Machine and stream config rework

src/machine/config.rs

@@ -1,32 +1,74 @@
-pub struct MachineConfig {
-    pub streams: StreamConfig,
-    pub toplevel: &'static str,
+/// Describes how the streams of a `crate::Machine` will be handled.
+///
+/// Defaults to using standard IO.
+pub struct StreamConfig {
+    pub(crate) inner: StreamConfigInner,
 }
 
-pub enum StreamConfig {
+impl Default for StreamConfig {
+    fn default() -> Self {
+        Self::stdio()
+    }
+}
+
+impl StreamConfig {
+    /// Binds the input, output and error streams to stdin, stdout and stderr.
+    pub fn stdio() -> Self {
+        StreamConfig {
+            inner: StreamConfigInner::Stdio,
+        }
+    }
+
+    /// Binds the output stream to a memory buffer, and the error stream to stderr.
+    ///
+    /// The input stream is ignored.
+    pub fn in_memory() -> Self {
+        StreamConfig {
+            inner: StreamConfigInner::Memory,
+        }
+    }
+}
+
+pub(crate) enum StreamConfigInner {
     Stdio,
     Memory,
 }
 
+/// Describes how a `crate::Machine` will be configured.
+pub struct MachineConfig {
+    pub(crate) streams: StreamConfig,
+    pub(crate) toplevel: &'static str,
+}
+
 impl Default for MachineConfig {
     fn default() -> Self {
         MachineConfig {
-            streams: StreamConfig::Stdio,
-            toplevel: include_str!("../toplevel.pl"),
+            streams: Default::default(),
+            toplevel: default_toplevel(),
         }
     }
 }
 
 impl MachineConfig {
-    pub fn in_memory() -> Self {
-        MachineConfig {
-            streams: StreamConfig::Memory,
-            ..Default::default()
-        }
+    /// Creates a default configuration.
+    pub fn new() -> Self {
+        Default::default()
     }
 
+    /// Uses the given `crate::StreamConfig` in this configuration. 
+    pub fn with_streams(mut self, streams: StreamConfig) -> Self {
+        self.streams = streams;
+        self
+    }
+
+    /// Uses the given toplevel in this configuration.
     pub fn with_toplevel(mut self, toplevel: &'static str) -> Self {
         self.toplevel = toplevel;
         self
     }
 }
+
+/// Returns a static string slice to the default toplevel
+pub fn default_toplevel() -> &'static str {
+    include_str!("../toplevel.pl")
+}