// SPDX-License-Identifier: MIT
// SPDX-FileCopyrightText: Copyright (C) 2023 Tsukasa OI <floss_ssdeep@irq.a4lg.com>.


/// An enumeration representing a cause of
/// a [fuzzy hash](crate::FuzzyHashData) parse error.
#[repr(u8)]
#[non_exhaustive]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ParseErrorKind {
    /// Block size: is empty.
    BlockSizeIsEmpty,
    /// Block size: is not valid.
    BlockSizeIsInvalid,
    /// Block size: is too large to parse.
    BlockSizeIsTooLarge,
    /// Block hash (either 1 or 2): block hash is too long.
    BlockHashIsTooLong,
    /// Any: an unexpected character is encountered.
    UnexpectedCharacter,
    /// Any: an unexpected end-of-string is encountered.
    UnexpectedEndOfString,
}

impl core::fmt::Display for ParseErrorKind {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        f.write_str(match self {
            ParseErrorKind::BlockHashIsTooLong    => "block hash is too long.",
            ParseErrorKind::BlockSizeIsEmpty      => "block size field is empty.",
            ParseErrorKind::BlockSizeIsInvalid    => "block size is not valid.",
            ParseErrorKind::BlockSizeIsTooLarge   => "block size is too large.",
            ParseErrorKind::UnexpectedCharacter   => "an unexpected character is encountered.",
            ParseErrorKind::UnexpectedEndOfString => "end-of-string is not expected.",
        })
    }
}


/// A part which (possibly) caused a
/// [fuzzy hash](crate::FuzzyHashData) parse error.
///
/// See [`FuzzyHashData`](crate::FuzzyHashData) for corresponding parts.
///
/// Since the parser ignores the file name part,
/// this part is not in this enumeration.
#[repr(u8)]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ParseErrorOrigin {
    /// Block size.
    BlockSize,
    /// Block hash 1.
    BlockHash1,
    /// Block hash 2.
    BlockHash2,
}

impl core::fmt::Display for ParseErrorOrigin {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        f.write_str(match self {
            ParseErrorOrigin::BlockSize  => "block size",
            ParseErrorOrigin::BlockHash1 => "block hash 1",
            ParseErrorOrigin::BlockHash2 => "block hash 2",
        })
    }
}


/// The error type for parse operations of
/// [`FuzzyHashData`](crate::FuzzyHashData).
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct ParseError(
    pub(crate) ParseErrorKind,
    pub(crate) ParseErrorOrigin,
    pub(crate) usize
);

/// The trait implementing a [`FuzzyHashData`](crate::FuzzyHashData) parse error.
pub trait ParseErrorInfo {
    /// Returns the cause of the error.
    fn kind(&self) -> ParseErrorKind;
    /// Returns the part which (possibly) caused the error.
    fn origin(&self) -> ParseErrorOrigin;
    /// Returns the offset which (possibly) caused the error.
    ///
    /// Note that this offset may not be exact but may be usable as a hint.
    fn offset(&self) -> usize;
}

impl ParseErrorInfo for ParseError {
    fn kind(&self) -> ParseErrorKind { self.0 }
    fn origin(&self) -> ParseErrorOrigin { self.1 }
    fn offset(&self) -> usize { self.2 }
}

impl core::fmt::Display for ParseError {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        write!(f, "Error occurred while parsing a fuzzy hash ({1}, at byte offset {2}): {0}",
            self.kind(),
            self.origin(),
            self.offset()
        )
    }
}

#[cfg(feature = "std")]
impl std::error::Error for ParseError {}


/// A type which represents a state after parsing a block hash.
///
/// Note that while some of them always represent one of error conditions,
/// some are valid depending on the context.
#[repr(u32)]
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(crate) enum BlockHashParseState {
    /// The end of the string is encountered.
    MetEndOfString,
    /// A comma character (`,`) is encountered.
    MetComma,
    /// A colon character (`:`) is encountered.
    MetColon,
    /// A block hash is too long so that would cause an overflow.
    OverflowError,
    /// An invalid Base64 alphabet (or just an unexpected character) is encountered.
    Base64Error,
}





// grcov-excl-br-start
#[cfg(test)]
mod tests {
    use super::*;
    #[cfg(feature = "alloc")]
    use alloc::format;
    #[cfg(feature = "alloc")]
    use crate::test_utils::test_auto_debug_for_enum;
    use crate::test_utils::test_auto_clone;

    #[test]
    fn test_parse_error_enums_clone() {
        test_auto_clone::<ParseErrorKind>(&ParseErrorKind::BlockHashIsTooLong);
        test_auto_clone::<ParseErrorOrigin>(&ParseErrorOrigin::BlockSize);
    }

    #[cfg(feature = "alloc")]
    #[test]
    fn test_parse_error_enums_display_and_debug() {
        // Display
        assert_eq!(format!("{}", ParseErrorKind::BlockHashIsTooLong),    "block hash is too long.");
        assert_eq!(format!("{}", ParseErrorKind::BlockSizeIsEmpty),      "block size field is empty.");
        assert_eq!(format!("{}", ParseErrorKind::BlockSizeIsInvalid),    "block size is not valid.");
        assert_eq!(format!("{}", ParseErrorKind::BlockSizeIsTooLarge),   "block size is too large.");
        assert_eq!(format!("{}", ParseErrorKind::UnexpectedCharacter),   "an unexpected character is encountered.");
        assert_eq!(format!("{}", ParseErrorKind::UnexpectedEndOfString), "end-of-string is not expected.");
        assert_eq!(format!("{}", ParseErrorOrigin::BlockSize),  "block size");
        assert_eq!(format!("{}", ParseErrorOrigin::BlockHash1), "block hash 1");
        assert_eq!(format!("{}", ParseErrorOrigin::BlockHash2), "block hash 2");
        // Debug
        test_auto_debug_for_enum!(
            ParseErrorKind,
            [
                BlockSizeIsEmpty,
                BlockSizeIsInvalid,
                BlockSizeIsTooLarge,
                BlockHashIsTooLong,
                UnexpectedCharacter,
                UnexpectedEndOfString,
            ]
        );
        test_auto_debug_for_enum!(
            ParseErrorOrigin,
            [
                BlockSize,
                BlockHash1,
                BlockHash2,
            ]
        );
    }

    #[test]
    fn test_block_hash_parse_state_clone() {
        test_auto_clone::<BlockHashParseState>(&BlockHashParseState::MetEndOfString);
    }

    #[cfg(feature = "alloc")]
    #[test]
    fn test_block_hash_parse_state_debug() {
        test_auto_debug_for_enum!(
            BlockHashParseState,
            [
                MetEndOfString,
                MetComma,
                MetColon,
                OverflowError,
                Base64Error,
            ]
        );
    }

    #[test]
    fn test_parse_error_basic() {
        let err = ParseError(ParseErrorKind::UnexpectedEndOfString, ParseErrorOrigin::BlockHash1, 2);
        test_auto_clone::<ParseError>(&err);
        assert_eq!(err.kind(), ParseErrorKind::UnexpectedEndOfString);
        assert_eq!(err.origin(), ParseErrorOrigin::BlockHash1);
        assert_eq!(err.offset(), 2);
    }

    #[cfg(feature = "alloc")]
    #[test]
    fn test_parse_error_display_and_debug() {
        let err_empty = ParseError(ParseErrorKind::UnexpectedEndOfString, ParseErrorOrigin::BlockSize, 0);
        let err_eos_bh1 = ParseError(ParseErrorKind::UnexpectedEndOfString, ParseErrorOrigin::BlockHash1, 2);
        let err_bs_invalid = ParseError(ParseErrorKind::BlockSizeIsInvalid, ParseErrorOrigin::BlockSize, 0);
        // Display
        assert_eq!(format!("{}", err_empty),
            "Error occurred while parsing a fuzzy hash (block size, at byte offset 0): end-of-string is not expected.");
        assert_eq!(format!("{}", err_eos_bh1),
            "Error occurred while parsing a fuzzy hash (block hash 1, at byte offset 2): end-of-string is not expected.");
        assert_eq!(format!("{}", err_bs_invalid),
            "Error occurred while parsing a fuzzy hash (block size, at byte offset 0): block size is not valid.");
        // Debug
        assert_eq!(format!("{:?}", err_empty), "ParseError(UnexpectedEndOfString, BlockSize, 0)");
        assert_eq!(format!("{:?}", err_eos_bh1), "ParseError(UnexpectedEndOfString, BlockHash1, 2)");
        assert_eq!(format!("{:?}", err_bs_invalid), "ParseError(BlockSizeIsInvalid, BlockSize, 0)");
    }
}
// grcov-excl-br-stop