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// © 2022 Christoph Grenz <https://grenz-bonn.de>
//
// SPDX-License-Identifier: MPL-2.0

#[cfg(feature = "std")]
use std::io;

/// Error creating an [`SqlState`], [`Class`] or [`Category`].
///
/// [`SqlState`]: `struct@super::SqlState`
/// [`SqlState`]: `struct@super::SqlState`
/// [`Class`]: `struct@super::Class`
/// [`Category`]: `super::Category`
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[cfg_attr(feature = "std", derive(thiserror::Error))]
pub enum ParseError {
	/// The byte at index `position` in the string was not a valid ASCII character in the range `A-Z`,`0-9`.
	#[cfg_attr(
		feature = "std",
		error("invalid character {byte:?} at position {position}")
	)]
	InvalidChar { byte: u8, position: usize },
	/// The source string didn't have the expected length.
	#[cfg_attr(
		feature = "std",
		error("wrong string length (expected {expected}, got {got})")
	)]
	WrongLength { expected: u8, got: usize },
}

impl ParseError {
	/// Returns the index of the first invalid byte, the position of the premature end or of the
	/// first superfluous byte.
	///
	/// ```
	/// # use sqlstate_inline::SqlState;
	/// if let Err(error) = SqlState::from_str("000!0") {
	///   let index = error.valid_up_to();
	///   assert_eq!(index, 3);
	/// } else {
	///   unreachable!("this is no valid SQLSTATE code");
	/// }
	/// ```
	pub const fn valid_up_to(&self) -> usize {
		match *self {
			Self::InvalidChar { position, .. } => position,
			Self::WrongLength { expected, got } if got > (expected as _) => expected as _,
			Self::WrongLength { got, .. } => got,
		}
	}
}

#[cfg(feature = "std")]
impl From<ParseError> for io::Error {
	/// Converts a `ParseError` to an `std::io::Error` of kind `InvalidData` for convenience.
	fn from(error: ParseError) -> Self {
		Self::new(io::ErrorKind::InvalidData, error)
	}
}

// Statically assert that an `Option<ParseError>` is at most as big as two pointers for
// architectures with usual pointer sizes (>= 32 bit).
//
// We want e.g. `Result<[Char; 5], ParseError>` to be this small, but this optimization is only
// supported since Rust 1.65
#[cfg(any(
	target_pointer_width = "32",
	target_pointer_width = "64",
	target_pointer_width = "128"
))]
const _: () =
	assert!(core::mem::size_of::<Option<ParseError>>() <= core::mem::size_of::<usize>() * 2);