// 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 failure::{Fail, ResultExt};
use keychain::{Identifier, Keychain};
use util::LOGGER;
use util::secp::pedersen;
use api;
use core::global;
use core::core::transaction::ProofMessageElements;
use types::{Error, ErrorKind, OutputData, OutputStatus, WalletConfig, WalletData};
use byteorder::{BigEndian, ByteOrder};

pub fn get_chain_height(config: &WalletConfig) -> Result<u64, Error> {
	let url = format!("{}/v1/chain", config.check_node_api_http_addr);

	match api::client::get::<api::Tip>(url.as_str()) {
		Ok(tip) => Ok(tip.height),
		Err(e) => {
			// if we got anything other than 200 back from server, bye
			error!(
				LOGGER,
				"get_chain_height: Restore failed... unable to contact API {}. Error: {}",
				config.check_node_api_http_addr,
				e
			);
			Err(e.context(ErrorKind::Node).into())
		}
	}
}

fn coinbase_status(output: &api::OutputPrintable) -> bool {
	match output.output_type {
		api::OutputType::Coinbase => true,
		api::OutputType::Transaction => false,
	}
}

pub fn outputs_batch_block(
	config: &WalletConfig,
	start_height: u64,
	end_height: u64,
) -> Result<Vec<api::BlockOutputs>, Error> {
	let query_param = format!(
		"start_height={}&end_height={}&include_rp",
		start_height, end_height
	);

	let url = format!(
		"{}/v1/chain/outputs/byheight?{}",
		config.check_node_api_http_addr, query_param,
	);

	match api::client::get::<Vec<api::BlockOutputs>>(url.as_str()) {
		Ok(outputs) => Ok(outputs),
		Err(e) => {
			// if we got anything other than 200 back from server, bye
			error!(
				LOGGER,
				"outputs_batch_block: Restore failed... unable to contact API {}. Error: {}",
				config.check_node_api_http_addr,
				e
			);
			Err(e.context(ErrorKind::Node))?
		}
	}
}

// TODO - wrap the many return values in a struct
fn find_outputs_with_key(
	keychain: &Keychain,
	block_outputs: api::BlockOutputs,
	key_iterations: &mut usize,
) -> Vec<(pedersen::Commitment, Identifier, u32, u64, u64, u64, bool)> {
	let mut wallet_outputs: Vec<(pedersen::Commitment, Identifier, u32, u64, u64, u64, bool)> =
		Vec::new();

	info!(
		LOGGER,
		"Scanning block {}, {} outputs, over {} key derivations",
		block_outputs.header.height,
		block_outputs.outputs.len(),
		*key_iterations,
	);

	// skey doesn't matter in this case
	let skey = keychain.derive_key_id(1).unwrap();
	for output in block_outputs.outputs.iter().filter(|x| !x.spent) {
		// attempt to unwind message from the RP and get a value.. note
		// this will only return okay if the value is included in the
		// message 3 times, indicating a strong match. Also, sec_key provided
		// to unwind in this case will be meaningless. With only the nonce known
		// only the first 32 bytes of the recovered message will be accurate
		let info = keychain
			.rewind_range_proof(&skey, output.commit, None, output.range_proof().unwrap())
			.unwrap();
		let message = ProofMessageElements::from_proof_message(info.message).unwrap();
		let value = message.value();
		if value.is_err() {
			continue;
		}
		// we have a match, now check through our key iterations to find a partial match
		let mut found = false;
		for i in 1..*key_iterations {
			let key_id = &keychain.derive_key_id(i as u32).unwrap();
			if !message.compare_bf_first_8(key_id) {
				continue;
			}
			found = true;
			// we have a partial match, let's just confirm
			let info = keychain
				.rewind_range_proof(key_id, output.commit, None, output.range_proof().unwrap())
				.unwrap();
			let message = ProofMessageElements::from_proof_message(info.message).unwrap();
			let value = message.value();
			if value.is_err() || !message.zeroes_correct() {
				continue;
			}
			let value = value.unwrap();
			info!(
				LOGGER,
				"Output found: {:?}, key_index: {:?}", output.commit, i,
			);

			// add it to result set here
			let commit_id = output.commit.0;

			let is_coinbase = coinbase_status(output);

			info!(LOGGER, "Amount: {}", value);

			let commit = keychain
				.commit_with_key_index(BigEndian::read_u64(&commit_id), i as u32)
				.expect("commit with key index");

			let height = block_outputs.header.height;
			let lock_height = if is_coinbase {
				height + global::coinbase_maturity()
			} else {
				0
			};

			wallet_outputs.push((
				commit,
				key_id.clone(),
				i as u32,
				value,
				height,
				lock_height,
				is_coinbase,
			));
		}
		if !found {
			warn!(
				LOGGER,
				"Very probable matching output found with amount: {} \
				 run restore again with a larger value of key_iterations to claim",
				message.value().unwrap()
			);
		}
	}
	debug!(
		LOGGER,
		"Found {} wallet_outputs for block {}",
		wallet_outputs.len(),
		block_outputs.header.height,
	);

	wallet_outputs
}

pub fn restore(
	config: &WalletConfig,
	keychain: &Keychain,
	key_derivations: u32,
) -> Result<(), Error> {
	// Don't proceed if wallet.dat has anything in it
	let is_empty = WalletData::read_wallet(&config.data_file_dir, |wallet_data| {
		Ok(wallet_data.outputs.len() == 0)
	}).context(ErrorKind::WalletData("could not read wallet"))?;
	if !is_empty {
		error!(
			LOGGER,
			"Not restoring. Please back up and remove existing wallet.dat first."
		);
		return Ok(());
	}

	// Get height of chain from node (we'll check again when done)
	let chain_height = get_chain_height(config)?;
	info!(
		LOGGER,
		"Starting restore: Chain height is {}.", chain_height
	);

	let batch_size = 100;
	// this will start here, then lower as outputs are found, moving backwards on
	// the chain
	let mut key_iterations = key_derivations as usize;
	let mut h = chain_height;
	while {
		let end_batch = h;
		if h >= batch_size {
			h -= batch_size;
		} else {
			h = 0;
		}
		let mut blocks = outputs_batch_block(config, h + 1, end_batch)?;
		blocks.reverse();

		let _ = WalletData::with_wallet(&config.data_file_dir, |wallet_data| {
			for block in blocks {
				let result_vec = find_outputs_with_key(keychain, block, &mut key_iterations);
				if result_vec.len() > 0 {
					for output in result_vec.clone() {
						let root_key_id = keychain.root_key_id();
						// Just plonk it in for now, and refresh actual values via wallet info
						// command later
						wallet_data.add_output(OutputData {
							root_key_id: root_key_id.clone(),
							key_id: output.1.clone(),
							n_child: output.2,
							value: output.3,
							status: OutputStatus::Unconfirmed,
							height: output.4,
							lock_height: output.5,
							is_coinbase: output.6,
							block: None,
							merkle_proof: None,
						});
					}
				}
			}
		});
		h > 0
	} {}
	Ok(())
}