Crate zzstat 

zzstat - Deterministic, Hardcode-Free MMORPG Stat Engine

A stat calculation engine designed for MMORPGs that provides:

• Deterministic stat resolution (same input → same output)
• Hardcode-free design (no built-in stat names like “HP” or “ATK”)
• Event-driven resolution (only resolves when invalidated)
• Phase-based transformation pipeline

Core Concepts

Stat Pipeline

Stats flow through a simple pipeline:

[StatSource] → [StatTransform] → [ResolvedStat]

1. Sources produce base values (additive)
2. Transforms modify values (can depend on other stats)
3. ResolvedStat contains the final value with full breakdown

Key Features

• Dependency Graph: Automatically resolves dependencies in correct order
• Cycle Detection: Prevents circular dependencies
• Caching: Resolved stats are cached until invalidated
• Context-Aware: Supports conditional calculations via StatContext
• Debug-Friendly: Full breakdown of sources and transforms

Example

use zzstat::*;
use zzstat::source::ConstantSource;
use zzstat::transform::MultiplicativeTransform;

let mut resolver = StatResolver::new();
let hp_id = StatId::from_str("HP");

// Register sources (additive)
resolver.register_source(hp_id.clone(), Box::new(ConstantSource(100.0)));
resolver.register_source(hp_id.clone(), Box::new(ConstantSource(50.0)));

// Register transform
resolver.register_transform(hp_id.clone(), Box::new(MultiplicativeTransform::new(1.5)));

// Resolve
let context = StatContext::new();
let resolved = resolver.resolve(&hp_id, &context).unwrap();
assert_eq!(resolved.value, 225.0); // (100 + 50) * 1.5

Modules

• stat_id - Stat identifier type
• source - Stat sources (produce base values)
• transform - Stat transforms (modify values)
• resolver - Main stat resolver
• resolved - Resolved stat results
• context - Context for conditional calculations
• graph - Dependency graph management
• error - Error types

Re-exports

pub use context::StatContext;

pub use error::StatError;

pub use resolved::ResolvedStat;

pub use resolver::StatResolver;

pub use stat_id::StatId;

pub use source::ConstantSource;

pub use source::MapSource;

pub use source::StatSource;

pub use transform::AdditiveTransform;

pub use transform::ClampTransform;

pub use transform::ConditionalTransform;

pub use transform::MultiplicativeTransform;

pub use transform::ScalingTransform;

pub use transform::StatTransform;

Modules

context

Context information for stat resolution.

error

Error types for stat resolution.

graph

Dependency graph module.

resolved

Resolved stat results module.

resolver

Stat resolver module.

source

Stat sources module.

stat_id

Stat identifier module.

transform

Stat transforms module.