use crate::driver::FileDriver;
use crate::zip::{ZipError, ZipFileInfo, ZipResult};
use std::io::{
    Error as IoError, ErrorKind as IoErrorKind, Read, Result as IoResult, Seek, SeekFrom, Write,
};

pub struct ZipFile<'d, Io> {
    io: &'d mut Io,
    info: &'d ZipFileInfo,

    bounds: (u64, u64),
    cursor: u64,
}

impl<'d, Io> FileDriver for ZipFile<'d, Io> {
    type Io = Io;
    type FileInfo = ZipFileInfo;

    fn info(&self) -> &Self::FileInfo {
        self.info
    }
}

impl<'d, Io: Read + Seek> ZipFile<'d, Io> {
    pub fn new(io: &'d mut Io, info: &'d ZipFileInfo) -> ZipResult<Self> {
        io.seek(SeekFrom::Start(info.header_pointer))?;
        let buf = {
            let mut buf = [0; 30];
            io.read(&mut buf)?;
            buf
        };
        if u32::from_le_bytes(buf[..4].try_into().unwrap()) != 0x04034b50 {
            return Err(ZipError::InvalidFileHeaderSignature.into());
        }
        let data_pointer = info.header_pointer
            + 30
            + u16::from_le_bytes(buf[26..28].try_into().unwrap()) as u64
            + u16::from_le_bytes(buf[28..30].try_into().unwrap()) as u64;
        io.seek(SeekFrom::Start(data_pointer))?;

        Ok(Self {
            io,
            info,

            bounds: (data_pointer, data_pointer + info.compressed_size),
            cursor: data_pointer,
        })
    }
}

impl<'d, Io: Read> Read for ZipFile<'d, Io> {
    fn read(&mut self, buf: &mut [u8]) -> IoResult<usize> {
        let upper = buf.len().min((self.bounds.1 - self.cursor) as usize);
        self.cursor += upper as u64;
        self.io.read(&mut buf[..upper])
    }
}

impl<'d, Io: Write> Write for ZipFile<'d, Io> {
    fn write(&mut self, buf: &[u8]) -> IoResult<usize> {
        todo!()
    }

    fn flush(&mut self) -> IoResult<()> {
        todo!()
    }
}

impl<'d, Io: Seek> Seek for ZipFile<'d, Io> {
    fn seek(&mut self, pos: SeekFrom) -> IoResult<u64> {
        self.cursor = match pos {
            SeekFrom::Start(offset) => self.bounds.0 + offset,
            SeekFrom::End(offset) => {
                let cursor = self.bounds.1.saturating_add_signed(offset);
                if cursor < self.bounds.0 {
                    return Err(IoError::new(
                        IoErrorKind::InvalidInput,
                        ZipError::NegativeFileOffset,
                    ));
                }
                cursor
            }
            SeekFrom::Current(offset) => {
                let cursor = self.cursor.saturating_add_signed(offset);
                if cursor < self.bounds.0 {
                    return Err(IoError::new(
                        IoErrorKind::InvalidInput,
                        ZipError::NegativeFileOffset,
                    ));
                }
                cursor
            }
        }
        .min(self.bounds.1);

        Ok(self.io.seek(SeekFrom::Start(self.cursor))? - self.bounds.0)
    }
}