Damage & Healing System

[FirebrickRed]

Summary

Handle damage application and healing during combat. Support multiple input modes (like attack rolls), damage resistance/vulnerability, temporary HP, and death triggers. Integrates with existing entity HP system and adds combat methods to CharacterSheet.

Phase: MVP Combat System
Systems: Combat System, HP Tracking, Dice Rolling

Prerequisites

• Combat Session Foundation & Initiative System #97 - Combat Session Foundation & Initiative System
• Entity HP Tracking & Damage System #82 - Entity HP Tracking (entity HP methods exist)

Goals

• Multiple damage input modes (auto roll, show mods, player roll, flat amount)
• Damage resistance (half damage) and vulnerability (double damage)
• Temporary HP consumed first
• Death triggers (entities die, players go unconscious)
• Healing commands with similar flexibility
• Combat log for all HP changes
• Add takeDamage() method to CharacterSheet

Commands

Damage Commands

# FLAT DAMAGE - Apply specific amount
/combat damage goblin_chief 14
> Goblin Chief takes 14 slashing damage!
> HP: 22 → 8

# ROLL DAMAGE - Roll dice and apply
/combat damage goblin_chief --roll 2d6+3
> Rolling damage: 2d6+3
> Result: [4][6] + 3 = 13 slashing damage
> Goblin Chief HP: 22 → 9

# SHOW MODS - Display damage modifiers
/combat damage goblin_chief --showmods
> Longsword damage: 1d8 + 3 (STR)
> [Roll and use /combat damage goblin_chief --roll <result> or flat amount]

# PLAYER TOTAL - Player provides final damage
/combat damage goblin_chief --total 17
> Goblin Chief takes 17 damage!
> HP: 22 → 5

Damage Types

# Specify damage type (for resistance/vulnerability)
/combat damage goblin_chief 14 --type fire
> Goblin Chief takes 14 fire damage!
> HP: 22 → 8

# With resistance
/combat damage fire_elemental 14 --type fire
> Fire Elemental has RESISTANCE to fire!
> 14 → 7 fire damage
> HP: 45 → 38

# With vulnerability
/combat damage skeleton 10 --type bludgeoning
> Skeleton is VULNERABLE to bludgeoning!
> 10 → 20 bludgeoning damage
> HP: 13 → 0
> Skeleton is destroyed!

Healing Commands

# Flat healing
/combat heal Alice 10
> Alice healed for 10 HP!
> HP: 15 → 25

# Roll healing
/combat heal Alice --roll 2d8+3
> Rolling healing: 2d8+3
> Result: [5][7] + 3 = 15 HP healed
> Alice HP: 15 → 30 (max: 32)

# Can't exceed max HP
/combat heal Alice 100
> Alice healed for 2 HP! (at max HP)
> HP: 30 → 32

Temporary HP

# Grant temporary HP
/combat temphp Alice 10
> Alice gains 10 temporary HP!
> Temp HP: 0 → 10

# Temp HP absorbed first
/combat damage Alice 15
> Alice takes 15 damage!
> Temp HP absorbs 10: 10 → 0
> Remaining 5 damage to HP: 32 → 27

Damage Calculation with Modifiers

// For weapon damage
int damageBonus = 0;

// Ability modifier (same logic as attack - STR/DEX/finesse)
if (weapon.hasProperty("finesse")) {
    damageBonus += Math.max(strMod, dexMod);
} else if (weapon.hasProperty("ranged")) {
    damageBonus += dexMod;
} else {
    damageBonus += strMod;
}

// Magic weapon bonus (future)
// damageBonus += weapon.getMagicDamageBonus();

// Roll damage dice + bonus
int damage = DiceRoller.parseDiceRoll(weapon.getDamageDice()) + damageBonus;

Critical Hit Damage

// Double the dice, not the modifier
// Longsword crit: 2d8 + 3 (not 2d8 + 6)

String baseDice = weapon.getDamageDice();  // "1d8"
String critDice = doubleDice(baseDice);     // "2d8"
int damage = DiceRoller.parseDiceRoll(critDice) + damageBonus;

Resistance & Vulnerability

// Check target's damage resistances/vulnerabilities
Set<String> resistances = target.getDamageResistances();
Set<String> vulnerabilities = target.getDamageVulnerabilities();
Set<String> immunities = target.getDamageImmunities();

if (immunities.contains(damageType)) {
    damage = 0;
    announce("IMMUNE to " + damageType);
} else if (resistances.contains(damageType)) {
    damage = damage / 2;  // Round down
    announce("RESISTANT to " + damageType);
} else if (vulnerabilities.contains(damageType)) {
    damage = damage * 2;
    announce("VULNERABLE to " + damageType);
}

Death Triggers

Entity Death (0 HP)

if (entity.getCurrentHp() <= 0) {
    entity.setDead(true);
    // Death behavior configured in #82
    broadcast(entity.getDisplayName() + " is defeated!");
    // Remove from combat, trigger loot (#77), etc.
}

Player Unconscious (0 HP)

if (player.getCurrentHealth() <= 0) {
    player.setCurrentHealth(0);  // Don't go negative for MVP
    markAsUnconscious(player);
    broadcast(player.getName() + " falls unconscious!");
    // Triggers death save system (#101)
}

CharacterSheet Combat Methods

// Add to CharacterSheet.java

public void takeDamage(int damage) {
    // Absorb with temp HP first
    if (tempHealth > 0) {
        int absorbed = Math.min(tempHealth, damage);
        tempHealth -= absorbed;
        damage -= absorbed;
    }
    
    // Apply remaining to current HP
    currentHealth = Math.max(0, currentHealth - damage);
}

public void heal(int amount) {
    currentHealth = Math.min(totalHealth, currentHealth + amount);
}

public void setTemporaryHp(int amount) {
    // Temp HP doesn't stack - take higher
    tempHealth = Math.max(tempHealth, amount);
}

public boolean isUnconscious() {
    return currentHealth <= 0;
}

Combat Log Output

[Combat Log]
Round 2 | Alice's Turn
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
DAMAGE: Alice → Goblin Chief
Weapon: Longsword
Damage Roll: 1d8+3 = [6]+3 = 9 slashing
Resistance: None
Final Damage: 9
HP Change: 22 → 13
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

DAMAGE: Goblin Chief → Alice  
Attack: Scimitar
Damage: 7 slashing
Temp HP Absorbed: 5
HP Change: 32 → 30
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

Massive Damage (Future)

Future config option:
- If single hit deals >= max HP, instant death
- Or CON save vs instant death
See #104 for config options

Tab Completion

• /combat damage <TAB> → List valid targets in combat
• /combat damage target --type <TAB> → List damage types (slashing, fire, etc.)
• /combat heal <TAB> → List valid targets in combat

Related Issues

• Entity HP Tracking & Damage System #82 - Entity HP Tracking (entity methods, death config)
• Combat Session Foundation & Initiative System #97 - Combat Foundation (prerequisite)
• Attack Roll System #99 - Attack Roll System (damage follows hit)
• Death Saves & Unconscious State #101 - Death Saves (triggered by player 0 HP)
• Combat Configuration System #104 - Combat Configuration (massive damage rules)