Simplify TVL median calculations

[DenisCarriere]

Enhancement Proposal

Collect protocol's last 24 hours worth of 10 minute TVL data points (144 periods)

Requirements to receive reward: triggers report action

1. Does protocol contain 21 hours worth of TVL oracle data points (126 periods)?
2. Compute median TVL value in USD & EOS
3. Is EOS TVL above min_tvl_report (ex: 200K EOS)

if all statements are true, send rewards

Result

• More forgiving when Yield+ oracle missing updateall actions (3 hours of missing data would force a full recalibration instead of 1 hour per 8 hour period)
• Simplify TVL median computation logic

Current mechanic

eosio.yield-contracts/contracts/oracle.yield/oracle.yield.cpp

Lines 450 to 482 in 477dc15

	// generate report TVL to Yield+ Rewards
	void oracle::generate_report( const name protocol, const time_point_sec period )
	{
	// yield config
	auto config = get_config();
	asset tvl = { 0, EOS };
	asset usd = { 0, USD };
	// slice values into 3 buckets of 8 hours each
	uint64_t current_time_sec = current_time_point().sec_since_epoch();
	uint64_t period_1 = current_time_sec - EIGHT_HOURS * 3;
	uint64_t period_2 = period_1 + EIGHT_HOURS;
	uint64_t period_3 = period_2 + EIGHT_HOURS;
	// retrieve datapoint from timepoint
	// skip generating report if any median contains no TVL
	auto median_1 = get_median( protocol, period_1, period_2 );
	if ( !median_1.tvl.amount ) return;
	auto median_2 = get_median( protocol, period_2, period_3 );
	if ( !median_2.tvl.amount ) return;
	auto median_3 = get_median( protocol, period_3, current_time_sec );
	if ( !median_3.tvl.amount ) return;
	// compute the average of the 3 windows median
	tvl += (median_1.tvl + median_2.tvl + median_3.tvl ) / 3;
	usd += (median_1.usd + median_2.usd + median_3.usd ) / 3;
	// send oracle report to Yield+ Rewards
	yield::report_action report( config.yield_contract, { get_self(), "active"_n });
	report.send( protocol, period, PERIOD_INTERVAL, tvl, usd );
	}