/*
MIT License

Copyright (c) 2021 Philipp Schuster

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/
//! Module for [`TarArchive`].

use crate::header::PosixHeader;
use crate::{TypeFlag, BLOCKSIZE};
use arrayvec::ArrayString;
use core::fmt::{Debug, Formatter};
use core::ptr;
use core::str::FromStr;

/// Describes an entry in a archive.
/// Currently only supports files but no directories.
pub struct ArchiveEntry<'a> {
    filename: ArrayString<100>,
    data: &'a [u8],
    size: usize,
}

#[allow(unused)]
impl<'a> ArchiveEntry<'a> {
    pub fn new(filename: ArrayString<100>, data: &'a [u8]) -> Self {
        ArchiveEntry {
            filename,
            data,
            size: data.len(),
        }
    }

    /// Filename of the entry. Max 99 characters.
    pub fn filename(&self) -> ArrayString<100> {
        self.filename
    }

    /// Data of the file.
    pub fn data(&self) -> &'a [u8] {
        self.data
    }

    /// Filesize in bytes.
    pub fn size(&self) -> usize {
        self.size
    }
}

impl<'a> Debug for ArchiveEntry<'a> {
    fn fmt(&self, f: &mut Formatter<'_>) -> core::fmt::Result {
        f.debug_struct("ArchiveEntry")
            .field("filename", &self.filename().as_str())
            .field("size", &self.size())
            .field("data", &"<bytes>")
            .finish()
    }
}

/// Wrapper type around the bytes, which represents an archive.
#[derive(Debug)]
pub struct TarArchive<'a> {
    data: &'a [u8],
}

#[allow(unused)]
impl<'a> TarArchive<'a> {
    /// Interprets the provided byte array as Tar archive.
    pub fn new(data: &'a [u8]) -> Self {
        assert_eq!(
            data.len() % BLOCKSIZE,
            0,
            "data must be a multiple of BLOCKSIZE={}",
            BLOCKSIZE
        );
        Self { data }
    }

    /// Iterates over all entries of the TAR Archive.
    /// Returns items of type [`ArchiveEntry`].
    pub fn entries(&self) -> ArchiveIterator {
        ArchiveIterator::new(self)
    }
}

/// Iterator over the files. Each iteration step starts
/// at the next Tar header entry.
#[derive(Debug)]
pub struct ArchiveIterator<'a> {
    archive: &'a TarArchive<'a>,
    block_index: usize,
}

impl<'a> ArchiveIterator<'a> {
    pub fn new(archive: &'a TarArchive<'a>) -> Self {
        Self {
            archive,
            block_index: 0,
        }
    }

    /// Returns a pointer to the next Header.
    fn next_hdr(&self, block_index: usize) -> *const PosixHeader {
        let hdr_ptr = &self.archive.data[block_index * BLOCKSIZE];
        let hdr_ptr = hdr_ptr as *const u8;
        hdr_ptr as *const PosixHeader
    }
}

impl<'a> Iterator for ArchiveIterator<'a> {
    type Item = ArchiveEntry<'a>;

    fn next(&mut self) -> Option<Self::Item> {
        if self.block_index * BLOCKSIZE >= self.archive.data.len() {
            log::warn!("Reached end of Tar archive data without finding zero/end blocks!");
            return None;
        }

        let hdr = self.next_hdr(self.block_index);
        let hdr = unsafe { ptr::read(hdr) };

        // check if we found end of archive
        if hdr.is_zero_block() {
            let next_hdr = unsafe { ptr::read(self.next_hdr(self.block_index + 1)) };
            if next_hdr.is_zero_block() {
                // gracefully terminated Archive
                log::debug!("End of Tar archive with two zero blocks!");
            } else {
                log::warn!("Zero block found at end of Tar archive, but only one instead of two!");
            }
            // end of archive
            return None;
        }

        if hdr.typeflag != TypeFlag::AREGTYPE && hdr.typeflag != TypeFlag::REGTYPE {
            log::warn!(
                "Found entry of type={:?}, but only files are supported",
                hdr.typeflag
            );
            return None;
        }

        // fetch data of file from next block(s)
        let block_count = hdr.payload_block_count();
        let i_begin = self.block_index * BLOCKSIZE;
        let i_end = i_begin + block_count * BLOCKSIZE;
        debug_assert!(i_end <= self.archive.data.len(), "index ouf of range!");
        // +1: hdr itself + data blocks
        self.block_index += block_count + 1;

        let file_block_bytes = &self.archive.data[i_begin..i_end];
        let file_bytes = &file_block_bytes[0..hdr.size.val()];

        Some(ArchiveEntry::new(
            ArrayString::from_str(hdr.name.as_string().as_str()).unwrap(),
            file_bytes,
        ))
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::vec::Vec;

    #[test]
    fn test_archive_list() {
        let archive = TarArchive::new(include_bytes!("../tests/gnu_tar_default.tar"));
        let entries = archive.entries().collect::<Vec<_>>();
        println!("{:#?}", entries);
    }

    #[test]
    fn test_archive_entries() {
        let archive = TarArchive::new(include_bytes!("../tests/gnu_tar_default.tar"));
        let entries = archive.entries().collect::<Vec<_>>();
        assert_archive_content(&entries);

        let archive = TarArchive::new(include_bytes!("../tests/gnu_tar_gnu.tar"));
        let entries = archive.entries().collect::<Vec<_>>();
        assert_archive_content(&entries);

        let archive = TarArchive::new(include_bytes!("../tests/gnu_tar_oldgnu.tar"));
        let entries = archive.entries().collect::<Vec<_>>();
        assert_archive_content(&entries);

        // UNSUPPORTED. Uses extensions.
        /*let archive = TarArchive::new(include_bytes!("../tests/gnu_tar_pax.tar"));
        let entries = archive.entries().collect::<Vec<_>>();
        assert_archive_content(&entries);*/

        // UNSUPPORTED. Uses extensions.
        /*let archive = TarArchive::new(include_bytes!("../tests/gnu_tar_posix.tar"));
        let entries = archive.entries().collect::<Vec<_>>();
        assert_archive_content(&entries);*/

        let archive = TarArchive::new(include_bytes!("../tests/gnu_tar_ustar.tar"));
        let entries = archive.entries().collect::<Vec<_>>();
        assert_archive_content(&entries);

        let archive = TarArchive::new(include_bytes!("../tests/gnu_tar_v7.tar"));
        let entries = archive.entries().collect::<Vec<_>>();
        assert_archive_content(&entries);
    }

    fn assert_archive_content(entries: &[ArchiveEntry]) {
        assert_eq!(entries.len(), 3);
        // order in that I stored the files into the archive
        assert_eq!(entries[0].filename().as_str(), "bye_world_513b.txt");
        assert_eq!(entries[0].size(), 513);
        assert_eq!(entries[0].data().len(), 513);
        assert_eq!(entries[1].filename().as_str(), "hello_world_513b.txt");
        assert_eq!(entries[1].size(), 513);
        assert_eq!(entries[1].data().len(), 513);
        assert_eq!(entries[2].filename().as_str(), "hello_world.txt");
        assert_eq!(entries[2].size(), 12);
        assert_eq!(entries[2].data().len(), 12);
    }
}