// Copyright 2024 Gabriel Bjørnager Jensen.
//
// This file is part of bzipper.
//
// bzipper is free software: you can redistribute
// it and/or modify it under the terms of the GNU
// Lesser General Public License as published by
// the Free Software Foundation, either version 3
// of the License, or (at your option) any later
// version.
//
// bzipper is distributed in the hope that it will
// be useful, but WITHOUT ANY WARRANTY; without
// even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Less-
// er General Public License along with bzipper. If
// not, see <https://www.gnu.org/licenses/>.

use core::fmt::{Display, Formatter};
use core::str::Utf8Error;

#[cfg(feature = "alloc")]
use alloc::boxed::Box;

/// Mapping of [`core::result::Result`].
pub type Result<T> = core::result::Result<T, Error>;

/// (De)serialisation failures.
///
/// These variants are used when deserialisation fails.
/// Serialisations are assumed infallible.
#[derive(Debug)]
pub enum Error {
	/// An array could not hold the requested amount of elements.
	ArrayTooShort { req: usize, len: usize },

	/// A string encountered an invalid UTF-8 sequence.
	BadString { source: Utf8Error },

	/// An implementor-defined error.
	///
	/// This is mainly useful if none of the predefined errors are appropriate.
	#[cfg(feature = "alloc")]
	#[cfg_attr(doc, doc(cfg(feature = "alloc")))]
	CustomError { source: Box<dyn core::error::Error> },

	/// Bytes were requested on an empty stream.
	EndOfStream { req: usize, rem: usize },

	/// A boolean encountered a value outside `0` and `1`.
	InvalidBoolean { value: u8 },

	/// An invalid code point was encountered.
	///
	/// This includes surrogate points in the inclusive range `U+D800` to `U+DFFF`, as well as values larger than `U+10FFFF`.
	InvalidCodePoint { value: u32 },

	/// An invalid enumeration descriminant was provided.
	InvalidDiscriminant { value: u32 },

	/// An `isize` value couldn't fit into `16` bits.
	IsizeOutOfRange { value: isize },

	/// A non-zero integer encountered the value `0`.
	NullInteger,

	/// A `usize` value couldn't fit into `16` bits.
	UsizeOutOfRange { value: usize },
}

impl Display for Error {
	fn fmt(&self, f: &mut Formatter) -> core::fmt::Result {
		use Error::*;

		match *self {
			ArrayTooShort { req, len }
			=> write!(f, "array of ({len}) element(s) cannot hold ({req})"),

			BadString { ref source }
			=> write!(f, "unable to parse utf8: \"{source}\""),

			#[cfg(feature = "alloc")]
			CustomError { ref source }
			=> write!(f, "{source}"),

			EndOfStream { req, rem }
			=> write!(f, "({req}) byte(s) were requested but only ({rem}) byte(s) were left"),

			InvalidBoolean { value }
			=> write!(f, "expected boolean but got {value:#02X}"),

			InvalidCodePoint { value }
			=> write!(f, "code point U+{value:04X} is not valid"),

			InvalidDiscriminant { value }
			=> write!(f, "discriminant ({value}) is not valid for the given enumeration"),

			IsizeOutOfRange { value }
			=> write!(f, "signed size value ({value}) cannot be serialised: must be in the range ({}) to ({})", i16::MIN, i16::MAX),

			NullInteger
			=> write!(f, "expected non-zero integer but got (0)"),

			UsizeOutOfRange { value }
			=> write!(f, "unsigned size value ({value}) cannot be serialised: must be at most ({})", u16::MAX),
		}
	}
}

impl core::error::Error for Error {
	fn source(&self) -> Option<&(dyn core::error::Error + 'static)> {
		use Error::*;

		match *self {
			BadString { ref source } => Some(source),

			#[cfg(feature = "alloc")]
			CustomError { ref source } => Some(source.as_ref()),

			_ => None,
		}
	}
}
