Set up plugin structure

src/error.rs

@@ -0,0 +1,31 @@
+use std::fmt;
+use std::io;
+
+pub enum Error {
+    Io(io::Error),
+}
+
+impl From<io::Error> for Error {
+    fn from(e: io::Error) -> Self {
+        Error::Io(e)
+    }
+}
+
+// Rust only supports `fn main() -> Result<(), E: Debug>`, so we implement `Debug`
+// manually to provide the error output we want.
+impl fmt::Debug for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Error::Io(e) => writeln!(f, "Failed to set up YubiKey: {}", e)?,
+        }
+        writeln!(f)?;
+        writeln!(
+            f,
+            "[ Did this not do what you expected? Could an error be more useful? ]"
+        )?;
+        write!(
+            f,
+            "[ Tell us: https://str4d.xyz/age-plugin-yubikey/report              ]"
+        )
+    }
+}

src/main.rs

@@ -1,3 +1,36 @@
-fn main() {
-    println!("Hello, world!");
+use age_plugin::run_state_machine;
+use gumdrop::Options;
+
+mod error;
+mod plugin;
+
+use error::Error;
+
+#[derive(Debug, Options)]
+struct PluginOptions {
+    #[options(help = "Print this help message and exit.")]
+    help: bool,
+
+    #[options(
+        help = "Run the given age plugin state machine. Internal use only.",
+        meta = "STATE-MACHINE",
+        no_short
+    )]
+    age_plugin: Option<String>,
+}
+
+fn main() -> Result<(), Error> {
+    let opts = PluginOptions::parse_args_default_or_exit();
+
+    if let Some(state_machine) = opts.age_plugin {
+        run_state_machine(
+            &state_machine,
+            || plugin::RecipientPlugin::default(),
+            || plugin::IdentityPlugin::default(),
+        )?;
+        Ok(())
+    } else {
+        // TODO: CLI identity generation
+        Ok(())
+    }
 }

src/plugin.rs

@@ -0,0 +1,43 @@
+use age_core::format::{FileKey, Stanza};
+use age_plugin::{
+    identity::{self, Callbacks, IdentityPluginV1},
+    recipient::{self, RecipientPluginV1},
+};
+use std::collections::HashMap;
+use std::io;
+
+#[derive(Debug, Default)]
+pub(crate) struct RecipientPlugin {}
+
+impl RecipientPluginV1 for RecipientPlugin {
+    fn add_recipients<'a, I: Iterator<Item = &'a str>>(
+        &mut self,
+        recipients: I,
+    ) -> Result<(), Vec<recipient::Error>> {
+        todo!()
+    }
+
+    fn wrap_file_key(&mut self, file_key: &FileKey) -> Result<Vec<Stanza>, Vec<recipient::Error>> {
+        todo!()
+    }
+}
+
+#[derive(Debug, Default)]
+pub(crate) struct IdentityPlugin {}
+
+impl IdentityPluginV1 for IdentityPlugin {
+    fn add_identities<'a, I: Iterator<Item = &'a str>>(
+        &mut self,
+        identities: I,
+    ) -> Result<(), Vec<identity::Error>> {
+        todo!()
+    }
+
+    fn unwrap_file_keys(
+        &mut self,
+        files: Vec<Vec<Stanza>>,
+        mut callbacks: impl Callbacks,
+    ) -> io::Result<HashMap<usize, Result<FileKey, Vec<identity::Error>>>> {
+        todo!()
+    }
+}