team", "1")   /* 1 = T, 2 = CT */
    g_pAirMul     = register_cvar("csb_kb_air_mul", "1.4")
    g_pMaxSpeed   = register_cvar("csb_kb_max_speed", "1200.0")

    RegisterHam(Ham_TakeDamage, "player", "fwTakeDamage")

    setupWeaponMultipliers()
}

setupWeaponMultipliers()
{
    /* default 1.0 for everything, then tune the ones that feel wrong */
    for (new i = 0; i < sizeof(g_fWeaponMul); i++)
        g_fWeaponMul[i] = 1.0

    g_fWeaponMul[CSW_KNIFE]   = 4.0
    g_fWeaponMul[CSW_AWP]     = 2.0
    g_fWeaponMul[CSW_SCOUT]   = 1.8
    g_fWeaponMul[CSW_M3]      = 0.6
    g_fWeaponMul[CSW_XM1014]  = 0.5
    g_fWeaponMul[CSW_DEAGLE]  = 1.6
    g_fWeaponMul[CSW_M249]    = 0.7
}

public fwTakeDamage(victim, inflictor, attacker, Float:damage, damagebits)
{
    if (!get_pcvar_num(g_pEnabled))
        return HAM_IGNORED

    if (attacker < 1 || attacker > get_maxplayers() || attacker == victim)
        return HAM_IGNORED

    if (!is_user_alive(victim) || !is_user_connected(attacker))
        return HAM_IGNORED

    /* only push players who are on the zombie team */
    if (get_user_team(victim) != get_pcvar_num(g_pZombieTeam))
        return HAM_IGNORED

    new weapon = get_user_weapon(attacker)
    new Float:mul = (weapon >= 0 && weapon < sizeof(g_fWeaponMul)) ? g_fWeaponMul[weapon] : 1.0

    /* direction: from attacker's aim, so grenades/knife still shove correctly */
    new Float:vAngle[3], Float:vForward[3]
    pev(attacker, pev_v_angle, vAngle)
    angle_vector(vAngle, ANGLEVECTOR_FORWARD, vForward)

    new Float:power = damage * get_pcvar_float(g_pPower) * mul

    /* zombies get shoved harder in the air, it looks better */
    new flags = pev(victim, pev_flags)
    if (!(flags & FL_ONGROUND))
        power *= get_pcvar_float(g_pAirMul)

    new Float:vel[3]
    pev(victim, pev_velocity, vel)

    vel[0] += vForward[0] * power
    vel[1] += vForward[1] * power
    vel[2] += vForward[2] * power * 0.35   /* a little lift, not a launch */

    /* clamp so a burst does not fling a zombie across the map */
    new Float:maxSpeed = get_pcvar_float(g_pMaxSpeed)
    new Float:speed = vector_length(vel)

    if (speed > maxSpeed && speed > 0.0)
    {
        new Float:scale = maxSpeed / speed
        vel[0] *= scale
        vel[1] *= scale
        vel[2] *= scale
    }

    set_pev(victim, pev_velocity, vel)

    return HAM_IGNORED
}