const float CBC_ORDER_EXCLUSIVE = 3;
const float CBC_ORDER_FIRST = 1;
const float CBC_ORDER_LAST = 2;
const float CBC_ORDER_ANY = 4;

float CallbackChain_ReturnValue; // read-only field of the current return value

entity CallbackChain_New(string name);
float CallbackChain_Add(entity cb, float() func, float order);
float CallbackChain_Remove(entity cb, float() func);
// a callback function is like this:
// float mycallback(entity me)
// {
//   do something
//   return r;
// }
float CallbackChain_Call(entity cb);

const float MUTATOR_REMOVING = 0;
const float MUTATOR_ADDING = 1;
const float MUTATOR_ROLLING_BACK = 2;
typedef float(float) mutatorfunc_t;
float Mutator_Add(mutatorfunc_t func, string name);
void Mutator_Remove(mutatorfunc_t func, string name); // calls error() on fail

#define MUTATOR_ADD(name) Mutator_Add(MUTATOR_##name, #name)
#define MUTATOR_REMOVE(name) Mutator_Remove(MUTATOR_##name, #name)
#define MUTATOR_DEFINITION(name) float MUTATOR_##name(float mode)
#define MUTATOR_DECLARATION(name) float MUTATOR_##name(float mode)
#define MUTATOR_HOOKFUNCTION(name) float HOOKFUNCTION_##name()
#define MUTATOR_HOOK(cb,func,order) do { if(mode == MUTATOR_ADDING) { if(!HOOK_##cb) HOOK_##cb = CallbackChain_New(#cb); if(!CallbackChain_Add(HOOK_##cb,HOOKFUNCTION_##func,order)) { print("HOOK FAILED: ", #func, "\n"); return 1; } } else if(mode == MUTATOR_REMOVING || mode == MUTATOR_ROLLING_BACK) { if(HOOK_##cb) CallbackChain_Remove(HOOK_##cb,HOOKFUNCTION_##func); } } while(0)
#define MUTATOR_ONADD if(mode == MUTATOR_ADDING)
#define MUTATOR_ONREMOVE if(mode == MUTATOR_REMOVING)
#define MUTATOR_ONROLLBACK_OR_REMOVE if(mode == MUTATOR_REMOVING || mode == MUTATOR_ROLLING_BACK)

#define MUTATOR_HOOKABLE(cb) entity HOOK_##cb
#define MUTATOR_CALLHOOK(cb) CallbackChain_Call(HOOK_##cb)

#define MUTATOR_RETURNVALUE CallbackChain_ReturnValue




// register all possible hooks here

MUTATOR_HOOKABLE(MakePlayerObserver);
	// called when a player becomes observer, after shared setup

MUTATOR_HOOKABLE(PutClientInServer);
	entity self; // client wanting to spawn

MUTATOR_HOOKABLE(PlayerSpawn);
	entity spawn_spot; // spot that was used, or world
	// called when a player spawns as player, after shared setup, before his weapon is chosen (so items may be changed in here)

MUTATOR_HOOKABLE(reset_map_global);
	// called in reset_map

MUTATOR_HOOKABLE(reset_map_players);
	// called in reset_map

MUTATOR_HOOKABLE(ForbidPlayerScore_Clear);
	// returns 1 if clearing player score shall not be allowed

MUTATOR_HOOKABLE(ClientDisconnect);
	// called when a player disconnects

MUTATOR_HOOKABLE(PlayerDies);
	// called when a player dies to e.g. remove stuff he was carrying.
	// INPUT:
		entity frag_inflictor;
		entity frag_attacker;
		entity frag_target; // same as self
		float frag_deathtype;

MUTATOR_HOOKABLE(PlayerJump);
	// called when a player presses the jump key
	// INPUT, OUTPUT:
		float player_multijump;
		float player_jumpheight;

MUTATOR_HOOKABLE(GiveFragsForKill);
	// called when someone was fragged by "self", and is expected to change frag_score to adjust scoring for the kill
	// INPUT:
		entity frag_attacker; // same as self
		entity frag_target;
	// INPUT, OUTPUT:
		float frag_score;

MUTATOR_HOOKABLE(MatchEnd);
	// called when the match ends

MUTATOR_HOOKABLE(GetTeamCount);
	// should adjust ret_float to contain the team count
	// INPUT, OUTPUT:
		float ret_float;

MUTATOR_HOOKABLE(SpectateCopy);
	// copies variables for spectating "other" to "self"
	// INPUT:
		entity other;

MUTATOR_HOOKABLE(ForbidThrowCurrentWeapon);
	// returns 1 if throwing the current weapon shall not be allowed

MUTATOR_HOOKABLE(WeaponRateFactor);
	// allows changing attack rate
	// INPUT, OUTPUT:
		float weapon_rate;

MUTATOR_HOOKABLE(SetStartItems);
	// adjusts {warmup_}start_{items,weapons,ammo_{cells,plasma,rockets,nails,shells,fuel}}

MUTATOR_HOOKABLE(BuildMutatorsString);
	// appends ":mutatorname" to ret_string for logging
	// INPUT, OUTPUT:
		string ret_string;

MUTATOR_HOOKABLE(BuildMutatorsPrettyString);
	// appends ", Mutator name" to ret_string for display
	// INPUT, OUTPUT:
		string ret_string;

MUTATOR_HOOKABLE(CustomizeWaypoint);
	// called every frame
	// customizes the waypoint for spectators
	// INPUT: self = waypoint, other = player, other.enemy = spectator

MUTATOR_HOOKABLE(FilterItem);
	// checks if the current item may be spawned (self.items and self.weapons may be read and written to, as well as the ammo_ fields)
	// return error to request removal

MUTATOR_HOOKABLE(TurretSpawn);
	// return error to request removal
	// INPUT: self - turret

MUTATOR_HOOKABLE(OnEntityPreSpawn);
	// return error to prevent entity spawn, or modify the entity

MUTATOR_HOOKABLE(PlayerPreThink);
	// runs in the event loop for players; is called for ALL player entities, also bots, also the dead, or spectators

MUTATOR_HOOKABLE(GetPressedKeys);
	// TODO change this into a general PlayerPostThink hook?

MUTATOR_HOOKABLE(PlayerPhysics);
	// called before any player physics, may adjust variables for movement,
	// is run AFTER bot code and idle checking

MUTATOR_HOOKABLE(GetCvars);
	// is meant to call GetCvars_handle*(get_cvars_s, get_cvars_f, cvarfield, "cvarname") for cvars this mutator needs from the client
	// INPUT:
		float get_cvars_f;
		string get_cvars_s;

MUTATOR_HOOKABLE(EditProjectile);
	// can edit any "just fired" projectile
	// INPUT:
		entity self;
		entity other;

MUTATOR_HOOKABLE(MonsterSpawn);
	// called when a monster spawns

MUTATOR_HOOKABLE(MonsterDies);
	// called when a monster dies
	// INPUT:
		entity frag_attacker;

MUTATOR_HOOKABLE(MonsterRespawn);
	// called when a monster wants to respawn
	// INPUT:
		entity other;

MUTATOR_HOOKABLE(MonsterDropItem);
	// called when a monster is dropping loot
	// INPUT, OUTPUT:
		.void() monster_loot;
		entity other;

MUTATOR_HOOKABLE(MonsterMove);
	// called when a monster moves
	// returning true makes the monster stop
	// INPUT:
		float monster_speed_run;
		float monster_speed_walk;
		entity monster_target;

MUTATOR_HOOKABLE(MonsterFindTarget);
	// called when a monster looks for another target

MUTATOR_HOOKABLE(MonsterCheckBossFlag);
    // called to change a random monster to a miniboss

MUTATOR_HOOKABLE(AllowMobSpawning);
	// called when a player tries to spawn a monster
	// return 1 to prevent spawning

MUTATOR_HOOKABLE(PlayerDamage_SplitHealthArmor);
	// called when a player gets damaged to e.g. remove stuff he was carrying.
	// INPUT:
		entity frag_inflictor;
		entity frag_attacker;
		entity frag_target; // same as self
		vector damage_force; // NOTE: this force already HAS been applied
	// INPUT, OUTPUT:
		float damage_take;
		float damage_save;

MUTATOR_HOOKABLE(PlayerDamage_Calculate);
	// called to adjust damage and force values which are applied to the player, used for e.g. strength damage/force multiplier
	// i'm not sure if I should change this around slightly (Naming of the entities, and also how they're done in g_damage).
	// INPUT:
		entity frag_attacker;
		entity frag_target;
		float frag_deathtype;
	// INPUT, OUTPUT:
		float frag_damage;
		float frag_mirrordamage;
		vector frag_force;

MUTATOR_HOOKABLE(PlayerPowerups);
	// called at the end of player_powerups() in cl_client.qc, used for manipulating the values which are set by powerup items.
	// INPUT
	entity self;
	float olditems; // also technically output, but since it is at the end of the function it's useless for that :P

MUTATOR_HOOKABLE(PlayerRegen);
	// called every player think frame
	// return 1 to disable regen
	// INPUT, OUTPUT:
		float regen_mod_max;
		float regen_mod_regen;
		float regen_mod_rot;
		float regen_mod_limit;

MUTATOR_HOOKABLE(PlayerUseKey);
	// called when the use key is pressed
	// if MUTATOR_RETURNVALUE is 1, don't do anything
	// return 1 if the use key actually did something

MUTATOR_HOOKABLE(SV_ParseClientCommand);
	// called when a client command is parsed
	// NOTE: hooks MUST start with if(MUTATOR_RETURNVALUE) return 0;
	// NOTE: return 1 if you handled the command, return 0 to continue handling
	// NOTE: THESE HOOKS MUST NEVER EVER CALL tokenize()
	// INPUT
	string cmd_name; // command name
	float cmd_argc; // also, argv() can be used
	string cmd_string; // whole command, use only if you really have to
	/*
		// example:
		MUTATOR_HOOKFUNCTION(foo_SV_ParseClientCommand)
		{
			if(MUTATOR_RETURNVALUE) // command was already handled?
				return 0;
			if(cmd_name == "echocvar" && cmd_argc >= 2)
			{
				print(cvar_string(argv(1)), "\n");
				return 1;
			}
			if(cmd_name == "echostring" && cmd_argc >= 2)
			{
				print(substring(cmd_string, argv_start_index(1), argv_end_index(-1) - argv_start_index(1)), "\n");
				return 1;
			}
			return 0;
		}
	*/

MUTATOR_HOOKABLE(Spawn_Score);
	// called when a spawnpoint is being evaluated
	// return 1 to make the spawnpoint unusable
	// INPUT
	entity self; // player wanting to spawn
	entity spawn_spot; // spot to be evaluated
	// IN+OUT
	vector spawn_score; // _x is priority, _y is "distance"

MUTATOR_HOOKABLE(SV_StartFrame);
	// runs globally each server frame

MUTATOR_HOOKABLE(SetModname);
	// OUT
	string modname; // name of the mutator/mod if it warrants showing as such in the server browser

MUTATOR_HOOKABLE(Item_Spawn);
	// called for each item being spawned on a map, including dropped weapons
	// return 1 to remove an item
	// INPUT
	entity self; // the item

MUTATOR_HOOKABLE(SetWeaponreplace);
	// IN
		entity self; // map entity
		entity other; // weapon info
	// IN+OUT
		string ret_string;

MUTATOR_HOOKABLE(Item_RespawnCountdown);
	// called when an item is about to respawn
	// INPUT+OUTPUT:
	string item_name;
	vector item_color;

MUTATOR_HOOKABLE(BotShouldAttack);
	// called when a bot checks a target to attack
	// INPUT
	entity checkentity;

MUTATOR_HOOKABLE(PortalTeleport);
	// called whenever a player goes through a portal gun teleport
	// allows you to strip a player of an item if they go through the teleporter to help prevent cheating
	// INPUT
	entity self;

MUTATOR_HOOKABLE(HelpMePing);
	// called whenever a player uses impulse 33 (help me) in cl_impulse.qc
	// normally help me ping uses self.waypointsprite_attachedforcarrier,
	// but if your mutator uses something different then you can handle it
	// in a special manner using this hook
	// INPUT
	entity self; // the player who pressed impulse 33

MUTATOR_HOOKABLE(VehicleSpawn);
	// called when a vehicle initializes
	// return true to remove the vehicle

MUTATOR_HOOKABLE(VehicleEnter);
	// called when a player enters a vehicle
	// allows mutators to set special settings in this event
	// INPUT
	entity vh_player; // player
	entity vh_vehicle; // vehicle

MUTATOR_HOOKABLE(VehicleTouch);
	// called when a player touches a vehicle
	// return true to stop player from entering the vehicle
	// INPUT
	entity self; // vehicle
	entity other; // player

MUTATOR_HOOKABLE(VehicleExit);
	// called when a player exits a vehicle
	// allows mutators to set special settings in this event
	// INPUT
	entity vh_player; // player
	entity vh_vehicle; // vehicle

MUTATOR_HOOKABLE(AbortSpeedrun);
	// called when a speedrun is aborted and the player is teleported back to start position
	// INPUT
	entity self; // player

MUTATOR_HOOKABLE(ItemTouch);
	// called at when a item is touched. Called early, can edit item properties.
	entity self;	// item
	entity other; 	// player
	const float MUT_ITEMTOUCH_CONTINUE = 0; // return this flag to make the function continue as normal
	const float MUT_ITEMTOUCH_RETURN = 1; // return this flag to make the function return (handled entirely by mutator)
	const float MUT_ITEMTOUCH_PICKUP = 2; // return this flag to have the item "picked up" and taken even after mutator handled it

MUTATOR_HOOKABLE(ClientConnect);
	// called at when a player connect
	entity self;	// player

MUTATOR_HOOKABLE(HavocBot_ChooseRole);
	entity self;

MUTATOR_HOOKABLE(AccuracyTargetValid);
	// called when a target is checked for accuracy
	entity frag_attacker; // attacker
	entity frag_target; // target
	const float MUT_ACCADD_VALID = 0; // return this flag to make the function continue if target is a client
	const float MUT_ACCADD_INVALID = 1; // return this flag to make the function always continue
	const float MUT_ACCADD_INDIFFERENT = 2; // return this flag to make the function always return