ADR 048: Multi Tire Gas Price System

message TierParams {
  uint32 priority = 1           // Tendermint mempool 中的优先级
  Coin initial_gas_price = 2    //
  uint32 parent_gas_target = 3  // 区块目标饱和度
  uint32 change_denominator = 4 // 决定变化速度
  Coin min_gas_price = 5        // 价格调整的可选下界
  Coin max_gas_price = 6        // 价格调整的可选上界
}

message Params {
  repeated TierParams tiers = 1;
}

def adjust_gas_price(gas_price, parent_gas_used, tier):
  if parent_gas_used == tier.parent_gas_target:
    return gas_price
  elif parent_gas_used > tier.parent_gas_target:
    gas_used_delta = parent_gas_used - tier.parent_gas_target
    gas_price_delta = max(gas_price * gas_used_delta // tier.parent_gas_target // tier.change_speed, 1)
    return gas_price + gas_price_delta
  else:
    gas_used_delta = parent_gas_target - parent_gas_used
    gas_price_delta = gas_price * gas_used_delta // parent_gas_target // tier.change_speed
    return gas_price - gas_price_delta

interface TieredTx:
  def tier(self) -> int:
    pass

def tx_tier(tx):
    if isinstance(tx, TieredTx):
      return tx.tier()
    else:
      # 自定义交易的默认层级
      return 0
    # 注意：我们可以按照“交易优先级”一节在这里添加更多规则 

class TierParams:
  '单个层级的 gas price 策略参数'
  priority: int           # Tendermint mempool 中的优先级
  initial_gas_price: Coin
  parent_gas_target: int
  change_speed: Decimal   # 0 表示不根据区块负载调整。

class Params:
    '协议参数'
    tiers: List[TierParams]

class State:
    '共识状态'
    # 上一个区块使用的总 gas；如果是第一个区块则为 None
    parent_gas_used: Optional[int]
    # 上一个区块中所有层级的 gas price
    gas_prices: List[Coin]

def begin_block():
    '调整 gas price'
    for i, tier in enumerate(Params.tiers):
        if State.parent_gas_used is None:
            # 为第一个区块初始化 gas price
	          State.gas_prices[i] = tier.initial_gas_price
        else:
            # 根据前一区块使用的 gas 调整 gas price
            State.gas_prices[i] = adjust_gas_price(State.gas_prices[i], State.parent_gas_used, tier)

def mempoolFeeTxHandler_checkTx(ctx, tx):
    # 验证者配置的 minimal-gas-price，在 deliver_tx 上下文中为 0
    validator_price = ctx.MinGasPrice()
    consensus_price = State.gas_prices[tx_tier(tx)]
    min_price = max(validator_price, consensus_price)

    # 0 表示 gas price cap 为无限大
    if tx.gas_price() > 0 and tx.gas_price() < min_price:
        return '手续费不足'
    return next_CheckTx(ctx, tx)

def txPriorityHandler_checkTx(ctx, tx):
    res, err := next_CheckTx(ctx, tx)
    # 将优先级传递给 Tendermint
    res.Priority = Params.tiers[tx_tier(tx)].priority
    return res, err

def end_block():
    '更新区块 gas 使用量'
    State.parent_gas_used = block_gas_meter.consumed()

message TierParams {
  uint32 priority = 1           // priority in tendermint mempool
  Coin initial_gas_price = 2    //
  uint32 parent_gas_target = 3  // the target saturation of block
  uint32 change_denominator = 4 // decides the change speed
  Coin min_gas_price = 5        // optional lower bound of the price adjustment
  Coin max_gas_price = 6        // optional upper bound of the price adjustment
}

message Params {
  repeated TierParams tiers = 1;
}

def adjust_gas_price(gas_price, parent_gas_used, tier):
  if parent_gas_used == tier.parent_gas_target:
    return gas_price
  elif parent_gas_used > tier.parent_gas_target:
    gas_used_delta = parent_gas_used - tier.parent_gas_target
    gas_price_delta = max(gas_price * gas_used_delta // tier.parent_gas_target // tier.change_speed, 1)
    return gas_price + gas_price_delta
  else:
    gas_used_delta = parent_gas_target - parent_gas_used
    gas_price_delta = gas_price * gas_used_delta // parent_gas_target // tier.change_speed
    return gas_price - gas_price_delta

interface TieredTx:
  def tier(self) -> int:
    pass

def tx_tier(tx):
    if isinstance(tx, TieredTx):
      return tx.tier()
    else:
      # default tier for custom transactions
      return 0
    # NOTE: we can add more rules here per "Tx Prioritization" section 

class TierParams:
  'gas price strategy parameters of one tier'
  priority: int           # priority in tendermint mempool
  initial_gas_price: Coin
  parent_gas_target: int
  change_speed: Decimal   # 0 means don't adjust for block load.

class Params:
    'protocol parameters'
    tiers: List[TierParams]

class State:
    'consensus state'
    # total gas used in last block, None when it's the first block
    parent_gas_used: Optional[int]
    # gas prices of last block for all tiers
    gas_prices: List[Coin]

def begin_block():
    'Adjust gas prices'
    for i, tier in enumerate(Params.tiers):
        if State.parent_gas_used is None:
            # initialized gas price for the first block
	          State.gas_prices[i] = tier.initial_gas_price
        else:
            # adjust gas price according to gas used in previous block
            State.gas_prices[i] = adjust_gas_price(State.gas_prices[i], State.parent_gas_used, tier)

def mempoolFeeTxHandler_checkTx(ctx, tx):
    # the minimal-gas-price configured by validator, zero in deliver_tx context
    validator_price = ctx.MinGasPrice()
    consensus_price = State.gas_prices[tx_tier(tx)]
    min_price = max(validator_price, consensus_price)

    # zero means infinity for gas price cap
    if tx.gas_price() > 0 and tx.gas_price() < min_price:
        return 'insufficient fees'
    return next_CheckTx(ctx, tx)

def txPriorityHandler_checkTx(ctx, tx):
    res, err := next_CheckTx(ctx, tx)
    # pass priority to tendermint
    res.Priority = Params.tiers[tx_tier(tx)].priority
    return res, err

def end_block():
    'Update block gas used'
    State.parent_gas_used = block_gas_meter.consumed()