implement a new sprout command line options mechanism

hack/dev/configs/shell.sprout.toml

@@ -0,0 +1,11 @@
+version = 1
+
+[extractors.boot.filesystem-device-match]
+has-item = "\\EFI\\BOOT\\shell.efi"
+
+[actions.chainload-shell]
+chainload.path = "$boot\\EFI\\BOOT\\shell.efi"
+
+[entries.xen]
+title = "Boot Shell"
+actions = ["chainload-shell"]

src/config/loader.rs

@@ -1,31 +1,36 @@
 use crate::config::{RootConfiguration, latest_version};
+use crate::options::SproutOptions;
 use crate::utils;
 use anyhow::{Context, Result, bail};
+use log::info;
 use std::ops::Deref;
 use toml::Value;
 use uefi::proto::device_path::LoadedImageDevicePath;
 
-/// Loads the raw configuration from the sprout.toml file as data.
-fn load_raw_config() -> Result<Vec<u8>> {
+/// Loads the raw configuration from the sprout config file as data.
+fn load_raw_config(options: &SproutOptions) -> Result<Vec<u8>> {
     // Open the LoadedImageDevicePath protocol to get the path to the current image.
     let current_image_device_path_protocol =
         uefi::boot::open_protocol_exclusive::<LoadedImageDevicePath>(uefi::boot::image_handle())
             .context("unable to get loaded image device path")?;
     // Acquire the device path as a boxed device path.
     let path = current_image_device_path_protocol.deref().to_boxed();
-    // Read the contents of the sprout.toml file.
-    let content = utils::read_file_contents(&path, "sprout.toml")
-        .context("unable to read sprout.toml file")?;
-    // Return the contents of the sprout.toml file.
+
+    info!("configuration file: {}", options.config);
+
+    // Read the contents of the sprout config file.
+    let content = utils::read_file_contents(&path, &options.config)
+        .context("unable to read sprout config file")?;
+    // Return the contents of the sprout config file.
     Ok(content)
 }
 
 /// Loads the [RootConfiguration] for Sprout.
-pub fn load() -> Result<RootConfiguration> {
-    // Load the raw configuration from the sprout.toml file.
-    let content = load_raw_config()?;
+pub fn load(options: &SproutOptions) -> Result<RootConfiguration> {
+    // Load the raw configuration from the sprout config file.
+    let content = load_raw_config(options)?;
     // Parse the raw configuration into a toml::Value which can represent any TOML file.
-    let value: Value = toml::from_slice(&content).context("unable to parse sprout.toml file")?;
+    let value: Value = toml::from_slice(&content).context("unable to parse sprout config file")?;
 
     // Check the version of the configuration without parsing the full configuration.
     let version = value

src/context.rs

@@ -1,4 +1,5 @@
 use crate::actions::ActionDeclaration;
+use crate::options::SproutOptions;
 use anyhow::Result;
 use anyhow::anyhow;
 use std::collections::{BTreeMap, BTreeSet};
@@ -13,15 +14,18 @@ pub struct RootContext {
     actions: BTreeMap<String, ActionDeclaration>,
     /// The device path of the loaded Sprout image.
     loaded_image_path: Option<Box<DevicePath>>,
+    /// The global options of Sprout.
+    options: SproutOptions,
 }
 
 impl RootContext {
     /// Creates a new root context with the `loaded_image_device_path` which will be stored
     /// in the context for easy access.
-    pub fn new(loaded_image_device_path: Box<DevicePath>) -> Self {
+    pub fn new(loaded_image_device_path: Box<DevicePath>, options: SproutOptions) -> Self {
         Self {
             actions: BTreeMap::new(),
             loaded_image_path: Some(loaded_image_device_path),
+            options,
         }
     }
 
@@ -41,6 +45,11 @@ impl RootContext {
             .as_deref()
             .ok_or_else(|| anyhow!("no loaded image path"))
     }
+
+    /// Access the global Sprout options.
+    pub fn options(&self) -> &SproutOptions {
+        &self.options
+    }
 }
 
 /// A context of Sprout. This is passed around different parts of Sprout and represents

src/main.rs

@@ -3,7 +3,7 @@
 
 use crate::context::{RootContext, SproutContext};
 use crate::phases::phase;
-use anyhow::{Context, Result, bail};
+use anyhow::{Context, Result};
 use log::info;
 use std::collections::BTreeMap;
 use std::ops::Deref;
@@ -37,6 +37,9 @@ pub mod phases;
 /// setup: Code that initializes the UEFI environment for Sprout.
 pub mod setup;
 
+/// options: Parse the options of the Sprout executable.
+pub mod options;
+
 /// utils: Utility functions that are used by other parts of Sprout.
 pub mod utils;
 
@@ -47,10 +50,13 @@ fn main() -> Result<()> {
     // Initialize the basic UEFI environment.
     setup::init()?;
 
+    // Parse the options to the sprout executable.
+    let options = options::parse().context("unable to parse options")?;
+
     // Load the configuration of sprout.
     // At this point, the configuration has been validated and the specified
     // version is checked to ensure compatibility.
-    let config = config::loader::load()?;
+    let config = config::loader::load(&options)?;
 
     // Load the root context.
     // This is done in a block to ensure the release of the LoadedImageDevicePath protocol.
@@ -64,7 +70,7 @@ fn main() -> Result<()> {
             "loaded image path: {}",
             loaded_image_path.to_string(DisplayOnly(false), AllowShortcuts(false))?
         );
-        RootContext::new(loaded_image_path)
+        RootContext::new(loaded_image_path, options)
     };
 
     // Insert the configuration actions into the root context.
@@ -144,9 +150,14 @@ fn main() -> Result<()> {
     // Execute the late phase.
     phase(context.clone(), &config.phases.late).context("unable to execute late phase")?;
 
-    // Pick the first entry from the list of final entries until a boot menu is implemented.
-    let Some((context, entry)) = final_entries.first() else {
-        bail!("no entries found");
+    // Use the boot option if possible, otherwise pick the first entry.
+    let (context, entry) = if let Some(ref boot) = context.root().options().boot {
+        final_entries
+            .iter()
+            .find(|(_context, entry)| &entry.title == boot)
+            .context(format!("unable to find entry: {boot}"))?
+    } else {
+        final_entries.first().context("no entries found")?
     };
 
     // Execute all the actions for the selected entry.

src/options.rs

@@ -0,0 +1,117 @@
+use anyhow::{Context, Result, bail};
+use std::collections::BTreeMap;
+
+/// Default configuration file path.
+const DEFAULT_CONFIG_PATH: &str = "\\sprout.toml";
+
+/// The parsed options of sprout.
+#[derive(Debug)]
+pub struct SproutOptions {
+    /// Path to a configuration file to load.
+    pub config: String,
+    /// Entry to boot without showing the boot menu.
+    pub boot: Option<String>,
+}
+
+/// The default Sprout options.
+impl Default for SproutOptions {
+    fn default() -> Self {
+        Self {
+            config: DEFAULT_CONFIG_PATH.to_string(),
+            boot: None,
+        }
+    }
+}
+
+/// For minimalism, we don't want a full argument parser. Instead, we use
+/// a simple --xyz = xyz: None and --abc 123 = abc: Some("123") format.
+/// We also support --abc=123 = abc: Some("123") format.
+fn parse_raw() -> Result<BTreeMap<String, Option<String>>> {
+    // Collect all the arguments to Sprout.
+    // Skip the first argument which is the path to our executable.
+    let args = std::env::args().skip(1).collect::<Vec<_>>();
+
+    // Represent options as key-value pairs.
+    let mut options = BTreeMap::new();
+
+    // Iterators makes this way easier.
+    let mut iterator = args.into_iter().peekable();
+
+    loop {
+        // Consume the next option, if any.
+        let Some(option) = iterator.next() else {
+            break;
+        };
+
+        // If the doesn't start with --, that is invalid.
+        if !option.starts_with("--") {
+            bail!("invalid option: {option}");
+        }
+
+        // Strip the -- prefix off.
+        let mut option = option["--".len()..].trim().to_string();
+
+        // An optional value.
+        let mut value = None;
+
+        // Check if the option is of the form --abc=123
+        if option.contains("=") {
+            let Some((part_key, part_value)) = option.split_once("=") else {
+                bail!("invalid option: {option}");
+            };
+
+            let part_key = part_key.to_string();
+            let part_value = part_value.to_string();
+            option = part_key;
+            value = Some(part_value);
+        }
+
+        if value.is_none() {
+            // Check for the next value.
+            let maybe_next = iterator.peek();
+
+            // If the next value isn't another option, set the value to the next value.
+            // Otherwise, it is an empty string.
+            value = if let Some(next) = maybe_next
+                && !next.starts_with("--")
+            {
+                iterator.next()
+            } else {
+                None
+            };
+        }
+
+        // Error on empty option names.
+        if option.is_empty() {
+            bail!("invalid empty option: {option}");
+        }
+
+        // Insert the option and the value into the map.
+        options.insert(option, value);
+    }
+    Ok(options)
+}
+
+/// Parse the arguments to Sprout as a [SproutOptions] structure.
+pub fn parse() -> Result<SproutOptions> {
+    // Use the default value of sprout options and have the raw options be parsed into it.
+    let mut result = SproutOptions::default();
+    let options = parse_raw().context("unable to parse options")?;
+
+    for (key, value) in options {
+        match key.as_str() {
+            "config" => {
+                // The configuration file to load.
+                result.config = value.context("--config option requires a value")?;
+            }
+
+            "boot" => {
+                // The entry to boot.
+                result.boot = Some(value.context("--boot option requires a value")?);
+            }
+
+            _ => bail!("unknown option: --{key}"),
+        }
+    }
+    Ok(result)
+}