spell_scripts

Table spell_scripts:
Id - Spell Id from spell_template
ScriptName - Assigned script name in core

Assignment .sql file located in each repo under sql/scriptdev2/spell.sql

Used to add custom behaviour to any spell. List of all available hooks can be found in core in SpellScript.h. This file contains a thorough explanation of when they occur. There are two types, SpellScript or AuraScript. Both auras have a plethora of examples available. Almost all variables which are meant to be alterable in spellscripts have an appropriate public function in Spell, Aura and SpellAuraHolder. Currently there is no DB equivalent to this system, mainly due to reverse engineering.

Examples:

Registering a script works using functions RegisterSpellScript, RegisterAuraScript or RegisterScript(this one is when its both aura and spellscript). By searching for these functions its also possible to find hundreds of examples.
Code example of registering:

RegisterSpellScript<EntangleFankriss>("spell_entangle_fankriss");

The above registers the script to ScriptName "spell_entangle_fankriss".
And this is its script:

struct EntangleFankriss : public SpellScript
{
    void OnEffectExecute(Spell* spell, SpellEffectIndex effIdx) const override
    {
        if (effIdx == EFFECT_INDEX_0)
        {
            uint32 spellId = 0;
            switch (spell->m_spellInfo->Id)
            {
                default:
                case SPELL_ENTANGLE_1: spellId = SPELL_SPAWN_VEKNISS_HATCHLING_1; break;
                case SPELL_ENTANGLE_2: spellId = SPELL_SPAWN_VEKNISS_HATCHLING_2; break;
                case SPELL_ENTANGLE_3: spellId = SPELL_SPAWN_VEKNISS_HATCHLING_3; break;
            }
            spell->GetCaster()->CastSpell(nullptr, spellId, TRIGGERED_OLD_TRIGGERED);
        }
    }
};

This script picks a spell, based on which spell is casting it, to be cast and caster casts it when Effect 0 is executed. It is used by three spells with similar behaviour hence the switch case.

struct GammeritaTurtleCamera : public SpellScript
{
    SpellCastResult OnCheckCast(Spell* spell, bool /*strict*/) const override
    {
        Unit* target = spell->m_targets.getUnitTarget();
        // Gammerita Turtle Camera can be cast only on this target
        if (!target || target->GetEntry() != 7977)
            return SPELL_FAILED_BAD_TARGETS;

        return SPELL_CAST_OK;
    }
};

This script restricts it to only work on Gammerita. There are many single target quest or other custom spells which need to work only on a specific target.

struct CallOfTheBeast : public AuraScript
{
    void OnApply(Aura* aura, bool apply) const override
    {
        if (apply)
            aura->GetTarget()->CastSpell(nullptr, SPELL_CALL_OF_THE_BEAST, TRIGGERED_OLD_TRIGGERED);
    }
};

This script triggers a cast of another spell on receiving an aura. A very common occurence.

struct DirtyDeeds : public AuraScript
{
    void OnApply(Aura* aura, bool apply) const override
    {
        if (aura->GetEffIndex() == EFFECT_INDEX_1)
            aura->GetTarget()->RegisterScriptedLocationAura(aura, SCRIPT_LOCATION_MELEE_DAMAGE_DONE, apply);
        else if (aura->GetEffIndex() == EFFECT_INDEX_2)
            aura->GetTarget()->RegisterScriptedLocationAura(aura, SCRIPT_LOCATION_MELEE_DAMAGE_DONE, apply);
    }

    void OnDamageCalculate(Aura* aura, Unit* victim, int32& /*advertisedBenefit*/, float& totalMod) const override
    {
        if (aura->GetEffIndex() == EFFECT_INDEX_0)
            return;

        if (victim->HasAuraState(AURA_STATE_HEALTHLESS_35_PERCENT))
        {
            Aura* eff0 = aura->GetHolder()->m_auras[EFFECT_INDEX_0];
            if (!eff0)
            {
                sLog.outError("Spell structure of DD (%u) changed.", aura->GetId());
                return;
            }

            // effect 0 have expected value but in negative state
            totalMod *= (-eff0->GetModifier()->m_amount + 100.0f) / 100.0f;
        }
    }
}

Scripts that utilize RegisterScriptedLocationAura are a bit more obtuse. They hook into Unit functions responsible for damage calculation. The registered script then calls OnDamageCalculate for the given application, and spells which it affects are defined by EffectSpellClassMask from spell_template (and in vanilla and tbc overriden in separate table spell_affect, but they function identically as fallback). They are used for conditional per-spell damage increases from either SPELL_AURA_DUMMY or SPELL_AURA_OVERRIDE_CLASS_SCRIPTS. In this specific case, Dirty Deeds applies its bonus to spells only when below 35% health. Commonly used by totems, librams and idols with the wording "spell damage/attack power for spell X up to Y.

The currently defined locations are:

enum AuraScriptLocation : uint32
{
    SCRIPT_LOCATION_MELEE_DAMAGE_DONE,
    SCRIPT_LOCATION_MELEE_DAMAGE_TAKEN,
    SCRIPT_LOCATION_SPELL_DAMAGE_DONE,
    SCRIPT_LOCATION_SPELL_DAMAGE_TAKEN,
    SCRIPT_LOCATION_SPELL_HEALING_DONE,
    SCRIPT_LOCATION_SPELL_HEALING_TAKEN,
    SCRIPT_LOCATION_MAX,
};