//! Nom Parsing the MoPaQ file format.
//! Sources:
//! - [The_MoPaQ_Archive_Format](https://web.archive.org/web/20120222093346/http://wiki.devklog.net/index.php?title=The_MoPaQ_Archive_Format)
//! - [MPyQ](https://github.com/arkx/mpyq/)

#![warn(missing_docs)]
use nom::bytes::complete::take;
use nom::error::dbg_dmp;
use nom::number::complete::{i32, u32, u8};
use nom::IResult;
use parser::MPQHashType;
use std::collections::HashMap;
use std::io::Read;
use thiserror::Error;

pub mod builder;
pub mod parser;
pub use builder::MPQBuilder;
use compress::zlib;
pub use parser::MPQBlockTableEntry;
pub use parser::MPQFileHeader;
pub use parser::MPQHashTableEntry;
pub use parser::MPQUserData;
use parser::LITTLE_ENDIAN;

// Unused flags:
// pub const MPQ_FILE_IMPLODE: u32 = 0x00000100;
// pub const MPQ_FILE_FIX_KEY: u32 = 0x00020000;
// pub const MPQ_FILE_DELETE_MARKER: u32 = 0x02000000;

/// The sector is compressed
pub const MPQ_FILE_COMPRESS: u32 = 0x00000200;
/// The sector is encrypted.
pub const MPQ_FILE_ENCRYPTED: u32 = 0x00010000;
/// The sector contains a single file/unit.
pub const MPQ_FILE_SINGLE_UNIT: u32 = 0x01000000;
/// The sector has cyclic redundancy check.
pub const MPQ_FILE_SECTOR_CRC: u32 = 0x04000000;
/// The sector exists (as opposed to marked as deleted)
pub const MPQ_FILE_EXISTS: u32 = 0x80000000;

/// The sector has no compression
pub const COMPRESSION_PLAINTEXT: u8 = 0;
/// The sector is compressed using [`zlib`]
pub const COMPRESSION_ZLIB: u8 = 2;
/// The sector is compressed using [`bzip2`]
pub const COMPRESSION_BZ2: u8 = 16;

/// A basic error enum, tho mustly unused.
#[derive(Error, Debug)]
pub enum MPQParserError {
    /// A section magic was Unexpected
    #[error("Unexpected Section")]
    UnexpectedSection,
}

/// The main MPQ object that contains the parsed entries
#[derive(Debug, Default)]
pub struct MPQ {
    /// The Archive Header containing format version, the offsets for the
    /// block table and hash table.
    pub archive_header: MPQFileHeader,
    /// The Archive may contain [`MPQUserData`], which is at the start of the file.
    pub user_data: Option<MPQUserData>,
    /// The hash table entries, after decryption and parsing
    pub hash_table_entries: Vec<MPQHashTableEntry>,
    /// The block table entries, after decryption and parsing
    pub block_table_entries: Vec<MPQBlockTableEntry>,
    /// The internal MPQ encryption table.
    pub encryption_table: HashMap<u32, u32>,
}

impl MPQ {
    /// Prepares the encryption table, this hashmap is used for block-sized
    /// decryption operations.
    fn prepare_encryption_table() -> HashMap<u32, u32> {
        let mut seed: u32 = 0x00100001;
        let mut res = HashMap::new();
        for i in (0..256).map(|x| x as u32) {
            let mut idx = i;
            for _ in 0..5 {
                seed = (seed * 125 + 3) % 0x2AAAAB;
                let temp1 = (seed & 0xFFFF) << 0x10;

                seed = (seed * 125 + 3) % 0x2AAAAB;
                let temp2 = seed & 0xFFFF;

                res.insert(idx, temp1 | temp2);

                idx += 0x100;
            }
        }
        res
    }

    /// Hash a string using MPQ's hash function
    ///
    /// `_hash` on MPyQ
    /// This function doesn't use self as the Builder also needs to access the same functionality.
    pub fn mpq_string_hash(
        encryption_table: &HashMap<u32, u32>,
        location: &str,
        hash_type: MPQHashType,
    ) -> u32 {
        let mut seed1: u64 = 0x7FED7FEDu64;
        let mut seed2: u64 = 0xEEEEEEEEu64;
        for ch in location.to_uppercase().chars() {
            let ch_ord: u32 = ch.into();
            let hash_type_idx: u32 = hash_type.try_into().unwrap();
            let value = match encryption_table.get(&((hash_type_idx << 8) + ch_ord)) {
                Some(val) => val,
                None => panic!(
                    "Couldn't find index in map for: {}",
                    (hash_type_idx << 8) + ch_ord
                ),
            };
            seed1 = (*value as u64 ^ (seed1 + seed2)) & 0xFFFFFFFFu64;
            seed2 = ch_ord as u64 + seed1 + seed2 + (seed2 << 5) + 3 & 0xFFFFFFFFu64;
        }
        tracing::trace!("Returning {} for location: {}", (seed1 as u32), location);
        seed1 as u32
    }

    /// Get the hash table entry corresponding to a given filename.
    ///
    /// A filename is hashed with both [`MPQHashType::HashA`] and [`MPQHashType::HashB`]
    /// to uniquely identify the filename in the archive
    pub fn get_hash_table_entry(&self, filename: &str) -> Option<MPQHashTableEntry> {
        let hash_a = Self::mpq_string_hash(&self.encryption_table, filename, MPQHashType::HashA);
        let hash_b = Self::mpq_string_hash(&self.encryption_table, filename, MPQHashType::HashB);
        for entry in &self.hash_table_entries {
            if entry.hash_a == hash_a && entry.hash_b == hash_b {
                tracing::debug!("Found filename: {}, as entry: {:?}", filename, entry);
                return Some(entry.clone());
            }
        }
        tracing::warn!("Unable to find hash table entry for {}", filename);
        None
    }

    /// Read the compression type and decompress file data accordingly.
    pub fn decompress(input: &[u8]) -> IResult<&[u8], Vec<u8>> {
        let mut data = vec![];
        let (tail, compression_type) = dbg_dmp(u8, "compression_type")(input)?;
        match compression_type {
            COMPRESSION_PLAINTEXT => {
                tracing::debug!("Plaintext (no compression)");
                data = tail[..].to_vec()
            }
            COMPRESSION_ZLIB => {
                tracing::debug!("Attempting ZLIB compression",);
                let mut d = zlib::Decoder::new(std::io::BufReader::new(tail));

                let _ = d.read_to_end(&mut data).unwrap();
            }
            COMPRESSION_BZ2 => {
                tracing::debug!("Attempting BZ2 compression",);
                let mut decompressor = bzip2::read::BzDecoder::new(tail);
                let _ = decompressor.read_to_end(&mut data).unwrap();
            }
            _ => panic!("Unsupported compression type: {}", compression_type),
        };

        Ok((tail, data))
    }

    /// Reads an embedded file inside the MPQ archive.
    #[tracing::instrument(level = "debug", skip(self, orig_input))]
    pub fn read_mpq_file_sector<'a>(
        &'a self,
        filename: &str,
        force_decompress: bool,
        orig_input: &'a [u8],
    ) -> IResult<&'a [u8], Vec<u8>> {
        let mut res = vec![];
        let hash_entry = match self.get_hash_table_entry(filename) {
            Some(val) => val,
            None => return Ok((orig_input, res)),
        };
        let block_entry = self.block_table_entries[hash_entry.block_table_index as usize].clone();
        tracing::debug!("block_entry {:?}", block_entry);
        // Read the block
        if block_entry.flags & MPQ_FILE_EXISTS == 0 {
            tracing::debug!("file is marked as deleted. Returning empty content");
            return Ok((orig_input, res));
        }
        if block_entry.archived_size == 0 {
            tracing::debug!("File is zero size. Returning empty content");
            return Ok((orig_input, res));
        }
        let offset = block_entry.offset as usize + self.archive_header.offset;
        let (tail, file_data) =
            dbg_dmp(take(block_entry.archived_size), "file_data")(&orig_input[offset..])?;

        tracing::debug!("Block table data: {}", parser::peek_hex(&file_data));
        if block_entry.flags & MPQ_FILE_ENCRYPTED != 0 {
            panic!("Encryption is not supported");
        }
        if block_entry.flags & MPQ_FILE_SINGLE_UNIT != 0 {
            tracing::debug!("File sector contains a single unit",);
            // Single unit files only need to be decompressed, but
            // compression only happens when at least one byte is gained.
            if block_entry.flags & MPQ_FILE_COMPRESS != 0 && force_decompress
                || block_entry.size > block_entry.archived_size
            {
                tracing::debug!("File needs to be decompressed",);
                let (_tail, decompressed_data) = Self::decompress(file_data)?;
                return Ok((tail, decompressed_data));
            } else {
                // File consists of many sectors. They all need to be
                // decompressed separately and united.
                let sector_size = 512 << self.archive_header.sector_size_shift;
                let mut sectors =
                    (block_entry.size as f32 / sector_size as f32).floor() as usize + 1usize;
                let crc = if block_entry.flags & MPQ_FILE_SECTOR_CRC != 0 {
                    sectors += 1;
                    true
                } else {
                    false
                };
                let mut positions: Vec<usize> = vec![];
                let mut position_file_index = &file_data[..4 * (sectors + 1)];
                for _ in 0..sectors + 1 {
                    // Note: MPyQ format for this is a list of '<I'
                    // as long as there are sectors + 1
                    // `'<%dI' % (sectors + 1)` (Not to confuse the `d` with
                    // double, it's for the `%` format operator.
                    let (new_pos_idx, position) =
                        dbg_dmp(u32(LITTLE_ENDIAN), "positions")(position_file_index)?;
                    positions.push(position as usize);
                    position_file_index = new_pos_idx;
                }
                let mut sector_bytes_left = block_entry.size as usize;
                let mut total_sectors = positions.len() - 1;
                if crc {
                    total_sectors -= 1;
                }

                for i in 0..total_sectors {
                    let mut sector = file_data[positions[i]..positions[i + 1]].to_vec();
                    if block_entry.flags & MPQ_FILE_COMPRESS != 0 && force_decompress
                        || sector_bytes_left as usize > sector.len()
                    {
                        let (_tail, mut decompressed_sector) =
                            Self::decompress(&file_data[positions[i]..positions[i + 1]])?;
                        res.append(&mut decompressed_sector);
                    } else {
                        res.append(&mut sector);
                    }

                    sector_bytes_left -= sector.len();
                }
                return Ok((tail, res));
            }
        }
        Ok((tail, res))
    }

    /// Decrypt hash or block table or a sector.
    ///
    /// `_decrypt` on MPyQ
    pub fn mpq_data_decrypt<'a>(
        encryption_table: &'a HashMap<u32, u32>,
        data: &'a [u8],
        key: u32,
    ) -> IResult<&'a [u8], Vec<u8>> {
        let mut seed1 = key as i64;
        let mut seed2 = 0xEEEEEEEEi64;
        let mut res = vec![];

        for i in 0..(data.len() as f32 / 4f32).floor() as usize {
            let encryption_table_value =
                match encryption_table.get(&(0x400 + (seed1 as u32 & 0xFF))) {
                    Some(val) => *val as i64,
                    None => {
                        tracing::error!(
                            "Encryption table value not found for: {}",
                            (0x400 + (seed1 & 0xFF) as i32)
                        );
                        continue;
                    }
                };
            seed2 += encryption_table_value;
            seed2 &= 0xFFFFFFFFi64;
            let (_tail, value) =
                dbg_dmp(i32(LITTLE_ENDIAN), "encrypted_value")(&data[i * 4..i * 4 + 4])?;
            let mut value = value as i64;
            value = (value as i64 ^ (seed1 + seed2)) & 0xFFFFFFFFi64;

            seed1 = ((!seed1 << 0x15) + 0x11111111) | (seed1 >> 0x0B);
            seed1 &= 0xFFFFFFFF;
            seed2 = value + seed2 + (seed2 << 5) + 3 & 0xFFFFFFFFi64;
            let mut le_packed_value = (value as i32).to_le_bytes().to_vec();

            // pack in little endian
            res.append(&mut le_packed_value);
        }

        Ok((data, res))
    }

    /// Returns the list of filenames and their respective size as contained in the MPQ archive.
    pub fn get_files(&self, orig_input: &[u8]) -> Vec<(String, usize)> {
        let mut res: Vec<(String, usize)> = vec![];
        let files: Vec<String> = match self.read_mpq_file_sector("(listfile)", false, orig_input) {
            Ok((_tail, file_buffer)) => {
                tracing::debug!(
                    "Successfully read '(listfile)' sector: {:?}",
                    parser::peek_hex(&file_buffer)
                );
                match std::str::from_utf8(&file_buffer) {
                    Ok(val) => val.lines().map(|x| x.to_string()).collect(),
                    Err(err) => {
                        panic!("Invalid UTF-8 sequence: {}", err);
                    }
                }
            }
            Err(err) => {
                panic!("Unable to read '(listfile)' sector: {:?}", err);
            }
        };
        for filename in files {
            let hash_entry = match self.get_hash_table_entry(&filename) {
                Some(val) => val,
                None => {
                    tracing::warn!("Unable to find hash entry for filename: {:?}", filename);
                    continue;
                }
            };
            let block_entry = &self.block_table_entries[hash_entry.block_table_index as usize];
            tracing::debug!("{} {1:>8} bytes", filename, block_entry.size as usize);
            res.push((filename, block_entry.size as usize));
        }
        res
    }
}