Business Logic

The @running-days/business-logic package contains pure functions for all core calculations. It has no I/O, no database access - just algorithms and transformations.

Philosophy

All business logic is:

Pure: Same inputs always produce same outputs
Testable: No external dependencies to mock
Portable: Can run in Node.js, browser, or edge runtime

Modules

Module	Description
Workout Processor	Parse, validate, and aggregate workout data
Streak Calculator	Calculate current, longest, and historical streaks
Achievement Service	Milestone detection and progress tracking

Installation

bash

pnpm add @running-days/business-logic

Usage

typescript

import {
  processWorkout,
  calculateStreaks,
  detectNewMilestones
} from '@running-days/business-logic';

// Process a raw workout from HealthKit
const workout = processWorkout(rawWorkout);

// Calculate streaks from daily stats
const streaks = calculateStreaks(dailyStats);

// Check for new achievement milestones
const newMilestones = detectNewMilestones(previousDays, currentDays);

Type Safety

All functions are fully typed. Import types from @running-days/types:

typescript

import type { Workout, DailyStats, Goal } from '@running-days/types';

Testing

The package has comprehensive unit tests:

bash

pnpm --filter @running-days/business-logic test

Tests cover:

Edge cases (timezone boundaries, leap years)
Invalid input handling
Performance with large datasets