use byteorder::{BigEndian, ByteOrder};
use crc::crc32;
use std::collections::HashMap;
use std::convert::TryFrom;
use std::io::Read;
use std::io::{Error, ErrorKind};
use xz2::read::{XzDecoder, XzEncoder};

pub const LZMA: &str = "lzma";

pub const BDF_HDR: &[u8; 11] = b"BDF\x01RAINBOW";
pub const NULL_BYTES: &[u8; 4] = &[0u8; 4];
pub const META_CHUNK_NAME: &str = "META";
pub const HTBL_CHUNK_NAME: &str = "HTBL";
pub const DTBL_CHUNK_NAME: &str = "DTBL";


#[derive(Debug, Clone)]
pub struct GenericChunk {
    pub length: u32,
    pub(crate) name: String,
    pub data: Vec<u8>,
    pub crc: u32,
}


#[derive(Debug, Clone)]
pub struct MetaChunk {
    pub chunk_count: u32,
    pub entries_per_chunk: u32,
    pub entry_count: u64,
    pub compression_method: Option<String>,
}


#[derive(Debug, Clone)]
pub struct HashLookupTable {
    pub entries: HashMap<u32, HashEntry>,
}


#[derive(Debug, Clone)]
pub struct HashEntry {
    pub(crate) id: u32,
    output_length: u32,
    name: String,
}


#[derive(Debug, Clone)]
pub struct DataEntry {
    pub plain: String,
    hashes: HashMap<String, Vec<u8>>,
}

impl GenericChunk {
    /// Serializes the chunk to a vector of bytes
    pub fn serialize(&mut self) -> Vec<u8> {
        let mut serialized: Vec<u8> = Vec::new();
        let mut length_raw = [0u8; 4];
        BigEndian::write_u32(&mut length_raw, self.length);
        serialized.append(&mut length_raw.to_vec());
        let name_raw = self.name.as_bytes();
        serialized.append(&mut name_raw.to_vec());
        serialized.append(&mut self.data);
        let mut crc_raw = [0u8; 4];
        BigEndian::write_u32(&mut crc_raw, self.crc);
        serialized.append(&mut crc_raw.to_vec());

        serialized
    }

    /// Returns the data entries of the chunk
    pub fn data_entries(
        &mut self,
        lookup_table: &HashLookupTable,
    ) -> Result<Vec<DataEntry>, Error> {
        if self.name == HTBL_CHUNK_NAME.to_string() {
            return Err(Error::new(ErrorKind::Other, "this is not a data chunk"));
        }
        let mut entries: Vec<DataEntry> = Vec::new();
        let mut position = 0;

        while self.data.len() > (position + 8) {
            let entry_length_raw = &self.data[position..position + 4];
            position += 4;
            let entry_length = BigEndian::read_u32(entry_length_raw);
            let entry_end = position + entry_length as usize;
            let pw_length_raw = &self.data[position..position + 4];
            position += 4;
            let pw_length = BigEndian::read_u32(pw_length_raw);
            let pw_plain_raw = &self.data[position..position + pw_length as usize];
            position += pw_length as usize;

            let pw_plain = String::from_utf8(pw_plain_raw.to_vec())
                .map_err(|err| {
                    format!(
                        "failed to parse plain password string ({}-{}): {:?}",
                        position,
                        position + pw_length as usize,
                        err
                    )
                })
                .unwrap();
            let mut hash_values: HashMap<String, Vec<u8>> = HashMap::new();
            while position < entry_end {
                let entry_id_raw = &self.data[position..position + 4];
                position += 4;
                let entry_id = BigEndian::read_u32(entry_id_raw);

                if let Some(hash_entry) = lookup_table.entries.get(&entry_id) {
                    let hash = &self.data[position..position + hash_entry.output_length as usize];
                    position += hash_entry.output_length as usize;
                    hash_values.insert(hash_entry.name.clone(), hash.to_vec());
                }
            }
            entries.push(DataEntry {
                plain: pw_plain,
                hashes: hash_values,
            })
        }

        Ok(entries)
    }

    /// Constructs the chunk from a Vec of Data entries and a hash lookup table
    pub fn from_data_entries(
        entries: &Vec<DataEntry>,
        lookup_table: &HashLookupTable,
    ) -> GenericChunk {
        let mut serialized_data: Vec<u8> = Vec::new();

        entries.iter().for_each(|entry| {
            serialized_data.append(&mut entry.serialize(&lookup_table));
        });
        let crc_sum = crc32::checksum_ieee(serialized_data.as_slice());

        GenericChunk {
            length: serialized_data.len() as u32,
            name: DTBL_CHUNK_NAME.to_string(),
            data: serialized_data,
            crc: crc_sum,
        }
    }

    /// Compresses the data of the chunk using lzma with a level of 6
    pub fn compress(&mut self, level: u32) -> Result<(), Error> {
        let data = self.data.as_slice();
        let mut compressor = XzEncoder::new(data, level);
        let mut compressed: Vec<u8> = Vec::new();
        compressor.read_to_end(&mut compressed)?;
        self.length = compressed.len() as u32;
        self.data = compressed;

        Ok(())
    }

    /// Decompresses the data of the chunk with lzma
    pub fn decompress(&mut self) -> Result<(), Error> {
        let data = self.data.as_slice();
        let mut decompressor = XzDecoder::new(data);
        let mut decompressed: Vec<u8> = Vec::new();
        decompressor.read_to_end(&mut decompressed)?;
        let crc = crc32::checksum_ieee(decompressed.as_slice());

        if crc != self.crc {
            return Err(Error::new(
                ErrorKind::InvalidData,
                "the crc doesn't match the decrypted data",
            ));
        }
        self.length = decompressed.len() as u32;
        self.data = decompressed;

        Ok(())
    }
}

impl From<&MetaChunk> for GenericChunk {
    fn from(chunk: &MetaChunk) -> GenericChunk {
        let serialized_data = chunk.serialize();
        let crc_sum = crc32::checksum_ieee(serialized_data.as_slice());

        GenericChunk {
            length: serialized_data.len() as u32,
            name: META_CHUNK_NAME.to_string(),
            data: serialized_data,
            crc: crc_sum,
        }
    }
}

impl From<&HashLookupTable> for GenericChunk {
    fn from(chunk: &HashLookupTable) -> GenericChunk {
        let serialized_data = chunk.serialize();
        let crc_sum = crc32::checksum_ieee(serialized_data.as_slice());

        GenericChunk {
            length: serialized_data.len() as u32,
            name: HTBL_CHUNK_NAME.to_string(),
            data: serialized_data,
            crc: crc_sum,
        }
    }
}

impl MetaChunk {
    /// Creates a new meta chunk
    pub fn new(entry_count: u64, entries_per_chunk: u32, compress: bool) -> Self {
        let compression_method = if compress {
            Some(LZMA.to_string())
        } else {
            None
        };
        let chunk_count = (entry_count as f64 / entries_per_chunk as f64).ceil() as u32;

        Self {
            chunk_count,
            entry_count,
            entries_per_chunk,
            compression_method,
        }
    }

    /// Serializes the chunk into bytes
    pub fn serialize(&self) -> Vec<u8> {
        let mut serialized_data: Vec<u8> = Vec::new();
        let mut chunk_count_raw = [0u8; 4];
        BigEndian::write_u32(&mut chunk_count_raw, self.chunk_count);
        serialized_data.append(&mut chunk_count_raw.to_vec());
        let mut entries_pc_raw = [0u8; 4];
        BigEndian::write_u32(&mut entries_pc_raw, self.entries_per_chunk);
        serialized_data.append(&mut entries_pc_raw.to_vec());
        let mut total_entries_raw = [0u8; 8];
        BigEndian::write_u64(&mut total_entries_raw, self.entry_count);
        serialized_data.append(&mut total_entries_raw.to_vec());
        let mut compression_method = self.compression_method.clone();

        if let Some(method) = &mut compression_method {
            serialized_data.append(&mut method.clone().into_bytes());
        } else {
            serialized_data.append(&mut vec![0, 0, 0, 0]);
        }

        serialized_data
    }
}

impl TryFrom<GenericChunk> for MetaChunk {
    type Error = Error;

    fn try_from(chunk: GenericChunk) -> Result<MetaChunk, Error> {
        if &chunk.name != META_CHUNK_NAME {
            return Err(Error::new(
                ErrorKind::InvalidData,
                "chunk name doesn't match",
            ));
        }
        if chunk.data.len() < 20 {
            return Err(Error::new(ErrorKind::InvalidData, "invalid chunk data"));
        }
        let chunk_count_raw = &chunk.data[0..4];
        let entries_per_chunk = &chunk.data[4..8];
        let total_number_of_entries = &chunk.data[8..16];
        let compression_method_raw = chunk.data[16..20].to_vec();
        let chunk_count = BigEndian::read_u32(chunk_count_raw);
        let entries_per_chunk = BigEndian::read_u32(entries_per_chunk);
        let entry_count = BigEndian::read_u64(total_number_of_entries);
        let compression_method = if &compression_method_raw != NULL_BYTES {
            Some(
                String::from_utf8(compression_method_raw)
                    .expect("Failed to parse compression method name!"),
            )
        } else {
            None
        };

        Ok(MetaChunk {
            chunk_count,
            entries_per_chunk,
            entry_count,
            compression_method,
        })
    }
}

impl HashLookupTable {

    /// Creates a new hash lookup table
    pub fn new(entries: HashMap<u32, HashEntry>) -> Self {
        Self { entries }
    }

    /// Returns an entry by the name of the hash function
    pub fn get_entry(&self, name: &String) -> Option<(&u32, &HashEntry)> {
        self.entries.iter().find(|(_, entry)| entry.name == *name)
    }

    /// Serializes the lookup table into a vector of bytes
    pub fn serialize(&self) -> Vec<u8> {
        let mut serialized_full: Vec<u8> = Vec::new();
        for (_, entry) in &self.entries {
            serialized_full.append(entry.serialize().as_mut())
        }

        serialized_full
    }
}

impl TryFrom<GenericChunk> for HashLookupTable {
    type Error = Error;

    fn try_from(chunk: GenericChunk) -> Result<HashLookupTable, Error> {
        if &chunk.name != HTBL_CHUNK_NAME {
            return Err(Error::new(
                ErrorKind::InvalidData,
                "chunk name doesn't match",
            ));
        }
        let mut hash_entries: HashMap<u32, HashEntry> = HashMap::new();
        let mut position = 0;
        while chunk.data.len() > (position + 12) {
            let id_raw = &chunk.data[position..position + 4];
            position += 4;
            let output_length_raw = &chunk.data[position..position + 4];
            position += 4;
            let name_length_raw = &chunk.data[position..position + 4];
            position += 4;
            let id = BigEndian::read_u32(id_raw);
            let output_length = BigEndian::read_u32(output_length_raw);
            let name_length = BigEndian::read_u32(name_length_raw);
            let name_raw = &chunk.data[position..position + name_length as usize];
            let name =
                String::from_utf8(name_raw.to_vec()).expect("Failed to parse hash function name!");
            hash_entries.insert(
                id,
                HashEntry {
                    id,
                    output_length,
                    name,
                },
            );
        }
        Ok(HashLookupTable {
            entries: hash_entries,
        })
    }
}

impl HashEntry {

    /// Creates a new hash entry
    pub fn new(name: String, output_length: u32) -> Self {
        Self {
            id: 0,
            name,
            output_length,
        }
    }

    /// Serializes the entry to a vector of bytes
    pub fn serialize(&self) -> Vec<u8> {
        let mut serialized: Vec<u8> = Vec::new();
        let mut id_raw = [0u8; 4];
        BigEndian::write_u32(&mut id_raw, self.id);
        serialized.append(&mut id_raw.to_vec());
        let mut output_length_raw = [0u8; 4];
        BigEndian::write_u32(&mut output_length_raw, self.output_length);
        serialized.append(&mut output_length_raw.to_vec());
        let mut name_raw = self.name.clone().into_bytes();
        let mut name_length_raw = [0u8; 4];
        BigEndian::write_u32(&mut name_length_raw, name_raw.len() as u32);
        serialized.append(&mut name_length_raw.to_vec());
        serialized.append(&mut name_raw);

        serialized
    }
}

impl DataEntry {
    pub fn new(plain: String) -> Self {
        Self {
            hashes: HashMap::new(),
            plain,
        }
    }

    /// Adds a hash to the hash values
    pub fn add_hash_value(&mut self, name: String, value: Vec<u8>) {
        self.hashes.insert(name, value);
    }

    /// Returns the hash value for a given name of a hash function
    pub fn get_hash_value(&self, name: String) -> Option<&Vec<u8>> {
        self.hashes.get(&name)
    }

    /// Serializes the entry to a vector of bytes
    pub fn serialize(&self, lookup_table: &HashLookupTable) -> Vec<u8> {
        let mut pw_plain_raw = self.plain.clone().into_bytes();
        let mut pw_length_raw = [0u8; 4];
        BigEndian::write_u32(&mut pw_length_raw, pw_plain_raw.len() as u32);
        let mut hash_data: Vec<u8> = Vec::new();
        for (name, value) in &self.hashes {
            if let Some((id, _)) = lookup_table.get_entry(&name) {
                let mut id_raw = [0u8; 4];
                BigEndian::write_u32(&mut id_raw, *id);
                hash_data.append(&mut id_raw.to_vec());
                hash_data.append(&mut value.clone())
            }
        }

        let mut length_total_raw = [0u8; 4];
        BigEndian::write_u32(
            &mut length_total_raw,
            4 + pw_plain_raw.len() as u32 + hash_data.len() as u32,
        );
        let mut serialized_data: Vec<u8> = Vec::new();
        serialized_data.append(&mut length_total_raw.to_vec());
        serialized_data.append(&mut pw_length_raw.to_vec());
        serialized_data.append(&mut pw_plain_raw);
        serialized_data.append(&mut hash_data);

        serialized_data
    }
}