use criterion::{black_box, criterion_group, criterion_main, Criterion};
use multihash::Multihash;

pub fn criterion_benchmark(c: &mut Criterion) {
    let file = "benchmark.tar";

    match std::fs::read(file) {
        Ok(tar_bytes) => {
            // warmup should take care of right sizing these
            let mut buffer = Vec::new();
            let mut path = String::new();

            c.bench_function("ingest-tar", |b| {
                b.iter(|| ingest_tar(&tar_bytes, &mut buffer, &mut path))
            });
        }
        Err(e) if e.kind() == std::io::ErrorKind::NotFound => {
            eprintln!("could not find {file:?}:");
            eprintln!("please download a linux kernel and unpack it to enable benchmark. specific version doesn't matter.");
        }
        Err(e) => panic!("failed to read the {file:?}: {e}"),
    }
}

fn ingest_tar(bytes: &[u8], buffer: &mut Vec<u8>, path: &mut String) {
    use ipld_core::cid::Cid;
    use rust_unixfs::dir::builder::{BufferingTreeBuilder, TreeOptions};
    use rust_unixfs::file::adder::FileAdder;
    use sha2::{Digest, Sha256};
    use std::io::Read;

    let mut archive = tar::Archive::new(std::io::Cursor::new(bytes));
    let entries = archive.entries().unwrap();

    let mut opts = TreeOptions::default();
    opts.wrap_with_directory();
    let mut tree = BufferingTreeBuilder::new(opts);

    for entry in entries {
        let mut entry = entry.expect("assuming good tar");

        let path_bytes = entry.path_bytes();
        let tmp_path = std::str::from_utf8(&path_bytes).unwrap();
        path.clear();
        path.push_str(tmp_path);

        if let Some(link_name) = entry.link_name_bytes() {
            let link_name =
                std::str::from_utf8(&link_name).expect("symlink targets should be utf8");

            buffer.clear();
            rust_unixfs::symlink::serialize_symlink_block(link_name, buffer);

            let len = buffer.len();

            #[allow(clippy::needless_borrows_for_generic_args)]
            let mh = Multihash::wrap(
                multihash_codetable::Code::Sha2_256.into(),
                &Sha256::digest(&buffer),
            )
            .unwrap();
            let cid = Cid::new_v0(mh).expect("sha2_256 is the correct multihash for cidv0");

            tree.put_link(path, cid, len as u64).unwrap();

            // save the &buffer[..]

            continue;
        }

        if !path.ends_with('/') {
            // TODO: reusing of adder
            let mut adder = FileAdder::default();

            // with the std::io::Read it'd be good to read into the fileadder, or read into ...
            // something. trying to acccess the buffer from inside FileAdder does not seem the be the
            // way to go.
            //
            // reusing the buffers between files would make a lot of sense as well

            if let Some(needed) = adder.size_hint().checked_sub(buffer.capacity()) {
                buffer.reserve(needed);
            }

            if let Some(mut needed) = adder.size_hint().checked_sub(buffer.len()) {
                let zeros = [0u8; 8];

                while needed > zeros.len() {
                    buffer.extend_from_slice(&zeros[..]);
                    needed -= zeros.len();
                }

                buffer.extend(std::iter::repeat(0).take(needed));
            }

            let mut total_written = 0usize;

            loop {
                match entry.read(&mut buffer[0..]).unwrap() {
                    0 => {
                        let blocks = adder.finish();
                        let (cid, subtotal) = blocks
                            .fold(
                                None,
                                |acc: Option<(Cid, usize)>, (cid, bytes): (Cid, Vec<u8>)| match acc
                                {
                                    Some((_, total)) => Some((cid, total + bytes.len())),
                                    None => Some((cid, bytes.len())),
                                },
                            )
                            .expect("this is probably always present");

                        total_written += subtotal;

                        tree.put_link(path, cid, total_written as u64).unwrap();
                        break;
                    }
                    n => {
                        let mut read = 0;
                        while read < n {
                            let (blocks, consumed) = adder.push(&buffer[read..n]);
                            read += consumed;
                            total_written += blocks.map(|(_, bytes)| bytes.len()).sum::<usize>();
                        }
                    }
                }
            }
        } else {
            tree.set_metadata(&path[..path.len() - 1], rust_unixfs::Metadata::default())
                .unwrap();
        }
    }

    let mut iter = tree.build();

    let mut last: Option<(Cid, u64, usize)> = None;

    while let Some(res) = iter.next_borrowed() {
        let res = res.unwrap();
        last = Some((res.cid.to_owned(), res.total_size, res.block.len()));
    }

    let last = last.unwrap();

    black_box(last);
}

criterion_group!(benches, criterion_benchmark);
criterion_main!(benches);