libmagic_rs/parser/

grammar.rs

// Copyright (c) 2025-2026 the libmagic-rs contributors
// SPDX-License-Identifier: Apache-2.0

//! Grammar parsing for magic files using nom parser combinators
//!
//! This module implements the parsing logic for magic file syntax, converting
//! text-based magic rules into the AST representation defined in ast.rs.

use nom::{
    IResult, Parser,
    branch::alt,
    bytes::complete::{tag, take_while},
    character::complete::{char, digit1, hex_digit1, multispace0, none_of, one_of},
    combinator::{map, opt, recognize},
    error::Error as NomError,
    multi::many0,
    sequence::pair,
};

use crate::parser::ast::{
    Endianness, MagicRule, OffsetSpec, Operator, StrengthModifier, TypeKind, Value,
};

/// Parse a decimal number with overflow protection
fn parse_decimal_number(input: &str) -> IResult<&str, i64> {
    let (input, digits) = digit1(input)?;

    // Check for potential overflow before parsing
    if digits.len() > 19 {
        // i64::MAX has 19 digits, so anything longer will definitely overflow
        return Err(nom::Err::Error(nom::error::Error::new(
            input,
            nom::error::ErrorKind::MapRes,
        )));
    }

    let number = digits.parse::<i64>().map_err(|_| {
        nom::Err::Error(nom::error::Error::new(input, nom::error::ErrorKind::MapRes))
    })?;
    Ok((input, number))
}

/// Parse a hexadecimal number (with 0x prefix) with overflow protection
fn parse_hex_number(input: &str) -> IResult<&str, i64> {
    let (input, _) = tag("0x")(input)?;
    let (input, hex_str) = hex_digit1(input)?;

    // Check for potential overflow - i64 can hold up to 16 hex digits (0x7FFFFFFFFFFFFFFF)
    if hex_str.len() > 16 {
        return Err(nom::Err::Error(nom::error::Error::new(
            input,
            nom::error::ErrorKind::MapRes,
        )));
    }

    let number = i64::from_str_radix(hex_str, 16).map_err(|_| {
        nom::Err::Error(nom::error::Error::new(input, nom::error::ErrorKind::MapRes))
    })?;

    Ok((input, number))
}

/// Parse a decimal or hexadecimal number
///
/// Supports both decimal (123, -456) and hexadecimal (0x1a2b, -0xFF) formats.
///
/// # Examples
///
/// ```
/// use libmagic_rs::parser::grammar::parse_number;
///
/// assert_eq!(parse_number("123"), Ok(("", 123)));
/// assert_eq!(parse_number("0x1a"), Ok(("", 26)));
/// assert_eq!(parse_number("-42"), Ok(("", -42)));
/// assert_eq!(parse_number("-0xFF"), Ok(("", -255)));
/// ```
///
/// # Errors
///
/// Returns a nom parsing error if:
/// - Input is empty or contains no valid digits
/// - Hexadecimal number lacks proper "0x" prefix or contains invalid hex digits
/// - Number cannot be parsed as a valid `i64` value
/// - Input contains invalid characters for the detected number format
pub fn parse_number(input: &str) -> IResult<&str, i64> {
    let (input, sign) = opt(char('-')).parse(input)?;
    let is_negative = sign.is_some();

    // Check if input starts with "0x" - if so, it must be a valid hex number
    let (input, number) = if input.starts_with("0x") {
        parse_hex_number(input)?
    } else {
        parse_decimal_number(input)?
    };

    // Apply sign with overflow checking
    let result = if is_negative {
        number.checked_neg().ok_or_else(|| {
            nom::Err::Error(nom::error::Error::new(input, nom::error::ErrorKind::MapRes))
        })?
    } else {
        number
    };

    Ok((input, result))
}

/// Parse an offset specification for absolute offsets
///
/// Supports decimal and hexadecimal formats, both positive and negative.
///
/// # Examples
///
/// ```
/// use libmagic_rs::parser::grammar::parse_offset;
/// use libmagic_rs::parser::ast::OffsetSpec;
///
/// assert_eq!(parse_offset("0"), Ok(("", OffsetSpec::Absolute(0))));
/// assert_eq!(parse_offset("123"), Ok(("", OffsetSpec::Absolute(123))));
/// assert_eq!(parse_offset("0x10"), Ok(("", OffsetSpec::Absolute(16))));
/// assert_eq!(parse_offset("-4"), Ok(("", OffsetSpec::Absolute(-4))));
/// assert_eq!(parse_offset("-0xFF"), Ok(("", OffsetSpec::Absolute(-255))));
/// ```
///
/// # Errors
///
/// Returns a nom parsing error if:
/// - The input contains invalid number format (propagated from `parse_number`)
/// - Input is empty or contains no parseable offset value
/// - The offset value cannot be represented as a valid `i64`
pub fn parse_offset(input: &str) -> IResult<&str, OffsetSpec> {
    let (input, _) = multispace0(input)?;
    let (input, offset_value) = parse_number(input)?;
    let (input, _) = multispace0(input)?;

    Ok((input, OffsetSpec::Absolute(offset_value)))
}

/// Parse comparison operators for magic rules
///
/// Supports both symbolic and text representations of operators:
/// - `=` or `==` for equality
/// - `!=` or `<>` for inequality
/// - `&` for bitwise AND
///
/// # Examples
///
/// ```
/// use libmagic_rs::parser::grammar::parse_operator;
/// use libmagic_rs::parser::ast::Operator;
///
/// assert_eq!(parse_operator("="), Ok(("", Operator::Equal)));
/// assert_eq!(parse_operator("=="), Ok(("", Operator::Equal)));
/// assert_eq!(parse_operator("!="), Ok(("", Operator::NotEqual)));
/// assert_eq!(parse_operator("<>"), Ok(("", Operator::NotEqual)));
/// assert_eq!(parse_operator("&"), Ok(("", Operator::BitwiseAnd)));
/// ```
///
/// # Errors
///
/// Returns a nom parsing error if:
/// - Input does not start with a recognized operator symbol
/// - Input is empty or contains no valid operator
/// - Operator syntax is incomplete (e.g., just `!` without `=`)
pub fn parse_operator(input: &str) -> IResult<&str, Operator> {
    let (input, _) = multispace0(input)?;

    // Try to parse each operator, starting with longer ones first
    if let Ok((remaining, _)) = tag::<&str, &str, nom::error::Error<&str>>("==")(input) {
        // Check that we don't have another '=' following (to reject "===")
        if remaining.starts_with('=') {
            return Err(nom::Err::Error(nom::error::Error::new(
                input,
                nom::error::ErrorKind::Tag,
            )));
        }
        let (remaining, _) = multispace0(remaining)?;
        return Ok((remaining, Operator::Equal));
    }

    if let Ok((remaining, _)) = tag::<&str, &str, nom::error::Error<&str>>("!=")(input) {
        let (remaining, _) = multispace0(remaining)?;
        return Ok((remaining, Operator::NotEqual));
    }

    if let Ok((remaining, _)) = tag::<&str, &str, nom::error::Error<&str>>("<>")(input) {
        let (remaining, _) = multispace0(remaining)?;
        return Ok((remaining, Operator::NotEqual));
    }

    if let Ok((remaining, _)) = tag::<&str, &str, nom::error::Error<&str>>("=")(input) {
        // Check that we don't have another '=' following (to reject "==")
        if remaining.starts_with('=') {
            return Err(nom::Err::Error(nom::error::Error::new(
                input,
                nom::error::ErrorKind::Tag,
            )));
        }
        let (remaining, _) = multispace0(remaining)?;
        return Ok((remaining, Operator::Equal));
    }

    if let Ok((remaining, _)) = tag::<&str, &str, nom::error::Error<&str>>("&")(input) {
        // Check that we don't have another '&' following (to reject "&&")
        if remaining.starts_with('&') {
            return Err(nom::Err::Error(nom::error::Error::new(
                input,
                nom::error::ErrorKind::Tag,
            )));
        }
        let (remaining, _) = multispace0(remaining)?;
        return Ok((remaining, Operator::BitwiseAnd));
    }

    // If no operator matches, return an error
    Err(nom::Err::Error(nom::error::Error::new(
        input,
        nom::error::ErrorKind::Tag,
    )))
}

/// Parse a single hex byte with \x prefix
fn parse_hex_byte_with_prefix(input: &str) -> IResult<&str, u8> {
    let (input, _) = tag("\\x")(input)?;
    let (input, hex_str) = recognize(pair(
        one_of("0123456789abcdefABCDEF"),
        one_of("0123456789abcdefABCDEF"),
    ))
    .parse(input)?;
    let byte_val = u8::from_str_radix(hex_str, 16)
        .map_err(|_| nom::Err::Error(NomError::new(input, nom::error::ErrorKind::MapRes)))?;
    Ok((input, byte_val))
}

/// Parse a hex byte sequence starting with \x prefix
fn parse_hex_bytes_with_prefix(input: &str) -> IResult<&str, Vec<u8>> {
    if input.starts_with("\\x") {
        many0(parse_hex_byte_with_prefix).parse(input)
    } else {
        Err(nom::Err::Error(NomError::new(
            input,
            nom::error::ErrorKind::Tag,
        )))
    }
}

/// Parse a mixed hex and ASCII sequence (like \x7fELF)
fn parse_mixed_hex_ascii(input: &str) -> IResult<&str, Vec<u8>> {
    // Must start with \ to be considered an escape sequence
    if !input.starts_with('\\') {
        return Err(nom::Err::Error(NomError::new(
            input,
            nom::error::ErrorKind::Tag,
        )));
    }

    let mut bytes = Vec::new();
    let mut remaining = input;

    while !remaining.is_empty() {
        // Try to parse escape sequences first (hex, octal, etc.)
        if let Ok((new_remaining, escaped_char)) = parse_escape_sequence(remaining) {
            bytes.push(escaped_char as u8);
            remaining = new_remaining;
        } else if let Ok((new_remaining, hex_byte)) = parse_hex_byte_with_prefix(remaining) {
            bytes.push(hex_byte);
            remaining = new_remaining;
        } else if let Ok((new_remaining, ascii_char)) =
            none_of::<&str, &str, NomError<&str>>(" \t\n\r")(remaining)
        {
            // Parse regular ASCII character (not whitespace)
            bytes.push(ascii_char as u8);
            remaining = new_remaining;
        } else {
            // Stop if we can't parse anything more
            break;
        }
    }

    if bytes.is_empty() {
        Err(nom::Err::Error(NomError::new(
            input,
            nom::error::ErrorKind::Tag,
        )))
    } else {
        Ok((remaining, bytes))
    }
}

/// Parse a hex byte sequence without prefix (only if it looks like pure hex bytes)
fn parse_hex_bytes_no_prefix(input: &str) -> IResult<&str, Vec<u8>> {
    // Only parse as hex bytes if:
    // 1. Input has even number of hex digits (pairs)
    // 2. All characters are hex digits
    // 3. Doesn't start with 0x (that's a number)
    // 4. Contains at least one non-decimal digit (a-f, A-F)

    if input.starts_with("0x") || input.starts_with('-') {
        return Err(nom::Err::Error(NomError::new(
            input,
            nom::error::ErrorKind::Tag,
        )));
    }

    let hex_chars: String = input.chars().take_while(char::is_ascii_hexdigit).collect();

    if hex_chars.is_empty() || hex_chars.len() % 2 != 0 {
        return Err(nom::Err::Error(NomError::new(
            input,
            nom::error::ErrorKind::Tag,
        )));
    }

    // Check if it contains non-decimal hex digits (a-f, A-F)
    let has_hex_letters = hex_chars
        .chars()
        .any(|c| matches!(c, 'a'..='f' | 'A'..='F'));
    if !has_hex_letters {
        return Err(nom::Err::Error(NomError::new(
            input,
            nom::error::ErrorKind::Tag,
        )));
    }

    // Parse pairs of hex digits
    let mut bytes = Vec::with_capacity(hex_chars.len() / 2);
    let mut chars = hex_chars.chars();
    while let (Some(c1), Some(c2)) = (chars.next(), chars.next()) {
        // Avoid format! allocation by parsing digits directly
        let digit1 = c1
            .to_digit(16)
            .ok_or_else(|| nom::Err::Error(NomError::new(input, nom::error::ErrorKind::MapRes)))?;
        let digit2 = c2
            .to_digit(16)
            .ok_or_else(|| nom::Err::Error(NomError::new(input, nom::error::ErrorKind::MapRes)))?;
        let byte_val = u8::try_from((digit1 << 4) | digit2)
            .map_err(|_| nom::Err::Error(NomError::new(input, nom::error::ErrorKind::MapRes)))?;
        bytes.push(byte_val);
    }

    let remaining = &input[hex_chars.len()..];
    Ok((remaining, bytes))
}

/// Parse a hex byte sequence (e.g., "\\x7f\\x45\\x4c\\x46", "7f454c46", or "\\x7fELF")
fn parse_hex_bytes(input: &str) -> IResult<&str, Vec<u8>> {
    alt((
        parse_mixed_hex_ascii,
        parse_hex_bytes_with_prefix,
        parse_hex_bytes_no_prefix,
    ))
    .parse(input)
}

/// Parse escape sequences in strings
fn parse_escape_sequence(input: &str) -> IResult<&str, char> {
    let (input, _) = char('\\')(input)?;

    // Try to parse octal escape sequence first (\377, \123, etc.)
    if let Ok((remaining, octal_str)) = recognize(pair(
        one_of::<&str, &str, NomError<&str>>("0123"),
        pair(
            one_of::<&str, &str, NomError<&str>>("01234567"),
            one_of::<&str, &str, NomError<&str>>("01234567"),
        ),
    ))
    .parse(input)
    {
        if let Ok(octal_value) = u8::from_str_radix(octal_str, 8) {
            return Ok((remaining, octal_value as char));
        }
    }

    // Parse standard escape sequences
    let (input, escaped_char) = one_of("nrt\\\"'0")(input)?;

    let result_char = match escaped_char {
        'n' => '\n',
        'r' => '\r',
        't' => '\t',
        '\\' => '\\',
        '"' => '"',
        '\'' => '\'',
        '0' => '\0',
        _ => escaped_char, // Fallback for other characters
    };

    Ok((input, result_char))
}

/// Parse a quoted string with escape sequences
fn parse_quoted_string(input: &str) -> IResult<&str, String> {
    let (input, _) = multispace0(input)?;
    let (input, _) = char('"')(input)?;

    let mut result = String::new();
    let mut remaining = input;

    loop {
        // Try to parse an escape sequence first
        if let Ok((new_remaining, escaped_char)) = parse_escape_sequence(remaining) {
            result.push(escaped_char);
            remaining = new_remaining;
            continue;
        }

        // If no escape sequence, try to parse a regular character (not quote or backslash)
        if let Ok((new_remaining, regular_char)) =
            none_of::<&str, &str, NomError<&str>>("\"\\")(remaining)
        {
            result.push(regular_char);
            remaining = new_remaining;
            continue;
        }

        // If neither worked, we should be at the closing quote
        break;
    }

    let (remaining, _) = char('"')(remaining)?;
    let (remaining, _) = multispace0(remaining)?;

    Ok((remaining, result))
}

/// Parse a numeric value (integer)
fn parse_numeric_value(input: &str) -> IResult<&str, Value> {
    let (input, _) = multispace0(input)?;
    let (input, number) = parse_number(input)?;
    let (input, _) = multispace0(input)?;

    // Convert to appropriate Value variant based on sign
    let value = if number >= 0 {
        Value::Uint(number.unsigned_abs())
    } else {
        Value::Int(number)
    };

    Ok((input, value))
}

/// Parse string and numeric literals for magic rule values
///
/// Supports:
/// - Quoted strings with escape sequences: "Hello\nWorld", "ELF\0"
/// - Numeric literals (decimal): 123, -456
/// - Numeric literals (hexadecimal): 0x1a2b, -0xFF
/// - Hex byte sequences: \\x7f\\x45\\x4c\\x46 or 7f454c46
///
/// # Examples
///
/// ```
/// use libmagic_rs::parser::grammar::parse_value;
/// use libmagic_rs::parser::ast::Value;
///
/// // String values
/// assert_eq!(parse_value("\"Hello\""), Ok(("", Value::String("Hello".to_string()))));
/// assert_eq!(parse_value("\"Line1\\nLine2\""), Ok(("", Value::String("Line1\nLine2".to_string()))));
///
/// // Numeric values
/// assert_eq!(parse_value("123"), Ok(("", Value::Uint(123))));
/// assert_eq!(parse_value("-456"), Ok(("", Value::Int(-456))));
/// assert_eq!(parse_value("0x1a"), Ok(("", Value::Uint(26))));
/// assert_eq!(parse_value("-0xFF"), Ok(("", Value::Int(-255))));
///
/// // Hex byte sequences
/// assert_eq!(parse_value("\\x7f\\x45"), Ok(("", Value::Bytes(vec![0x7f, 0x45]))));
/// ```
///
/// # Errors
///
/// Returns a nom parsing error if:
/// - Input is empty or contains no valid value
/// - Quoted string is not properly terminated
/// - Numeric value cannot be parsed as a valid integer
/// - Hex byte sequence contains invalid hex digits
/// - Input contains invalid characters for the detected value format
pub fn parse_value(input: &str) -> IResult<&str, Value> {
    let (input, _) = multispace0(input)?;

    // Handle empty input case - should fail for magic rules
    if input.is_empty() {
        return Err(nom::Err::Error(NomError::new(
            input,
            nom::error::ErrorKind::Tag,
        )));
    }

    // Try to parse different value types in order of specificity
    let (input, value) = alt((
        // Try quoted string first
        map(parse_quoted_string, Value::String),
        // Try hex byte sequence before numeric (to catch patterns like "7f", "ab", "\\x7fELF", etc.)
        map(parse_hex_bytes, Value::Bytes),
        // Try numeric value last (for pure numbers like 0x123, 1, etc.)
        parse_numeric_value,
    ))
    .parse(input)?;

    Ok((input, value))
}

#[cfg(test)]
mod tests {
    use super::*;

    /// Helper function to test parsing with various whitespace patterns
    #[allow(dead_code)] // TODO: Use this helper in future whitespace tests
    fn test_with_whitespace_variants<T, F>(input: &str, expected: &T, parser: F)
    where
        T: Clone + PartialEq + std::fmt::Debug,
        F: Fn(&str) -> IResult<&str, T>,
    {
        // Test with various whitespace patterns - pre-allocate Vec with known capacity
        let mut whitespace_variants = Vec::with_capacity(9);
        whitespace_variants.extend([
            format!(" {input}"),    // Leading space
            format!("  {input}"),   // Leading spaces
            format!("\t{input}"),   // Leading tab
            format!("{input} "),    // Trailing space
            format!("{input}  "),   // Trailing spaces
            format!("{input}\t"),   // Trailing tab
            format!(" {input} "),   // Both leading and trailing space
            format!("  {input}  "), // Both leading and trailing spaces
            format!("\t{input}\t"), // Both leading and trailing tabs
        ]);

        for variant in whitespace_variants {
            assert_eq!(
                parser(&variant),
                Ok(("", expected.clone())),
                "Failed to parse with whitespace: '{variant}'"
            );
        }
    }

    /// Helper function to test number parsing with remaining input
    fn test_number_with_remaining_input() {
        // Pre-allocate with known capacity for better performance
        let test_cases = [
            ("123abc", 123, "abc"),
            ("0xFF rest", 255, " rest"),
            ("-42 more", -42, " more"),
            ("0x10,next", 16, ",next"),
        ];

        for (input, expected_num, expected_remaining) in test_cases {
            assert_eq!(
                parse_number(input),
                Ok((expected_remaining, expected_num)),
                "Failed to parse number with remaining input: '{input}'"
            );
        }
    }

    #[test]
    fn test_parse_decimal_number() {
        assert_eq!(parse_decimal_number("123"), Ok(("", 123)));
        assert_eq!(parse_decimal_number("0"), Ok(("", 0)));
        assert_eq!(parse_decimal_number("999"), Ok(("", 999)));

        // Should fail on non-digits
        assert!(parse_decimal_number("abc").is_err());
        assert!(parse_decimal_number("").is_err());
    }

    #[test]
    fn test_parse_hex_number() {
        assert_eq!(parse_hex_number("0x0"), Ok(("", 0)));
        assert_eq!(parse_hex_number("0x10"), Ok(("", 16)));
        assert_eq!(parse_hex_number("0xFF"), Ok(("", 255)));
        assert_eq!(parse_hex_number("0xabc"), Ok(("", 2748)));
        assert_eq!(parse_hex_number("0xABC"), Ok(("", 2748)));

        // Should fail without 0x prefix
        assert!(parse_hex_number("FF").is_err());
        assert!(parse_hex_number("10").is_err());

        // Should fail on invalid hex digits
        assert!(parse_hex_number("0xGG").is_err());
    }

    #[test]
    fn test_parse_number_positive() {
        // Decimal numbers
        assert_eq!(parse_number("0"), Ok(("", 0)));
        assert_eq!(parse_number("123"), Ok(("", 123)));
        assert_eq!(parse_number("999"), Ok(("", 999)));

        // Hexadecimal numbers
        assert_eq!(parse_number("0x0"), Ok(("", 0)));
        assert_eq!(parse_number("0x10"), Ok(("", 16)));
        assert_eq!(parse_number("0xFF"), Ok(("", 255)));
        assert_eq!(parse_number("0xabc"), Ok(("", 2748)));
    }

    #[test]
    fn test_parse_number_negative() {
        // Negative decimal numbers
        assert_eq!(parse_number("-1"), Ok(("", -1)));
        assert_eq!(parse_number("-123"), Ok(("", -123)));
        assert_eq!(parse_number("-999"), Ok(("", -999)));

        // Negative hexadecimal numbers
        assert_eq!(parse_number("-0x1"), Ok(("", -1)));
        assert_eq!(parse_number("-0x10"), Ok(("", -16)));
        assert_eq!(parse_number("-0xFF"), Ok(("", -255)));
        assert_eq!(parse_number("-0xabc"), Ok(("", -2748)));
    }

    #[test]
    fn test_parse_number_edge_cases() {
        // Zero with different formats
        assert_eq!(parse_number("0"), Ok(("", 0)));
        assert_eq!(parse_number("-0"), Ok(("", 0)));
        assert_eq!(parse_number("0x0"), Ok(("", 0)));
        assert_eq!(parse_number("-0x0"), Ok(("", 0)));

        // Large numbers
        assert_eq!(parse_number("2147483647"), Ok(("", 2_147_483_647))); // i32::MAX
        assert_eq!(parse_number("-2147483648"), Ok(("", -2_147_483_648))); // i32::MIN
        assert_eq!(parse_number("0x7FFFFFFF"), Ok(("", 2_147_483_647))); // i32::MAX in hex

        // Should fail on invalid input
        assert!(parse_number("").is_err());
        assert!(parse_number("abc").is_err());
        assert!(parse_number("0xGG").is_err());
        assert!(parse_number("--123").is_err());
    }

    #[test]
    fn test_parse_number_with_remaining_input() {
        // Use helper function to reduce code duplication
        test_number_with_remaining_input();
    }

    #[test]
    fn test_parse_offset_absolute_positive() {
        assert_eq!(parse_offset("0"), Ok(("", OffsetSpec::Absolute(0))));
        assert_eq!(parse_offset("123"), Ok(("", OffsetSpec::Absolute(123))));
        assert_eq!(parse_offset("999"), Ok(("", OffsetSpec::Absolute(999))));

        // Hexadecimal offsets
        assert_eq!(parse_offset("0x0"), Ok(("", OffsetSpec::Absolute(0))));
        assert_eq!(parse_offset("0x10"), Ok(("", OffsetSpec::Absolute(16))));
        assert_eq!(parse_offset("0xFF"), Ok(("", OffsetSpec::Absolute(255))));
        assert_eq!(parse_offset("0xabc"), Ok(("", OffsetSpec::Absolute(2748))));
    }

    #[test]
    fn test_parse_offset_absolute_negative() {
        assert_eq!(parse_offset("-1"), Ok(("", OffsetSpec::Absolute(-1))));
        assert_eq!(parse_offset("-123"), Ok(("", OffsetSpec::Absolute(-123))));
        assert_eq!(parse_offset("-999"), Ok(("", OffsetSpec::Absolute(-999))));

        // Negative hexadecimal offsets
        assert_eq!(parse_offset("-0x1"), Ok(("", OffsetSpec::Absolute(-1))));
        assert_eq!(parse_offset("-0x10"), Ok(("", OffsetSpec::Absolute(-16))));
        assert_eq!(parse_offset("-0xFF"), Ok(("", OffsetSpec::Absolute(-255))));
        assert_eq!(
            parse_offset("-0xabc"),
            Ok(("", OffsetSpec::Absolute(-2748)))
        );
    }

    #[test]
    fn test_parse_offset_with_whitespace() {
        // Leading whitespace
        assert_eq!(parse_offset(" 123"), Ok(("", OffsetSpec::Absolute(123))));
        assert_eq!(parse_offset("  0x10"), Ok(("", OffsetSpec::Absolute(16))));
        assert_eq!(parse_offset("\t-42"), Ok(("", OffsetSpec::Absolute(-42))));

        // Trailing whitespace
        assert_eq!(parse_offset("123 "), Ok(("", OffsetSpec::Absolute(123))));
        assert_eq!(parse_offset("0x10  "), Ok(("", OffsetSpec::Absolute(16))));
        assert_eq!(parse_offset("-42\t"), Ok(("", OffsetSpec::Absolute(-42))));

        // Both leading and trailing whitespace
        assert_eq!(parse_offset(" 123 "), Ok(("", OffsetSpec::Absolute(123))));
        assert_eq!(parse_offset("  0x10  "), Ok(("", OffsetSpec::Absolute(16))));
        assert_eq!(parse_offset("\t-42\t"), Ok(("", OffsetSpec::Absolute(-42))));
    }

    #[test]
    fn test_parse_offset_with_remaining_input() {
        // Should parse offset and leave remaining input
        assert_eq!(
            parse_offset("123 byte"),
            Ok(("byte", OffsetSpec::Absolute(123)))
        );
        assert_eq!(parse_offset("0xFF ="), Ok(("=", OffsetSpec::Absolute(255))));
        assert_eq!(
            parse_offset("-42,next"),
            Ok((",next", OffsetSpec::Absolute(-42)))
        );
        assert_eq!(
            parse_offset("0x10\tlong"),
            Ok(("long", OffsetSpec::Absolute(16)))
        );
    }

    #[test]
    fn test_parse_offset_edge_cases() {
        // Zero with different formats
        assert_eq!(parse_offset("0"), Ok(("", OffsetSpec::Absolute(0))));
        assert_eq!(parse_offset("-0"), Ok(("", OffsetSpec::Absolute(0))));
        assert_eq!(parse_offset("0x0"), Ok(("", OffsetSpec::Absolute(0))));
        assert_eq!(parse_offset("-0x0"), Ok(("", OffsetSpec::Absolute(0))));

        // Large offsets
        assert_eq!(
            parse_offset("2147483647"),
            Ok(("", OffsetSpec::Absolute(2_147_483_647)))
        );
        assert_eq!(
            parse_offset("-2147483648"),
            Ok(("", OffsetSpec::Absolute(-2_147_483_648)))
        );
        assert_eq!(
            parse_offset("0x7FFFFFFF"),
            Ok(("", OffsetSpec::Absolute(2_147_483_647)))
        );

        // Should fail on invalid input
        assert!(parse_offset("").is_err());
        assert!(parse_offset("abc").is_err());
        assert!(parse_offset("0xGG").is_err());
        assert!(parse_offset("--123").is_err());
    }

    #[test]
    fn test_parse_offset_common_magic_file_values() {
        // Common offsets found in magic files
        assert_eq!(parse_offset("0"), Ok(("", OffsetSpec::Absolute(0)))); // File start
        assert_eq!(parse_offset("4"), Ok(("", OffsetSpec::Absolute(4)))); // After magic number
        assert_eq!(parse_offset("16"), Ok(("", OffsetSpec::Absolute(16)))); // Common header offset
        assert_eq!(parse_offset("0x10"), Ok(("", OffsetSpec::Absolute(16)))); // Same as above in hex
        assert_eq!(parse_offset("512"), Ok(("", OffsetSpec::Absolute(512)))); // Sector boundary
        assert_eq!(parse_offset("0x200"), Ok(("", OffsetSpec::Absolute(512)))); // Same in hex

        // Negative offsets (from end of file)
        assert_eq!(parse_offset("-4"), Ok(("", OffsetSpec::Absolute(-4)))); // 4 bytes from end
        assert_eq!(parse_offset("-16"), Ok(("", OffsetSpec::Absolute(-16)))); // 16 bytes from end
        assert_eq!(parse_offset("-0x10"), Ok(("", OffsetSpec::Absolute(-16)))); // Same in hex
    }

    #[test]
    fn test_parse_offset_boundary_values() {
        // Test boundary values that might cause issues
        assert_eq!(parse_offset("1"), Ok(("", OffsetSpec::Absolute(1))));
        assert_eq!(parse_offset("-1"), Ok(("", OffsetSpec::Absolute(-1))));

        // Powers of 2 (common in binary formats)
        assert_eq!(parse_offset("256"), Ok(("", OffsetSpec::Absolute(256))));
        assert_eq!(parse_offset("0x100"), Ok(("", OffsetSpec::Absolute(256))));
        assert_eq!(parse_offset("1024"), Ok(("", OffsetSpec::Absolute(1024))));
        assert_eq!(parse_offset("0x400"), Ok(("", OffsetSpec::Absolute(1024))));

        // Large but reasonable file offsets
        assert_eq!(
            parse_offset("1048576"),
            Ok(("", OffsetSpec::Absolute(1_048_576)))
        ); // 1MB
        assert_eq!(
            parse_offset("0x100000"),
            Ok(("", OffsetSpec::Absolute(1_048_576)))
        );
    }

    // Operator parsing tests
    #[test]
    fn test_parse_operator_equality() {
        // Single equals sign
        assert_eq!(parse_operator("="), Ok(("", Operator::Equal)));

        // Double equals sign
        assert_eq!(parse_operator("=="), Ok(("", Operator::Equal)));

        // With whitespace
        assert_eq!(parse_operator(" = "), Ok(("", Operator::Equal)));
        assert_eq!(parse_operator("  ==  "), Ok(("", Operator::Equal)));
        assert_eq!(parse_operator("\t=\t"), Ok(("", Operator::Equal)));
    }

    #[test]
    fn test_parse_operator_inequality() {
        // Not equals
        assert_eq!(parse_operator("!="), Ok(("", Operator::NotEqual)));

        // Alternative not equals syntax
        assert_eq!(parse_operator("<>"), Ok(("", Operator::NotEqual)));

        // With whitespace
        assert_eq!(parse_operator(" != "), Ok(("", Operator::NotEqual)));
        assert_eq!(parse_operator("  <>  "), Ok(("", Operator::NotEqual)));
        assert_eq!(parse_operator("\t!=\t"), Ok(("", Operator::NotEqual)));
    }

    #[test]
    fn test_parse_operator_bitwise_and() {
        // Bitwise AND
        assert_eq!(parse_operator("&"), Ok(("", Operator::BitwiseAnd)));

        // With whitespace
        assert_eq!(parse_operator(" & "), Ok(("", Operator::BitwiseAnd)));
        assert_eq!(parse_operator("  &  "), Ok(("", Operator::BitwiseAnd)));
        assert_eq!(parse_operator("\t&\t"), Ok(("", Operator::BitwiseAnd)));
    }

    #[test]
    fn test_parse_operator_with_remaining_input() {
        // Should parse operator and leave remaining input
        assert_eq!(parse_operator("= 123"), Ok(("123", Operator::Equal)));
        assert_eq!(
            parse_operator("!= value"),
            Ok(("value", Operator::NotEqual))
        );
        assert_eq!(parse_operator("& 0xFF"), Ok(("0xFF", Operator::BitwiseAnd)));
        assert_eq!(
            parse_operator("== \"string\""),
            Ok(("\"string\"", Operator::Equal))
        );
        assert_eq!(parse_operator("<> test"), Ok(("test", Operator::NotEqual)));
    }

    #[test]
    fn test_parse_operator_precedence() {
        // Test that longer operators are matched first
        // This ensures "==" is parsed as Equal, not "=" followed by "="
        assert_eq!(parse_operator("=="), Ok(("", Operator::Equal)));
        assert_eq!(parse_operator("== extra"), Ok(("extra", Operator::Equal)));

        // Test that "!=" is parsed correctly, not as "!" followed by "="
        assert_eq!(parse_operator("!="), Ok(("", Operator::NotEqual)));
        assert_eq!(
            parse_operator("!= extra"),
            Ok(("extra", Operator::NotEqual))
        );

        // Test that "<>" is parsed correctly
        assert_eq!(parse_operator("<>"), Ok(("", Operator::NotEqual)));
        assert_eq!(
            parse_operator("<> extra"),
            Ok(("extra", Operator::NotEqual))
        );
    }

    #[test]
    fn test_parse_operator_invalid_input() {
        // Should fail on invalid operators
        assert!(parse_operator("").is_err());
        assert!(parse_operator("abc").is_err());
        assert!(parse_operator("123").is_err());
        assert!(parse_operator(">").is_err());
        assert!(parse_operator("<").is_err());
        assert!(parse_operator("!").is_err());
        assert!(parse_operator("===").is_err()); // Too many equals
        assert!(parse_operator("&&").is_err()); // Double ampersand not supported
    }

    #[test]
    fn test_parse_operator_edge_cases() {
        // Test operators at start of various contexts - multispace0 consumes all whitespace
        assert_eq!(parse_operator("=\n"), Ok(("", Operator::Equal)));
        assert_eq!(parse_operator("!=\r\n"), Ok(("", Operator::NotEqual)));
        assert_eq!(parse_operator("&\t\t"), Ok(("", Operator::BitwiseAnd)));

        // Test with mixed whitespace
        assert_eq!(parse_operator(" \t = \t "), Ok(("", Operator::Equal)));
        assert_eq!(parse_operator("\t != \t"), Ok(("", Operator::NotEqual)));
        assert_eq!(parse_operator(" \t& \t "), Ok(("", Operator::BitwiseAnd)));
    }

    #[test]
    fn test_parse_operator_common_magic_file_patterns() {
        // Test patterns commonly found in magic files
        assert_eq!(
            parse_operator("= 0x7f454c46"),
            Ok(("0x7f454c46", Operator::Equal))
        );
        assert_eq!(parse_operator("!= 0"), Ok(("0", Operator::NotEqual)));
        assert_eq!(
            parse_operator("& 0xFF00"),
            Ok(("0xFF00", Operator::BitwiseAnd))
        );
        assert_eq!(
            parse_operator("== \"ELF\""),
            Ok(("\"ELF\"", Operator::Equal))
        );
        assert_eq!(parse_operator("<> \"\""), Ok(("\"\"", Operator::NotEqual)));

        // Test with various spacing patterns found in real magic files
        assert_eq!(
            parse_operator("=\t0x504b0304"),
            Ok(("0x504b0304", Operator::Equal))
        );
        assert_eq!(parse_operator("!=  0"), Ok(("0", Operator::NotEqual)));
        assert_eq!(
            parse_operator("&   0xFFFF"),
            Ok(("0xFFFF", Operator::BitwiseAnd))
        );
    }

    #[test]
    fn test_parse_operator_all_variants() {
        // Ensure all operator variants are tested
        let test_cases = [
            ("=", Operator::Equal),
            ("==", Operator::Equal),
            ("!=", Operator::NotEqual),
            ("<>", Operator::NotEqual),
            ("&", Operator::BitwiseAnd),
        ];

        for (input, expected) in test_cases {
            assert_eq!(
                parse_operator(input),
                Ok(("", expected)),
                "Failed to parse operator: '{input}'"
            );
        }
    }

    // Value parsing tests
    #[test]
    fn test_parse_hex_bytes_with_backslash_x() {
        // Single hex byte with \x prefix
        assert_eq!(parse_hex_bytes("\\x7f"), Ok(("", vec![0x7f])));
        assert_eq!(parse_hex_bytes("\\x45"), Ok(("", vec![0x45])));
        assert_eq!(parse_hex_bytes("\\x00"), Ok(("", vec![0x00])));
        assert_eq!(parse_hex_bytes("\\xFF"), Ok(("", vec![0xFF])));

        // Multiple hex bytes with \x prefix
        assert_eq!(
            parse_hex_bytes("\\x7f\\x45\\x4c\\x46"),
            Ok(("", vec![0x7f, 0x45, 0x4c, 0x46]))
        );
        assert_eq!(
            parse_hex_bytes("\\x50\\x4b\\x03\\x04"),
            Ok(("", vec![0x50, 0x4b, 0x03, 0x04]))
        );
    }

    #[test]
    fn test_parse_hex_bytes_without_prefix() {
        // Single hex byte without prefix (only works if it contains hex letters)
        assert_eq!(parse_hex_bytes("7f"), Ok(("", vec![0x7f])));
        assert_eq!(
            parse_hex_bytes("45"),
            Err(nom::Err::Error(NomError::new(
                "45",
                nom::error::ErrorKind::Tag
            )))
        ); // No hex letters
        assert_eq!(parse_hex_bytes("ab"), Ok(("", vec![0xab])));
        assert_eq!(parse_hex_bytes("FF"), Ok(("", vec![0xFF])));

        // Multiple hex bytes without prefix
        assert_eq!(
            parse_hex_bytes("7f454c46"),
            Ok(("", vec![0x7f, 0x45, 0x4c, 0x46]))
        );
        assert_eq!(
            parse_hex_bytes("504b0304"),
            Ok(("", vec![0x50, 0x4b, 0x03, 0x04]))
        );
    }

    #[test]
    fn test_parse_hex_bytes_mixed_case() {
        // Test mixed case hex digits
        assert_eq!(parse_hex_bytes("aB"), Ok(("", vec![0xab])));
        assert_eq!(parse_hex_bytes("Cd"), Ok(("", vec![0xcd])));
        assert_eq!(parse_hex_bytes("\\xEf"), Ok(("", vec![0xef])));
        assert_eq!(parse_hex_bytes("\\x1A"), Ok(("", vec![0x1a])));
    }

    #[test]
    fn test_parse_hex_bytes_empty() {
        // Empty input should return error (no hex bytes to parse)
        assert_eq!(
            parse_hex_bytes(""),
            Err(nom::Err::Error(NomError::new(
                "",
                nom::error::ErrorKind::Tag
            )))
        );
    }

    #[test]
    fn test_parse_hex_bytes_with_remaining_input() {
        // Should parse hex bytes and leave remaining input
        assert_eq!(
            parse_hex_bytes("7f45 rest"),
            Ok((" rest", vec![0x7f, 0x45]))
        );
        assert_eq!(
            parse_hex_bytes("\\x50\\x4b next"),
            Ok((" next", vec![0x50, 0x4b]))
        );
        assert_eq!(parse_hex_bytes("ab\""), Ok(("\"", vec![0xab])));
    }

    #[test]
    fn test_parse_escape_sequence() {
        // Standard escape sequences
        assert_eq!(parse_escape_sequence("\\n"), Ok(("", '\n')));
        assert_eq!(parse_escape_sequence("\\r"), Ok(("", '\r')));
        assert_eq!(parse_escape_sequence("\\t"), Ok(("", '\t')));
        assert_eq!(parse_escape_sequence("\\\\"), Ok(("", '\\')));
        assert_eq!(parse_escape_sequence("\\\""), Ok(("", '"')));
        assert_eq!(parse_escape_sequence("\\'"), Ok(("", '\'')));
        assert_eq!(parse_escape_sequence("\\0"), Ok(("", '\0')));
    }

    #[test]
    fn test_parse_escape_sequence_with_remaining() {
        // Should parse escape and leave remaining input
        assert_eq!(parse_escape_sequence("\\n rest"), Ok((" rest", '\n')));
        assert_eq!(parse_escape_sequence("\\t\""), Ok(("\"", '\t')));
    }

    #[test]
    fn test_parse_escape_sequence_invalid() {
        // Should fail on invalid escape sequences
        assert!(parse_escape_sequence("n").is_err()); // Missing backslash
        assert!(parse_escape_sequence("\\").is_err()); // Incomplete escape
        assert!(parse_escape_sequence("").is_err()); // Empty input
    }

    #[test]
    fn test_parse_quoted_string_simple() {
        // Simple quoted strings
        assert_eq!(
            parse_quoted_string("\"hello\""),
            Ok(("", "hello".to_string()))
        );
        assert_eq!(
            parse_quoted_string("\"world\""),
            Ok(("", "world".to_string()))
        );
        assert_eq!(parse_quoted_string("\"\""), Ok(("", String::new())));
    }

    #[test]
    fn test_parse_quoted_string_with_escapes() {
        // Strings with escape sequences
        assert_eq!(
            parse_quoted_string("\"Hello\\nWorld\""),
            Ok(("", "Hello\nWorld".to_string()))
        );
        assert_eq!(
            parse_quoted_string("\"Tab\\tSeparated\""),
            Ok(("", "Tab\tSeparated".to_string()))
        );
        assert_eq!(
            parse_quoted_string("\"Quote: \\\"text\\\"\""),
            Ok(("", "Quote: \"text\"".to_string()))
        );
        assert_eq!(
            parse_quoted_string("\"Backslash: \\\\\""),
            Ok(("", "Backslash: \\".to_string()))
        );
        assert_eq!(
            parse_quoted_string("\"Null\\0terminated\""),
            Ok(("", "Null\0terminated".to_string()))
        );
    }

    #[test]
    fn test_parse_quoted_string_with_whitespace() {
        // Strings with leading/trailing whitespace
        assert_eq!(
            parse_quoted_string(" \"hello\" "),
            Ok(("", "hello".to_string()))
        );
        assert_eq!(
            parse_quoted_string("\t\"world\"\t"),
            Ok(("", "world".to_string()))
        );
        assert_eq!(
            parse_quoted_string("  \"test\"  "),
            Ok(("", "test".to_string()))
        );
    }

    #[test]
    fn test_parse_quoted_string_with_remaining_input() {
        // Should parse string and leave remaining input
        assert_eq!(
            parse_quoted_string("\"hello\" world"),
            Ok(("world", "hello".to_string()))
        );
        assert_eq!(
            parse_quoted_string("\"test\" = 123"),
            Ok(("= 123", "test".to_string()))
        );
    }

    #[test]
    fn test_parse_quoted_string_invalid() {
        // Should fail on invalid quoted strings
        assert!(parse_quoted_string("hello").is_err()); // No quotes
        assert!(parse_quoted_string("\"hello").is_err()); // Missing closing quote
        assert!(parse_quoted_string("hello\"").is_err()); // Missing opening quote
        assert!(parse_quoted_string("").is_err()); // Empty input
    }

    #[test]
    fn test_parse_numeric_value_positive() {
        // Positive integers
        assert_eq!(parse_numeric_value("0"), Ok(("", Value::Uint(0))));
        assert_eq!(parse_numeric_value("123"), Ok(("", Value::Uint(123))));
        assert_eq!(parse_numeric_value("999"), Ok(("", Value::Uint(999))));

        // Positive hex values
        assert_eq!(parse_numeric_value("0x0"), Ok(("", Value::Uint(0))));
        assert_eq!(parse_numeric_value("0x10"), Ok(("", Value::Uint(16))));
        assert_eq!(parse_numeric_value("0xFF"), Ok(("", Value::Uint(255))));
        assert_eq!(parse_numeric_value("0xabc"), Ok(("", Value::Uint(2748))));
    }

    #[test]
    fn test_parse_numeric_value_negative() {
        // Negative integers
        assert_eq!(parse_numeric_value("-1"), Ok(("", Value::Int(-1))));
        assert_eq!(parse_numeric_value("-123"), Ok(("", Value::Int(-123))));
        assert_eq!(parse_numeric_value("-999"), Ok(("", Value::Int(-999))));

        // Negative hex values
        assert_eq!(parse_numeric_value("-0x1"), Ok(("", Value::Int(-1))));
        assert_eq!(parse_numeric_value("-0x10"), Ok(("", Value::Int(-16))));
        assert_eq!(parse_numeric_value("-0xFF"), Ok(("", Value::Int(-255))));
        assert_eq!(parse_numeric_value("-0xabc"), Ok(("", Value::Int(-2748))));
    }

    #[test]
    fn test_parse_numeric_value_with_whitespace() {
        // With leading/trailing whitespace
        assert_eq!(parse_numeric_value(" 123 "), Ok(("", Value::Uint(123))));
        assert_eq!(parse_numeric_value("\t-456\t"), Ok(("", Value::Int(-456))));
        assert_eq!(parse_numeric_value("  0xFF  "), Ok(("", Value::Uint(255))));
    }

    #[test]
    fn test_parse_numeric_value_with_remaining_input() {
        // Should parse number and leave remaining input (numeric parser consumes trailing whitespace)
        assert_eq!(
            parse_numeric_value("123 rest"),
            Ok(("rest", Value::Uint(123)))
        );
        assert_eq!(
            parse_numeric_value("-456 more"),
            Ok(("more", Value::Int(-456)))
        );
        assert_eq!(parse_numeric_value("0xFF)"), Ok((")", Value::Uint(255))));
    }

    #[test]
    fn test_parse_value_string_literals() {
        // String value parsing
        assert_eq!(
            parse_value("\"hello\""),
            Ok(("", Value::String("hello".to_string())))
        );
        assert_eq!(
            parse_value("\"ELF\""),
            Ok(("", Value::String("ELF".to_string())))
        );
        assert_eq!(parse_value("\"\""), Ok(("", Value::String(String::new()))));

        // String with escape sequences
        assert_eq!(
            parse_value("\"Line1\\nLine2\""),
            Ok(("", Value::String("Line1\nLine2".to_string())))
        );
        assert_eq!(
            parse_value("\"Tab\\tSeparated\""),
            Ok(("", Value::String("Tab\tSeparated".to_string())))
        );
        assert_eq!(
            parse_value("\"Null\\0Term\""),
            Ok(("", Value::String("Null\0Term".to_string())))
        );
    }

    #[test]
    fn test_parse_value_numeric_literals() {
        // Positive integers
        assert_eq!(parse_value("0"), Ok(("", Value::Uint(0))));
        assert_eq!(parse_value("123"), Ok(("", Value::Uint(123))));
        assert_eq!(parse_value("999"), Ok(("", Value::Uint(999))));

        // Negative integers
        assert_eq!(parse_value("-1"), Ok(("", Value::Int(-1))));
        assert_eq!(parse_value("-123"), Ok(("", Value::Int(-123))));
        assert_eq!(parse_value("-999"), Ok(("", Value::Int(-999))));

        // Hexadecimal values
        assert_eq!(parse_value("0x0"), Ok(("", Value::Uint(0))));
        assert_eq!(parse_value("0x10"), Ok(("", Value::Uint(16))));
        assert_eq!(parse_value("0xFF"), Ok(("", Value::Uint(255))));
        assert_eq!(parse_value("-0xFF"), Ok(("", Value::Int(-255))));
    }

    #[test]
    fn test_parse_value_hex_byte_sequences() {
        // Hex bytes with \x prefix
        assert_eq!(parse_value("\\x7f"), Ok(("", Value::Bytes(vec![0x7f]))));
        assert_eq!(
            parse_value("\\x7f\\x45\\x4c\\x46"),
            Ok(("", Value::Bytes(vec![0x7f, 0x45, 0x4c, 0x46])))
        );

        // Hex bytes without prefix
        assert_eq!(parse_value("7f"), Ok(("", Value::Bytes(vec![0x7f]))));
        assert_eq!(
            parse_value("7f454c46"),
            Ok(("", Value::Bytes(vec![0x7f, 0x45, 0x4c, 0x46])))
        );

        // Mixed case
        assert_eq!(parse_value("aB"), Ok(("", Value::Bytes(vec![0xab]))));
        assert_eq!(parse_value("\\xCd"), Ok(("", Value::Bytes(vec![0xcd]))));
    }

    #[test]
    fn test_parse_value_with_whitespace() {
        // All value types with whitespace - trailing whitespace is consumed by individual parsers
        assert_eq!(
            parse_value(" \"hello\" "),
            Ok(("", Value::String("hello".to_string())))
        );
        assert_eq!(parse_value("  123  "), Ok(("", Value::Uint(123))));
        assert_eq!(parse_value("\t-456\t"), Ok(("", Value::Int(-456))));
        // Hex bytes don't consume trailing whitespace by themselves
        assert_eq!(
            parse_value("  \\x7f\\x45  "),
            Ok(("  ", Value::Bytes(vec![0x7f, 0x45])))
        );
    }

    #[test]
    fn test_parse_value_with_remaining_input() {
        // Should parse value and leave remaining input
        // Note: Individual parsers handle whitespace differently
        assert_eq!(
            parse_value("\"hello\" world"),
            Ok(("world", Value::String("hello".to_string())))
        );
        assert_eq!(
            parse_value("123 rest"),
            Ok(("rest", Value::Uint(123))) // Numeric parser consumes trailing space
        );
        assert_eq!(
            parse_value("-456 more"),
            Ok(("more", Value::Int(-456))) // Numeric parser consumes trailing space
        );
        assert_eq!(
            parse_value("\\x7f\\x45 next"),
            Ok((" next", Value::Bytes(vec![0x7f, 0x45]))) // Hex bytes don't consume trailing space
        );
    }

    #[test]
    fn test_parse_value_edge_cases() {
        // Zero values in different formats
        assert_eq!(parse_value("0"), Ok(("", Value::Uint(0))));
        assert_eq!(parse_value("-0"), Ok(("", Value::Uint(0))));
        assert_eq!(parse_value("0x0"), Ok(("", Value::Uint(0))));
        assert_eq!(parse_value("-0x0"), Ok(("", Value::Uint(0))));

        // Large values
        assert_eq!(
            parse_value("2147483647"),
            Ok(("", Value::Uint(2_147_483_647)))
        );
        assert_eq!(
            parse_value("-2147483648"),
            Ok(("", Value::Int(-2_147_483_648)))
        );
        assert_eq!(
            parse_value("0x7FFFFFFF"),
            Ok(("", Value::Uint(2_147_483_647)))
        );

        // Empty input should fail
        assert!(parse_value("").is_err());
    }

    #[test]
    fn test_parse_value_invalid_input() {
        // Should fail on completely invalid input
        assert!(parse_value("xyz").is_err()); // Not a valid value format
        assert!(parse_value("0xGG").is_err()); // Invalid hex digits
        assert!(parse_value("\"unclosed").is_err()); // Unclosed string
        assert!(parse_value("--123").is_err()); // Invalid number format
    }

    #[test]
    fn test_parse_value_common_magic_file_patterns() {
        // Test patterns commonly found in magic files
        assert_eq!(
            parse_value("0x7f454c46"),
            Ok(("", Value::Uint(0x7f45_4c46)))
        );
        assert_eq!(
            parse_value("\"ELF\""),
            Ok(("", Value::String("ELF".to_string())))
        );
        assert_eq!(
            parse_value("\\x50\\x4b\\x03\\x04"),
            Ok(("", Value::Bytes(vec![0x50, 0x4b, 0x03, 0x04])))
        );
        assert_eq!(
            parse_value("\"\\377ELF\""),
            Ok(("", Value::String("\u{00ff}ELF".to_string())))
        );
        assert_eq!(parse_value("0"), Ok(("", Value::Uint(0))));
        assert_eq!(parse_value("-1"), Ok(("", Value::Int(-1))));
    }

    #[test]
    fn test_parse_value_type_precedence() {
        // Test that parsing precedence works correctly
        // Quoted strings should be parsed as strings, not hex bytes
        assert_eq!(
            parse_value("\"7f\""),
            Ok(("", Value::String("7f".to_string())))
        );

        // Hex patterns should be parsed as bytes when not quoted
        assert_eq!(parse_value("7f"), Ok(("", Value::Bytes(vec![0x7f]))));

        // Numbers should be parsed as numbers when they don't look like hex bytes
        assert_eq!(parse_value("123"), Ok(("", Value::Uint(123))));
        assert_eq!(parse_value("-123"), Ok(("", Value::Int(-123))));

        // Hex numbers with 0x prefix should be parsed as numbers
        assert_eq!(parse_value("0x123"), Ok(("", Value::Uint(0x123))));
    }

    #[test]
    fn test_parse_value_boundary_conditions() {
        // Test boundary conditions for different value types

        // Single character strings
        assert_eq!(
            parse_value("\"a\""),
            Ok(("", Value::String("a".to_string())))
        );
        assert_eq!(
            parse_value("\"1\""),
            Ok(("", Value::String("1".to_string())))
        );

        // Single hex byte
        assert_eq!(parse_value("ab"), Ok(("", Value::Bytes(vec![0xab]))));
        assert_eq!(parse_value("\\x00"), Ok(("", Value::Bytes(vec![0x00]))));

        // Minimum and maximum values
        assert_eq!(parse_value("1"), Ok(("", Value::Uint(1))));
        assert_eq!(parse_value("-1"), Ok(("", Value::Int(-1))));

        // Powers of 2 (common in binary formats)
        assert_eq!(parse_value("256"), Ok(("", Value::Uint(256))));
        assert_eq!(parse_value("0x100"), Ok(("", Value::Uint(256))));
        assert_eq!(parse_value("1024"), Ok(("", Value::Uint(1024))));
        assert_eq!(parse_value("0x400"), Ok(("", Value::Uint(1024))));
    }

    #[test]
    fn test_parse_operator_whitespace_handling() {
        // Test comprehensive whitespace handling
        let operators = ["=", "==", "!=", "<>", "&"];
        let whitespace_patterns = [
            "",     // No whitespace
            " ",    // Single space
            "  ",   // Multiple spaces
            "\t",   // Tab
            "\t\t", // Multiple tabs
            " \t",  // Mixed space and tab
            "\t ",  // Mixed tab and space
        ];

        for op in operators {
            for leading_ws in whitespace_patterns {
                for trailing_ws in whitespace_patterns {
                    let input = format!("{leading_ws}{op}{trailing_ws}");
                    let result = parse_operator(&input);

                    assert!(
                        result.is_ok(),
                        "Failed to parse operator with whitespace: '{input}'"
                    );

                    let (remaining, _) = result.unwrap();
                    assert_eq!(remaining, "", "Unexpected remaining input for: '{input}'");
                }
            }
        }
    }
}
/// Parse a type specification (byte, short, long, string, etc.)
///
/// Supports various type formats found in magic files:
/// - `byte` - single byte
/// - `short` - 16-bit integer (native endian)
/// - `leshort` - 16-bit little-endian integer
/// - `beshort` - 16-bit big-endian integer
/// - `long` - 32-bit integer (native endian)
/// - `lelong` - 32-bit little-endian integer
/// - `belong` - 32-bit big-endian integer
/// - `string` - null-terminated string
///
/// # Examples
///
/// ```
/// use libmagic_rs::parser::grammar::parse_type;
/// use libmagic_rs::parser::ast::{TypeKind, Endianness};
///
/// assert_eq!(parse_type("byte"), Ok(("", TypeKind::Byte)));
/// assert_eq!(parse_type("leshort"), Ok(("", TypeKind::Short { endian: Endianness::Little, signed: false })));
/// assert_eq!(parse_type("string"), Ok(("", TypeKind::String { max_length: None })));
/// ```
/// Parse a type specification with optional attached operator
/// Parse a type specification followed by an optional operator
///
/// # Errors
/// Returns a nom parsing error if the input doesn't match the expected format
pub fn parse_type_and_operator(input: &str) -> IResult<&str, (TypeKind, Option<Operator>)> {
    let (input, _) = multispace0(input)?;

    let (input, type_name) = alt((
        tag("lelong"),
        tag("belong"),
        tag("leshort"),
        tag("beshort"),
        tag("long"),
        tag("short"),
        tag("byte"),
        tag("string"),
    ))
    .parse(input)?;

    // Check for attached operator with mask (like &0xf0000000)
    let (input, attached_op) = opt(alt((
        // Parse &mask format
        map(pair(char('&'), parse_number), |(_, mask)| {
            Operator::BitwiseAndMask(mask.unsigned_abs())
        }),
        // Parse standalone & (for backward compatibility)
        map(char('&'), |_| Operator::BitwiseAnd),
        // Add more operators as needed
    )))
    .parse(input)?;

    let (input, _) = multispace0(input)?;

    let type_kind = match type_name {
        "byte" => TypeKind::Byte,
        "short" => TypeKind::Short {
            endian: Endianness::Native,
            signed: false,
        },
        "leshort" => TypeKind::Short {
            endian: Endianness::Little,
            signed: false,
        },
        "beshort" => TypeKind::Short {
            endian: Endianness::Big,
            signed: false,
        },
        "long" => TypeKind::Long {
            endian: Endianness::Native,
            signed: false,
        },
        "lelong" => TypeKind::Long {
            endian: Endianness::Little,
            signed: false,
        },
        "belong" => TypeKind::Long {
            endian: Endianness::Big,
            signed: false,
        },
        "string" => TypeKind::String { max_length: None },
        _ => unreachable!("Parser should only match known types"),
    };

    Ok((input, (type_kind, attached_op)))
}

/// Parse a type specification (backward compatibility)
/// Parse a type specification (byte, short, long, string, etc.)
///
/// # Errors
/// Returns a nom parsing error if the input doesn't match any known type
pub fn parse_type(input: &str) -> IResult<&str, TypeKind> {
    let (input, (type_kind, _)) = parse_type_and_operator(input)?;
    Ok((input, type_kind))
}

/// Parse the indentation level and offset for magic rules
///
/// Handles both absolute offsets and hierarchical child rules with `>` prefix.
/// Child rules can be nested multiple levels deep with multiple `>` characters.
///
/// # Examples
///
/// ```
/// use libmagic_rs::parser::grammar::parse_rule_offset;
/// use libmagic_rs::parser::ast::OffsetSpec;
///
/// // Absolute offset
/// assert_eq!(parse_rule_offset("0"), Ok(("", (0, OffsetSpec::Absolute(0)))));
/// assert_eq!(parse_rule_offset("16"), Ok(("", (0, OffsetSpec::Absolute(16)))));
///
/// // Child rule (level 1)
/// assert_eq!(parse_rule_offset(">4"), Ok(("", (1, OffsetSpec::Absolute(4)))));
///
/// // Nested child rule (level 2)
/// assert_eq!(parse_rule_offset(">>8"), Ok(("", (2, OffsetSpec::Absolute(8)))));
/// ```
/// Parse rule offset with hierarchy level (> prefixes) and offset specification
///
/// # Errors
/// Returns a nom parsing error if the input doesn't match the expected offset format
pub fn parse_rule_offset(input: &str) -> IResult<&str, (u32, OffsetSpec)> {
    let (input, _) = multispace0(input)?;

    // Count the number of '>' characters for nesting level
    let (input, level_chars) = many0(char('>')).parse(input)?;
    let level = u32::try_from(level_chars.len()).unwrap_or(0);

    // Parse the offset after the '>' characters
    let (input, offset_spec) = parse_offset(input)?;

    Ok((input, (level, offset_spec)))
}

/// Parse the message part of a magic rule
///
/// The message is everything after the value until the end of the line.
/// It may contain format specifiers and can be empty.
///
/// # Examples
///
/// ```
/// use libmagic_rs::parser::grammar::parse_message;
///
/// assert_eq!(parse_message("ELF executable"), Ok(("", "ELF executable".to_string())));
/// assert_eq!(parse_message(""), Ok(("", "".to_string())));
/// assert_eq!(parse_message("  \tPDF document  "), Ok(("", "PDF document".to_string())));
/// ```
/// Parse the message/description part of a magic rule
///
/// # Errors
/// Returns a nom parsing error if the input cannot be parsed as a message
pub fn parse_message(input: &str) -> IResult<&str, String> {
    let (input, _) = multispace0(input)?;

    // Take everything until end of line, trimming whitespace
    // Use take_while instead of take_while1 to handle empty messages
    let (input, message_text) = take_while(|c: char| c != '\n' && c != '\r').parse(input)?;
    let message = message_text.trim().to_string();

    Ok((input, message))
}

/// Parse a strength directive (`!:strength` line)
///
/// Parses the `!:strength` directive that modifies rule strength.
/// Format: `!:strength [+|-|*|/|=]N` or `!:strength N`
///
/// # Examples
///
/// ```
/// use libmagic_rs::parser::grammar::parse_strength_directive;
/// use libmagic_rs::parser::ast::StrengthModifier;
///
/// assert_eq!(parse_strength_directive("!:strength +10"), Ok(("", StrengthModifier::Add(10))));
/// assert_eq!(parse_strength_directive("!:strength -5"), Ok(("", StrengthModifier::Subtract(5))));
/// assert_eq!(parse_strength_directive("!:strength *2"), Ok(("", StrengthModifier::Multiply(2))));
/// assert_eq!(parse_strength_directive("!:strength /2"), Ok(("", StrengthModifier::Divide(2))));
/// assert_eq!(parse_strength_directive("!:strength =50"), Ok(("", StrengthModifier::Set(50))));
/// assert_eq!(parse_strength_directive("!:strength 50"), Ok(("", StrengthModifier::Set(50))));
/// ```
///
/// # Errors
///
/// Returns a nom parsing error if:
/// - Input doesn't start with `!:strength`
/// - The modifier value cannot be parsed as a valid integer
/// - The operator is invalid
pub fn parse_strength_directive(input: &str) -> IResult<&str, StrengthModifier> {
    // Helper to safely convert i64 to i32 with clamping to valid strength range.
    // This prevents silent truncation to 0 on overflow while keeping values in bounds.
    fn clamp_to_i32(n: i64) -> i32 {
        // Use i64::from for lossless conversion, then clamp and convert back
        let clamped = n.clamp(i64::from(i32::MIN), i64::from(i32::MAX));
        // Safe to unwrap: clamped value is guaranteed to be in i32 range
        i32::try_from(clamped).unwrap()
    }

    let (input, _) = multispace0(input)?;
    let (input, _) = tag("!:strength")(input)?;
    let (input, _) = multispace0(input)?;

    // Parse the operator: +, -, *, /, = or bare number (implies =)
    let (input, modifier) = alt((
        // +N -> Add
        map(pair(char('+'), parse_number), |(_, n)| {
            StrengthModifier::Add(clamp_to_i32(n))
        }),
        // -N -> Subtract (note: parse_number handles negative, so we need special handling)
        map(pair(char('-'), parse_decimal_number), |(_, n)| {
            StrengthModifier::Subtract(clamp_to_i32(n))
        }),
        // *N -> Multiply
        map(pair(char('*'), parse_number), |(_, n)| {
            StrengthModifier::Multiply(clamp_to_i32(n))
        }),
        // /N -> Divide
        map(pair(char('/'), parse_number), |(_, n)| {
            StrengthModifier::Divide(clamp_to_i32(n))
        }),
        // =N -> Set
        map(pair(char('='), parse_number), |(_, n)| {
            StrengthModifier::Set(clamp_to_i32(n))
        }),
        // Bare number -> Set
        map(parse_number, |n| StrengthModifier::Set(clamp_to_i32(n))),
    ))
    .parse(input)?;

    Ok((input, modifier))
}

/// Check if a line is a strength directive (starts with !:strength)
///
/// # Examples
///
/// ```
/// use libmagic_rs::parser::grammar::is_strength_directive;
///
/// assert!(is_strength_directive("!:strength +10"));
/// assert!(is_strength_directive("  !:strength -5"));
/// assert!(!is_strength_directive("0 byte 1"));
/// ```
#[must_use]
pub fn is_strength_directive(input: &str) -> bool {
    input.trim().starts_with("!:strength")
}

/// Parse a complete magic rule line from text format
///
/// Parses a complete magic rule in the format:
/// `[>...]offset type [operator] value [message]`
///
/// Where:
/// - `>...` indicates child rule nesting level (optional)
/// - `offset` is the byte offset to read from
/// - `type` is the data type (byte, short, long, string, etc.)
/// - `operator` is the comparison operator (=, !=, &) - defaults to = if omitted
/// - `value` is the expected value to compare against
/// - `message` is the human-readable description (optional)
///
/// # Examples
///
/// ```
/// use libmagic_rs::parser::grammar::parse_magic_rule;
/// use libmagic_rs::parser::ast::{MagicRule, OffsetSpec, TypeKind, Operator, Value};
///
/// // Basic rule
/// let input = "0 string \\x7fELF ELF executable";
/// let (_, rule) = parse_magic_rule(input).unwrap();
/// assert_eq!(rule.level, 0);
/// assert_eq!(rule.message, "ELF executable");
///
/// // Child rule
/// let input = ">4 byte 1 32-bit";
/// let (_, rule) = parse_magic_rule(input).unwrap();
/// assert_eq!(rule.level, 1);
/// assert_eq!(rule.message, "32-bit");
/// ```
///
/// # Errors
///
/// Returns a nom parsing error if:
/// - The offset specification is invalid
/// - The type specification is not recognized
/// - The operator is invalid (if present)
/// - The value cannot be parsed
/// - The input format doesn't match the expected magic rule syntax
pub fn parse_magic_rule(input: &str) -> IResult<&str, MagicRule> {
    let (input, _) = multispace0(input)?;

    // Parse the offset with nesting level
    let (input, (level, offset)) = parse_rule_offset(input)?;

    // Parse the type and any attached operator
    let (input, (typ, attached_op)) = parse_type_and_operator(input)?;

    // Try to parse a separate operator (optional - use attached operator if present)
    let (input, separate_op) = opt(parse_operator).parse(input)?;
    let op = attached_op.or(separate_op).unwrap_or(Operator::Equal);

    // Parse the value
    let (input, value) = parse_value(input)?;

    // Parse the message (optional - everything remaining on the line)
    let (input, message) = if input.trim().is_empty() {
        (input, String::new())
    } else {
        parse_message(input)?
    };

    let rule = MagicRule {
        offset,
        typ,
        op,
        value,
        message,
        children: vec![], // Children will be added during hierarchical parsing
        level,
        strength_modifier: None, // Will be set during directive parsing
    };

    Ok((input, rule))
}

/// Parse a comment line (starts with #)
///
/// Comments in magic files start with '#' and continue to the end of the line.
/// This function consumes the entire comment line.
///
/// # Examples
///
/// ```
/// use libmagic_rs::parser::grammar::parse_comment;
///
/// assert_eq!(parse_comment("# This is a comment"), Ok(("", "This is a comment".to_string())));
/// assert_eq!(parse_comment("#"), Ok(("", "".to_string())));
/// ```
/// Parse a comment line (starting with #)
///
/// # Errors
/// Returns a nom parsing error if the input is not a valid comment
pub fn parse_comment(input: &str) -> IResult<&str, String> {
    let (input, _) = multispace0(input)?;
    let (input, _) = char('#').parse(input)?;
    let (input, comment_text) = take_while(|c: char| c != '\n' && c != '\r').parse(input)?;
    let comment = comment_text.trim().to_string();
    Ok((input, comment))
}

/// Check if a line is empty or contains only whitespace
///
/// # Examples
///
/// ```
/// use libmagic_rs::parser::grammar::is_empty_line;
///
/// assert!(is_empty_line(""));
/// assert!(is_empty_line("   "));
/// assert!(is_empty_line("\t\t"));
/// assert!(!is_empty_line("0 byte 1"));
/// ```
#[must_use]
pub fn is_empty_line(input: &str) -> bool {
    input.trim().is_empty()
}

/// Check if a line is a comment (starts with #)
///
/// # Examples
///
/// ```
/// use libmagic_rs::parser::grammar::is_comment_line;
///
/// assert!(is_comment_line("# This is a comment"));
/// assert!(is_comment_line("#"));
/// assert!(is_comment_line("  # Indented comment"));
/// assert!(!is_comment_line("0 byte 1"));
/// ```
#[must_use]
pub fn is_comment_line(input: &str) -> bool {
    input.trim().starts_with('#')
}

/// Check if a line ends with a continuation character (\)
///
/// Magic files support line continuation with backslash at the end of lines.
///
/// # Examples
///
/// ```
/// use libmagic_rs::parser::grammar::has_continuation;
///
/// assert!(has_continuation("0 string test \\"));
/// assert!(has_continuation("message continues \\"));
/// assert!(!has_continuation("0 string test"));
/// ```
#[must_use]
pub fn has_continuation(input: &str) -> bool {
    input.trim_end().ends_with('\\')
}
// Tests for new magic rule parsing functions

#[test]
fn test_parse_type_basic() {
    assert_eq!(parse_type("byte"), Ok(("", TypeKind::Byte)));
    assert_eq!(
        parse_type("short"),
        Ok((
            "",
            TypeKind::Short {
                endian: Endianness::Native,
                signed: false
            }
        ))
    );
    assert_eq!(
        parse_type("long"),
        Ok((
            "",
            TypeKind::Long {
                endian: Endianness::Native,
                signed: false
            }
        ))
    );
    assert_eq!(
        parse_type("string"),
        Ok(("", TypeKind::String { max_length: None }))
    );
}

#[test]
fn test_parse_type_endianness() {
    assert_eq!(
        parse_type("leshort"),
        Ok((
            "",
            TypeKind::Short {
                endian: Endianness::Little,
                signed: false
            }
        ))
    );
    assert_eq!(
        parse_type("beshort"),
        Ok((
            "",
            TypeKind::Short {
                endian: Endianness::Big,
                signed: false
            }
        ))
    );
    assert_eq!(
        parse_type("lelong"),
        Ok((
            "",
            TypeKind::Long {
                endian: Endianness::Little,
                signed: false
            }
        ))
    );
    assert_eq!(
        parse_type("belong"),
        Ok((
            "",
            TypeKind::Long {
                endian: Endianness::Big,
                signed: false
            }
        ))
    );
}

#[test]
fn test_parse_type_with_whitespace() {
    assert_eq!(parse_type(" byte "), Ok(("", TypeKind::Byte)));
    assert_eq!(
        parse_type("\tstring\t"),
        Ok(("", TypeKind::String { max_length: None }))
    );
    assert_eq!(
        parse_type("  lelong  "),
        Ok((
            "",
            TypeKind::Long {
                endian: Endianness::Little,
                signed: false
            }
        ))
    );
}

#[test]
fn test_parse_type_with_remaining_input() {
    assert_eq!(parse_type("byte ="), Ok(("=", TypeKind::Byte)));
    assert_eq!(
        parse_type("string \\x7f"),
        Ok(("\\x7f", TypeKind::String { max_length: None }))
    );
}

#[test]
fn test_parse_type_invalid() {
    assert!(parse_type("").is_err());
    assert!(parse_type("invalid").is_err());
    assert!(parse_type("int").is_err());
    assert!(parse_type("float").is_err());
}

#[test]
fn test_parse_rule_offset_absolute() {
    assert_eq!(
        parse_rule_offset("0"),
        Ok(("", (0, OffsetSpec::Absolute(0))))
    );
    assert_eq!(
        parse_rule_offset("16"),
        Ok(("", (0, OffsetSpec::Absolute(16))))
    );
    assert_eq!(
        parse_rule_offset("0x10"),
        Ok(("", (0, OffsetSpec::Absolute(16))))
    );
    assert_eq!(
        parse_rule_offset("-4"),
        Ok(("", (0, OffsetSpec::Absolute(-4))))
    );
}

#[test]
fn test_parse_rule_offset_child_rules() {
    assert_eq!(
        parse_rule_offset(">4"),
        Ok(("", (1, OffsetSpec::Absolute(4))))
    );
    assert_eq!(
        parse_rule_offset(">>8"),
        Ok(("", (2, OffsetSpec::Absolute(8))))
    );
    assert_eq!(
        parse_rule_offset(">>>12"),
        Ok(("", (3, OffsetSpec::Absolute(12))))
    );
}

#[test]
fn test_parse_rule_offset_with_whitespace() {
    assert_eq!(
        parse_rule_offset(" 0 "),
        Ok(("", (0, OffsetSpec::Absolute(0))))
    );
    assert_eq!(
        parse_rule_offset("  >4  "),
        Ok(("", (1, OffsetSpec::Absolute(4))))
    );
    assert_eq!(
        parse_rule_offset("\t>>0x10\t"),
        Ok(("", (2, OffsetSpec::Absolute(16))))
    );
}

#[test]
fn test_parse_rule_offset_with_remaining_input() {
    assert_eq!(
        parse_rule_offset("0 byte"),
        Ok(("byte", (0, OffsetSpec::Absolute(0))))
    );
    assert_eq!(
        parse_rule_offset(">4 string"),
        Ok(("string", (1, OffsetSpec::Absolute(4))))
    );
}

#[test]
fn test_parse_message_basic() {
    assert_eq!(
        parse_message("ELF executable"),
        Ok(("", "ELF executable".to_string()))
    );
    assert_eq!(
        parse_message("PDF document"),
        Ok(("", "PDF document".to_string()))
    );
    assert_eq!(parse_message(""), Ok(("", String::new())));
}

#[test]
fn test_parse_message_with_whitespace() {
    assert_eq!(
        parse_message("  ELF executable  "),
        Ok(("", "ELF executable".to_string()))
    );
    assert_eq!(
        parse_message("\tPDF document\t"),
        Ok(("", "PDF document".to_string()))
    );
    assert_eq!(parse_message("   "), Ok(("", String::new())));
}

#[test]
fn test_parse_message_complex() {
    assert_eq!(
        parse_message("ELF 64-bit LSB executable"),
        Ok(("", "ELF 64-bit LSB executable".to_string()))
    );
    assert_eq!(
        parse_message("ZIP archive, version %d.%d"),
        Ok(("", "ZIP archive, version %d.%d".to_string()))
    );
}

#[test]
fn test_parse_magic_rule_basic() {
    let input = "0 string \\x7fELF ELF executable";
    let (remaining, rule) = parse_magic_rule(input).unwrap();

    assert_eq!(remaining, "");
    assert_eq!(rule.level, 0);
    assert_eq!(rule.offset, OffsetSpec::Absolute(0));
    assert_eq!(rule.typ, TypeKind::String { max_length: None });
    assert_eq!(rule.op, Operator::Equal);
    assert_eq!(rule.value, Value::Bytes(vec![0x7f, 0x45, 0x4c, 0x46]));
    assert_eq!(rule.message, "ELF executable");
    assert!(rule.children.is_empty());
}

#[test]
fn test_parse_magic_rule_child() {
    let input = ">4 byte 1 32-bit";
    let (remaining, rule) = parse_magic_rule(input).unwrap();

    assert_eq!(remaining, "");
    assert_eq!(rule.level, 1);
    assert_eq!(rule.offset, OffsetSpec::Absolute(4));
    assert_eq!(rule.typ, TypeKind::Byte);
    assert_eq!(rule.op, Operator::Equal);
    assert_eq!(rule.value, Value::Uint(1));
    assert_eq!(rule.message, "32-bit");
}

#[test]
fn test_parse_magic_rule_with_operator() {
    let input = "0 lelong&0xf0000000 0x10000000 MIPS-II";
    let (remaining, rule) = parse_magic_rule(input).unwrap();

    assert_eq!(remaining, "");
    assert_eq!(rule.level, 0);
    assert_eq!(rule.offset, OffsetSpec::Absolute(0));
    assert_eq!(
        rule.typ,
        TypeKind::Long {
            endian: Endianness::Little,
            signed: false
        }
    );
    assert_eq!(rule.op, Operator::BitwiseAndMask(0xf000_0000));
    assert_eq!(rule.value, Value::Uint(0x1000_0000));
    assert_eq!(rule.message, "MIPS-II");
}

#[test]
fn test_parse_magic_rule_no_message() {
    let input = "0 byte 0x7f";
    let (remaining, rule) = parse_magic_rule(input).unwrap();

    assert_eq!(remaining, "");
    assert_eq!(rule.level, 0);
    assert_eq!(rule.offset, OffsetSpec::Absolute(0));
    assert_eq!(rule.typ, TypeKind::Byte);
    assert_eq!(rule.op, Operator::Equal);
    assert_eq!(rule.value, Value::Uint(0x7f));
    assert_eq!(rule.message, "");
}

#[test]
fn test_parse_magic_rule_nested() {
    let input = ">>8 leshort 0x014c Microsoft COFF";
    let (remaining, rule) = parse_magic_rule(input).unwrap();

    assert_eq!(remaining, "");
    assert_eq!(rule.level, 2);
    assert_eq!(rule.offset, OffsetSpec::Absolute(8));
    assert_eq!(
        rule.typ,
        TypeKind::Short {
            endian: Endianness::Little,
            signed: false
        }
    );
    assert_eq!(rule.op, Operator::Equal);
    assert_eq!(rule.value, Value::Uint(0x014c));
    assert_eq!(rule.message, "Microsoft COFF");
}

#[test]
fn test_parse_magic_rule_with_whitespace() {
    let input = "  >  4   byte   =   1   32-bit  ";
    let (remaining, rule) = parse_magic_rule(input).unwrap();

    assert_eq!(remaining, "");
    assert_eq!(rule.level, 1);
    assert_eq!(rule.offset, OffsetSpec::Absolute(4));
    assert_eq!(rule.typ, TypeKind::Byte);
    assert_eq!(rule.op, Operator::Equal);
    assert_eq!(rule.value, Value::Uint(1));
    assert_eq!(rule.message, "32-bit");
}

#[test]
fn test_parse_magic_rule_string_value() {
    let input = "0 string \"PK\" ZIP archive";
    let (remaining, rule) = parse_magic_rule(input).unwrap();

    assert_eq!(remaining, "");
    assert_eq!(rule.level, 0);
    assert_eq!(rule.offset, OffsetSpec::Absolute(0));
    assert_eq!(rule.typ, TypeKind::String { max_length: None });
    assert_eq!(rule.op, Operator::Equal);
    assert_eq!(rule.value, Value::String("PK".to_string()));
    assert_eq!(rule.message, "ZIP archive");
}

#[test]
fn test_parse_magic_rule_hex_offset() {
    let input = "0x10 belong 0x12345678 Test data";
    let (remaining, rule) = parse_magic_rule(input).unwrap();

    assert_eq!(remaining, "");
    assert_eq!(rule.level, 0);
    assert_eq!(rule.offset, OffsetSpec::Absolute(16));
    assert_eq!(
        rule.typ,
        TypeKind::Long {
            endian: Endianness::Big,
            signed: false
        }
    );
    assert_eq!(rule.op, Operator::Equal);
    assert_eq!(rule.value, Value::Uint(0x1234_5678));
    assert_eq!(rule.message, "Test data");
}

#[test]
fn test_parse_magic_rule_negative_offset() {
    let input = "-4 byte 0 End marker";
    let (remaining, rule) = parse_magic_rule(input).unwrap();

    assert_eq!(remaining, "");
    assert_eq!(rule.level, 0);
    assert_eq!(rule.offset, OffsetSpec::Absolute(-4));
    assert_eq!(rule.typ, TypeKind::Byte);
    assert_eq!(rule.op, Operator::Equal);
    assert_eq!(rule.value, Value::Uint(0));
    assert_eq!(rule.message, "End marker");
}

#[test]
fn test_parse_comment() {
    assert_eq!(
        parse_comment("# This is a comment"),
        Ok(("", "This is a comment".to_string()))
    );
    assert_eq!(parse_comment("#"), Ok(("", String::new())));
    assert_eq!(
        parse_comment("# ELF executables"),
        Ok(("", "ELF executables".to_string()))
    );
}

#[test]
fn test_parse_comment_with_whitespace() {
    assert_eq!(
        parse_comment("  # Indented comment  "),
        Ok(("", "Indented comment".to_string()))
    );
    assert_eq!(
        parse_comment("\t#\tTabbed comment\t"),
        Ok(("", "Tabbed comment".to_string()))
    );
}

#[test]
fn test_is_empty_line() {
    assert!(is_empty_line(""));
    assert!(is_empty_line("   "));
    assert!(is_empty_line("\t\t"));
    assert!(is_empty_line(" \t \t "));
    assert!(!is_empty_line("0 byte 1"));
    assert!(!is_empty_line("  # comment"));
}

#[test]
fn test_is_comment_line() {
    assert!(is_comment_line("# This is a comment"));
    assert!(is_comment_line("#"));
    assert!(is_comment_line("  # Indented comment"));
    assert!(is_comment_line("\t# Tabbed comment"));
    assert!(!is_comment_line("0 byte 1"));
    assert!(!is_comment_line("string test"));
}

#[test]
fn test_has_continuation() {
    assert!(has_continuation("0 string test \\"));
    assert!(has_continuation("message continues \\"));
    assert!(has_continuation("line ends with backslash\\"));
    assert!(has_continuation("  trailing whitespace  \\  "));
    assert!(!has_continuation("0 string test"));
    assert!(!has_continuation("no continuation"));
    assert!(!has_continuation("backslash in middle \\ here"));
}

#[test]
fn test_parse_magic_rule_real_world_examples() {
    // Real examples from /usr/share/file/magic/elf
    let examples = [
        "0 string \\177ELF ELF",
        ">4 byte 1 32-bit",
        ">4 byte 2 64-bit",
        ">5 byte 1 LSB",
        ">5 byte 2 MSB",
        ">>0 lelong&0xf0000000 0x10000000 MIPS-II",
    ];

    for example in examples {
        let result = parse_magic_rule(example);
        assert!(
            result.is_ok(),
            "Failed to parse real-world example: '{example}'"
        );

        let (remaining, rule) = result.unwrap();
        assert_eq!(remaining, "", "Unexpected remaining input for: '{example}'");
        assert!(
            !rule.message.is_empty() || example.contains("\\177ELF"),
            "Empty message for: '{example}'"
        );
    }
}

#[test]
fn test_parse_magic_rule_edge_cases() {
    // Test various edge cases
    let edge_cases = [
        ("0 byte 0", 0, TypeKind::Byte, Value::Uint(0), ""),
        (
            ">>>16 string \"\" Empty string",
            3,
            TypeKind::String { max_length: None },
            Value::String(String::new()),
            "Empty string",
        ),
        (
            "0x100 lelong 0xFFFFFFFF Max value",
            0,
            TypeKind::Long {
                endian: Endianness::Little,
                signed: false,
            },
            Value::Uint(0xFFFF_FFFF),
            "Max value",
        ),
    ];

    for (input, expected_level, expected_type, expected_value, expected_message) in edge_cases {
        let (remaining, rule) = parse_magic_rule(input).unwrap();
        assert_eq!(remaining, "");
        assert_eq!(rule.level, expected_level);
        assert_eq!(rule.typ, expected_type);
        assert_eq!(rule.value, expected_value);
        assert_eq!(rule.message, expected_message);
    }
}

#[test]
fn test_parse_magic_rule_invalid_input() {
    let invalid_inputs = [
        "",               // Empty input
        "invalid format", // No valid offset
        "0",              // Missing type
        "0 invalid_type", // Invalid type
        "0 byte",         // Missing value
    ];

    for invalid_input in invalid_inputs {
        let result = parse_magic_rule(invalid_input);
        assert!(
            result.is_err(),
            "Should fail to parse invalid input: '{invalid_input}'"
        );
    }
}

// Strength directive tests
#[test]
fn test_parse_strength_directive_add() {
    assert_eq!(
        parse_strength_directive("!:strength +10"),
        Ok(("", StrengthModifier::Add(10)))
    );
    assert_eq!(
        parse_strength_directive("!:strength +0"),
        Ok(("", StrengthModifier::Add(0)))
    );
    assert_eq!(
        parse_strength_directive("!:strength +100"),
        Ok(("", StrengthModifier::Add(100)))
    );
}

#[test]
fn test_parse_strength_directive_subtract() {
    assert_eq!(
        parse_strength_directive("!:strength -5"),
        Ok(("", StrengthModifier::Subtract(5)))
    );
    assert_eq!(
        parse_strength_directive("!:strength -0"),
        Ok(("", StrengthModifier::Subtract(0)))
    );
    assert_eq!(
        parse_strength_directive("!:strength -50"),
        Ok(("", StrengthModifier::Subtract(50)))
    );
}

#[test]
fn test_parse_strength_directive_multiply() {
    assert_eq!(
        parse_strength_directive("!:strength *2"),
        Ok(("", StrengthModifier::Multiply(2)))
    );
    assert_eq!(
        parse_strength_directive("!:strength *10"),
        Ok(("", StrengthModifier::Multiply(10)))
    );
}

#[test]
fn test_parse_strength_directive_divide() {
    assert_eq!(
        parse_strength_directive("!:strength /2"),
        Ok(("", StrengthModifier::Divide(2)))
    );
    assert_eq!(
        parse_strength_directive("!:strength /10"),
        Ok(("", StrengthModifier::Divide(10)))
    );
}

#[test]
fn test_parse_strength_directive_set_explicit() {
    assert_eq!(
        parse_strength_directive("!:strength =50"),
        Ok(("", StrengthModifier::Set(50)))
    );
    assert_eq!(
        parse_strength_directive("!:strength =0"),
        Ok(("", StrengthModifier::Set(0)))
    );
    assert_eq!(
        parse_strength_directive("!:strength =100"),
        Ok(("", StrengthModifier::Set(100)))
    );
}

#[test]
fn test_parse_strength_directive_set_bare() {
    // Bare number implies Set
    assert_eq!(
        parse_strength_directive("!:strength 50"),
        Ok(("", StrengthModifier::Set(50)))
    );
    assert_eq!(
        parse_strength_directive("!:strength 0"),
        Ok(("", StrengthModifier::Set(0)))
    );
    assert_eq!(
        parse_strength_directive("!:strength 100"),
        Ok(("", StrengthModifier::Set(100)))
    );
}

#[test]
fn test_parse_strength_directive_with_whitespace() {
    assert_eq!(
        parse_strength_directive("  !:strength +10"),
        Ok(("", StrengthModifier::Add(10)))
    );
    assert_eq!(
        parse_strength_directive("\t!:strength -5"),
        Ok(("", StrengthModifier::Subtract(5)))
    );
    assert_eq!(
        parse_strength_directive("!:strength  *2"),
        Ok(("", StrengthModifier::Multiply(2)))
    );
    assert_eq!(
        parse_strength_directive("!:strength   50"),
        Ok(("", StrengthModifier::Set(50)))
    );
}

#[test]
fn test_parse_strength_directive_with_remaining_input() {
    // Should leave remaining content after the directive
    assert_eq!(
        parse_strength_directive("!:strength +10 extra"),
        Ok((" extra", StrengthModifier::Add(10)))
    );
    assert_eq!(
        parse_strength_directive("!:strength 50\n"),
        Ok(("\n", StrengthModifier::Set(50)))
    );
}

#[test]
fn test_parse_strength_directive_invalid() {
    // Should fail on invalid input
    assert!(parse_strength_directive("").is_err());
    assert!(parse_strength_directive("!:invalid").is_err());
    assert!(parse_strength_directive("strength +10").is_err());
    assert!(parse_strength_directive("0 byte 1").is_err());
}

#[test]
fn test_is_strength_directive() {
    assert!(is_strength_directive("!:strength +10"));
    assert!(is_strength_directive("!:strength -5"));
    assert!(is_strength_directive("!:strength 50"));
    assert!(is_strength_directive("  !:strength +10"));
    assert!(is_strength_directive("\t!:strength *2"));

    assert!(!is_strength_directive("0 byte 1"));
    assert!(!is_strength_directive("# comment"));
    assert!(!is_strength_directive(""));
    assert!(!is_strength_directive("!:mime application/pdf"));
}