Move 'Envrionment' into its own source

1 files changed, 43 insertions, 0 deletions

diff --git a/src/env.rs b/src/env.rs
new file mode 100644
index 0000000..612b97d
--- /dev/null
+++ b/src/env.rs
@@ -0,0 +1,43 @@
+use std::env;
+use std::error::Error;
+
+use source;
+use value::Value;
+
+#[derive(Clone)]
+pub struct Environment {
+    /// Optional prefix that would restrict environment consideration
+    /// to only variables which begin with that prefix.
+    prefix: Option<String>,
+}
+
+impl Environment {
+    pub fn new<'a, T>(prefix: T) -> Environment
+        where T: Into<Option<&'a str>>
+    {
+        Environment { prefix: prefix.into().map(String::from) }
+    }
+}
+
+impl source::SourceBuilder for Environment {
+    fn build(&self) -> Result<Box<source::Source>, Box<Error>> {
+        Ok(Box::new(self.clone()))
+    }
+}
+
+impl source::Source for Environment {
+    fn get(&self, key: &str) -> Option<Value> {
+        let mut env_key = String::new();
+
+        // Apply prefix
+        if let Some(ref prefix) = self.prefix {
+            env_key.push_str(prefix);
+            env_key.push('_');
+        }
+
+        env_key.push_str(&key.to_uppercase());
+
+        // Attempt to retreive environment variable and coerce into a Value
+        env::var(env_key.clone()).ok().map(Value::from)
+    }
+}