//! C-compatible (`#[repr(C)]`) error types for CSS parsing failures.

//!

//! Mirrors `core::num::ParseFloatError` and `core::num::ParseIntError` for FFI use,

//! and provides generic invalid-value error wrappers.

use crate::corety::AzString;

/// Simple "invalid value" error, used for basic parsing failures

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

pub struct InvalidValueErr<'a>(pub &'a str);

/// Owned version of `InvalidValueErr` with `AzString`.

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

#[repr(C)]

pub struct InvalidValueErrOwned {

    pub value: AzString,

}

/// C-compatible enum mirroring `core::num::ParseFloatError` internals.

///

/// `core::num::ParseFloatError` is a 1-byte enum with variants `Empty` and `Invalid`,

/// but its `kind` field is private. We mirror the variants here for FFI compatibility.

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

#[repr(C)]

pub enum ParseFloatError {

    /// Input string was empty.

    Empty,

    /// Input string was not a valid float literal.

    Invalid,

}

impl ParseFloatError {

    /// Convert from `core::num::ParseFloatError` by comparing against known error instances.

        // Compare against the known Empty error instance to avoid

        // relying on Display message wording or allocating a format string.

        } else {

        }

    /// Reconstruct a `core::num::ParseFloatError` from our C-compatible variant.

        }

}

impl core::fmt::Display for ParseFloatError {

        }

}

impl From<core::num::ParseFloatError> for ParseFloatError {

}

/// C-compatible enum mirroring `core::num::ParseIntError` internals.

///

/// `core::num::ParseIntError` is a 1-byte enum with variants matching `IntErrorKind`.

/// We mirror them here for FFI compatibility.

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

#[repr(C)]

pub enum ParseIntError {

    /// Input string was empty.

    Empty,

    /// Input contained an invalid digit.

    InvalidDigit,

    /// Input overflowed the target integer type (positive).

    PosOverflow,

    /// Input overflowed the target integer type (negative).

    NegOverflow,

    /// Input was zero but zero is not allowed (rarely used).

    Zero,

}

impl ParseIntError {

    /// Convert from `core::num::ParseIntError` using the stable `kind()` method.

        use core::num::IntErrorKind;

        }

    /// Reconstruct a `core::num::ParseIntError` from our C-compatible variant.

            Self::Zero => {

                // Zero variant cannot be reproduced on stable Rust; falls back to InvalidDigit.

                // Note: round-tripping Zero through to_std() then from_std() yields InvalidDigit.

            }

        }

}

impl core::fmt::Display for ParseIntError {

        }

}

impl From<core::num::ParseIntError> for ParseIntError {

}

/// Wrapper for a `ParseFloatError` paired with the input string that failed.

/// Used by multiple Owned error enums that need to store both the error and input.

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

#[repr(C)]

pub struct ParseFloatErrorWithInput {

    pub error: ParseFloatError,

    pub input: AzString,

}

/// Wrapper for `WrongNumberOfComponents` errors in CSS filter/transform parsing.

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

#[repr(C)]

pub struct WrongComponentCountError {

    pub expected: usize,

    pub got: usize,

    pub input: AzString,

}

impl InvalidValueErr<'_> {

}

impl InvalidValueErrOwned {

}

#[cfg(test)]

#[allow(clippy::too_many_lines)]

mod autotest_generated {

    use core::num::IntErrorKind;

    use std::{

        collections::hash_map::DefaultHasher,

        hash::{Hash, Hasher},

    };

    use super::*;

    // =====================================================================

    // helpers

    // =====================================================================

    /// Parse `s` as `T`, expecting failure, and funnel the std error through

    /// the private `from_std` constructor under test.

    fn float_kind<T>(s: &str) -> ParseFloatError

    where

        T: core::str::FromStr<Err = core::num::ParseFloatError>,

    {

        match s.parse::<T>() {

            Ok(_) => panic!("expected {s:?} to FAIL to parse as a float"),

            Err(e) => ParseFloatError::from_std(&e),

        }

    }

    fn int_kind<T>(s: &str) -> ParseIntError

    where

        T: core::str::FromStr<Err = core::num::ParseIntError>,

    {

        match s.parse::<T>() {

            Ok(_) => panic!("expected {s:?} to FAIL to parse as an integer"),

            Err(e) => ParseIntError::from_std(&e),

        }

    }

    fn std_float_err(s: &str) -> core::num::ParseFloatError {

        s.parse::<f32>().expect_err("input should not parse")

    }

    fn std_int_err(s: &str) -> core::num::ParseIntError {

        s.parse::<i32>().expect_err("input should not parse")

    }

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

        let mut h = DefaultHasher::new();

        v.hash(&mut h);

        h.finish()

    }

    const ALL_FLOAT: [ParseFloatError; 2] = [ParseFloatError::Empty, ParseFloatError::Invalid];

    const ALL_INT: [ParseIntError; 5] = [

        ParseIntError::Empty,

        ParseIntError::InvalidDigit,

        ParseIntError::PosOverflow,

        ParseIntError::NegOverflow,

        ParseIntError::Zero,

    ];

    // =====================================================================

    // ParseFloatError::from_std  (constructor, private)

    // =====================================================================

    #[test]

    fn float_from_std_empty_string_maps_to_empty() {

        assert_eq!(float_kind::<f32>(""), ParseFloatError::Empty);

        // The comparison instance inside `from_std` is built from `f32`; an error

        // produced by an `f64` parse must still classify as `Empty` (std compares

        // the private `kind`, not the source type).

        assert_eq!(float_kind::<f64>(""), ParseFloatError::Empty);

    }

    #[test]

    fn float_from_std_blank_input_is_invalid_not_empty() {

        // A string that *looks* empty but is not: `from_std` must NOT collapse

        // these into `Empty`, because std trims nothing.

        for s in [

            " ",

            "  ",

            "\t",

            "\n",

            "\r\n",

            "\u{a0}",    // NBSP

            "\u{feff}",  // BOM

            "\u{200b}",  // zero-width space

            "\u{0}",     // NUL

        ] {

            assert_eq!(

                float_kind::<f32>(s),

                ParseFloatError::Invalid,

                "blank-ish input {s:?} must be Invalid, not Empty"

            );

        }

    }

    #[test]

    fn float_from_std_malformed_inputs_are_invalid() {

        for s in [

            "x", ".", "-", "+", "e", "e5", "5e", "1.2.3", "0x1f", "1,5", "--1", "++1", "1 ", " 1",

            "1_0", "NaNx", "infinit", "1/2", "abc", "1e", "1e+", "-.",

        ] {

            assert_eq!(

                float_kind::<f32>(s),

                ParseFloatError::Invalid,

                "malformed input {s:?} should be Invalid"

            );

        }

    }

    #[test]

    fn float_from_std_non_ascii_digits_are_invalid() {

        for s in [

            "١٢٣",     // Arabic-Indic digits

            "１２３",  // fullwidth digits

            "½",       // vulgar fraction

            "😀",

            "٣.٥",

            "1\u{301}", // combining acute after a valid digit

            "Ⅻ",        // roman numeral

        ] {

            assert_eq!(

                float_kind::<f32>(s),

                ParseFloatError::Invalid,

                "unicode input {s:?} should be Invalid"

            );

        }

    }

    #[test]

    fn float_from_std_huge_malformed_input_does_not_panic_or_hang() {

        let mut huge = "9".repeat(100_000);

        huge.push('x');

        assert_eq!(float_kind::<f32>(&huge), ParseFloatError::Invalid);

        // 100k leading zeros followed by garbage: still just Invalid.

        let mut zeros = "0".repeat(100_000);

        zeros.push_str("..");

        assert_eq!(float_kind::<f32>(&zeros), ParseFloatError::Invalid);

    }

    #[test]

    fn float_from_impl_agrees_with_from_std() {

        for s in ["", " ", "x", "1.2.3", "😀"] {

            let a: ParseFloatError = std_float_err(s).into();

            let b = ParseFloatError::from_std(&std_float_err(s));

            assert_eq!(a, b, "From<> and from_std disagree for {s:?}");

        }

    }

    // =====================================================================

    // float numeric limits: magnitude overflow never reaches our error type

    // =====================================================================

    #[test]

    fn float_magnitude_overflow_saturates_to_infinity_instead_of_erroring() {

        // No `ParseFloatError` is produced for out-of-range magnitudes — std

        // saturates. Anything relying on an "overflow" variant would be wrong.

        assert!(

            "1e400".parse::<f32>().expect("saturates, does not error").is_infinite(),

            "huge positive exponent should saturate to +inf"

        );

        assert!("-1e400".parse::<f32>().expect("saturates").is_sign_negative());

        assert_eq!("1e-400".parse::<f32>().expect("underflows to zero"), 0.0);

        let huge = "9".repeat(100_000);

        assert!(huge.parse::<f32>().expect("saturates").is_infinite());

    }

    #[test]

    fn float_nan_and_inf_literals_parse_and_never_error() {

        assert!("nan".parse::<f32>().expect("nan is valid").is_nan());

        assert!("NaN".parse::<f32>().expect("NaN is valid").is_nan());

        assert!("inf".parse::<f32>().expect("inf is valid").is_infinite());

        assert!("infinity".parse::<f32>().expect("infinity is valid").is_infinite());

        assert!("-inf".parse::<f32>().expect("-inf is valid").is_sign_negative());

        assert!("-0".parse::<f32>().expect("-0 is valid").is_sign_negative());

    }

    // =====================================================================

    // ParseFloatError::to_std  (getter) + round-trip

    // =====================================================================

    #[test]

    fn float_to_std_returns_the_matching_std_error() {

        assert_eq!(ParseFloatError::Empty.to_std(), std_float_err(""));

        assert_eq!(ParseFloatError::Invalid.to_std(), std_float_err("x"));

    }

    #[test]

    fn float_to_std_variants_stay_distinct() {

        // If these ever collapsed, `from_std` would misclassify every error.

        assert_ne!(ParseFloatError::Empty.to_std(), ParseFloatError::Invalid.to_std());

    }

    #[test]

    fn float_to_std_is_deterministic() {

        for v in ALL_FLOAT {

            assert_eq!(v.to_std(), v.to_std(), "to_std() must be stable for {v:?}");

        }

    }

    #[test]

    fn float_round_trip_encode_decode_is_identity() {

        for v in ALL_FLOAT {

            assert_eq!(ParseFloatError::from_std(&v.to_std()), v, "round-trip lost {v:?}");

            assert_eq!(ParseFloatError::from(v.to_std()), v);

        }

    }

    // =====================================================================

    // ParseIntError::from_std  (constructor, private)

    // =====================================================================

    #[test]

    fn int_from_std_empty_string_maps_to_empty_for_every_width() {

        assert_eq!(int_kind::<i8>(""), ParseIntError::Empty);

        assert_eq!(int_kind::<u8>(""), ParseIntError::Empty);

        assert_eq!(int_kind::<i32>(""), ParseIntError::Empty);

        assert_eq!(int_kind::<u128>(""), ParseIntError::Empty);

        assert_eq!(int_kind::<usize>(""), ParseIntError::Empty);

        assert_eq!(int_kind::<isize>(""), ParseIntError::Empty);

    }

    #[test]

    fn int_from_std_malformed_inputs_are_invalid_digit() {

        for s in [

            "x", " ", "  ", "\t", "+", "-", "+-1", "--1", "1 ", " 1", "1_000", "0x10", "1.0",

            "1e3", "abc", "\u{0}", "1\u{0}", "٣", "１２３", "😀", "½", ",", "1,000",

        ] {

            assert_eq!(

                int_kind::<i32>(s),

                ParseIntError::InvalidDigit,

                "malformed input {s:?} should be InvalidDigit"

            );

        }

    }

    #[test]

    fn int_from_std_negative_into_unsigned_is_invalid_digit_not_neg_overflow() {

        // std rejects the '-' sign as a digit for unsigned types rather than

        // reporting NegOverflow — a classifier that assumed otherwise would be wrong.

        assert_eq!(int_kind::<u32>("-1"), ParseIntError::InvalidDigit);

        assert_eq!(int_kind::<u8>("-0"), ParseIntError::InvalidDigit);

        assert_eq!(int_kind::<u128>("-99999999999999999999999999"), ParseIntError::InvalidDigit);

    }

    #[test]

    fn int_from_std_positive_overflow_boundaries() {

        // exactly MAX parses; MAX + 1 overflows.

        assert_eq!(i32::MAX.to_string().parse::<i32>(), Ok(i32::MAX));

        assert_eq!(int_kind::<i32>("2147483648"), ParseIntError::PosOverflow);

        assert_eq!(u8::MAX.to_string().parse::<u8>(), Ok(u8::MAX));

        assert_eq!(int_kind::<u8>("256"), ParseIntError::PosOverflow);

        assert_eq!(i8::MAX.to_string().parse::<i8>(), Ok(i8::MAX));

        assert_eq!(int_kind::<i8>("128"), ParseIntError::PosOverflow);

        assert_eq!(

            int_kind::<u128>("340282366920938463463374607431768211456"),

            ParseIntError::PosOverflow

        );

    }

    #[test]

    fn int_from_std_negative_overflow_boundaries() {

        assert_eq!(i32::MIN.to_string().parse::<i32>(), Ok(i32::MIN));

        assert_eq!(int_kind::<i32>("-2147483649"), ParseIntError::NegOverflow);

        assert_eq!(i8::MIN.to_string().parse::<i8>(), Ok(i8::MIN));

        assert_eq!(int_kind::<i8>("-129"), ParseIntError::NegOverflow);

        assert_eq!(int_kind::<i128>("-99999999999999999999999999999999999999999"), ParseIntError::NegOverflow);

    }

    #[test]

    fn int_from_std_huge_digit_runs_overflow_without_panic() {

        let huge = "9".repeat(10_000);

        assert_eq!(int_kind::<i32>(&huge), ParseIntError::PosOverflow);

        assert_eq!(int_kind::<u128>(&huge), ParseIntError::PosOverflow);

        let huge_neg = format!("-{huge}");

        assert_eq!(int_kind::<i64>(&huge_neg), ParseIntError::NegOverflow);

    }

    #[test]

    fn int_leading_zeros_do_not_produce_a_false_overflow() {

        // 10k leading zeros: the digit loop multiplies by 10 each step, so a naive

        // overflow check would trip here. It must still parse cleanly.

        let padded = format!("{}5", "0".repeat(10_000));

        assert_eq!(padded.parse::<i32>(), Ok(5));

        assert_eq!("0000000000000000000000000000005".parse::<i32>(), Ok(5));

    }

    #[test]

    fn int_from_std_zero_variant_is_reachable_via_nonzero_types() {

        // Contrary to the note on `to_std`, `IntErrorKind::Zero` IS constructible on

        // stable via the NonZero* parsers — so `from_std` really can return `Zero`.

        assert_eq!(int_kind::<core::num::NonZeroU8>("0"), ParseIntError::Zero);

        assert_eq!(int_kind::<core::num::NonZeroI32>("0"), ParseIntError::Zero);

        assert_eq!(int_kind::<core::num::NonZeroUsize>("0"), ParseIntError::Zero);

        // ...while other failures on the same type keep their own classification.

        assert_eq!(int_kind::<core::num::NonZeroU8>(""), ParseIntError::Empty);

        assert_eq!(int_kind::<core::num::NonZeroU8>("x"), ParseIntError::InvalidDigit);

        assert_eq!(int_kind::<core::num::NonZeroU8>("256"), ParseIntError::PosOverflow);

    }

    #[test]

    fn int_from_impl_agrees_with_from_std() {

        for s in ["", "x", "99999999999999999999", "-99999999999999999999", "😀"] {

            let a: ParseIntError = std_int_err(s).into();

            let b = ParseIntError::from_std(&std_int_err(s));

            assert_eq!(a, b, "From<> and from_std disagree for {s:?}");

        }

    }

    // =====================================================================

    // ParseIntError::to_std  (getter) + round-trip

    // =====================================================================

    #[test]

    fn int_to_std_maps_each_variant_onto_the_expected_std_kind() {

        assert!(matches!(ParseIntError::Empty.to_std().kind(), IntErrorKind::Empty));

        assert!(matches!(ParseIntError::InvalidDigit.to_std().kind(), IntErrorKind::InvalidDigit));

        assert!(matches!(ParseIntError::PosOverflow.to_std().kind(), IntErrorKind::PosOverflow));

        assert!(matches!(ParseIntError::NegOverflow.to_std().kind(), IntErrorKind::NegOverflow));

        // Documented lossy case: `Zero` degrades to an InvalidDigit std error.

        assert!(matches!(ParseIntError::Zero.to_std().kind(), IntErrorKind::InvalidDigit));

    }

    #[test]

    fn int_to_std_is_deterministic() {

        for v in ALL_INT {

            assert_eq!(v.to_std(), v.to_std(), "to_std() must be stable for {v:?}");

        }

    }

    #[test]

    fn int_round_trip_encode_decode_is_identity_except_for_zero() {

        for v in [

            ParseIntError::Empty,

            ParseIntError::InvalidDigit,

            ParseIntError::PosOverflow,

            ParseIntError::NegOverflow,

        ] {

            assert_eq!(ParseIntError::from_std(&v.to_std()), v, "round-trip lost {v:?}");

            assert_eq!(ParseIntError::from(v.to_std()), v);

        }

        // `Zero` is the one variant that does NOT survive to_std() -> from_std(),

        // exactly as the code comments document. (It is *not* an un-representable

        // kind though — see `int_from_std_zero_variant_is_reachable_via_nonzero_types`.)

        assert_eq!(

            ParseIntError::from_std(&ParseIntError::Zero.to_std()),

            ParseIntError::InvalidDigit,

            "Zero round-trip is documented as lossy"

        );

    }

    #[test]

    fn int_to_std_variants_stay_distinct_where_they_must() {

        let empty = ParseIntError::Empty.to_std();

        let invalid = ParseIntError::InvalidDigit.to_std();

        let pos = ParseIntError::PosOverflow.to_std();

        let neg = ParseIntError::NegOverflow.to_std();

        assert_ne!(empty, invalid);

        assert_ne!(invalid, pos);

        assert_ne!(pos, neg);

        assert_ne!(empty, neg);

        // Zero aliases InvalidDigit (documented).

        assert_eq!(ParseIntError::Zero.to_std(), invalid);

    }

    // =====================================================================

    // Display / Debug (serializers)

    // =====================================================================

    #[test]

    fn display_output_is_non_empty_and_unique_per_variant() {

        let float_msgs: Vec<String> = ALL_FLOAT.iter().map(ToString::to_string).collect();

        for m in &float_msgs {

            assert!(!m.is_empty(), "float Display must not be empty");

        }

        assert_ne!(float_msgs[0], float_msgs[1], "float variants must be distinguishable");

        let int_msgs: Vec<String> = ALL_INT.iter().map(ToString::to_string).collect();

        for m in &int_msgs {

            assert!(!m.is_empty(), "int Display must not be empty");

        }

        for i in 0..int_msgs.len() {

            for j in (i + 1)..int_msgs.len() {

                assert_ne!(int_msgs[i], int_msgs[j], "int variants {i}/{j} share a message");

            }

        }

    }

    #[test]

    fn display_mirrors_the_std_error_messages() {

        // The whole point of these types is to be a faithful FFI mirror of the std

        // errors; if std ever reworded a message, this catches the drift.

        assert_eq!(ParseFloatError::Empty.to_string(), std_float_err("").to_string());

        assert_eq!(ParseFloatError::Invalid.to_string(), std_float_err("x").to_string());

        assert_eq!(ParseIntError::Empty.to_string(), std_int_err("").to_string());

        assert_eq!(ParseIntError::InvalidDigit.to_string(), std_int_err("x").to_string());

        assert_eq!(

            ParseIntError::PosOverflow.to_string(),

            std_int_err("99999999999999999999").to_string()

        );

        assert_eq!(

            ParseIntError::NegOverflow.to_string(),

            std_int_err("-99999999999999999999").to_string()

        );

        // `Zero` cannot go through `to_std()` (it aliases InvalidDigit), so compare

        // against a genuine Zero-kind error obtained from a NonZero parse.

        let std_zero = "0"

            .parse::<core::num::NonZeroU8>()

            .expect_err("parsing 0 as NonZeroU8 must fail");

        assert!(matches!(std_zero.kind(), IntErrorKind::Zero));

        assert_eq!(ParseIntError::Zero.to_string(), std_zero.to_string());

    }

    #[test]

    fn display_with_formatter_flags_does_not_panic() {

        for v in ALL_INT {

            let msg = v.to_string();

            let padded = format!("{v:>60}");

            assert!(!padded.is_empty());

            assert!(padded.contains(&msg), "padding must not corrupt the message");

            // precision / fill / alternate flags: no panic, still produces output

            assert!(!format!("{v:.3}").is_empty());

            assert!(!format!("{v:*^10}").is_empty());

            assert!(!format!("{v:#?}").is_empty());

        }

        for v in ALL_FLOAT {

            assert!(!format!("{v:>60}").is_empty());

            assert!(!format!("{v:.1}").is_empty());

            assert!(!format!("{v:?}").is_empty());

        }

    }

    #[test]

    fn debug_output_names_the_variant() {

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

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

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

    }

    // =====================================================================

    // derived-trait invariants (Eq / Ord / Hash / Copy)

    // =====================================================================

    #[test]

    fn error_enums_have_consistent_eq_hash_and_ord() {

        for (i, a) in ALL_INT.iter().enumerate() {

            assert_eq!(hash_of(a), hash_of(&ALL_INT[i]), "equal values must hash equal");

            for (j, b) in ALL_INT.iter().enumerate() {

                assert_eq!(a == b, i == j, "only identical variants may compare equal");

                assert_eq!(a.cmp(b), i.cmp(&j), "Ord must follow declaration order");

            }

        }

        assert!(ParseFloatError::Empty < ParseFloatError::Invalid);

        assert_eq!(hash_of(&ParseFloatError::Empty), hash_of(&ParseFloatError::Empty));

        assert_ne!(ParseFloatError::Empty, ParseFloatError::Invalid);

    }

    #[test]

    fn error_enums_are_copy_and_survive_a_sort() {

        let mut v = [

            ParseIntError::Zero,

            ParseIntError::Empty,

            ParseIntError::NegOverflow,

            ParseIntError::InvalidDigit,

            ParseIntError::PosOverflow,

        ];

        v.sort_unstable();

        assert_eq!(v, ALL_INT);

        let a = ParseIntError::Zero;

        let b = a; // Copy, not move

        assert_eq!(a, b);

    }

    // =====================================================================

    // InvalidValueErr::to_contained / InvalidValueErrOwned::to_shared

    // =====================================================================

    #[test]

    fn invalid_value_err_round_trips_through_owned() {

        for s in [

            "",

            "a",

            "border-radius",

            "   ",

            "\n\t",

            "börder-radiüs 😀",

            "٣.٥",

            "\u{feff}leading-bom",

            "trailing-nul\u{0}",

            "a\u{0}b",

        ] {

            let shared = InvalidValueErr(s);

            let owned = shared.to_contained();

            assert_eq!(owned.value.as_str(), s, "to_contained lost {s:?}");

            assert_eq!(owned.to_shared(), shared, "round-trip changed {s:?}");

            assert_eq!(owned.to_shared().0, s);

        }

    }

    #[test]

    fn invalid_value_err_empty_string_is_not_confused_with_default() {

        let owned = InvalidValueErr("").to_contained();

        assert_eq!(owned.value, AzString::default());

        assert!(owned.value.as_str().is_empty());

        assert_eq!(owned.to_shared(), InvalidValueErr(""));

        assert_eq!(owned, InvalidValueErrOwned { value: AzString::default() });

    }

    #[test]

    fn invalid_value_err_preserves_interior_nul_bytes() {

        // If the AzString conversion ever went through a C-string, this would

        // truncate at the NUL.

        let s = "a\u{0}b";

        let owned = InvalidValueErr(s).to_contained();

        assert_eq!(owned.value.as_bytes(), b"a\0b");

        assert_eq!(owned.value.as_str().len(), 3);

        assert_eq!(owned.to_shared().0.len(), 3);

    }

    #[test]

    fn to_contained_deep_copies_and_outlives_its_source() {

        let owned = {

            let src = String::from("temporary-buffer");

            let copied = InvalidValueErr(src.as_str()).to_contained();

            assert!(

                !core::ptr::eq(copied.value.as_str().as_ptr(), src.as_str().as_ptr()),

                "to_contained must copy, not alias the borrowed input"

            );

            drop(src);

            copied

        };

        assert_eq!(owned.value.as_str(), "temporary-buffer");

    }

    #[test]

    fn to_shared_borrows_the_owned_buffer_without_copying() {

        let owned = InvalidValueErr("shared-buffer").to_contained();

        let shared = owned.to_shared();

        assert!(

            core::ptr::eq(shared.0.as_ptr(), owned.value.as_str().as_ptr()),

            "to_shared must borrow the existing buffer"

        );

        // calling it twice yields the same view

        assert_eq!(owned.to_shared(), owned.to_shared());

    }

    #[test]

    fn invalid_value_err_handles_a_huge_payload() {

        let big = "ü".repeat(100_000); // 200_000 bytes, non-ASCII

        let owned = InvalidValueErr(big.as_str()).to_contained();

        assert_eq!(owned.value.as_str().len(), big.len());

        assert_eq!(owned.value.as_bytes().len(), 200_000);

        assert_eq!(owned.to_shared().0, big.as_str());

        assert_eq!(owned.clone(), owned);

    }

    #[test]

    fn invalid_value_err_owned_equality_is_by_content() {

        let a = InvalidValueErr("x").to_contained();

        let b = InvalidValueErrOwned { value: AzString::from("x") };

        let c = InvalidValueErrOwned { value: AzString::from("y") };

        assert_eq!(a, b);

        assert_ne!(a, c);

        assert_eq!(a.clone(), a);

        assert_eq!(a.to_shared(), b.to_shared());

    }

    // =====================================================================

    // ParseFloatErrorWithInput / WrongComponentCountError

    // =====================================================================

    #[test]

    fn parse_float_error_with_input_keeps_error_and_input_together() {

        let input = "1.2.3";

        let err = ParseFloatErrorWithInput {

            error: ParseFloatError::from(std_float_err(input)),

            input: AzString::from(input),

        };

        assert_eq!(err.error, ParseFloatError::Invalid);

        assert_eq!(err.input.as_str(), input);

        assert_eq!(err.clone(), err);

        let empty = ParseFloatErrorWithInput {

            error: ParseFloatError::from(std_float_err("")),

            input: AzString::default(),

        };

        assert_eq!(empty.error, ParseFloatError::Empty);

        assert!(empty.input.as_str().is_empty());

        assert_ne!(empty, err);

        assert!(!format!("{err:?}").is_empty());

    }

    #[test]

    fn wrong_component_count_error_survives_usize_extremes() {

        let e = WrongComponentCountError {

            expected: usize::MAX,

            got: 0,

            input: AzString::from("rgba(1)"),

        };

        assert_eq!(e.expected, usize::MAX);

        assert_eq!(e.got, 0);

        assert_eq!(e.input.as_str(), "rgba(1)");

        assert_eq!(e.clone(), e);

        assert!(!format!("{e:?}").is_empty());

        let same_but_got_max = WrongComponentCountError {

            expected: usize::MAX,

            got: usize::MAX,

            input: AzString::from("rgba(1)"),

        };

        assert_ne!(e, same_but_got_max, "`got` participates in equality");

        // A 0-expected / 0-got degenerate error is still constructible and inert.

        let zeroed = WrongComponentCountError {

            expected: 0,

            got: 0,

            input: AzString::default(),

        };

        assert_eq!(zeroed.expected, zeroed.got);

        assert!(zeroed.input.as_str().is_empty());

    }

}