♻️ Major code restructuring

src/config/data.rs

@@ -0,0 +1,136 @@
+use crate::config::error::*;
+use crate::config::path;
+use crate::config::source::Source;
+use crate::config::value::Value;
+
+use serde::de::Deserialize;
+
+use std::collections::HashMap;
+use std::fmt::Debug;
+
+#[derive(Clone, Debug)]
+enum ConfigKind {
+    // A mutable configuration. This is the default.
+    Mutable {
+        defaults: HashMap<path::Expression, Value>,
+        overrides: HashMap<path::Expression, Value>,
+        sources: Vec<Box<dyn Source + Send + Sync>>,
+    },
+}
+
+impl Default for ConfigKind {
+    fn default() -> Self {
+        ConfigKind::Mutable {
+            defaults: HashMap::new(),
+            overrides: HashMap::new(),
+            sources: Vec::new(),
+        }
+    }
+}
+
+/// A prioritized configuration repository. It maintains a set of configuration sources, fetches
+/// values to populate those, and provides them according to the source's priority.
+#[derive(Default, Clone, Debug)]
+pub struct ConfigData {
+    kind: ConfigKind,
+    /// Root of the cached configuration.
+    pub cache: Value,
+}
+
+impl ConfigData {
+    /// Merge in a configuration property source.
+    pub fn merge<T>(&mut self, source: T) -> Result<&mut ConfigData>
+    where
+        T: 'static,
+        T: Source + Send + Sync,
+    {
+        match self.kind {
+            ConfigKind::Mutable {
+                ref mut sources, ..
+            } => {
+                sources.push(Box::new(source));
+            }
+        }
+
+        self.refresh()
+    }
+
+    /// Refresh the configuration cache with fresh data from added sources.
+    ///
+    /// Configuration is automatically refreshed after a mutation operation (`set`, `merge`,
+    /// `set_default`, etc.).
+    pub fn refresh(&mut self) -> Result<&mut ConfigData> {
+        self.cache = match self.kind {
+            // TODO: We need to actually merge in all the stuff.
+            ConfigKind::Mutable {
+                ref overrides,
+                ref sources,
+                ref defaults,
+            } => {
+                let mut cache: Value = HashMap::<String, Value>::new().into();
+
+                // Add defaults.
+                for (key, val) in defaults {
+                    key.set(&mut cache, val.clone());
+                }
+
+                // Add sources.
+                sources.collect_to(&mut cache)?;
+
+                // Add overrides.
+                for (key, val) in overrides {
+                    key.set(&mut cache, val.clone());
+                }
+
+                cache
+            }
+        };
+
+        Ok(self)
+    }
+
+    pub fn set_default<T>(&mut self, key: &str, value: T) -> Result<&mut ConfigData>
+    where
+        T: Into<Value>,
+    {
+        match self.kind {
+            ConfigKind::Mutable {
+                ref mut defaults, ..
+            } => {
+                defaults.insert(key.parse()?, value.into());
+            }
+        };
+
+        self.refresh()
+    }
+
+    pub fn set<T>(&mut self, key: &str, value: T) -> Result<&mut ConfigData>
+    where
+        T: Into<Value>,
+    {
+        match self.kind {
+            ConfigKind::Mutable {
+                ref mut overrides, ..
+            } => {
+                overrides.insert(key.parse()?, value.into());
+            }
+        };
+
+        self.refresh()
+    }
+
+    /// Attempt to deserialize the entire configuration into the requested type.
+    pub fn try_into<'de, T: Deserialize<'de>>(self) -> Result<T> {
+        T::deserialize(self)
+    }
+}
+
+impl Source for ConfigData {
+    fn clone_into_box(&self) -> Box<dyn Source + Send + Sync> {
+        Box::new((*self).clone())
+    }
+
+    fn collect(&self) -> Result<HashMap<String, Value>> {
+        self.cache.clone().into_table()
+    }
+}