use crate::compression::no_header_decompress;
use crate::crc::Jamcrc;
use crate::dat::{BlockHeader, CompressionMode};
use binrw::BinRead;
use std::io::{Read, Seek, SeekFrom};

const CRC: Jamcrc = Jamcrc::new();

/// Calculates a hash for `index` files from a game path.
pub fn calculate_hash(path: &str) -> u64 {
    let lowercase = path.to_lowercase();

    let pos = lowercase.rfind('/').unwrap();

    let (directory, filename) = lowercase.split_at(pos);

    let directory_crc = CRC.checksum(directory.as_bytes());
    let filename_crc = CRC.checksum(filename[1..filename.len()].as_bytes());

    (directory_crc as u64) << 32 | (filename_crc as u64)
}

pub fn read_data_block<T: Read + Seek>(mut buf: T, starting_position: u64) -> Option<Vec<u8>> {
    buf.seek(SeekFrom::Start(starting_position)).ok()?;

    let block_header = BlockHeader::read(&mut buf).unwrap();

    match block_header.compression {
        CompressionMode::Compressed {
            compressed_length,
            decompressed_length,
        } => {
            let mut compressed_data: Vec<u8> = vec![0; compressed_length as usize];
            buf.read_exact(&mut compressed_data).ok()?;

            let mut decompressed_data: Vec<u8> = vec![0; decompressed_length as usize];
            if !no_header_decompress(&mut compressed_data, &mut decompressed_data) {
                return None;
            }

            Some(decompressed_data)
        }
        CompressionMode::Uncompressed { file_size } => {
            let mut local_data: Vec<u8> = vec![0; file_size as usize];
            buf.read_exact(&mut local_data).ok()?;

            Some(local_data)
        }
    }
}

/// A fixed version of read_data_block accounting for differing compressed block sizes in ZiPatch files.
pub fn read_data_block_patch<T: Read + Seek>(mut buf: T) -> Option<Vec<u8>> {
    let block_header = BlockHeader::read(&mut buf).unwrap();

    match block_header.compression {
        CompressionMode::Compressed {
            compressed_length,
            decompressed_length,
        } => {
            let compressed_length: usize =
                ((compressed_length as usize + 143) & 0xFFFFFF80) - (block_header.size as usize);

            let mut compressed_data: Vec<u8> = vec![0; compressed_length as usize];
            buf.read_exact(&mut compressed_data).ok()?;

            let mut decompressed_data: Vec<u8> = vec![0; decompressed_length as usize];
            if !no_header_decompress(&mut compressed_data, &mut decompressed_data) {
                return None;
            }

            Some(decompressed_data)
        }
        CompressionMode::Uncompressed { file_size } => {
            let new_file_size: usize = (file_size as usize + 143) & 0xFFFFFF80;

            let mut local_data: Vec<u8> = vec![0; file_size as usize];
            buf.read_exact(&mut local_data).ok()?;

            buf.seek(SeekFrom::Current(
                (new_file_size as usize - block_header.size as usize - file_size as usize) as i64,
            ))
            .ok()?;

            Some(local_data)
        }
    }
}