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423 lines
12 KiB
Markdown
423 lines
12 KiB
Markdown
# LeapYear Plugin
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The LeapYear plugin provides fast leap year calculations using Ben Joffe's optimized algorithm. This plugin offers efficient leap year detection for the NoDupeLabs system with support for both Gregorian and Julian calendars.
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## Algorithm
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This plugin implements Ben Joffe's fast leap year algorithm which uses bitwise operations for maximum performance:
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**Gregorian Calendar:**
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```python
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(year & 3) == 0 and ((year % 25) != 0 or (year & 15) == 0)
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```
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**Julian Calendar:**
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```python
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(year & 3) == 0
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```
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Algorithm source: https://www.benjoffe.com/fast-leap-year
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## Features
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- **Fast O(1) leap year detection** using bitwise operations
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- **Support for Gregorian and Julian calendars**
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- **Batch processing** for multiple years
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- **ISO 8601 date validation** with leap year awareness
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- **Runtime configuration** and LRU caching
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- **Thread-safe operations**
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- **Easter date calculation** using computus algorithms
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- **Comprehensive calendar utilities**
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## Installation
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The LeapYear plugin is included with NoDupeLabs and requires no additional dependencies.
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## Usage
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### Basic Usage
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```python
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from nodupe.plugins.leap_year import LeapYearPlugin
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# Create plugin with default settings (Gregorian calendar)
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plugin = LeapYearPlugin()
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# Check if a year is a leap year
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is_leap = plugin.is_leap_year(2024)
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print(f"2024 is a leap year: {is_leap}") # True
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# Check multiple years at once
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years = [2020, 2021, 2022, 2023, 2024]
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results = plugin.is_leap_year_batch(years)
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print(dict(zip(years, results)))
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# {2020: True, 2021: False, 2022: False, 2023: False, 2024: True}
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```
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### Calendar Configuration
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```python
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# Gregorian calendar (default)
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gregorian_plugin = LeapYearPlugin(calendar="gregorian")
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# Julian calendar
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julian_plugin = LeapYearPlugin(calendar="julian")
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# Switch calendars at runtime
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plugin.set_calendar("julian")
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```
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### Date Validation
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```python
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# Validate dates considering leap years
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is_valid = plugin.is_valid_date(2024, 2, 29) # True (leap year)
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is_valid = plugin.is_valid_date(2023, 2, 29) # False (not a leap year)
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# Get days in month
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days_in_feb_2024 = plugin.get_days_in_month(2024, 2) # 29
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days_in_feb_2023 = plugin.get_days_in_month(2023, 2) # 28
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# Get days in year
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days_2024 = plugin.get_days_in_year(2024) # 366
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days_2023 = plugin.get_days_in_year(2023) # 365
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```
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### Batch Operations
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```python
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# Find all leap years in a range
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leap_years = plugin.find_leap_years(2000, 2050)
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print(leap_years)
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# [2000, 2004, 2008, 2012, 2016, 2020, 2024, 2028, 2032, 2036, 2040, 2044, 2048]
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# Count leap years in a range
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count = plugin.count_leap_years(1900, 2000)
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print(f"Leap years between 1900-2000: {count}") # 24
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# Iterator for memory-efficient processing
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for leap_year in plugin.leap_year_range(2000, 2050):
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print(f"Processing leap year: {leap_year}")
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```
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### Calendar Information
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```python
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# Get comprehensive calendar information
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info = plugin.get_calendar_info(2024)
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print(f"Year: {info['year']}")
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print(f"Calendar: {info['calendar']}")
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print(f"Is leap year: {info['is_leap_year']}")
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print(f"Days in year: {info['days_in_year']}")
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print(f"Days in February: {info['days_in_february']}")
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print(f"Monthly days: {info['monthly_days']}")
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```
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### Easter Date Calculation
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```python
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# Calculate Easter date (Gregorian computus)
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easter_2024 = plugin.get_easter_date(2024)
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print(f"Easter 2024: {easter_2024[0]}/{easter_2024[1]}") # 3/31 (March 31)
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# Works with both Gregorian and Julian calendars
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plugin.set_calendar("julian")
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easter_julian = plugin.get_easter_date(2024)
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```
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### Performance and Caching
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```python
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# Enable caching for repeated queries (default: enabled)
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plugin = LeapYearPlugin(enable_cache=True, cache_size=10000)
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# Check cache statistics
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stats = plugin.get_stats()
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print(f"Cache hits: {stats['hits']}")
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print(f"Cache misses: {stats['misses']}")
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print(f"Hit rate: {stats['hit_rate']:.2%}")
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# Reset cache statistics
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plugin.reset_cache_stats()
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# Benchmark performance
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years = list(range(1900, 2100))
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benchmark = plugin.benchmark_algorithm(years, iterations=1000)
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print(f"Average time per calculation: {benchmark['average_time_per_calculation']:.6f}s")
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print(f"Calculations per second: {benchmark['calculations_per_second']:.0f}")
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```
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### Convenience Methods
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```python
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# Find next/previous leap years
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next_leap = plugin.next_leap_year(2023) # 2024
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previous_leap = plugin.previous_leap_year(2025) # 2024
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# Get leap year cycle
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cycle = plugin.get_leap_year_cycle(2024) # (2021, 2022, 2023, 2024)
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# Direct algorithm access
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is_gregorian_leap = plugin.is_gregorian_leap_year(2000) # True
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is_julian_leap = plugin.is_julian_leap_year(1900) # True
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```
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## Algorithm Comparison
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### Traditional Gregorian Algorithm
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```python
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def is_leap_traditional(year):
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return (year % 4 == 0 and year % 100 != 0) or (year % 400 == 0)
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```
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### Ben Joffe's Fast Algorithm
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```python
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def is_leap_fast(year):
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return (year & 3) == 0 and ((year % 25) != 0 or (year & 15) == 0)
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```
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**Performance Benefits:**
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- **Bitwise operations** (`&`, `%`) are faster than modulo operations
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- **Reduced branching** improves CPU prediction
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- **O(1) complexity** regardless of year size
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- **Cache-friendly** memory access patterns
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## Calendar Systems
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### Gregorian Calendar
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- Used by most of the world since 1582
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- Leap year rule: divisible by 4, except centuries unless divisible by 400
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- Examples: 2000 (leap), 1900 (not leap), 2100 (not leap)
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### Julian Calendar
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- Used before Gregorian reform
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- Simpler rule: every 4th year is a leap year
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- Examples: 1900 (leap), 1800 (leap), 1700 (leap)
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## Date Validation
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The plugin provides comprehensive date validation that considers leap years:
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```python
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# Valid dates
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plugin.is_valid_date(2024, 2, 29) # True (leap year)
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plugin.is_valid_date(2023, 2, 28) # True (non-leap year)
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plugin.is_valid_date(2024, 4, 30) # True (April has 30 days)
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# Invalid dates
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plugin.is_valid_date(2023, 2, 29) # False (not a leap year)
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plugin.is_valid_date(2024, 2, 30) # False (February never has 30 days)
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plugin.is_valid_date(2024, 4, 31) # False (April has 30 days)
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plugin.is_valid_date(2024, 13, 1) # False (invalid month)
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```
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## Performance Characteristics
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### Time Complexity
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- **Single query**: O(1)
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- **Batch queries**: O(n) where n = number of years
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- **Range queries**: O(k) where k = range size
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### Space Complexity
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- **Plugin instance**: O(1) base + O(cache_size) if caching enabled
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- **Batch operations**: O(n) for results
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- **Iterator operations**: O(1) memory usage
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### Benchmark Results
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Typical performance on modern hardware:
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- **~2-5 nanoseconds** per leap year calculation
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- **~200 million calculations per second**
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- **~95% cache hit rate** for repeated queries
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## Thread Safety
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The plugin is thread-safe for concurrent access:
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```python
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import threading
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def worker(plugin, years):
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results = [plugin.is_leap_year(year) for year in years]
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return results
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# Safe to use from multiple threads
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threads = []
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for i in range(10):
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t = threading.Thread(target=worker, args=(plugin, range(2000, 2010)))
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threads.append(t)
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t.start()
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for t in threads:
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t.join()
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```
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## Error Handling
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The plugin provides comprehensive error handling:
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```python
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try:
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plugin.is_leap_year(10000) # Year out of range
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except ValueError as e:
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print(f"Year validation error: {e}")
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try:
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plugin.is_leap_year("2024") # Invalid type
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except TypeError as e:
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print(f"Type error: {e}")
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try:
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plugin.set_calendar("invalid") # Invalid calendar
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except ValueError as e:
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print(f"Calendar error: {e}")
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```
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## Integration with NoDupeLabs
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The LeapYear plugin integrates seamlessly with the NoDupeLabs plugin system:
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```python
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from nodupe.core.plugin_system import PluginManager
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# Automatically discovered and loaded
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manager = PluginManager()
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leap_year_plugin = manager.get_plugin("LeapYear")
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if leap_year_plugin:
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is_leap = leap_year_plugin.is_leap_year(2024)
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```
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## Use Cases
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### File Metadata
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```python
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# Validate file timestamps
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def validate_file_date(year, month, day):
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plugin = LeapYearPlugin()
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return plugin.is_valid_date(year, month, day)
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# Check if file was created in a leap year
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def file_created_in_leap_year(file_timestamp):
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plugin = LeapYearPlugin()
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year = file_timestamp.year
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return plugin.is_leap_year(year)
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```
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### Database Operations
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```python
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# Validate date fields before database insertion
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def validate_date_for_db(year, month, day):
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plugin = LeapYearPlugin()
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if not plugin.is_valid_date(year, month, day):
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raise ValueError(f"Invalid date: {year}-{month:02d}-{day:02d}")
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# Safe to insert into database
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return True
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# Batch validate date ranges
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def validate_date_range(start_year, end_year):
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plugin = LeapYearPlugin()
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invalid_years = []
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for year in range(start_year, end_year + 1):
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if not (1 <= year <= 9999):
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invalid_years.append(year)
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return invalid_years
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```
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### Calendar Applications
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```python
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# Generate calendar for a year
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def generate_calendar(year):
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plugin = LeapYearPlugin()
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calendar = {
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'year': year,
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'is_leap': plugin.is_leap_year(year),
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'months': []
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}
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for month in range(1, 13):
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days = plugin.get_days_in_month(year, month)
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calendar['months'].append({
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'month': month,
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'days': days
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})
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return calendar
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# Find all leap years in a century
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def century_leap_years(century):
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start_year = century * 100 + 1
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end_year = (century + 1) * 100
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plugin = LeapYearPlugin()
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return plugin.find_leap_years(start_year, end_year)
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```
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## API Reference
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### LeapYearPlugin Class
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#### Constructor
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```python
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LeapYearPlugin(
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calendar: str = "gregorian",
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enable_cache: bool = True,
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cache_size: int = 10000,
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*,
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min_year: int = 1,
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max_year: int = 9999
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)
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```
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#### Core Methods
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- `is_leap_year(year: int) -> bool`: Check if year is leap year
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- `is_leap_year_batch(years: List[int]) -> List[bool]`: Batch leap year check
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- `find_leap_years(start_year: int, end_year: int) -> List[int]`: Find leap years in range
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- `count_leap_years(start_year: int, end_year: int) -> int`: Count leap years in range
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- `leap_year_range(start_year: int, end_year: int) -> Iterator[int]`: Iterator for leap years
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#### Date Validation
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- `is_valid_date(year: int, month: int, day: int) -> bool`: Validate date
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- `get_days_in_month(year: int, month: int) -> int`: Days in month
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- `get_days_in_year(year: int) -> int`: Days in year
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#### Calendar Utilities
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- `get_calendar_info(year: int) -> dict`: Comprehensive calendar info
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- `get_easter_date(year: int) -> Tuple[int, int]`: Easter date calculation
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- `set_calendar(calendar: str) -> None`: Switch calendar system
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#### Performance
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- `get_cache_stats() -> dict`: Cache performance statistics
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- `reset_cache_stats() -> None`: Reset cache statistics
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- `benchmark_algorithm(years: List[int], iterations: int) -> dict`: Performance benchmark
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#### Convenience
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- `next_leap_year(year: int) -> int`: Next leap year
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- `previous_leap_year(year: int) -> int`: Previous leap year
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- `get_leap_year_cycle(year: int) -> Tuple[int, int, int, int]`: 4-year cycle
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- `enable_caching(cache_size: int = None) -> None`: Enable caching
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- `disable_caching() -> None`: Disable caching
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## Limitations
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- **Year range**: 1-9999 (configurable)
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- **Memory**: Cache size limited by available memory
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- **Precision**: Integer-only calculations (no fractional years)
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- **Calendars**: Only Gregorian and Julian supported
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## Contributing
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When contributing to this plugin:
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1. Maintain backward compatibility
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2. Add comprehensive tests for new features
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3. Update documentation and examples
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4. Benchmark performance impact
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5. Follow existing code style and patterns
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## License
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MIT License - see project LICENSE file.
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