use xvfb-run to create headless anki if no running instance is available

flake.nix

@@ -20,7 +20,7 @@
     toolchain = fenix.packages.x86_64-linux.minimal.toolchain;
   in {
     devShells.x86_64-linux.default = pkgs.mkShell {
-      buildInputs = [toolchain];
+      buildInputs = [toolchain pkgs.xvfb-run];
       shellHook = ''
         export RUSTUP_TOOLCHAIN=${toolchain}
       '';
@@ -30,7 +30,12 @@
         cargo = toolchain;
         rustc = toolchain;
       }).buildPackage {
+        nativeBuildInputs = [pkgs.makeWrapper];
         src = ./.;
+        postInstall = ''
+          wrapProgram $out/bin/anki-cli \
+          --prefix PATH : ${pkgs.xvfb-run}/bin
+        '';
       };
   };
 }

src/main.rs

@@ -7,7 +7,12 @@ use crossterm::{
     terminal::*,
 };
 use nanohtml2text::html2text;
-use std::io::stdout;
+use std::{
+    io::stdout,
+    process::{Command, Stdio},
+    thread,
+    time::Duration,
+};
 
 const GOOD: char = '3';
 const AGAIN: char = '1';
@@ -22,7 +27,29 @@ fn main() {
 
 fn init(anki: &AnkiClient) {
     clear_screen();
-    let decks = anki.request(DeckNamesRequest {}).unwrap();
+    let mut decks = anki.request(DeckNamesRequest {});
+    if let Err(_) = decks {
+        clear_screen();
+        display_text("initializing headless anki...");
+        Command::new("bash")
+            .arg("-c")
+            .arg("QT_QPA_PLATFORM=xcb xvfb-run -a anki")
+            .stdin(Stdio::null())
+            .stdout(Stdio::null())
+            .stderr(Stdio::null())
+            .spawn()
+            .unwrap();
+        loop {
+            thread::sleep(Duration::from_secs(1));
+            display_text(".");
+            decks = anki.request(DeckNamesRequest {});
+            if let Ok(_) = decks {
+                clear_screen();
+                break;
+            }
+        }
+    }
+    let decks = decks.unwrap();
     for (index, title) in decks.clone().into_iter().enumerate() {
         // 0th index is Default, which is not predictable
         if index > 0 {