CombatMetrics

**## Overview

CombatMetrics is a lightweight, high-performance combat tracking plugin for Paper 1.21+ servers. It accurately detects and displays Critical Hits and Sprint Combo Hits in real-time using the player's Action Bar. The plugin faithfully replicates vanilla Minecraft's exact combat mechanics, ensuring that every tracked hit matches what would trigger the corresponding subtitle/particle effect in the base game.

Core Concept

┌─────────────────────────────────────────────────────────────────────┐
│ COMBATMETRICS FLOW │
├─────────────────────────────────────────────────────────────────────┤
│ │
│ PLAYER ATTACKS ENTITY │
│ │ │
│ ▼ │
│ ┌────────────────────┐ ┌────────────────────┐ │
│ │ Check Critical │ │ Check Combo │ │
│ │ Hit Conditions │ │ Hit Conditions │ │
│ │ (11 Checks) │ │ (3 Checks) │ │
│ └─────────┬──────────┘ └─────────┬──────────┘ │
│ │ │ │
│ ▼ ▼ │
│ ┌────────────────────┐ ┌────────────────────┐ │
│ │ Increment Crit │ │ Increment Combo │ │
│ │ Counter │ │ Counter │ │
│ └─────────┬──────────┘ └─────────┬──────────┘ │
│ │ │ │
│ └───────────┬───────────────┘ │
│ ▼ │
│ ┌────────────────────────┐ │
│ │ UPDATE ACTION BAR │ │
│ │ [ ☠ CRITS: X | ⚔ COMBO: Y ] │
│ └────────────────────────┘ │
│ │ │
│ ▼ │
│ ┌────────────────────────┐ │
│ │ No hit for 2 seconds? │ │
│ │ → Reset counters to 0 │ │
│ └────────────────────────┘ │
│ │
└─────────────────────────────────────────────────────────────────────┘

---

✨ Features

Core Features

Feature	Description
Critical Hit Tracking	Detects vanilla-accurate critical hits using 11 strict conditions
Combo Hit Tracking	Detects sprint knockback hits for combo counting
Real-Time Display	Shows live counters in the Action Bar
Auto Reset	Counters automatically reset after 2 seconds of inactivity
Left-Aligned Display	Text positioned on left side of screen for better visibility
Hit Highlighting	Brief green flash when a hit is registered

Persistence Features

Feature	Description
Per-Player Toggle	Each player can enable/disable their display
Survives Relog	Preference saved using PersistentDataContainer
Survives Restart	Settings persist across server restarts
No External Storage	Data stored directly on player entity

⚡ Performance Features

Feature	Description
Async Timer Checks	Reset detection runs on async thread
Efficient Data Storage	ConcurrentHashMap for thread-safe access
Minimal Overhead	Early-return conditions prevent unnecessary processing
Lazy Initialization	Data created only when player attacks
Lightweight Task	Timer runs every 5 ticks (0.25 seconds)

---

☠️ Critical Hit Detection

CombatMetrics uses vanilla-accurate detection that matches Minecraft's exact critical hit requirements. A hit is only counted as critical if ALL conditions are met:

Condition Checklist

#	Condition	Method Used	Explanation
1	Falling	fallDistance > 0.0	Player must have positive fall distance
2	Airborne	!isOnGround()	Player cannot be touching the ground
3	Not Climbing	!isClimbing()	Cannot be on ladder, vine, or scaffolding
4	Not In Water	!isInWater()	Cannot be submerged in water
5	Not In Lava	!isInLava()	Cannot be submerged in lava
6	Not Swimming	!isSwimming()	Cannot be using swimming animation
7	Not Gliding	!isGliding()	Cannot be flying with Elytra
8	No Blindness	!hasPotionEffect(BLINDNESS)	Blindness effect blocks crits
9	No Slow Falling	!hasPotionEffect(SLOW_FALLING)	Slow falling prevents crits
10	Not Mounted	!isInsideVehicle()	Cannot be riding any entity
11	Charged Attack	getAttackCooldown() > 0.9	Attack must be 90%+ charged

Visual Representation

CRITICAL HIT VALIDATION

Player State Check Result
══════════════════════════════════════════

fallDistance > 0 ? ───────────→ ✓ PASS
│
▼
!isOnGround() ? ───────────→ ✓ PASS
│
▼
!isClimbing() ? ───────────→ ✓ PASS
│
▼
!isInWater() ? ───────────→ ✓ PASS
│
▼
!isInLava() ? ───────────→ ✓ PASS
│
▼
!isSwimming() ? ───────────→ ✓ PASS
│
▼
!isGliding() ? ───────────→ ✓ PASS
│
▼
No BLINDNESS ? ───────────→ ✓ PASS
│
▼
No SLOW_FALLING ? ───────────→ ✓ PASS
│
▼
!isInsideVehicle()? ───────────→ ✓ PASS
│
▼
attackCooldown > 0.9? ─────────→ ✓ PASS
│
▼
══════════════════════════════════════════
│
▼
★ CRITICAL HIT REGISTERED ★

---

⚔️ Combo Hit Detection

Combo hits detect sprint knockback attacks - the enhanced knockback applied when a player hits an enemy while sprinting.

Condition Checklist

#	Condition	Method Used	Explanation
1	Sprinting	isSprinting()	Player must be actively sprinting
2	Charged Attack	getAttackCooldown() > 0.9	Attack must be 90%+ charged
3	Living Target	instanceof LivingEntity	Target must be able to receive knockback

Visual Representation

COMBO HIT VALIDATION

Player State Check Result
══════════════════════════════════════════

isSprinting() ? ───────────→ ✓ PASS
│
▼
attackCooldown > 0.9? ─────────→ ✓ PASS
│
▼
Target is Living? ───────────→ ✓ PASS
│
▼
══════════════════════════════════════════
│
▼
★ COMBO HIT REGISTERED ★

---

️ Visual Display System

Action Bar Format

┌─────────────────────────────────────────────────────────────────────┐
│ │
│ [ ☠ CRITS: 5 | ⚔ COMBO: 3 ] │
│ ↑ ↑ │
│ └── Left-aligned content └── Invisible spacing pushes left │
│ │
└─────────────────────────────────────────────────────────────────────┘

Color Scheme

Element	Color	Style
[ ]	Dark Gray	Normal
☠	Dark Red	Normal
CRITS:	Red	Bold
Crit Count	White	Normal
|	Dark Gray	Normal
⚔	Gold	Normal
COMBO:	Yellow	Bold
Combo Count	White	Normal

Hit Highlight Effect

When a hit is registered, the corresponding counter briefly highlights:

Normal Display:
[ ☠ CRITS: 5 | ⚔ COMBO: 3 ]
↑ ↑
White White

After Critical Hit (3 ticks):
[ ☠ CRITS: 6 | ⚔ COMBO: 3 ]
↑
GREEN + BOLD

After Combo Hit (3 ticks):
[ ☠ CRITS: 6 | ⚔ COMBO: 4 ]
↑
GREEN + BOLD

Left-Alignment Technique

Minecraft's Action Bar centers text by default. To achieve left-alignment:

// Append invisible spacing after the content
Component content = actualContent
.append(Component.text(" ") // ~80 spaces
.color(NamedTextColor.BLACK)); // Invisible

This pushes the visible content to the left side of the screen, near the health/armor display.

---

⏱️ Reset Timer System

How It Works

┌─────────────────────────────────────────────────────────────────────┐
│ RESET TIMER SYSTEM │
├─────────────────────────────────────────────────────────────────────┤
│ │
│ TIME ──────────────────────────────────────────────────────→ │
│ │
│ HIT! RESET! │
│ │ │ │
│ ▼ ▼ │
│ ●━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━● │
│ │←────────────── 2000ms (40 ticks) ──────────────→│ │
│ │ │ │
│ lastHitTime currentTime │
│ │
│ │
│ [Async Task - Every 5 ticks] │
│ │ │
│ ▼ │
│ if (currentTime - lastHitTime >= 2000ms) { │
│ resetCounter(); │
│ updateActionBar(); // Show 0 briefly │
│ } │
│ │
└─────────────────────────────────────────────────────────────────────┘

Independent Timers

Critical and Combo counters have separate timers:

SCENARIO: Player lands a crit, then keeps doing combo hits

Time: 0s 1s 2s 3s 4s 5s
│ │ │ │ │ │
Crits: [1]─────[1]─────[0] (reset at 2s)
│ │ │
Combos: [1]────[2]────[3]────[4]─────[4]─────[0]
↑ ↑
last combo reset at 5s

Grace Period

After counters reset to 0, there's a brief 500ms grace period before the display clears entirely:

HIT! → 2 seconds → RESET TO 0 → 500ms → CLEAR DISPLAY
↓
Show "[ ☠ CRITS: 0 | ⚔ COMBO: 0 ]" briefly

---

Commands & Permissions

Commands

Command	Description	Permission
/metrics toggle	Enable/disable action bar display	combatmetrics.use
/metrics status	View current stats and settings	combatmetrics.use
/metrics reset	Reset both counters to zero	combatmetrics.use

Command Aliases

• /combatmetrics
• /cm

Permissions

Permission	Default	Description
combatmetrics.use	true	Access to all player commands
combatmetrics.admin	op	Reserved for future admin features

Command Output Examples

Toggle ON:

✓ Combat Metrics ENABLED
Your combat stats will now display in the action bar.

Toggle OFF:

✗ Combat Metrics DISABLED
Action bar display has been turned off.

Status:

══════ Combat Metrics Status ══════
Display: ENABLED
Current Session:
☠ Critical Hits: 15
⚔ Combo Hits: 23

Reset:

↺ Counters have been reset!

---

Data Persistence

PersistentDataContainer (PDC) Storage

┌─────────────────────────────────────────────────────────────────────┐
│ PERSISTENCE SYSTEM │
├─────────────────────────────────────────────────────────────────────┤
│ │
│ Namespace: combatmetrics │
│ Key: metrics_display_enabled │
│ Type: BYTE │
│ │
│ Values: │
│ 0 = Display DISABLED │
│ 1 = Display ENABLED │
│ null = Default to ENABLED │
│ │
│ Storage Location: Player Entity NBT Data │
│ │
└─────────────────────────────────────────────────────────────────────┘

Persistence Benefits

Benefit	Description
No Files	No YAML/JSON configuration files per player
No Database	No MySQL/SQLite required
Automatic	Saved with player data automatically
Reliable	Survives crashes, restarts, and relogs
Lightweight	Single byte per player

---

⚡ Performance Analysis

Memory Usage

Per Player:
┌────────────────────────────────────┐
│ MetricData Object │
├────────────────────────────────────┤
│ int critCount = 4 bytes │
│ int comboCount = 4 bytes │
│ long lastCritTime = 8 bytes │
│ long lastComboTime = 8 bytes │
│ boolean needsUpdate = 1 byte │
│ Object overhead ≈ 16 bytes │
├────────────────────────────────────┤
│ TOTAL ≈ 41 bytes │
└────────────────────────────────────┘

100 Players = ~4.1 KB memory
1000 Players = ~41 KB memory

CPU Usage

Task	Frequency	Cost
Damage Event Handler	Per attack	Very Low (early returns)
Async Reset Checker	Every 5 ticks	Minimal (simple timestamp comparison)
Action Bar Update	On hit/reset	Low (Component creation)

Optimization Techniques Used

Technique	Implementation
Early Returns	Check cooldown first before other conditions
Async Processing	Timer checks run off main thread
ConcurrentHashMap	Thread-safe without locks
Lazy Loading	MetricData created on first attack
Minimal Allocations	Reuse patterns where possible
Event Priority	MONITOR priority - runs after other plugins

---

Event Flow

Complete Event Lifecycle

┌─────────────────────────────────────────────────────────────────────┐
│ COMPLETE EVENT FLOW │
├─────────────────────────────────────────────────────────────────────┤
│ │
│ 1. EntityDamageByEntityEvent Fired │
│ │ │
│ ▼ │
│ 2. Check: Damager is Player? │
│ │ NO → EXIT │
│ │ YES ↓ │
│ ▼ │
│ 3. Check: Target is LivingEntity? │
│ │ NO → EXIT │
│ │ YES ↓ │
│ ▼ │
│ 4. Check: Attack Cooldown > 0.9? │
│ │ NO → EXIT (weak attack) │
│ │ YES ↓ │
│ ▼ │
│ 5. Check Critical Hit Conditions (11 checks) │
│ │ PASS → Increment Crit Counter │
│ ▼ │
│ 6. Check Combo Hit Conditions (2 checks) │
│ │ PASS → Increment Combo Counter │
│ ▼ │
│ 7. Either counter incremented? │
│ │ NO → EXIT │
│ │ YES ↓ │
│ ▼ │
│ 8. Check: Display Enabled for Player? │
│ │ NO → EXIT │
│ │ YES ↓ │
│ ▼ │
│ 9. Update Action Bar with Highlight │
│ │ │
│ ▼ │
│ 10. Schedule Highlight Removal (3 ticks) │
│ │
└─────────────────────────────────────────────────────────────────────┘

Async Reset Task Flow

┌─────────────────────────────────────────────────────────────────────┐
│ ASYNC RESET TASK │
├─────────────────────────────────────────────────────────────────────┤
│ │
│ [Runs every 5 ticks on Async Thread] │
│ │ │
│ ▼ │
│ FOR each online player: │
│ │ │
│ ▼ │
│ Get MetricData (if exists) │
│ │ NULL → SKIP │
│ │ EXISTS ↓ │
│ ▼ │
│ Check: shouldResetCrit(currentTime)? │
│ │ YES → resetCrit() │
│ ▼ │
│ Check: shouldResetCombo(currentTime)? │
│ │ YES → resetCombo() │
│ ▼ │
│ Any reset occurred? │
│ │ NO → CONTINUE │
│ │ YES ↓ │
│ ▼ │
│ Schedule SYNC task: │
│ - Update action bar │
│ - Or clear if both expired │
│ │
└─────────────────────────────────────────────────────────────────────┘

---

Use Cases

PvP Servers

Use Case	Benefit
Competitive PvP	Players can track their crit consistency
Practice Servers	Train timing for critical hits
Combo Training	Improve sprint-reset techniques
Tournaments	Verify critical hit mechanics

PvE Servers

Use Case	Benefit
Mob Farming	Optimize damage output
Boss Fights	Track DPS effectiveness
Speedrunning	Monitor combat efficiency

Content Creators

Use Case	Benefit
YouTube/Twitch	Visual feedback for viewers
Tutorials	Demonstrate critical hit mechanics
Challenges	Create crit-based achievements

---

Statistics Tracking

What Gets Tracked

Metric	Description	Reset Condition
Crit Count	Total critical hits in current streak	2 seconds no crit
Combo Count	Total combo hits in current streak	2 seconds no combo
Last Crit Time	Timestamp of most recent crit	On reset
Last Combo Time	Timestamp of most recent combo	On reset

What Is NOT Tracked

Not Tracked	Reason
All-time statistics	Would require database storage
Damage numbers	Beyond plugin scope
Kill/death counts	Other plugins handle this
Weapon types	Not relevant to hit detection

---

Developer API

Accessing CombatMetrics

// Get plugin instance
CombatMetrics plugin = CombatMetrics.getInstance();

// Get the metric manager
MetricManager manager = plugin.getMetricManager();

Reading Player Data

// Get current stats
MetricData data = manager.getMetricData(player);
int crits = data.getCritCount();
int combos = data.getComboCount();

// Check if display is enabled
boolean enabled = manager.isDisplayEnabled(player);

Modifying Player Data

// Manually register hits
manager.registerCriticalHit(player);
manager.registerComboHit(player);

// Reset counters
manager.resetCounters(player);

// Toggle display
boolean newState = manager.toggleDisplay(player);
manager.setDisplayEnabled(player, true);

Custom Action Bar Updates

// Get data and update display
MetricData data = manager.getMetricData(player);
manager.updateActionBar(player, data);

// Update with highlight effect
manager.showHitWithHighlight(player, true, false); // Highlight crit

--

Compatibility

Server Software

Software	Compatible	Notes
Paper 1.21.1+	✅	Primary target
Paper 1.21.2	✅	Fully supported
Paper 1.21.3	✅	Fully supported
Paper 1.21.4	✅	Fully supported
Paper 1.21.5	✅	Fully supported
Paper 1.21.6	✅	Fully supported
Paper 1.21.7	✅	Fully supported
Paper 1.21.8	✅	Fully supported
Spigot	⚠️	May work, untested
Bukkit	❌	Missing Adventure API
Folia	⚠️	Requires region-aware modifications

Java Versions

Java	Compatible
Java 21	✅ Required
Java 22+	✅ Should work
Java 17	❌ Too old for Paper 1.21

Plugin Conflicts

Plugin Type	Compatibility
Combat plugins	✅ Runs on MONITOR priority
Action bar plugins	⚠️ May overwrite display
Anticheat plugins	✅ No conflicts
Protection plugins	✅ Respects cancelled events

---

Installation

Step-by-Step

1. Download the CombatMetrics-1.0.0.jar file
2. Stop your server
3. Place the JAR in your plugins/ folder
4. Start your server
5. Verify with /plugins - should show green

First-Time Setup

No configuration required! The plugin works out of the box:

• Display is enabled by default for all players
• Players can toggle with /metrics toggle
• Settings automatically persist

---

Changelog

Version 1.0.0

• Initial release
• Critical hit detection (11 conditions)
• Combo hit detection (3 conditions)
• Action bar display with left-alignment
• Auto-reset after 2 seconds
• PDC-based persistence
• Toggle/status/reset commands
• Async timer task
• Hit highlight effects

---

FAQ

Q: Why doesn't it detect my critical hits?

A: Ensure your attack is fully charged (90%+) and you're falling without any blocking conditions (water, climbing, slow falling, etc.)

Q: Can both Crit and Combo trigger on the same hit?

A: Yes! If you're falling AND sprinting with a charged attack, both counters will increment.

Q: Does this work in creative mode?

A: Yes, but attack cooldown is always 1.0 in creative, so timing doesn't matter.

Q: Will this cause lag?

A: No. The plugin uses async processing and minimal memory. Tested with 100+ players.

Q: Can I customize the display colors?

A: Not in this version. Colors are hardcoded for consistency.

Q: Does it track hits on all entities?

A: Only hits on LivingEntity (mobs, players, animals, etc.)

---

Summary

CombatMetrics provides:

✅ Accurate vanilla-matching critical hit detection ✅ Real-time action bar display ✅ Automatic 2-second reset timers ✅ Persistent per-player preferences ✅ Performant async processing ✅ Simple toggle commands ✅ Zero configuration required ✅ Zero dependencies

Perfect for PvP servers, practice servers, and any server where players want to track their combat effectiveness!**