use tiff::{
    decoder::Decoder,
    tags::{IfdPointer, Tag},
};

// This file has the following IFD structure:
//
// ```
// IFD -> IFD -> IFD
//        |-> IFD
//        |-> IFD -> IFD
//        |          \-> IFD -> IFD
//        \-> IFD
// ```
//
// where the main chain of IFD has 3 images, the second of which has several sub-IFDs and some have
// more nested IFDs.
const TEST_IMAGE_SUBIFD: &str = "./tests/subsubifds.tif";
use std::fs::File;

#[test]
fn decode_seek_chain() {
    let file = File::open(TEST_IMAGE_SUBIFD).expect("Cannot open test image");
    let mut decoder = Decoder::new(file).expect("Invalid format to create decoder");

    // Remember the offsets in the first iteration.
    let offset0 = decoder.ifd_pointer().expect("First IFD pointer not found");
    decoder.next_image().unwrap();
    let offset1 = decoder.ifd_pointer().expect("Second IFD pointer not found");
    decoder.next_image().unwrap();
    let offset2 = decoder.ifd_pointer().expect("Third IFD pointer not found");
    assert!(!decoder.more_images());

    // Ensure we can seek, to do this again.
    decoder
        .seek_to_image(0)
        .expect("Failed to seek to first image");
    assert_eq!(Some(offset0), decoder.ifd_pointer());
    decoder.next_image().unwrap();
    assert_eq!(Some(offset1), decoder.ifd_pointer());
    decoder.next_image().unwrap();
    assert_eq!(Some(offset2), decoder.ifd_pointer());
    assert!(!decoder.more_images());
}

#[test]
fn decode_seek_recover() {
    let file = File::open(TEST_IMAGE_SUBIFD).expect("Cannot open test image");
    let mut decoder = Decoder::new(file).expect("Invalid format to create decoder");

    // Remember the offsets in the first iteration.
    let offset0 = decoder.ifd_pointer().expect("First IFD pointer not found");
    decoder.next_image().unwrap();
    let offset1 = decoder.ifd_pointer().expect("Second IFD pointer not found");
    decoder.next_image().unwrap();
    let offset2 = decoder.ifd_pointer().expect("Third IFD pointer not found");

    // oops!
    let fails = decoder.restart_at_image(IfdPointer(0xdead_beef));
    assert!(fails.is_err());

    // However we can recover by restarting our seek.
    decoder
        .restart_at_image(offset0)
        .expect("Failed to restart IFDs from first image");
    assert_eq!(Some(offset0), decoder.ifd_pointer());
    decoder.next_image().unwrap();
    assert_eq!(Some(offset1), decoder.ifd_pointer());
    decoder.next_image().unwrap();
    assert_eq!(Some(offset2), decoder.ifd_pointer());
}

#[test]
fn decode_seek_directory() {
    let file = File::open(TEST_IMAGE_SUBIFD).expect("Cannot open test image");
    let mut decoder = Decoder::new(file).expect("Invalid format to create decoder");

    let offset = decoder.ifd_pointer().expect("First IFD pointer not found");
    let img0 = decoder.read_image().unwrap();

    decoder.next_image().unwrap();
    let img1 = decoder.read_image().unwrap();
    assert_ne!(img0, img1);

    {
        // Due to the special test file structure.
        let subifd = decoder
            .get_tag(Tag::SubIfd)
            .unwrap()
            .into_ifd_vec()
            .unwrap()[0];

        // Let's try to manually interpret this as an image.
        decoder
            .restart_at_directory(subifd)
            .expect("Failed to restart IFDs at SubIfd");
        decoder
            .current_directory_as_image()
            .expect("Failed to read SubIfd image");

        assert_eq!(decoder.dimensions().unwrap(), (32, 32));
        let subimage = decoder.read_image().unwrap();
        // Verify we did not accidentally read another image.
        assert_ne!(img0, subimage);
        assert_ne!(img1, subimage);
    }

    // And finally, seek back to the first image.
    decoder
        .restart_at_image(offset)
        .expect("First IFD no longer readable");
    assert_eq!(Some(offset), decoder.ifd_pointer());

    let img0_try2 = decoder.read_image().unwrap();
    assert_eq!(img0, img0_try2);
}

#[test]
fn decode_subifds() {
    let explore_chain = |decoder: &mut Decoder<_>, subifds: &mut Vec<_>| {
        let mut len = 0usize;

        loop {
            len += 1;

            if let Ok(subifd) = decoder.get_tag(Tag::SubIfd) {
                let prelen = subifds.len();
                subifds.extend(subifd.into_ifd_vec().expect("Failed to decode SubIfd tag"));
                eprintln!("New roots: {:?}", &subifds[prelen..]);
            } else {
                eprintln!("No roots");
            }

            if !decoder.more_images() {
                break;
            }

            decoder.next_image().unwrap();
        }

        len
    };

    let file = File::open(TEST_IMAGE_SUBIFD).expect("Cannot open test image");
    let mut decoder = Decoder::new(file).expect("Invalid format to create decoder");

    let mut subifds = vec![];
    let mut chain_lengths = vec![];
    chain_lengths.push(explore_chain(&mut decoder, &mut subifds));

    while !subifds.is_empty() {
        let root = subifds.remove(0);
        let manual_directory = decoder.read_directory(root).unwrap();
        eprintln!("Manual directory: {:?}", manual_directory);

        decoder.restart_at_directory(root).unwrap();
        let prelen = subifds.len();
        chain_lengths.push(explore_chain(&mut decoder, &mut subifds));
        eprintln!("Chains roots: {:?}", &subifds[prelen..]);
    }

    // Traversal Order in this graph:
    // Image 0 -> Image 1 -> Image 2
    //            |-> Image 3
    //            |-> Image 4 -> Image 5
    //            |              \-> Image 7 -> Image 8
    //            \-> Image 6
    assert_eq!(chain_lengths, [3, 1, 2, 1, 2]);
}