//! Hash-able floating-point wrappers, percentage values, and CSS size

//! metric types used by the CSS property system.

use core::fmt;

use std::num::ParseFloatError;

use crate::corety::AzString;

/// Multiplier for floating point accuracy.

///

/// Elements such as px or %

/// are only accurate until a certain number of decimal points, therefore

/// they have to be casted to isizes in order to make the f32 values

/// hash-able: Css has a relatively low precision here, roughly 3 digits, i.e

/// `1.001 == 1.0`

pub const FP_PRECISION_MULTIPLIER: f32 = 1000.0;

const FP_PRECISION_MULTIPLIER_CONST: isize = crate::cast::f32_to_isize(FP_PRECISION_MULTIPLIER);

/// Wrapper around `FloatValue`, represents a percentage instead

/// of just being a regular floating-point value, i.e `5` = `5%`

#[derive(Default, Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]

#[repr(C)]

pub struct PercentageValue {

    number: FloatValue,

}

impl_option!(

    PercentageValue,

    OptionPercentageValue,

    [Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash]

);

impl fmt::Display for PercentageValue {

}

impl PercentageValue {

    /// Same as `PercentageValue::new()`, but only accepts whole numbers.

    /// Uses isize arithmetic to avoid floating-point in const context.

    #[inline]

    #[must_use]

    /// Creates a `PercentageValue` from a fractional number in const context.

    ///

    /// # Arguments

    /// * `pre_comma` - The integer part (e.g., 100 for 100.5%)

    /// * `post_comma` - The fractional part as digits (e.g., 5 for 0.5%)

    ///

    /// # Examples

    /// ```

    /// // 100% = const_new_fractional(100, 0)

    /// // 50.5% = const_new_fractional(50, 5)

    /// ```

    #[inline]

    #[must_use]

    #[inline]

    #[must_use]

    // NOTE: no get() function, to avoid confusion with "150%"

    #[inline]

    #[must_use]

    #[inline]

    #[must_use]

}

/// Wrapper around an f32 value that is internally casted to an isize,

/// in order to provide hash-ability (to avoid numerical instability).

#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]

#[repr(C)]

pub struct FloatValue {

    pub(crate) number: isize,

}

impl fmt::Display for FloatValue {

}

impl ::core::fmt::Debug for FloatValue {

}

impl Default for FloatValue {

        const DEFAULT_FLV: FloatValue = FloatValue::const_new(0);

}

impl FloatValue {

    /// Same as `FloatValue::new()`, but only accepts whole numbers.

    /// Uses isize arithmetic to avoid floating-point in const context.

    #[inline]

    #[must_use]

    /// Creates a `FloatValue` from a fractional number in const context.

    ///

    /// This uses integer arithmetic to represent fractional values like 1.5, 0.83, etc.

    /// in const context without relying on f32 operations.

    ///

    /// The function automatically detects the number of decimal places in `post_comma`

    /// and supports up to 3 decimal places. If more digits are provided, only the first

    /// 3 are used (truncation, not rounding).

    ///

    /// # Arguments

    /// * `pre_comma` - The integer part (e.g., 1 for 1.5)

    /// * `post_comma` - The fractional part as digits (e.g., 5 for 0.5, 52 for 0.52, 523 for 0.523)

    ///

    /// # Examples

    /// ```

    /// // 1.5 = const_new_fractional(1, 5)

    /// // 1.52 = const_new_fractional(1, 52)

    /// // 1.523 = const_new_fractional(1, 523)

    /// // 0.83 = const_new_fractional(0, 83)

    /// // 1.17 = const_new_fractional(1, 17)

    /// // 2.123456 -> 2.123 (truncated to 3 decimal places)

    /// ```

    #[inline]

    #[must_use]

        // Get absolute value for digit counting

        } else {

        };

        // Determine the number of digits and extract only the first 3

        // Note: We limit to values that fit in 32-bit isize for WASM compatibility

            // 1 digit: 5 → 0.5

            // 2 digits: 83 → 0.83

            // 3 digits: 523 → 0.523

        } else {

            // 4+ digits: keep only the first 3 (e.g. 5234 → 523 → 0.523).

            // A fixed division ladder cannot bound the digit count for

            // arbitrarily large `post_comma` (an 11-digit value keeps 4 digits,

            // etc.), letting the "fraction" grow past 1.0 and corrupt the

            // integer part. Reduce until strictly below 1000 so the result is

            // always a proper 3-digit fraction.

        };

        // Calculate fractional part

        // Apply sign: if post_comma is negative, negate the fractional part

        } else {

        };

        // For negative pre_comma, the fractional part should also be negative

        // E.g., -1.5 = -1 + (-0.5), not -1 + 0.5

        } else {

        };

    #[inline]

    #[must_use]

    #[inline]

    #[must_use]

    /// Returns the raw encoded `isize` (the f32 value scaled by

    /// `FP_PRECISION_MULTIPLIER`). Exposed so external callers can

    /// round-trip the value through the compact-cache encoding without

    /// re-multiplying through f32.

    #[inline]

    #[must_use]

    #[inline]

    #[allow(clippy::suboptimal_flops)] // explicit FP; mul_add slower without +fma

    #[must_use]

}

impl From<f32> for FloatValue {

    #[inline]

}

/// Enum representing the metric associated with a number (px, pt, em, etc.)

#[derive(Debug, Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]

#[repr(C)]

#[derive(Default)]

pub enum SizeMetric {

    #[default]

    Px,

    Pt,

    Em,

    Rem,

    In,

    Cm,

    Mm,

    Percent,

    /// Viewport width: 1vw = 1% of viewport width

    Vw,

    /// Viewport height: 1vh = 1% of viewport height

    Vh,

    /// Viewport minimum: 1vmin = 1% of smaller viewport dimension

    Vmin,

    /// Viewport maximum: 1vmax = 1% of larger viewport dimension

    Vmax,

}

impl fmt::Display for SizeMetric {

        use self::SizeMetric::{Cm, Em, In, Mm, Percent, Pt, Px, Rem, Vh, Vmax, Vmin, Vw};

        }

}

/// # Errors

///

/// Returns an error if `input` is not a valid CSS `float-value` value.

#[allow(variant_size_differences)]

// repr(C,u8) FFI enum: boxing the large variant would change the C ABI (api.json bindings); size

// disparity accepted

#[derive(Clone, PartialEq, Eq)]

#[repr(C, u8)]

pub enum PercentageParseError {

    ValueParseErr(crate::props::basic::error::ParseFloatError),

    NoPercentSign,

    InvalidUnit(AzString),

}

impl_debug_as_display!(PercentageParseError);

impl From<ParseFloatError> for PercentageParseError {

}

impl_display! { PercentageParseError, {

    ValueParseErr(e) => format!("\"{}\"", e),

    NoPercentSign => format!("No percent sign after number"),

    InvalidUnit(u) => format!("Error parsing percentage: invalid unit \"{}\"", u.as_str()),

}}

#[allow(variant_size_differences)]

// repr(C,u8) FFI enum: boxing the large variant would change the C ABI (api.json bindings); size

// disparity accepted

#[derive(Debug, Clone, PartialEq, Eq)]

#[repr(C, u8)]

pub enum PercentageParseErrorOwned {

    ValueParseErr(crate::props::basic::error::ParseFloatError),

    NoPercentSign,

    InvalidUnit(AzString),

}

impl PercentageParseError {

    #[must_use]

        }

}

impl PercentageParseErrorOwned {

    #[must_use]

        }

}

/// Parse "1.2" or "120%" (similar to `parse_pixel_value`)

/// # Errors

///

/// Returns an error if `input` is not a valid CSS `percentage-value` value.

    }

        }

    }

#[cfg(all(test, feature = "parser"))]

mod tests {

    // Tests assert that parsed values equal the exact source literals.

    #![allow(clippy::float_cmp)]

    use super::*;

    #[test]

    #[test]

        // With percent sign

            0.755

        );

        // As a ratio

        // Errors

            PercentageParseError::InvalidUnit(_)

        ));

    #[test]

        // Single digit post_comma (1 decimal place)

    #[test]

        // Two digits post_comma (2 decimal places)

    #[test]

        // Three digits post_comma (3 decimal places)

    #[test]

        // More than 3 digits should be truncated (not rounded)

        // 4 digits: 5234 → 523 → 0.523

        // 5 digits: 12345 → 123 → 0.123

        // 6 digits: 123456 → 123 → 1.123

        // 7 digits: 9876543 → 987 → 0.987

        // 10 digits

    #[test]

        // Negative pre_comma values

        // Negative post_comma (unusual case - treated as negative fractional part)

    #[test]

        // Zero

        // Large integer part

        // Maximum precision (3 digits)

        // Small fractional values

    #[test]

        // Test actual values used in ua_css.rs

        // H1: 2em

        // H2: 1.5em

        // H3: 1.17em

        // H4: 1em

        // H5: 0.83em

        // H6: 0.67em

        // Margins: 0.67em

        // Margins: 0.83em

        // Margins: 1.33em

        // Margins: 1.67em

        // Margins: 2.33em

    #[test]

        // Verify consistency between const_new_fractional and new()

}

#[cfg(test)]

#[allow(

    clippy::float_cmp,

    clippy::unreadable_literal,

    clippy::excessive_precision

)]

mod autotest_generated {

    use std::{

        collections::{hash_map::DefaultHasher, HashSet},

        hash::{Hash, Hasher},

    };

    use super::*;

    use crate::props::basic::error::ParseFloatError as CssParseFloatError;

    /// Largest `isize` that `const_new` can scale by `FP_PRECISION_MULTIPLIER`

    /// without overflowing the multiplication.

    const MAX_SAFE_CONST_NEW: isize = isize::MAX / 1000;

    const MIN_SAFE_CONST_NEW: isize = isize::MIN / 1000;

    fn hash_of<T: Hash>(v: &T) -> u64 {

        let mut h = DefaultHasher::new();

        v.hash(&mut h);

        h.finish()

    }

    // ------------------------------------------------------- FloatValue::new ---

    #[test]

    fn float_value_new_never_produces_a_non_finite_get() {

        // `get()` decodes an isize, so it must be finite for *every* input,

        // including the ones that overflow the f32 multiply inside `new()`.

        for v in [

            f32::NAN,

            f32::INFINITY,

            f32::NEG_INFINITY,

            f32::MAX,

            f32::MIN,

            f32::MIN_POSITIVE,

            -f32::MIN_POSITIVE,

            0.0,

            -0.0,

            1e30,

            -1e30,

        ] {

            let got = FloatValue::new(v).get();

            assert!(

                got.is_finite(),

                "FloatValue::new({v}).get() leaked a non-finite value: {got}"

            );

        }

    }

    #[test]

    fn float_value_new_saturates_at_the_isize_bounds() {

        // f32 -> isize `as` casts saturate; +inf/-inf and anything that overflows

        // the *1000 multiply must clamp instead of wrapping.

        assert_eq!(FloatValue::new(f32::INFINITY).number(), isize::MAX);

        assert_eq!(FloatValue::new(f32::NEG_INFINITY).number(), isize::MIN);

        // f32::MAX * 1000.0 overflows to +inf before the cast.

        assert_eq!(FloatValue::new(f32::MAX).number(), isize::MAX);

        assert_eq!(FloatValue::new(f32::MIN).number(), isize::MIN);

    }

    #[test]

    fn float_value_new_collapses_nan_to_zero() {

        // NaN `as isize` is defined to be 0 — assert it, so a future hand-rolled

        // cast that panics or wraps is caught.

        let nan = FloatValue::new(f32::NAN);

        assert_eq!(nan.number(), 0);

        assert_eq!(nan.get(), 0.0);

        // ...and NaN is therefore *equal* to the default value, not unequal-to-itself.

        assert_eq!(nan, FloatValue::default());

        assert_eq!(hash_of(&nan), hash_of(&FloatValue::default()));

    }

    #[test]

    fn float_value_new_does_not_leak_negative_zero() {

        let neg_zero = FloatValue::new(-0.0);

        assert_eq!(neg_zero.number(), 0);

        assert!(

            neg_zero.get().is_sign_positive(),

            "-0.0 round-tripped back out as a negative zero"

        );

        assert_eq!(neg_zero, FloatValue::new(0.0));

    }

    #[test]

    fn float_value_new_underflows_subnormals_to_zero() {

        // Anything below 1/1000 truncates away entirely.

        assert_eq!(FloatValue::new(f32::MIN_POSITIVE).number(), 0);

        assert_eq!(FloatValue::new(1e-30).number(), 0);

        assert_eq!(FloatValue::new(0.0009).number(), 0);

    }

    #[test]

    fn float_value_new_truncates_toward_zero_not_to_nearest() {

        // Encoding is `(v * 1000) as isize`, i.e. truncation — 0.0019 must NOT

        // round up to 0.002, and the negative side must truncate toward zero too.

        assert_eq!(FloatValue::new(0.0019).number(), 1);

        assert_eq!(FloatValue::new(0.0019).get(), 0.001);

        assert_eq!(FloatValue::new(-0.0019).number(), -1);

        assert_eq!(FloatValue::new(-0.0019).get(), -0.001);

    }

    #[test]

    fn float_value_quantizes_below_the_precision_limit() {

        // The type's whole purpose: sub-precision differences collapse, so that

        // Eq/Hash are stable. 4th decimal is dropped, 3rd is kept.

        assert_eq!(FloatValue::new(1.0001), FloatValue::new(1.0));

        assert_ne!(FloatValue::new(1.001), FloatValue::new(1.0));

    }

    #[test]

    fn float_value_eq_implies_equal_hash() {

        // Eq + Hash must agree — the type exists purely to be hash-able.

        for (a, b) in [

            (1.0_f32, 1.0004_f32),

            (-2.5, -2.5001),

            (0.0, -0.0),

            (f32::NAN, f32::NAN),

        ] {

            let (a, b) = (FloatValue::new(a), FloatValue::new(b));

            assert_eq!(a, b, "expected {a:?} == {b:?}");

            assert_eq!(hash_of(&a), hash_of(&b), "{a:?} == {b:?} but hashes differ");

        }

    }

    #[test]

    fn float_value_ord_agrees_with_get() {

        // Ord is derived on the encoded isize; it must stay monotonic w.r.t. get().

        let mut vals: Vec<FloatValue> = [3.5_f32, -1.0, 0.0, 100.25, -0.001, 2.0]

            .into_iter()

            .map(FloatValue::new)

            .collect();

        vals.sort();

        for w in vals.windows(2) {

            assert!(

                w[0].get() <= w[1].get(),

                "sort order disagrees with get(): {:?} then {:?}",

                w[0],

                w[1]

            );

        }

    }

    // -------------------------------------------------- FloatValue::const_new ---

    #[test]

    fn const_new_matches_the_documented_encoding() {

        assert_eq!(FP_PRECISION_MULTIPLIER, 1000.0);

        assert_eq!(FloatValue::const_new(0).number(), 0);

        assert_eq!(FloatValue::const_new(1).number(), 1000);

        assert_eq!(FloatValue::const_new(-1).number(), -1000);

        assert_eq!(FloatValue::const_new(0), FloatValue::default());

    }

    #[test]

    fn const_new_agrees_with_new_for_whole_numbers() {

        for n in [-1000_isize, -7, -1, 0, 1, 7, 1000, 65_536] {

            let c = FloatValue::const_new(n);

            let r = FloatValue::new(n as f32);

            assert_eq!(

                c, r,

                "const_new({n}) = {c:?} disagrees with new({n}.0) = {r:?}"

            );

        }

    }

    #[test]

    fn const_new_survives_the_largest_non_overflowing_inputs() {

        // `const_new` is a bare `value * 1000`, so isize::MAX/1000 is the last

        // input it can take without overflowing. Pin that boundary: anything at

        // or below it must be exact and must not panic.

        let hi = FloatValue::const_new(MAX_SAFE_CONST_NEW);

        assert_eq!(hi.number(), MAX_SAFE_CONST_NEW * 1000);

        assert!(hi.get().is_finite());

        let lo = FloatValue::const_new(MIN_SAFE_CONST_NEW);

        assert_eq!(lo.number(), MIN_SAFE_CONST_NEW * 1000);

        assert!(lo.get().is_finite());

        assert!(lo < hi);

    }

    // --------------------------------------- FloatValue::const_new_fractional ---

    #[test]

    fn const_new_fractional_zero_and_sign_handling() {

        assert_eq!(FloatValue::const_new_fractional(0, 0).number(), 0);

        // Negative pre_comma pulls the fraction negative too (-1.5, not -0.5).

        assert_eq!(FloatValue::const_new_fractional(-1, 5).number(), -1500);

        // Negative post_comma subtracts from a positive pre_comma.

        assert_eq!(FloatValue::const_new_fractional(1, -5).number(), 500);

        assert_eq!(FloatValue::const_new_fractional(0, -50).number(), -500);

    }

    #[test]

    fn const_new_fractional_never_panics_on_extreme_post_comma() {

        // post_comma is an unbounded isize; the digit-count ladder must not

        // divide by zero, overflow, or produce a non-finite decode.

        for post in [

            9_isize,

            99,

            999,

            9_999,

            99_999,

            999_999,

            9_999_999,

            99_999_999,

            999_999_999,

            isize::MAX,

        ] {

            let v = FloatValue::const_new_fractional(0, post);

            assert!(

                v.get().is_finite(),

                "const_new_fractional(0, {post}) decoded to a non-finite value"

            );

        }

    }

    #[test]

    fn const_new_fractional_truncates_to_three_decimals() {

        // Documented: only the first 3 digits of post_comma are used, truncated.

        assert_eq!(FloatValue::const_new_fractional(0, 5234).number(), 523);

        assert_eq!(FloatValue::const_new_fractional(1, 123_456).number(), 1123);

        // 10 digits is the largest post_comma the ladder still truncates correctly.

        assert_eq!(

            FloatValue::const_new_fractional(2, 1_234_567_890).number(),

            2123

        );

    }

    #[test]

    fn const_new_fractional_boundary_between_digit_buckets() {

        // Every `abs_post < 10^k` bucket edge: 9/10, 99/100, 999/1000.

        assert_eq!(FloatValue::const_new_fractional(0, 9).get(), 0.9);

        assert_eq!(FloatValue::const_new_fractional(0, 10).get(), 0.1);

        assert_eq!(FloatValue::const_new_fractional(0, 99).get(), 0.99);

        assert_eq!(FloatValue::const_new_fractional(0, 100).get(), 0.1);

        assert_eq!(FloatValue::const_new_fractional(0, 999).get(), 0.999);

    }

    #[test]

    fn const_new_fractional_cannot_express_a_leading_zero_fraction() {

        // The bucket is picked from the *digit count* of post_comma, so a leading

        // zero is unrepresentable in an integer argument: 0.05 has no spelling.

        // Both of the obvious attempts land on 0.5 instead. Pin the footgun so a

        // caller writing `(0, 50)` for "0.05em" is caught by this test, not by a

        // 10x-too-large margin on screen.

        assert_eq!(FloatValue::const_new_fractional(0, 5).get(), 0.5);

        assert_eq!(FloatValue::const_new_fractional(0, 50).get(), 0.5);

        assert_eq!(FloatValue::const_new_fractional(0, 500).get(), 0.5);

    }

    // ------------------------------------------------- FloatValue::interpolate ---

    #[test]

    fn interpolate_endpoints_are_exact() {

        let a = FloatValue::new(0.0);

        let b = FloatValue::new(10.0);

        assert_eq!(a.interpolate(&b, 0.0), a);

        assert_eq!(a.interpolate(&b, 1.0), b);

        assert_eq!(a.interpolate(&b, 0.5).get(), 5.0);

        // Reversed direction.

        assert_eq!(b.interpolate(&a, 0.5).get(), 5.0);

    }

    #[test]

    fn interpolate_extrapolates_outside_zero_one() {

        // t is not clamped — assert the (documented-by-absence) extrapolation

        // rather than silently assuming a clamp that isn't there.

        let a = FloatValue::new(0.0);

        let b = FloatValue::new(10.0);

        assert_eq!(a.interpolate(&b, 2.0).get(), 20.0);

        assert_eq!(a.interpolate(&b, -1.0).get(), -10.0);

    }

    #[test]

    fn interpolate_with_nan_or_infinite_t_stays_finite() {

        let a = FloatValue::new(0.0);

        let b = FloatValue::new(10.0);

        // NaN t -> NaN interpolant -> `as isize` collapses to 0.

        assert_eq!(a.interpolate(&b, f32::NAN).number(), 0);

        // +inf t with a non-zero delta -> +inf -> saturates to isize::MAX.

        assert_eq!(a.interpolate(&b, f32::INFINITY).number(), isize::MAX);

        assert_eq!(a.interpolate(&b, f32::NEG_INFINITY).number(), isize::MIN);

        // inf * 0.0 delta is NaN -> collapses to 0 (self is NOT preserved here).

        assert_eq!(a.interpolate(&a, f32::INFINITY).number(), 0);

        for t in [

            f32::NAN,

            f32::INFINITY,

            f32::NEG_INFINITY,

            f32::MAX,

            f32::MIN,

        ] {

            assert!(

                a.interpolate(&b, t).get().is_finite(),

                "interpolate(t = {t}) leaked a non-finite value"

            );

        }

    }

    #[test]

    fn interpolate_between_saturated_extremes_does_not_panic() {

        let lo = FloatValue::new(f32::NEG_INFINITY); // isize::MIN

        let hi = FloatValue::new(f32::INFINITY); // isize::MAX

        for t in [0.0, 0.5, 1.0, -1.0, 2.0, f32::NAN] {

            assert!(lo.interpolate(&hi, t).get().is_finite());

            assert!(hi.interpolate(&lo, t).get().is_finite());

        }

    }

    // -------------------------------------------------------- round-tripping ---

    #[test]

    fn float_value_round_trips_through_display_and_parse() {

        // encode == decode: every value that is exactly representable at 3

        // decimals must survive Display -> parse_float_value -> FloatValue.

        for v in [0.0_f32, 1.5, -2.25, 100.0, 0.001, -0.001, 999.999, -0.5] {

            let fv = FloatValue::new(v);

            let round_tripped = parse_float_value(&fv.to_string())

                .unwrap_or_else(|e| panic!("Display of {fv:?} did not re-parse: {e}"));

            assert_eq!(

                fv, round_tripped,

                "round-trip changed {fv:?} into {round_tripped:?}"

            );

        }

    }

    #[test]

    fn float_value_number_round_trips_through_get() {

        // number() is the compact-cache encoding; get() must be its exact inverse

        // (scaled) for values inside the f32-exact integer range.

        for raw in [0_isize, 1, -1, 1500, -1500, 999_999, -999_999] {

            let fv = FloatValue::new(raw as f32 / 1000.0);

            assert_eq!(fv.number(), raw, "number() lost the encoding for {raw}");

        }

    }

    #[test]

    fn float_value_display_and_debug_agree() {

        // Debug is hand-written to forward to Display; a divergence means the

        // manual impl drifted.

        for v in [0.0_f32, -1.25, 1e6, f32::INFINITY, f32::NAN] {

            let fv = FloatValue::new(v);

            assert_eq!(format!("{fv:?}"), format!("{fv}"));

            assert!(!format!("{fv}").is_empty());

            // Whatever we print must itself be a parseable float.

            assert!(fv.to_string().parse::<f32>().is_ok());

        }

        assert_eq!(FloatValue::default().to_string(), "0");

    }

    // ---------------------------------------------------------- SizeMetric ---

    #[test]

    fn size_metric_display_is_non_empty_and_unique() {

        use SizeMetric::{Cm, Em, In, Mm, Percent, Pt, Px, Rem, Vh, Vmax, Vmin, Vw};

        let all = [Px, Pt, Em, Rem, In, Cm, Mm, Percent, Vw, Vh, Vmin, Vmax];

        let mut seen = HashSet::new();

        for m in all {

            let s = m.to_string();

            assert!(!s.is_empty(), "{m:?} renders as an empty string");

            assert!(

                seen.insert(s.clone()),

                "two SizeMetric variants both render as {s:?} (copy-paste in Display)"

            );

        }

        assert_eq!(seen.len(), all.len());

    }

    #[test]

    fn size_metric_display_matches_the_css_unit_tokens() {

        assert_eq!(SizeMetric::Px.to_string(), "px");

        assert_eq!(SizeMetric::Pt.to_string(), "pt");

        assert_eq!(SizeMetric::Em.to_string(), "em");

        assert_eq!(SizeMetric::Rem.to_string(), "rem");

        assert_eq!(SizeMetric::In.to_string(), "in");

        assert_eq!(SizeMetric::Cm.to_string(), "cm");

        assert_eq!(SizeMetric::Mm.to_string(), "mm");

        assert_eq!(SizeMetric::Percent.to_string(), "%");

        assert_eq!(SizeMetric::Vw.to_string(), "vw");

        assert_eq!(SizeMetric::Vh.to_string(), "vh");

        assert_eq!(SizeMetric::Vmin.to_string(), "vmin");

        assert_eq!(SizeMetric::Vmax.to_string(), "vmax");

    }

    #[test]

    fn size_metric_default_is_px() {

        assert_eq!(SizeMetric::default(), SizeMetric::Px);

        assert_eq!(SizeMetric::default().to_string(), "px");

    }

    // -------------------------------------------------------- PercentageValue ---

    #[test]

    fn percentage_value_normalized_divides_by_a_hundred() {

        assert_eq!(PercentageValue::new(50.0).normalized(), 0.5);

        assert_eq!(PercentageValue::new(0.0).normalized(), 0.0);

        assert_eq!(PercentageValue::new(-25.0).normalized(), -0.25);

        assert_eq!(PercentageValue::const_new(100).normalized(), 1.0);

        assert_eq!(PercentageValue::default().normalized(), 0.0);

    }

    #[test]

    fn percentage_value_normalized_is_always_finite() {

        for v in [

            f32::NAN,

            f32::INFINITY,

            f32::NEG_INFINITY,

            f32::MAX,

            f32::MIN,

        ] {

            let n = PercentageValue::new(v).normalized();

            assert!(

                n.is_finite(),

                "PercentageValue::new({v}).normalized() leaked {n}"

            );

        }

        // NaN collapses to the default, exactly like FloatValue.

        assert_eq!(PercentageValue::new(f32::NAN), PercentageValue::default());

    }

    #[test]

    fn percentage_value_const_new_boundaries_do_not_panic() {

        assert_eq!(PercentageValue::const_new(0), PercentageValue::default());

        assert!(PercentageValue::const_new(MAX_SAFE_CONST_NEW)

            .normalized()

            .is_finite());

        assert!(PercentageValue::const_new(MIN_SAFE_CONST_NEW)

            .normalized()

            .is_finite());

        assert!(

            PercentageValue::const_new(MIN_SAFE_CONST_NEW)

                < PercentageValue::const_new(MAX_SAFE_CONST_NEW)

        );

    }

    #[test]

    fn percentage_value_const_new_fractional_matches_the_docs() {

        // 100% = const_new_fractional(100, 0); 50.5% = const_new_fractional(50, 5)

        assert_eq!(

            PercentageValue::const_new_fractional(100, 0).normalized(),

            1.0

        );

        assert!((PercentageValue::const_new_fractional(50, 5).normalized() - 0.505).abs() < 1e-5);

        assert_eq!(

            PercentageValue::const_new_fractional(100, 0),

            PercentageValue::const_new(100)

        );

    }

    #[test]

    fn percentage_value_interpolate_endpoints_and_nan() {

        let a = PercentageValue::new(0.0);

        let b = PercentageValue::new(100.0);

        assert_eq!(a.interpolate(&b, 0.0), a);

        assert_eq!(a.interpolate(&b, 1.0), b);

        assert_eq!(a.interpolate(&b, 0.5).normalized(), 0.5);

        // NaN / inf t must not panic and must stay finite.

        assert_eq!(a.interpolate(&b, f32::NAN).normalized(), 0.0);

        assert!(a.interpolate(&b, f32::INFINITY).normalized().is_finite());

        assert!(a

            .interpolate(&b, f32::NEG_INFINITY)

            .normalized()

            .is_finite());

    }

    #[test]

    fn percentage_value_display_round_trips_through_the_parser() {

        for v in [0.0_f32, 50.0, 100.0, 150.0, -25.0, 75.5, 0.5] {

            let p = PercentageValue::new(v);

            let s = p.to_string();

            assert!(s.ends_with('%'), "Display lost the percent sign: {s:?}");

            let back = parse_percentage_value(&s)

                .unwrap_or_else(|e| panic!("Display of {p:?} ({s:?}) did not re-parse: {e}"));

            assert!(

                (back.normalized() - p.normalized()).abs() < 1e-4,

                "round-trip drifted: {p:?} -> {s:?} -> {back:?}"

            );

        }

    }

    // ----------------------------------------------------- parse_float_value ---

    #[test]

    fn parse_float_value_positive_control() {

        assert_eq!(parse_float_value("0").unwrap().number(), 0);

        assert_eq!(parse_float_value("1.5").unwrap().number(), 1500);

        assert_eq!(parse_float_value("-1.5").unwrap().number(), -1500);

        assert_eq!(parse_float_value("+2").unwrap().number(), 2000);

        // Rust's f32 parser accepts these shorthand forms.

        assert_eq!(parse_float_value(".5").unwrap().number(), 500);

        assert_eq!(parse_float_value("5.").unwrap().number(), 5000);

    }

    #[test]

    fn parse_float_value_rejects_empty_and_whitespace() {

        assert!(parse_float_value("").is_err());

        assert!(parse_float_value("   ").is_err());

        assert!(parse_float_value("\t\n\r ").is_err());

    }

    #[test]

    fn parse_float_value_rejects_garbage() {

        for input in [

            "abc",

            "1_000",

            "1,5",

            "0x10",

            "1.2.3",

            "--1",

            "1e",

            "e5",

            "5 5",

            "1/2",

            ";",

            "\0",

            "5;garbage",

            "50px",

            "5%",

        ] {

            assert!(

                parse_float_value(input).is_err(),

                "garbage input {input:?} was accepted"

            );

        }

    }

    #[test]

    fn parse_float_value_trims_but_does_not_tolerate_inner_junk() {

        assert_eq!(parse_float_value("  1.5  ").unwrap().number(), 1500);

        assert!(parse_float_value("1.5 garbage").is_err());

    }

    #[test]

    fn parse_float_value_boundary_numbers_saturate_instead_of_panicking() {

        // -0 must not leak a negative zero out of the encoding.

        assert_eq!(parse_float_value("-0").unwrap().number(), 0);

        assert!(parse_float_value("-0").unwrap().get().is_sign_positive());

        // Rust parses "NaN"/"inf" successfully; the encoding must then defuse them.

        assert_eq!(parse_float_value("NaN").unwrap().number(), 0);

        assert_eq!(parse_float_value("inf").unwrap().number(), isize::MAX);

        assert_eq!(parse_float_value("infinity").unwrap().number(), isize::MAX);

        assert_eq!(parse_float_value("-inf").unwrap().number(), isize::MIN);

        // Overflow of the f32 parse itself is Ok(inf) in Rust, then saturates.

        assert_eq!(parse_float_value("1e400").unwrap().number(), isize::MAX);

        assert_eq!(parse_float_value("-1e400").unwrap().number(), isize::MIN);

        // Underflow is Ok(0.0).

        assert_eq!(parse_float_value("1e-400").unwrap().number(), 0);

        // i64::MAX / f64::MAX as literals: no panic, still finite after decode.

        for input in [

            "9223372036854775807",

            "-9223372036854775808",

            "179769313486231570000000000000000000000000000000000",

        ] {

            let v = parse_float_value(input)

                .unwrap_or_else(|e| panic!("{input:?} should parse as f32, got {e}"));

            assert!(v.get().is_finite(), "{input:?} decoded to {}", v.get());

        }

    }

    #[test]

    fn parse_float_value_unicode_does_not_panic() {

        // Multi-byte input must be rejected, never sliced mid-codepoint.

        for input in [

            "\u{1F600}",  // emoji

            "5\u{1F600}", // digit + emoji

            "\u{0665}",   // ARABIC-INDIC DIGIT FIVE (is_numeric() == true)

            "5\u{0301}",  // digit + combining acute

            "\u{00BD}",   // ½ (No category, is_numeric() == true)

            "\u{FF15}",   // FULLWIDTH DIGIT FIVE

            "\u{200B}5",  // zero-width space + digit

            "\u{2212}5",  // U+2212 MINUS SIGN (not ASCII '-')

        ] {

            assert!(

                parse_float_value(input).is_err(),

                "non-ASCII input {input:?} was accepted as a float"

            );

        }

    }

    #[test]

    fn parse_float_value_extremely_long_input_terminates() {

        // 200k digits: must not hang, must not panic; Rust yields Ok(inf), which

        // then saturates in the encoding.

        let huge = "9".repeat(200_000);

        // Rejecting is acceptable too — just don't panic/hang on the huge input.

        if let Ok(v) = parse_float_value(&huge) {

            assert!(v.get().is_finite(), "200k digits decoded to {}", v.get());

        }

        // Long *garbage* must be rejected rather than scanned quadratically.

        let long_junk = "a".repeat(200_000);

        assert!(parse_float_value(&long_junk).is_err());

    }

    #[test]

    fn parse_float_value_deeply_nested_input_does_not_stack_overflow() {

        let nested = "(".repeat(10_000);

        assert!(parse_float_value(&nested).is_err());

        let nested_pair = format!("{}5{}", "(".repeat(10_000), ")".repeat(10_000));

        assert!(parse_float_value(&nested_pair).is_err());

    }

    // ------------------------------------------------ parse_percentage_value ---

    #[test]

    fn parse_percentage_value_positive_control() {

        assert_eq!(parse_percentage_value("50%").unwrap().normalized(), 0.5);

        assert_eq!(parse_percentage_value("0%").unwrap().normalized(), 0.0);

        assert_eq!(parse_percentage_value("-25%").unwrap().normalized(), -0.25);

        // A bare number is a *ratio*, not a percent: "0.5" == "50%".

        assert_eq!(

            parse_percentage_value("0.5").unwrap(),

            parse_percentage_value("50%").unwrap()

        );

    }

    #[test]

    fn parse_percentage_value_bare_number_is_multiplied_by_a_hundred() {

        // Easy to misread: "50" (no sign) is 5000%, not 50%.

        assert_eq!(parse_percentage_value("50").unwrap().normalized(), 50.0);

        assert_ne!(

            parse_percentage_value("50").unwrap(),

            parse_percentage_value("50%").unwrap()

        );

    }

    #[test]

    fn parse_percentage_value_rejects_empty_and_whitespace() {

        assert!(matches!(

            parse_percentage_value(""),

            Err(PercentageParseError::ValueParseErr(_))

        ));

        assert!(matches!(

            parse_percentage_value("   "),

            Err(PercentageParseError::ValueParseErr(_))

        ));

        assert!(matches!(

            parse_percentage_value("\t\n"),

            Err(PercentageParseError::ValueParseErr(_))

        ));

        assert!(parse_percentage_value("%").is_err());

    }

    #[test]

    fn parse_percentage_value_rejects_garbage_without_panicking() {

        for input in [

            "abc", "fifty%", "%50", "50%%", "5 0 %", "--5%", "1.2.3%", ";", "\0", "NaN", "inf",

            "-inf",

        ] {

            assert!(

                parse_percentage_value(input).is_err(),

                "garbage input {input:?} was accepted"

            );

        }

    }

    #[test]

    fn parse_percentage_value_reports_invalid_units() {

        for (input, unit) in [("50px", "px"), ("50em", "em"), ("1.5rem", "rem")] {

            match parse_percentage_value(input) {

                Err(PercentageParseError::InvalidUnit(u)) => assert_eq!(u.as_str(), unit),

                other => panic!("{input:?} should be InvalidUnit({unit:?}), got {other:?}"),