chore(Embedded): impl Serialize to content id for it

- needed for template engines using serialization for
  data access

3 files changed, 47 insertions, 1 deletions

diff --git a/Cargo.toml b/Cargo.toml
index f6d63a6..605e1a7 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -21,6 +21,7 @@ failure = "0.1.1"
 futures = "0.1.14"
 vec1 = { git="https://github.com/1aim/vec1" }
 soft-ascii-string = "0.2.0"
+serde = { version="1.0.64", optional=true }
 
 
 
@@ -37,4 +38,5 @@ optional = true
 
 [features]
 default = []
-askama-engine = ["askama"]
\ No newline at end of file
+askama-engine = ["askama"]
+serialize-content-id = ["serde"]
\ No newline at end of file
diff --git a/src/lib.rs b/src/lib.rs
index 763eb10..6d4f430 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -11,6 +11,9 @@ extern crate soft_ascii_string;
 #[macro_use]
 extern crate vec1;
 
+#[cfg(feature="serialize-content-id")]
+extern crate serde;
+
 #[cfg(feature="askama-engine")]
 #[cfg_attr(test, macro_use)]
 extern crate askama;
diff --git a/src/resource/mod.rs b/src/resource/mod.rs
index 38e7123..9bcd090 100644
--- a/src/resource/mod.rs
+++ b/src/resource/mod.rs
@@ -3,11 +3,22 @@ use std::ops::Deref;
 use mail::Context;
 use headers::components::ContentId;
 use mail::Resource;
+#[cfg(feature="serialize-content-id")]
+use serde::{Serialize, Serializer, ser};
 
 pub use headers::components::DispositionKind as Disposition;
 
 mod impl_inspect;
 
+/// # Serialize (feature `serialize-content-id`)
+///
+/// If serialized this struct **turns into it's
+/// content id failing if it has no content id**.
+///
+/// Normally this struct would not be serializeable
+/// (Resource isn't) but for template engines which
+/// use serialization for data access serializing it
+/// to it's content id string is quite use full
 #[derive(Debug, Clone)]
 pub struct Embedded {
     content_id: Option<ContentId>,
@@ -70,6 +81,19 @@ impl Embedded {
     }
 }
 
+#[cfg(feature="serialize-content-id")]
+impl<'a> Serialize for Embedded {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        where S: Serializer
+    {
+        if let Some(cid) = self.content_id() {
+            cid.serialize(serializer)
+        } else {
+            Err(ser::Error::custom("can not serialize Embedded without content id"))
+        }
+    }
+}
+
 pub trait InspectEmbeddedResources {
     fn inspect_resources(&self, visitor: &mut FnMut(&Embedded));
     fn inspect_resources_mut(&mut self, visitor: &mut FnMut(&mut Embedded));
@@ -93,6 +117,15 @@ impl Into<Resource> for Embedded {
 }
 
 
+/// # Serialize (feature `serialize-content-id`)
+///
+/// If serialized this struct **turns into it's
+/// content id**.
+///
+/// Normally this struct would not be serializeable
+/// (Resource isn't) but for template engines which
+/// use serialization for data access serializing it
+/// to it's content id string is quite use full
 #[derive(Debug, Clone)]
 pub struct EmbeddedWithCId {
     inner: Embedded
@@ -138,6 +171,14 @@ impl EmbeddedWithCId {
     }
 }
 
+#[cfg(feature="serialize-content-id")]
+impl<'a> Serialize for EmbeddedWithCId {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+        where S: Serializer
+    {
+        self.content_id().serialize(serializer)
+    }
+}
 impl Into<Resource> for EmbeddedWithCId {
     fn into(self) -> Resource {
         let EmbeddedWithCId { inner } = self;