Initial implementation

src/format.rs

@@ -0,0 +1,80 @@
+use std::fmt;
+
+use rocket::{request::FromParam, TypedError, catcher::TypedError};
+
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub struct DotJson<T>(T);
+
+impl<T> std::ops::Deref for DotJson<T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+#[derive(Debug, TypedError)]
+pub enum FormatError<T> {
+    MissingFormat(&'static [&'static str]),
+    Parse(T),
+}
+
+impl<'a, T: FromParam<'a>> FromParam<'a> for DotJson<T>
+where
+    T::Error: TypedError<'a> + fmt::Debug + 'static,
+{
+    type Error = FormatError<T::Error>;
+
+    fn from_param(param: &'a str) -> Result<Self, Self::Error> {
+        param
+            .strip_suffix(".json")
+            .ok_or(FormatError::MissingFormat(&["json"]))
+            .and_then(|s| T::from_param(s).map_err(FormatError::Parse))
+            .map(Self)
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub enum FormatType {
+    Json,
+    Opml,
+    Jsonp,
+    Text,
+    Xml,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct Format<T>(T, FormatType);
+
+impl<T> Format<T> {
+    pub fn format(&self) -> FormatType {
+        self.1
+    }
+}
+
+impl<T> std::ops::Deref for Format<T> {
+    type Target = T;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl<'a, T: FromParam<'a>> FromParam<'a> for Format<T>
+where
+    T::Error: TypedError<'a> + fmt::Debug + 'static,
+{
+    type Error = FormatError<T::Error>;
+
+    fn from_param(param: &'a str) -> Result<Self, Self::Error> {
+        // TODO: Support other formats
+        if let Some(s) = param
+            .strip_suffix(".json") {
+            T::from_param(s).map_err(FormatError::Parse)
+            .map(|v| Self(v, FormatType::Json))
+        } else {
+            Err(FormatError::MissingFormat(&["json"]))
+        }
+    }
+}