Share a card's image from the preview

A share button beside the preview's close button sends the face being
shown at Scryfall's large size: on desktop the image is decoded and put on
the clipboard (tauri-plugin-clipboard-manager); on Android it's saved to
the cache and handed to the system share sheet by a small in-repo plugin
(SharePlugin.kt) through the app's FileProvider. The preview's corner
buttons are also a little larger.

crates/mtgc-core/src/http.rs

@@ -51,3 +51,24 @@ pub(crate) fn get_json<T: serde::de::DeserializeOwned>(url: &str) -> Result<T> {
         .call()?
         .into_json()?)
 }
+
+/// Most bytes [`fetch_image`] will read. Scryfall's largest card scans are a
+/// few hundred kilobytes; this only stops a bad URL streaming forever.
+const MAX_IMAGE_BYTES: u64 = 20 << 20;
+
+/// GET a card image (a Scryfall scan) as bytes, for sharing or copying it.
+/// HTTPS only.
+pub fn fetch_image(url: &str) -> Result<Vec<u8>> {
+    if !url.starts_with("https://") {
+        return Err(crate::error::CoreError::Other(format!("not an https image URL: {url}")));
+    }
+    let mut bytes = Vec::new();
+    agent()
+        .get(url)
+        .set("User-Agent", USER_AGENT)
+        .call()?
+        .into_reader()
+        .take(MAX_IMAGE_BYTES)
+        .read_to_end(&mut bytes)?;
+    Ok(bytes)
+}

crates/mtgc-core/src/lib.rs

@@ -28,6 +28,7 @@ use std::path::Path;
 use rusqlite::Connection;
 
 pub use error::{CoreError, Result};
+pub use http::fetch_image;
 pub use model::{
     CardRef, ColorSet, Deck, DeckEntry, LegalStatus, Legalities, LibraryCard, LibraryCopy,
     LibraryFacets, LibraryFilter, LibraryStats, PrintingRef,