implement new argument parser with --help support

src/options.rs

@@ -1,3 +1,7 @@
+use crate::options::parser::{OptionDescription, OptionForm, OptionsRepresentable};
+use anyhow::{Context, Result, bail};
+use std::collections::BTreeMap;
+
 /// The Sprout options parser.
 pub mod parser;
 
@@ -22,3 +26,59 @@ impl Default for SproutOptions {
         }
     }
 }
+
+/// The options parser mechanism for Sprout.
+impl OptionsRepresentable for SproutOptions {
+    /// Produce the [SproutOptions] structure.
+    type Output = Self;
+
+    /// All the Sprout options that are defined.
+    fn options() -> &'static [(&'static str, OptionDescription<'static>)] {
+        &[
+            (
+                "config",
+                OptionDescription {
+                    description: "Path to Sprout configuration file",
+                    form: OptionForm::Value,
+                },
+            ),
+            (
+                "boot",
+                OptionDescription {
+                    description: "Entry to boot, bypassing the menu",
+                    form: OptionForm::Value,
+                },
+            ),
+            (
+                "help",
+                OptionDescription {
+                    description: "Display Sprout Help",
+                    form: OptionForm::Help,
+                },
+            ),
+        ]
+    }
+
+    /// Produces [SproutOptions] from the parsed raw `options` map.
+    fn produce(options: BTreeMap<String, Option<String>>) -> Result<Self> {
+        // Use the default value of sprout options and have the raw options be parsed into it.
+        let mut result = Self::default();
+
+        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)
+    }
+}