use crate::{
    paranoid_hash::{hash_helper::slice_as_chunks, Hasher},
    Error, Result,
};

#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq, PartialOrd, Ord)]
pub struct MD2 {
    checksum: [u8; 16],
    buffer: [u8; 48],
    count: usize,
    is_done: bool,
}

impl Hasher for MD2 {
    fn update(&mut self, data: &[u8]) -> Result<()> {
        if self.is_done {
            return Err(Error::UpdatingAfterFinished);
        }

        if data.len() % Self::BLOCK_SIZE != 0 {
            return Err(Error::DataLengthMismatched(data.len(), Self::BLOCK_SIZE));
        }

        self.count = self.count.wrapping_add(data.len());

        let block_chunks: &[[u8; Self::BLOCK_SIZE]] = slice_as_chunks(data);

        for block_chunk in block_chunks {
            self.update_block(block_chunk);
        }

        Ok(())
    }

    fn update_last(&mut self, data: &[u8]) -> Result<()> {
        if self.is_done {
            return Err(Error::UpdatingAfterFinished);
        }

        if data.len() > Self::BLOCK_SIZE {
            return Err(Error::DataTooLarge(data.len(), Self::BLOCK_SIZE));
        }

        self.count = self.count.wrapping_add(data.len());
        let mut padding_num = (16 - (self.count % 16)) as u8;
        if padding_num == 0 {
            padding_num = 16;
        }

        let mut padding = [padding_num; 32];
        padding[0..data.len()].clone_from_slice(data);
        let padding_slice = if data.len() < 16 {
            &padding[0..16]
        } else {
            &padding[..]
        };

        self.update(padding_slice)?;
        let checksum = self.checksum;
        self.update_block(&checksum);

        self.is_done = true;

        Ok(())
    }

    fn digest(&self) -> Result<&[u8]> {
        if !self.is_done {
            return Err(Error::NotFinished);
        }

        Ok(&self.buffer[..Self::DIGEST_SIZE])
    }

    fn reset(&mut self) {
        *self = Self::new();
    }

    fn block_size(&self) -> usize {
        Self::BLOCK_SIZE
    }

    fn digest_size(&self) -> usize {
        Self::DIGEST_SIZE
    }
}

impl MD2 {
    pub const BLOCK_SIZE: usize = 16;
    pub const DIGEST_SIZE: usize = 16;

    pub const fn new() -> Self {
        Self {
            buffer: [0; 48],
            checksum: [0; 16],
            count: 0,
            is_done: false,
        }
    }

    #[inline]
    fn update_block(&mut self, block: &[u8; Self::BLOCK_SIZE]) {
        let mut t = *self.checksum.last().unwrap();
        for i in 0..16 {
            self.checksum[i] ^= S_TABLE[(block[i] ^ t) as usize];
            t = self.checksum[i];
        }

        let x = &mut self.buffer;
        for i in 0..16 {
            x[i + 16] = block[i];
            x[i + 32] = x[i] ^ block[i];
        }

        let mut t = 0u8;
        for i in 0..18 {
            for x in x.iter_mut() {
                *x ^= S_TABLE[t as usize];
                t = *x;
            }
            t = t.wrapping_add(i);
        }
    }
}

const S_TABLE: [u8; 256] = [
    0x29, 0x2E, 0x43, 0xC9, 0xA2, 0xD8, 0x7C, 0x01, 0x3D, 0x36, 0x54, 0xA1, 0xEC, 0xF0, 0x06, 0x13,
    0x62, 0xA7, 0x05, 0xF3, 0xC0, 0xC7, 0x73, 0x8C, 0x98, 0x93, 0x2B, 0xD9, 0xBC, 0x4C, 0x82, 0xCA,
    0x1E, 0x9B, 0x57, 0x3C, 0xFD, 0xD4, 0xE0, 0x16, 0x67, 0x42, 0x6F, 0x18, 0x8A, 0x17, 0xE5, 0x12,
    0xBE, 0x4E, 0xC4, 0xD6, 0xDA, 0x9E, 0xDE, 0x49, 0xA0, 0xFB, 0xF5, 0x8E, 0xBB, 0x2F, 0xEE, 0x7A,
    0xA9, 0x68, 0x79, 0x91, 0x15, 0xB2, 0x07, 0x3F, 0x94, 0xC2, 0x10, 0x89, 0x0B, 0x22, 0x5F, 0x21,
    0x80, 0x7F, 0x5D, 0x9A, 0x5A, 0x90, 0x32, 0x27, 0x35, 0x3E, 0xCC, 0xE7, 0xBF, 0xF7, 0x97, 0x03,
    0xFF, 0x19, 0x30, 0xB3, 0x48, 0xA5, 0xB5, 0xD1, 0xD7, 0x5E, 0x92, 0x2A, 0xAC, 0x56, 0xAA, 0xC6,
    0x4F, 0xB8, 0x38, 0xD2, 0x96, 0xA4, 0x7D, 0xB6, 0x76, 0xFC, 0x6B, 0xE2, 0x9C, 0x74, 0x04, 0xF1,
    0x45, 0x9D, 0x70, 0x59, 0x64, 0x71, 0x87, 0x20, 0x86, 0x5B, 0xCF, 0x65, 0xE6, 0x2D, 0xA8, 0x02,
    0x1B, 0x60, 0x25, 0xAD, 0xAE, 0xB0, 0xB9, 0xF6, 0x1C, 0x46, 0x61, 0x69, 0x34, 0x40, 0x7E, 0x0F,
    0x55, 0x47, 0xA3, 0x23, 0xDD, 0x51, 0xAF, 0x3A, 0xC3, 0x5C, 0xF9, 0xCE, 0xBA, 0xC5, 0xEA, 0x26,
    0x2C, 0x53, 0x0D, 0x6E, 0x85, 0x28, 0x84, 0x09, 0xD3, 0xDF, 0xCD, 0xF4, 0x41, 0x81, 0x4D, 0x52,
    0x6A, 0xDC, 0x37, 0xC8, 0x6C, 0xC1, 0xAB, 0xFA, 0x24, 0xE1, 0x7B, 0x08, 0x0C, 0xBD, 0xB1, 0x4A,
    0x78, 0x88, 0x95, 0x8B, 0xE3, 0x63, 0xE8, 0x6D, 0xE9, 0xCB, 0xD5, 0xFE, 0x3B, 0x00, 0x1D, 0x39,
    0xF2, 0xEF, 0xB7, 0x0E, 0x66, 0x58, 0xD0, 0xE4, 0xA6, 0x77, 0x72, 0xF8, 0xEB, 0x75, 0x4B, 0x0A,
    0x31, 0x44, 0x50, 0xB4, 0x8F, 0xED, 0x1F, 0x1A, 0xDB, 0x99, 0x8D, 0x33, 0x9F, 0x11, 0x83, 0x14,
];

#[cfg(test)]
mod tests {
    use crate::paranoid_hash::{
        tester::{HasherTestWrapper, TestData},
        Hasher,
    };

    use super::MD2;

    const TESTS: &[TestData] = &[
        TestData {
            data: "".as_bytes(),
            repeat: 1,
            result: "8350e5a3e24c153df2275c9f80692773",
        },
        TestData {
            data: "a".as_bytes(),
            repeat: 1,
            result: "32ec01ec4a6dac72c0ab96fb34c0b5d1",
        },
        TestData {
            data: "abc".as_bytes(),
            repeat: 1,
            result: "da853b0d3f88d99b30283a69e6ded6bb",
        },
        TestData {
            data: "message digest".as_bytes(),
            repeat: 1,
            result: "ab4f496bfb2a530b219ff33031fe06b0",
        },
        TestData {
            data: "abcdefghijklmnopqrstuvwxyz".as_bytes(),
            repeat: 1,
            result: "4e8ddff3650292ab5a4108c3aa47940b",
        },
        TestData {
            data: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789".as_bytes(),
            repeat: 1,
            result: "da33def2a42df13975352846c30338cd",
        },
        TestData {
            data:
                "12345678901234567890123456789012345678901234567890123456789012345678901234567890"
                    .as_bytes(),
            repeat: 1,
            result: "d5976f79d83d3a0dc9806c3c66f3efd8",
        },
    ];

    #[test]
    fn tests_from_rfc() {
        HasherTestWrapper::new(MD2::new()).run_tests(TESTS);
    }

    #[test]
    #[should_panic]
    fn panic_test1() {
        let mut hasher = MD2::new();
        hasher
            .update("Not multiple of block size".as_bytes())
            .unwrap();
    }

    #[test]
    #[should_panic]
    fn panic_test2() {
        let mut hasher = MD2::new();
        hasher
            .update_last("Not less or equal to block size".as_bytes())
            .unwrap();
    }
}