open-standards/wai/wai-rs/tests/floor.rs

//! The mandatory floor (SPEC §5: PNG, FLAC, zstd) in a build with the `floor` feature and no
//! other: the library decodes each, and the `wai` binary encodes PNG and zstd and decodes all
//! three, with no system codec library linked. A codec outside the floor is refused, saying
//! which build has it.
#![cfg(feature = "floor")]

use std::path::{Path, PathBuf};
use std::process::Command;
use wai::codecs::{audio, image, text};

fn tmp(name: &str) -> PathBuf {
    let d = std::env::temp_dir().join(format!("wai-floor-{name}-{}", std::process::id()));
    let _ = std::fs::remove_dir_all(&d);
    std::fs::create_dir_all(&d).unwrap();
    d
}

fn wai(args: &[&str]) -> std::process::Output {
    Command::new(env!("CARGO_BIN_EXE_wai")).args(args).output().expect("wai runs")
}

/// CRC-8 (polynomial 0x07) and CRC-16 (0x8005) of RFC 9639 §9.1.8 and §9.3.
fn crc8(b: &[u8]) -> u8 {
    b.iter().fold(0u8, |mut c, &x| {
        c ^= x;
        for _ in 0..8 {
            c = if c & 0x80 != 0 { (c << 1) ^ 0x07 } else { c << 1 };
        }
        c
    })
}

fn crc16(b: &[u8]) -> u16 {
    b.iter().fold(0u16, |mut c, &x| {
        c ^= (x as u16) << 8;
        for _ in 0..8 {
            c = if c & 0x8000 != 0 { (c << 1) ^ 0x8005 } else { c << 1 };
        }
        c
    })
}

/// A FLAC stream (RFC 9639) of one frame of sixteen 16-bit mono samples at 8 kHz, in a
/// verbatim subframe: written field by field, so the test needs no encoder.
fn flac(samples: &[i16; 16]) -> Vec<u8> {
    let mut b = b"fLaC".to_vec();
    b.extend_from_slice(&[0x80, 0, 0, 34]); // the last metadata block: STREAMINFO, 34 bytes
    b.extend_from_slice(&16u16.to_be_bytes()); // min and max block size
    b.extend_from_slice(&16u16.to_be_bytes());
    b.extend_from_slice(&[0, 0, 0, 0, 0, 0]); // frame sizes unknown
    // 20 bits sample rate (8000), 3 bits channels-1 (0), 5 bits bps-1 (15), 36 bits samples (16).
    let v: u64 = (8000u64 << 44) | (15u64 << 36) | 16;
    b.extend_from_slice(&v.to_be_bytes());
    b.extend_from_slice(&[0; 16]); // MD5 unknown
    let start = b.len();
    // Sync, fixed blocking; block size from an 8-bit field, rate from STREAMINFO; mono, 16 bits;
    // frame 0; block size - 1.
    b.extend_from_slice(&[0xff, 0xf8, 0x60, 0x08, 0x00, 15]);
    let c = crc8(&b[start..]);
    b.push(c);
    b.push(0x02); // a verbatim subframe, no wasted bits
    for s in samples {
        b.extend_from_slice(&s.to_be_bytes());
    }
    let c = crc16(&b[start..]);
    b.extend_from_slice(&c.to_be_bytes());
    b
}

#[test]
fn the_library_decodes_the_floor() {
    let rgb: Vec<u8> = (0..4 * 3 * 3).map(|i| (i * 7) as u8).collect();
    let png = image::png_encode(&rgb, 3, 4).unwrap();
    assert_eq!(image::png_decode(&png).unwrap(), (rgb, 3, 4));
    let s: [i16; 16] = std::array::from_fn(|i| (i as i16 - 8) * 1000);
    let (pcm, rate) = audio::flac_decode(&flac(&s)).unwrap();
    assert_eq!(rate, 8000);
    assert_eq!(pcm, s.iter().map(|&x| x as f32 / 32768.0).collect::<Vec<_>>());
    let t = b"the mandatory floor".repeat(20);
    assert_eq!(text::zstd_decode(&text::zstd_encode(&t, 3).unwrap()).unwrap(), t);
    assert_eq!(wai::floor_capabilities(), &["wai.image.png", "wai.audio.flac", "wai.text.zstd"]);
}

fn ok(o: &std::process::Output) {
    assert!(o.status.success(), "{}{}", String::from_utf8_lossy(&o.stdout), String::from_utf8_lossy(&o.stderr));
}

fn s(p: &Path) -> &str {
    p.to_str().unwrap()
}

#[test]
fn the_cli_encodes_png_and_zstd_and_decodes_the_floor() {
    let d = tmp("cli");
    // PNG: a 4x3 picture in, the same pixels out.
    let rgb: Vec<u8> = (0..36).map(|i| (i * 5) as u8).collect();
    std::fs::write(d.join("pic.rgb"), &rgb).unwrap();
    std::fs::write(d.join("pic.rgb.meta"), "3 4\n").unwrap();
    ok(&wai(&["encode", "png", s(&d.join("pic.rgb")), "-o", s(&d.join("pic.wai"))]));
    ok(&wai(&["decode", s(&d.join("pic.wai")), "-o", s(&d.join("pic.out"))]));
    assert_eq!(std::fs::read(d.join("pic.out")).unwrap(), rgb);
    // zstd.
    let t = b"carried, compressed and rebuilt".repeat(9);
    std::fs::write(d.join("t.txt"), &t).unwrap();
    ok(&wai(&["encode", "zstd", s(&d.join("t.txt")), "-o", s(&d.join("t.wai"))]));
    ok(&wai(&["decode", s(&d.join("t.wai")), "-o", s(&d.join("t.out"))]));
    assert_eq!(std::fs::read(d.join("t.out")).unwrap(), t);
    // FLAC: wrapped as it comes, decoded by the floor.
    let smp: [i16; 16] = std::array::from_fn(|i| (i as i16) * 300);
    std::fs::write(d.join("a.flac"), flac(&smp)).unwrap();
    ok(&wai(&["wrap", "wai.audio.flac", s(&d.join("a.flac")), "-o", s(&d.join("a.wai"))]));
    ok(&wai(&["decode", s(&d.join("a.wai")), "-o", s(&d.join("a.f32"))]));
    let f: Vec<u8> = smp.iter().flat_map(|&x| (x as f32 / 32768.0).to_le_bytes()).collect();
    assert_eq!(std::fs::read(d.join("a.f32")).unwrap(), f);
    assert_eq!(std::fs::read_to_string(d.join("a.f32.meta")).unwrap().trim(), "8000");
    let _ = std::fs::remove_dir_all(&d);
}

#[cfg(not(feature = "codecs"))]
#[test]
fn a_codec_outside_the_floor_is_refused_naming_the_build_that_has_it() {
    let d = tmp("outside");
    std::fs::write(d.join("x.txt"), b"x").unwrap();
    let o = wai(&["encode", "xz", s(&d.join("x.txt")), "-o", s(&d.join("x.wai"))]);
    assert!(!o.status.success());
    assert!(String::from_utf8_lossy(&o.stderr).contains("`codecs` feature"), "{}", String::from_utf8_lossy(&o.stderr));
    // A payload the floor does not decode is inert here, never guessed.
    std::fs::write(d.join("y.jxl"), b"\xff\x0a").unwrap();
    ok(&wai(&["wrap", "wai.image.jxl", s(&d.join("y.jxl")), "-o", s(&d.join("y.wai"))]));
    let o = wai(&["decode", s(&d.join("y.wai")), "-o", s(&d.join("y.out"))]);
    assert!(!o.status.success() && String::from_utf8_lossy(&o.stderr).contains("inert"), "{}", String::from_utf8_lossy(&o.stderr));
    let _ = std::fs::remove_dir_all(&d);
}