Images that point at one of this hub's file pages render as the raw file (closes #346); a proposal's diffs over the API, GET …/proposals/N/diff (refs oxygenhub-android#4) 70c3d02998a2

- **A proposal's diffs over the API (oxygenhub-android#4).** `GET /api/v1/repos/OWNER/NAME/proposals/N/diff` gives each file the proposal changes with its diff (three lines of context, in the shape a change's files have), as the proposal page shows them, for the Android app's proposal view.

- **Images that point at a file's page show (#346).** Markdown left an image's full or root-relative address alone, so `![…](https://oxygenhub.io/OWNER/NAME/file/main/x.png)` (the address a file's page shows, as the doomsdayone/tetriblox wiki's screenshots use) pointed an `<img>` at an HTML page and showed broken. An image of one of this hub's file pages now renders as that file's raw bytes (`…/raw/REF/PATH`), as GitHub does for `blob/` images; links keep the page, and other sites' addresses are untouched.

        .route("/repos/{owner}/{name}/proposals/{number}/diff", get(proposal_diff))

/// `GET …/proposals/{number}/diff`: each file the proposal changes with its

/// diff (three lines of context, as a change's), as the proposal page shows

/// them, for clients that draw diffs (oxygenhub-android#4).

async fn proposal_diff(

    State(app): State<Shared>,

    headers: HeaderMap,

    Path((owner, name, number)): Path<(String, String, i64)>,

) -> Result<Json<Vec<FileChange>>, ApiError> {

    let c = caller(&app, &headers).await?;

    let (repo, row, _) = reach(&app, &c, &owner, &name, Access::Read).await?;

    let p = db::proposals::get(&app.db, row.id, number).await?.ok_or_else(|| not_found("no such proposal"))?;

    let loaded = crate::web::proposals::load(&app, &repo, p).await?;

    Ok(Json(loaded.files.into_iter().map(file_change).collect()))

}

    // Images of this hub's file pages render as their raw files.

    render::markdown::set_origin(config.base_url());

            let src = raw_image(&dest_url, &origin()).unwrap_or_else(|| rebase(&dest_url, base_raw));

            Event::Start(Tag::Image { link_type, dest_url: src.into(), title, id })

/// This hub's own origin (`https://oxygenhub.io`), so an image written as

/// a full address of one of its file pages is still recognised.

static ORIGIN: std::sync::RwLock<String> = std::sync::RwLock::new(String::new());

/// Set when the hub is built, from its base URL.

pub fn set_origin(base_url: &str) {

    *ORIGIN.write().unwrap() = base_url.trim_end_matches('/').to_string();

}

fn origin() -> String {

    ORIGIN.read().unwrap().clone()

}

/// An image that points at one of this hub's file pages

/// (`[ORIGIN]/OWNER/NAME/file/REF/PATH`, the address a file's page shows)

/// is that file's raw bytes (`…/raw/REF/PATH`): the page is HTML, which an

/// `<img>` cannot show, as GitHub turns `blob/` images into raw ones.

fn raw_image(url: &str, origin: &str) -> Option<String> {

    let (host, path) = if url.starts_with('/') && !url.starts_with("//") {

        ("", url)

    } else if !origin.is_empty() && url.strip_prefix(origin).is_some_and(|p| p.starts_with('/')) {

        (origin, &url[origin.len()..])

    } else {

        return None;

    };

    let mut parts = path[1..].splitn(4, '/');

    let (owner, name, kind, rest) = (parts.next()?, parts.next()?, parts.next()?, parts.next()?);

    (kind == "file" && !owner.is_empty() && !name.is_empty() && !rest.is_empty()).then(|| format!("{host}/{owner}/{name}/raw/{rest}"))

}

    }

    /// An image of one of this hub's file pages is its raw file: by full

    /// address or by path; another site's, a link, or a raw address stay.

    #[test]

    fn an_image_of_a_file_page_is_its_raw_file() {

        let o = "https://hub.example";

        assert_eq!(

            raw_image("https://hub.example/doomsdayone/tetriblox/file/main/docs/images/screens/menu.png", o).as_deref(),

            Some("https://hub.example/doomsdayone/tetriblox/raw/main/docs/images/screens/menu.png")

        );

        assert_eq!(raw_image("/a/b/file/v1.0/x.png", o).as_deref(), Some("/a/b/raw/v1.0/x.png"));

        assert_eq!(raw_image("https://elsewhere.example/a/b/file/main/x.png", o), None);

        assert_eq!(raw_image("https://hub.example.evil/a/b/file/main/x.png", o), None);

        assert_eq!(raw_image("/a/b/raw/main/x.png", o), None);

        assert_eq!(raw_image("//cdn.example/a/b/file/main/x.png", o), None);

        assert_eq!(raw_image("img.png", o), None);

        // Through render, with the origin set: only the image changes.

        set_origin("https://hub.example/");

        let html = render("[page](https://hub.example/a/b/file/main/x.png) ![x](https://hub.example/a/b/file/main/x.png)", "/p/", "/p/");

        assert!(html.contains("href=\"https://hub.example/a/b/file/main/x.png\""), "{html}");

        assert!(html.contains("src=\"https://hub.example/a/b/raw/main/x.png\""), "{html}");

    // The same files with their diffs, as a change's (oxygenhub-android#4).

    let (st, v) = api(app, "GET", "/api/v1/repos/andy/demo/proposals/2/diff", None, None).await;

    assert_eq!(st, StatusCode::OK, "{v}");

    assert_eq!((v[0]["path"].as_str(), v[0]["added"].as_u64(), v[0]["truncated"].as_bool()), (Some("a.txt"), Some(1), Some(false)), "{v}");

    let lines: Vec<(String, String)> = v[0]["lines"]

        .as_array()

        .unwrap()

        .iter()

        .map(|l| (l["kind"].as_str().unwrap().to_string(), l["text"].as_str().unwrap().to_string()))

        .collect();

    assert_eq!(lines, vec![("context".into(), "a".into()), ("add".into(), "A".into())], "{v}");

    assert_eq!(v[1]["kind"], "added");

    assert_eq!(api(app, "GET", "/api/v1/repos/andy/demo/proposals/99/diff", None, None).await.0, StatusCode::NOT_FOUND);