iridium-units 0.1.0

//! Imperial/US customary units.
//!
//! This module provides common Imperial and US customary units.
//!
//! # Examples
//!
//! ```
//! use iridium_units::prelude::*;
//!
//! // Marathon distance
//! let marathon = 42.195 * KM;
//! let in_miles = marathon.to(MILE).unwrap();
//! assert!((in_miles.value() - 26.219).abs() < 0.001);
//!
//! // Weight conversion
//! let weight = 150.0 * POUND;
//! let in_kg = weight.to(KG).unwrap();
//! assert!((in_kg.value() - 68.04).abs() < 0.01);
//! ```

use crate::dimension::{Dimension, Rational16};
use crate::unit::base::BaseUnit;

// Conversion factors
const INCH_M: f64 = 0.0254; // m (exact)
const FOOT_M: f64 = 0.3048; // m (exact)
const YARD_M: f64 = 0.9144; // m (exact)
const MILE_M: f64 = 1609.344; // m (exact)
const NAUTICAL_MILE_M: f64 = 1852.0; // m (exact)

const POUND_KG: f64 = 0.45359237; // kg (exact)
const OUNCE_KG: f64 = 0.028349523125; // kg (exact)
const TON_KG: f64 = 907.18474; // kg (short ton)
const LONG_TON_KG: f64 = 1016.0469088; // kg (long ton)

// Volume
const GALLON_US_M3: f64 = 0.003785411784; // m^3 (exact)
const GALLON_IMP_M3: f64 = 0.00454609; // m^3 (exact)
const FLUID_OUNCE_US_M3: f64 = 2.9573529562e-5; // m^3
const PINT_US_M3: f64 = 4.73176473e-4; // m^3
const QUART_US_M3: f64 = 9.46352946e-4; // m^3

// Shared dimension constants
const DIM_VOLUME: Dimension = Dimension::LENGTH.pow(Rational16::new(3, 1));
const DIM_FORCE: Dimension = Dimension::MASS
    .mul(&Dimension::LENGTH)
    .mul(&Dimension::TIME.pow(Rational16::new(-2, 1)));
const DIM_PRESSURE: Dimension = Dimension::MASS
    .mul(&Dimension::LENGTH.pow(Rational16::new(-1, 1)))
    .mul(&Dimension::TIME.pow(Rational16::new(-2, 1)));
const DIM_ENERGY: Dimension = Dimension::MASS
    .mul(&Dimension::LENGTH.pow(Rational16::new(2, 1)))
    .mul(&Dimension::TIME.pow(Rational16::new(-2, 1)));
const DIM_POWER: Dimension = Dimension::MASS
    .mul(&Dimension::LENGTH.pow(Rational16::new(2, 1)))
    .mul(&Dimension::TIME.pow(Rational16::new(-3, 1)));
const DIM_SPEED: Dimension = Dimension::LENGTH.mul(&Dimension::TIME.pow(Rational16::new(-1, 1)));

// =============================================================================
// Length Units
// =============================================================================

/// Inch (2.54 cm exactly)
pub const INCH: BaseUnit =
    BaseUnit::new("inch", "in", &["inch", "inches"], Dimension::LENGTH, INCH_M);

/// Foot (12 inches)
pub const FOOT: BaseUnit =
    BaseUnit::new("foot", "ft", &["foot", "feet"], Dimension::LENGTH, FOOT_M);

/// Yard (3 feet)
pub const YARD: BaseUnit =
    BaseUnit::new("yard", "yd", &["yard", "yards"], Dimension::LENGTH, YARD_M);

/// Mile (5280 feet)
pub const MILE: BaseUnit =
    BaseUnit::new("mile", "mi", &["mile", "miles"], Dimension::LENGTH, MILE_M);

/// Nautical mile (1852 m exactly)
pub const NAUTICAL_MILE: BaseUnit = BaseUnit::new(
    "nautical_mile",
    "nmi",
    &["NM"],
    Dimension::LENGTH,
    NAUTICAL_MILE_M,
);

/// Fathom (6 feet)
pub const FATHOM: BaseUnit = BaseUnit::new(
    "fathom",
    "fathom",
    &["fathoms"],
    Dimension::LENGTH,
    6.0 * FOOT_M,
);

/// Furlong (660 feet)
pub const FURLONG: BaseUnit = BaseUnit::new(
    "furlong",
    "fur",
    &["furlong", "furlongs"],
    Dimension::LENGTH,
    660.0 * FOOT_M,
);

/// Thou / mil (0.001 inch)
pub const THOU: BaseUnit =
    BaseUnit::new("thou", "thou", &["mil"], Dimension::LENGTH, INCH_M / 1000.0);

// =============================================================================
// Mass Units
// =============================================================================

/// Pound (avoirdupois)
pub const POUND: BaseUnit = BaseUnit::new(
    "pound",
    "lb",
    &["lbm", "pound", "pounds"],
    Dimension::MASS,
    POUND_KG,
);

/// Ounce (avoirdupois)
pub const OUNCE: BaseUnit = BaseUnit::new(
    "ounce",
    "oz",
    &["ounce", "ounces"],
    Dimension::MASS,
    OUNCE_KG,
);

/// Short ton (2000 lb)
pub const TON: BaseUnit = BaseUnit::new("ton", "ton", &["short_ton"], Dimension::MASS, TON_KG);

/// Long ton (2240 lb)
pub const LONG_TON: BaseUnit = BaseUnit::new(
    "long_ton",
    "long_ton",
    &["imperial_ton"],
    Dimension::MASS,
    LONG_TON_KG,
);

/// Grain (1/7000 lb)
pub const GRAIN: BaseUnit = BaseUnit::new(
    "grain",
    "gr",
    &["grain", "grains"],
    Dimension::MASS,
    POUND_KG / 7000.0,
);

/// Stone (14 lb)
pub const STONE: BaseUnit =
    BaseUnit::new("stone", "st", &["stone"], Dimension::MASS, 14.0 * POUND_KG);

// =============================================================================
// Volume Units (US)
// =============================================================================

/// US gallon
pub const GALLON: BaseUnit = BaseUnit::new(
    "gallon",
    "gal",
    &["gallon", "gallons"],
    DIM_VOLUME,
    GALLON_US_M3,
);

/// Imperial gallon
pub const IMPERIAL_GALLON: BaseUnit =
    BaseUnit::new("imperial_gallon", "imp_gal", &[], DIM_VOLUME, GALLON_IMP_M3);

/// US fluid ounce
pub const FLUID_OUNCE: BaseUnit = BaseUnit::new(
    "fluid_ounce",
    "fl_oz",
    &["floz"],
    DIM_VOLUME,
    FLUID_OUNCE_US_M3,
);

/// US pint
pub const PINT: BaseUnit = BaseUnit::new("pint", "pt", &["pint", "pints"], DIM_VOLUME, PINT_US_M3);

/// US quart
pub const QUART: BaseUnit =
    BaseUnit::new("quart", "qt", &["quart", "quarts"], DIM_VOLUME, QUART_US_M3);

/// Cubic inch
pub const CUBIC_INCH: BaseUnit = BaseUnit::new(
    "cubic_inch",
    "in^3",
    &["cu_in"],
    DIM_VOLUME,
    INCH_M * INCH_M * INCH_M,
);

/// Cubic foot
pub const CUBIC_FOOT: BaseUnit = BaseUnit::new(
    "cubic_foot",
    "ft^3",
    &["cu_ft"],
    DIM_VOLUME,
    FOOT_M * FOOT_M * FOOT_M,
);

// =============================================================================
// Force and Pressure
// =============================================================================

/// Pound-force
pub const POUND_FORCE: BaseUnit =
    BaseUnit::new("pound_force", "lbf", &[], DIM_FORCE, POUND_KG * 9.80665);

/// Pounds per square inch
pub const PSI: BaseUnit = BaseUnit::new(
    "psi",
    "psi",
    &[],
    DIM_PRESSURE,
    POUND_KG * 9.80665 / (INCH_M * INCH_M),
);

// =============================================================================
// Temperature (offsets handled in equivalencies)
// =============================================================================

/// Rankine (absolute temperature in Fahrenheit scale)
/// ΔR = ΔK * 9/5
pub const RANKINE: BaseUnit =
    BaseUnit::new("rankine", "R", &["degR"], Dimension::TEMPERATURE, 5.0 / 9.0);

// =============================================================================
// Energy
// =============================================================================

/// British thermal unit (IT)
pub const BTU: BaseUnit = BaseUnit::new("btu", "BTU", &["Btu"], DIM_ENERGY, 1055.05585);

/// Therm (100,000 BTU)
pub const THERM: BaseUnit = BaseUnit::new("therm", "therm", &[], DIM_ENERGY, 1.055e8);

/// Foot-pound
pub const FOOT_POUND: BaseUnit =
    BaseUnit::new("foot_pound", "ft_lbf", &["ft_lb"], DIM_ENERGY, 1.355818);

// =============================================================================
// Power
// =============================================================================

/// Horsepower (mechanical)
pub const HORSEPOWER: BaseUnit = BaseUnit::new("horsepower", "hp", &[], DIM_POWER, 745.69987);

// =============================================================================
// Speed
// =============================================================================

/// Miles per hour
pub const MPH: BaseUnit = BaseUnit::new("mph", "mph", &["mi/h"], DIM_SPEED, MILE_M / 3600.0);

/// Knot (nautical mile per hour)
pub const KNOT: BaseUnit = BaseUnit::new(
    "knot",
    "kn",
    &["kt", "knot", "knots"],
    DIM_SPEED,
    NAUTICAL_MILE_M / 3600.0,
);

#[cfg(test)]
mod tests {
    use super::*;
    use crate::systems::si::{CM, KG, M};

    #[test]
    fn test_foot_to_meters() {
        let q = 1.0 * FOOT;
        let q_m = q.to(M).unwrap();
        assert!((q_m.value() - 0.3048).abs() < 1e-10);
    }

    #[test]
    fn test_inch_to_cm() {
        let q = 1.0 * INCH;
        let q_cm = q.to(CM).unwrap();
        assert!((q_cm.value() - 2.54).abs() < 1e-10);
    }

    #[test]
    fn test_pound_to_kg() {
        let q = 1.0 * POUND;
        let q_kg = q.to(KG).unwrap();
        assert!((q_kg.value() - 0.45359237).abs() < 1e-10);
    }

    #[test]
    fn test_mile_to_km() {
        let q = 1.0 * MILE;
        let q_m = q.to(M).unwrap();
        assert!((q_m.value() - 1609.344).abs() < 1e-10);
    }
}