// 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.

//! Transaction buinding functions

use api;
use core::ser;
use failure::ResultExt;
use keychain::{Identifier, Keychain};
use libtx::slate::Slate;
use libtx::{build, tx_fee};
use libwallet::client;
use libwallet::internal::{selection, updater};
use libwallet::types::{TxWrapper, WalletBackend};
use libwallet::{Error, ErrorKind};
use util;
use util::LOGGER;

/// Receive a tranaction, modifying the slate accordingly (which can then be
/// sent back to sender for posting)
pub fn receive_tx<T: WalletBackend>(wallet: &mut T, slate: &mut Slate) -> Result<(), Error> {
	// create an output using the amount in the slate
	let (_, mut context, receiver_create_fn) =
		selection::build_recipient_output_with_slate(wallet, slate).unwrap();

	// fill public keys
	let _ = slate.fill_round_1(
		wallet.keychain(),
		&mut context.sec_key,
		&context.sec_nonce,
		1,
	)?;

	// perform partial sig
	let _ = slate.fill_round_2(wallet.keychain(), &context.sec_key, &context.sec_nonce, 1)?;

	// Save output in wallet
	let _ = receiver_create_fn(wallet);

	Ok(())
}

/// Issue a new transaction to the provided sender by spending some of our
/// wallet
/// Outputs. The destination can be "stdout" (for command line) (currently
/// disabled) or a URL to the recipients wallet receiver (to be implemented).
/// TBD: this just does a straight http request to recipient.. split this out
/// somehow
pub fn issue_send_tx<T: WalletBackend>(
	wallet: &mut T,
	amount: u64,
	minimum_confirmations: u64,
	dest: &str,
	max_outputs: usize,
	selection_strategy_is_use_all: bool,
	fluff: bool,
) -> Result<(), Error> {
	// TODO: Stdout option, probably in a separate implementation
	if &dest[..4] != "http" {
		panic!(
			"dest formatted as {} but send -d expected stdout or http://IP:port",
			dest
		);
	}

	updater::refresh_outputs(wallet)?;

	// Get lock height
	let chain_tip = updater::get_tip_from_node(wallet.node_url())?;
	let current_height = chain_tip.height;
	// ensure outputs we're selecting are up to date
	updater::refresh_outputs(wallet)?;

	let lock_height = current_height;

	// Sender selects outputs into a new slate and save our corresponding keyss in
	// a transaction context. The secret key in our transaction context will be
	// randomly selected. This returns the public slate, and a closure that locks
	// our inputs and outputs once we're convinced the transaction exchange went
	// according to plan
	// This function is just a big helper to do all of that, in theory
	// this process can be split up in any way
	let (mut slate, mut context, sender_lock_fn) = selection::build_send_tx_slate(
		wallet,
		2,
		amount,
		current_height,
		minimum_confirmations,
		lock_height,
		max_outputs,
		selection_strategy_is_use_all,
	)?;

	// Generate a kernel offset and subtract from our context's secret key. Store
	// the offset in the slate's transaction kernel, and adds our public key
	// information to the slate
	let _ = slate.fill_round_1(
		wallet.keychain(),
		&mut context.sec_key,
		&context.sec_nonce,
		0,
	)?;

	let url = format!("{}/v1/wallet/foreign/receive_tx", dest);
	debug!(LOGGER, "Posting partial transaction to {}", url);
	let mut slate = match client::send_slate(&url, &slate, fluff).context(ErrorKind::Node) {
		Ok(s) => s,
		Err(e) => {
			error!(
				LOGGER,
				"Communication with receiver failed on SenderInitiation send. Aborting transaction"
			);
			return Err(e)?;
		}
	};

	let _ = slate.fill_round_2(wallet.keychain(), &context.sec_key, &context.sec_nonce, 0)?;

	// Final transaction can be built by anyone at this stage
	slate.finalize(wallet.keychain())?;

	// So let's post it
	let tx_hex = util::to_hex(ser::ser_vec(&slate.tx).unwrap());
	let url;
	if fluff {
		url = format!("{}/v1/pool/push?fluff", wallet.node_url(),);
	} else {
		url = format!("{}/v1/pool/push", wallet.node_url());
	}
	api::client::post(url.as_str(), &TxWrapper { tx_hex: tx_hex }).context(ErrorKind::Node)?;

	// All good so, lock our inputs
	sender_lock_fn(wallet)?;
	Ok(())
}

/// Issue a burn tx
pub fn issue_burn_tx<T: WalletBackend>(
	wallet: &mut T,
	amount: u64,
	minimum_confirmations: u64,
	max_outputs: usize,
) -> Result<(), Error> {
	let keychain = &Keychain::burn_enabled(wallet.keychain(), &Identifier::zero());

	let chain_tip = updater::get_tip_from_node(wallet.node_url())?;
	let current_height = chain_tip.height;

	let _ = updater::refresh_outputs(wallet);

	let key_id = keychain.root_key_id();

	// select some spendable coins from the wallet
	let coins = wallet.read_wallet(|wallet_data| {
		Ok(wallet_data.select_coins(
			key_id.clone(),
			amount,
			current_height,
			minimum_confirmations,
			max_outputs,
			false,
		))
	})?;

	debug!(LOGGER, "selected some coins - {}", coins.len());

	let fee = tx_fee(coins.len(), 2, selection::coins_proof_count(&coins), None);
	let (mut parts, _) = selection::inputs_and_change(&coins, wallet, current_height, amount, fee)?;

	// add burn output and fees
	parts.push(build::output(amount - fee, Identifier::zero()));

	// finalize the burn transaction and send
	let tx_burn = build::transaction(parts, &keychain)?;
	tx_burn.validate()?;

	let tx_hex = util::to_hex(ser::ser_vec(&tx_burn).unwrap());
	let url = format!("{}/v1/pool/push", wallet.node_url());
	let _: () =
		api::client::post(url.as_str(), &TxWrapper { tx_hex: tx_hex }).context(ErrorKind::Node)?;
	Ok(())
}

#[cfg(test)]
mod test {
	use keychain::Keychain;
	use libtx::build;

	#[test]
	// demonstrate that input.commitment == referenced output.commitment
	// based on the public key and amount begin spent
	fn output_commitment_equals_input_commitment_on_spend() {
		let keychain = Keychain::from_random_seed().unwrap();
		let key_id1 = keychain.derive_key_id(1).unwrap();

		let tx1 = build::transaction(vec![build::output(105, key_id1.clone())], &keychain).unwrap();
		let tx2 = build::transaction(vec![build::input(105, key_id1.clone())], &keychain).unwrap();

		assert_eq!(tx1.outputs[0].features, tx2.inputs[0].features);
		assert_eq!(tx1.outputs[0].commitment(), tx2.inputs[0].commitment());
	}
}