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use std::{fmt, usize};
use stringr::Stringr;
use thiserror::Error;

#[derive(Debug, PartialEq, Eq, Clone)]
pub struct Signature {
    pub first_wildcard: Option<usize>,
    pub first_byte: Option<usize>,
    pub matching_indices: Vec<usize>,
    pub length: usize,
    pub pattern: Vec<u8>,
    pub mask: Vec<char>,
    pub sig: String,
    pub offset: usize,
}

impl fmt::Display for Signature {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match Signature::format(&self.sig) {
            Ok(s) => write!(f, "{}", s),
            Err(e) => write!(f, "{}", e),
        }
    }
}

#[derive(Error, Debug, Clone, PartialEq, Eq)]
pub enum SignatureParseError {
    #[error(
        "Signature length(excluding whitespace) must be divisible by 2, but was of length {0}"
    )]
    InvalidLength(usize),
    #[error("Signature must contain only hexadecimal characters, but was {0}")]
    InvalidString(String),
}

impl Signature {
    pub fn get_pattern_and_mask_from_signature(
        signature: &str,
    ) -> Result<(Vec<u8>, Vec<char>), SignatureParseError> {
        let signature = signature.remove_whitespace();
        if signature.len() % 2 != 0 {
            return Err(SignatureParseError::InvalidLength(signature.len()));
        }

        let split = signature.splitn(2);
        let mut bytes = Vec::with_capacity(split.len());
        let mut mask = Vec::with_capacity(split.len());

        for c in split {
            if c.contains('?') {
                bytes.push(0);
                mask.push('?');
            } else {
                bytes.push(
                    u8::from_str_radix(&c, 16)
                        .map_err(|_e| SignatureParseError::InvalidString(c))?,
                );
                mask.push('x');
            }
        }

        Ok((bytes, mask))
    }

    pub fn new(signature: &str, offset: usize) -> Result<Signature, SignatureParseError> {
        let (pattern, mask) = Signature::get_pattern_and_mask_from_signature(signature)?;
        let indices = mask
            .iter()
            .enumerate()
            .filter_map(|(i, &m)| (m == 'x').then(|| i))
            .collect();

        return Ok(Signature {
            first_wildcard: mask.iter().position(|&c| c == '?'),
            first_byte: mask.iter().position(|&c| c == 'x'),
            matching_indices: indices,
            length: pattern.len(),
            pattern,
            mask,
            sig: Signature::format(signature)?,
            offset,
        });
    }

    pub fn format(signature: &str) -> Result<String, SignatureParseError> {
        let signature = signature.remove_whitespace();
        if signature.len() % 2 != 0 {
            return Err(SignatureParseError::InvalidLength(signature.len()));
        }

        Ok(signature.splitn_separator(2, " ").to_ascii_uppercase())
    }
}

#[cfg(test)]
mod test {
    #[test]
    fn test_invalid_length() {
        let signature = "123";
        let signature = super::Signature::new(signature, 0);
        assert!(signature.is_err());
        assert_eq!(
            signature.unwrap_err(),
            super::SignatureParseError::InvalidLength(3)
        );
    }

    #[test]
    fn test_invalid_string() {
        let signature = "zz";
        let signature = super::Signature::new(signature, 0);
        assert!(signature.is_err());
        assert_eq!(
            signature.unwrap_err(),
            super::SignatureParseError::InvalidString("zz".to_string())
        );
    }

    #[test]
    fn test_valid_signature() {
        let signature = "12 34 56 78";
        let signature = super::Signature::new(signature, 0);
        assert!(signature.is_ok());
        assert_eq!(
            signature.unwrap(),
            super::Signature {
                first_wildcard: None,
                first_byte: Some(0),
                matching_indices: vec![0, 1, 2, 3],
                length: 4,
                pattern: vec![0x12, 0x34, 0x56, 0x78],
                mask: vec!['x', 'x', 'x', 'x'],
                sig: "12 34 56 78".to_string(),
                offset: 0,
            }
        );
    }

    #[test]
    fn test_valid_signature_with_wildcards() {
        let signature = "12 ?? 56 78";
        let signature = super::Signature::new(signature, 0);
        assert!(signature.is_ok());
        assert_eq!(
            signature.unwrap(),
            super::Signature {
                first_wildcard: Some(1),
                first_byte: Some(0),
                matching_indices: vec![0, 2, 3],
                length: 4,
                pattern: vec![0x12, 0x00, 0x56, 0x78],
                mask: vec!['x', '?', 'x', 'x'],
                sig: "12 ?? 56 78".to_string(),
                offset: 0,
            }
        );
    }

    #[test]
    fn test_formatting() {
        let signatures = vec![
            ("abcd", "AB CD"),
            ("a b c D", "AB CD"),
            ("a b c d 12 34 56 78", "AB CD 12 34 56 78"),
        ];
        for (sig, formatted) in signatures {
            let signature = super::Signature::format(sig);
            assert!(signature.is_ok());
            let signature = signature.unwrap();
            assert_eq!(signature, formatted);
        }
    }
}