ShortId implementation (and CompactBlock) (#637)

* [wip] short_id implementation (first attempt)
todo - make this more reusable (a trait?) so we can use it for inputs/outputs/kernels easily

* factor short_id support out into ShortIdentifiable trait

* block can now be converted to compact_block
rename existing block.compact() -> block.cut_through()

* expose compact block representation via block api endpoint
optional with ?compact query param

api/src/handlers.rs

@@ -385,9 +385,13 @@ impl Handler for ChainHandler {
 	}
 }
 
-// Gets block details given either a hash or height.
-// GET /v1/block/<hash>
-// GET /v1/block/<height>
+/// Gets block details given either a hash or height.
+/// GET /v1/blocks/<hash>
+/// GET /v1/blocks/<height>
+///
+/// Optionally return results as "compact blocks" by passing "?compact" query param
+/// GET /v1/blocks/<hash>?compact
+///
 pub struct BlockHandler {
 	pub chain: Arc<chain::Chain>,
 }
@@ -398,6 +402,11 @@ impl BlockHandler {
 		Ok(BlockPrintable::from_block(&block, self.chain.clone(), false))
 	}
 
+	fn get_compact_block(&self, h: &Hash) -> Result<CompactBlockPrintable, Error> {
+		let block = self.chain.clone().get_block(h).map_err(|_| Error::NotFound)?;
+		Ok(CompactBlockPrintable::from_compact_block(&block.as_compact_block()))
+	}
+
 	// Try to decode the string as a height or a hash.
 	fn parse_input(&self, input: String) -> Result<Hash, Error> {
 		if let Ok(height) = input.parse() {
@@ -426,8 +435,21 @@ impl Handler for BlockHandler {
 		}
 		let el = *path_elems.last().unwrap();
 		let h = try!(self.parse_input(el.to_string()));
-		let b = try!(self.get_block(&h));
-		json_response(&b)
+
+		let mut compact = false;
+		if let Ok(params) = req.get_ref::<UrlEncodedQuery>() {
+			if let Some(_) = params.get("compact") {
+				compact = true;
+			}
+		}
+
+		if compact {
+			let b = try!(self.get_compact_block(&h));
+			json_response(&b)
+		} else {
+			let b = try!(self.get_block(&h));
+			json_response(&b)
+		}
 	}
 }
 

api/src/types.rs

@@ -367,6 +367,30 @@ impl BlockPrintable {
 	}
 }
 
+#[derive(Debug, Serialize, Deserialize, Clone)]
+pub struct CompactBlockPrintable {
+	/// The block header
+	pub header: BlockHeaderPrintable,
+	/// Inputs (hex short_ids)
+	pub inputs: Vec<String>,
+	/// Outputs (hex short_ids)
+	pub outputs: Vec<String>,
+	/// Kernels (hex short_ids)
+	pub kernels: Vec<String>,
+}
+
+impl CompactBlockPrintable {
+	/// Convert a compact block into a printable representation suitable for api response
+	pub fn from_compact_block(cb: &core::CompactBlock) -> CompactBlockPrintable {
+		CompactBlockPrintable {
+			header: BlockHeaderPrintable::from_header(&cb.header),
+			inputs: cb.inputs.iter().map(|x| x.to_hex()).collect(),
+			outputs: cb.outputs.iter().map(|x| x.to_hex()).collect(),
+			kernels: cb.kernels.iter().map(|x| x.to_hex()).collect(),
+		}
+	}
+}
+
 // For wallet reconstruction, include the header info along with the
 // transactions in the block
 #[derive(Debug, Serialize, Deserialize, Clone)]