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const BITS_IN_BYTE: u8 = 8;

pub struct QwordTable<'a> {
    data: &'a Vec<u8>,
}

impl<'a> QwordTable<'a> {
    pub fn from_bytes(data: &Vec<u8>) -> QwordTable {
        QwordTable { data }
    }

    /// Formats a vector of bytes as a qword table.
    ///
    /// # Arguments
    ///
    /// * `data` - The bytes to format.
    pub fn format(self: &QwordTable<'a>) -> String {
        let mut result = self.format_qword_table_header();
        let num_qwords = self.data.len().div_euclid(BITS_IN_BYTE as usize);
        // Append full qwords
        for i in 0..num_qwords {
            let from_byte_ix = i * BITS_IN_BYTE as usize;
            let to_byte_ix = from_byte_ix + BITS_IN_BYTE as usize;
            let qword_number: usize = i + 1;
            result.push_str(&self.format_qword_row(
                qword_number,
                &self.data[from_byte_ix..to_byte_ix],
                BITS_IN_BYTE as usize,
            ));
        }
        // Append final bytes
        let remaining_bytes = self.data.len().rem_euclid(BITS_IN_BYTE as usize);
        let from_byte_ix: usize = num_qwords * BITS_IN_BYTE as usize;
        let to_byte_ix: usize = from_byte_ix + remaining_bytes as usize;
        let qword_number: usize = num_qwords + 1;
        result.push_str(&self.format_qword_row(
            qword_number,
            &self.data[from_byte_ix..to_byte_ix],
            remaining_bytes,
        ));
        result
    }

    /// Formats the header for a qword table.
    fn format_qword_table_header(self: &QwordTable<'a>) -> String {
        // Top border
        let mut result = String::from("       +");
        result.push_str(&(0..BITS_IN_BYTE).map(|_| "--------+").collect::<String>());
        // Append table label
        result.push_str("\n Bytes |");
        // Append column labels
        result.push_str(
            &(0..BITS_IN_BYTE)
                .map(|i| format!(" Byte {} |", i))
                .collect::<String>(),
        );
        // Append bottom border
        result.push_str("\n+------+");
        result.push_str(&(0..BITS_IN_BYTE).map(|_| "--------+").collect::<String>());
        result.push_str("\n");
        result
    }

    /// Formats a row of bytes in a qword table.
    ///
    /// # Arguments
    ///
    /// * `qword_number` - The sequence number of this qword.
    /// * `data` - The bytes within the qword to format.
    /// * `num_bytes` - The number of bytes to format.
    fn format_qword_row(
        self: &QwordTable<'a>,
        qword_number: usize,
        data: &[u8],
        num_bytes: usize,
    ) -> String {
        if data.len() != num_bytes {
            return format!(
                "ERROR: Data must contain exactly {} bytes. QWORD: {}\n",
                num_bytes, qword_number
            );
        }

        // Row header
        let mut result = String::from("|QWORD |");
        // Append byte values
        result.push_str(
            &(0..num_bytes)
                .map(|i| format!("{:0>8b}|", data[i]))
                .collect::<String>(),
        );
        // Append qword number
        result.push_str(&format!("\n|{:^6}|", qword_number));
        // Append byte value
        result.push_str(
            &(0..num_bytes)
                .map(|i| format!("{:>8}|", format!("({})", data[i])))
                .collect::<String>(),
        );
        // Append bottom border
        result.push_str("\n+------+");
        result.push_str(&(0..num_bytes).map(|_| "--------+").collect::<String>());
        result.push_str("\n");
        result
    }
}

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

    #[test]
    fn test_one_byte() {
        let data = vec![129];
        let table: QwordTable = QwordTable::from_bytes(&data);

        let expected = "       +--------+--------+--------+--------+--------+--------+--------+--------+\n Bytes | Byte 0 | Byte 1 | Byte 2 | Byte 3 | Byte 4 | Byte 5 | Byte 6 | Byte 7 |\n+------+--------+--------+--------+--------+--------+--------+--------+--------+\n|QWORD |10000001|\n|  1   |   (129)|\n+------+--------+\n";

        assert_eq!(expected, table.format());
    }
}