grin/api/src/handlers/utils.rs

// Copyright 2018 The Grin Developers
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use chain;
use core::core::{OutputFeatures, OutputIdentifier};
use failure::ResultExt;
use rest::*;
use std::sync::{Arc, Weak};
use types::*;
use util;
use util::secp::pedersen::Commitment;

// All handlers use `Weak` references instead of `Arc` to avoid cycles that
// can never be destroyed. These 2 functions are simple helpers to reduce the
// boilerplate of dealing with `Weak`.
pub fn w<T>(weak: &Weak<T>) -> Arc<T> {
	weak.upgrade().unwrap()
}

/// Retrieves an output from the chain given a commit id (a tiny bit iteratively)
pub fn get_output(
	chain: &Weak<chain::Chain>,
	id: &str,
) -> Result<(Output, OutputIdentifier), Error> {
	let c = util::from_hex(String::from(id)).context(ErrorKind::Argument(format!(
		"Not a valid commitment: {}",
		id
	)))?;
	let commit = Commitment::from_vec(c);

	// We need the features here to be able to generate the necessary hash
	// to compare against the hash in the output MMR.
	// For now we can just try both (but this probably needs to be part of the api
	// params)
	let outputs = [
		OutputIdentifier::new(OutputFeatures::DEFAULT_OUTPUT, &commit),
		OutputIdentifier::new(OutputFeatures::COINBASE_OUTPUT, &commit),
	];

	for x in outputs.iter() {
		if let Ok(_) = w(chain).is_unspent(&x) {
			let block_height = w(chain).get_header_for_output(&x).unwrap().height;
			return Ok((Output::new(&commit, block_height), x.clone()));
		}
	}
	Err(ErrorKind::NotFound)?
}