LP Token Methods

name: public(immutable(String[64]))

@external
def __init__(
    _name: String[64],
    _symbol: String[32],
    _coins: address[N_COINS],
    _math: address,
    _weth: address,
    _salt: bytes32,
    packed_precisions: uint256,
    packed_A_gamma: uint256,
    packed_fee_params: uint256,
    packed_rebalancing_params: uint256,
    packed_prices: uint256,
):

    WETH20 = _weth
    MATH = Math(_math)

    self.factory = msg.sender

    name = _name
    symbol = _symbol
    coins = _coins

    self.packed_precisions = packed_precisions  # <------- Precisions of coins
    #                            are calculated as 10**(18 - coin.decimals()).

    self.initial_A_gamma = packed_A_gamma  # <------------------- A and gamma.
    self.future_A_gamma = packed_A_gamma

    self.packed_rebalancing_params = packed_rebalancing_params  # <-- Contains
    #               rebalancing params: allowed_extra_profit, adjustment_step,
    #                                                         and ma_exp_time.

    self.packed_fee_params = packed_fee_params  # <-------------- Contains Fee
    #                                  params: mid_fee, out_fee and fee_gamma.

    self.price_scale_packed = packed_prices
    self.price_oracle_packed = packed_prices
    self.last_prices_packed = packed_prices
    self.last_prices_timestamp = block.timestamp
    self.xcp_profit_a = 10**18

    #         Cache DOMAIN_SEPARATOR. If chain.id is not CACHED_CHAIN_ID, then
    #     DOMAIN_SEPARATOR will be re-calculated each time `permit` is called.
    #                   Otherwise, it will always use CACHED_DOMAIN_SEPARATOR.
    #                       see: `_domain_separator()` for its implementation.
    NAME_HASH = keccak256(name)
    salt = _salt
    CACHED_CHAIN_ID = chain.id
    CACHED_DOMAIN_SEPARATOR = keccak256(
        _abi_encode(
            EIP712_TYPEHASH,
            NAME_HASH,
            VERSION_HASH,
            chain.id,
            self,
            salt,
        )
    )

    log Transfer(empty(address), self, 0)  # <------- Fire empty transfer from
    #                                       0x0 to self for indexers to catch.

symbol: public(immutable(String[32]))

@external
def __init__(
    _name: String[64],
    _symbol: String[32],
    _coins: address[N_COINS],
    _math: address,
    _weth: address,
    _salt: bytes32,
    packed_precisions: uint256,
    packed_A_gamma: uint256,
    packed_fee_params: uint256,
    packed_rebalancing_params: uint256,
    packed_prices: uint256,
):

    WETH20 = _weth
    MATH = Math(_math)

    self.factory = msg.sender

    name = _name
    symbol = _symbol
    coins = _coins

    self.packed_precisions = packed_precisions  # <------- Precisions of coins
    #                            are calculated as 10**(18 - coin.decimals()).

    self.initial_A_gamma = packed_A_gamma  # <------------------- A and gamma.
    self.future_A_gamma = packed_A_gamma

    self.packed_rebalancing_params = packed_rebalancing_params  # <-- Contains
    #               rebalancing params: allowed_extra_profit, adjustment_step,
    #                                                         and ma_exp_time.

    self.packed_fee_params = packed_fee_params  # <-------------- Contains Fee
    #                                  params: mid_fee, out_fee and fee_gamma.

    self.price_scale_packed = packed_prices
    self.price_oracle_packed = packed_prices
    self.last_prices_packed = packed_prices
    self.last_prices_timestamp = block.timestamp
    self.xcp_profit_a = 10**18

    #         Cache DOMAIN_SEPARATOR. If chain.id is not CACHED_CHAIN_ID, then
    #     DOMAIN_SEPARATOR will be re-calculated each time `permit` is called.
    #                   Otherwise, it will always use CACHED_DOMAIN_SEPARATOR.
    #                       see: `_domain_separator()` for its implementation.
    NAME_HASH = keccak256(name)
    salt = _salt
    CACHED_CHAIN_ID = chain.id
    CACHED_DOMAIN_SEPARATOR = keccak256(
        _abi_encode(
            EIP712_TYPEHASH,
            NAME_HASH,
            VERSION_HASH,
            chain.id,
            self,
            salt,
        )
    )

    log Transfer(empty(address), self, 0)  # <------- Fire empty transfer from
    #                                       0x0 to self for indexers to catch.

decimals: public(constant(uint8)) = 18

version: public(constant(String[8])) = "v2.0.0"

balanceOf: public(HashMap[address, uint256])

totalSupply: public(uint256)

event Transfer:
    sender: indexed(address)
    receiver: indexed(address)
    value: uint256

@external
def transfer(_to: address, _value: uint256) -> bool:
    """
    @dev Transfer token for a specified address
    @param _to The address to transfer to.
    @param _value The amount to be transferred.
    @return bool True on successful transfer. Reverts otherwise.
    """
    self._transfer(msg.sender, _to, _value)
    return True

@internal
def _transfer(_from: address, _to: address, _value: uint256):
    assert _to not in [self, empty(address)]

    self.balanceOf[_from] -= _value
    self.balanceOf[_to] += _value

    log Transfer(_from, _to, _value)

event Transfer:
    sender: indexed(address)
    receiver: indexed(address)
    value: uint256

@external
def transferFrom(_from: address, _to: address, _value: uint256) -> bool:
    """
    @dev Transfer tokens from one address to another.
    @param _from address The address which you want to send tokens from
    @param _to address The address which you want to transfer to
    @param _value uint256 the amount of tokens to be transferred
    @return bool True on successul transfer. Reverts otherwise.
    """
    _allowance: uint256 = self.allowance[_from][msg.sender]
    if _allowance != max_value(uint256):
        self._approve(_from, msg.sender, _allowance - _value)

    self._transfer(_from, _to, _value)
    return True

@internal
def _transfer(_from: address, _to: address, _value: uint256):
    assert _to not in [self, empty(address)]

    self.balanceOf[_from] -= _value
    self.balanceOf[_to] += _value

    log Transfer(_from, _to, _value)

event Approval:
    owner: indexed(address)
    spender: indexed(address)
    value: uint256

@external
def approve(_spender: address, _value: uint256) -> bool:
    """
    @notice Allow `_spender` to transfer up to `_value` amount
            of tokens from the caller's account.
    @dev Non-zero to non-zero approvals are allowed, but should
        be used cautiously. The methods increaseAllowance + decreaseAllowance
        are available to prevent any front-running that may occur.
    @param _spender The account permitted to spend up to `_value` amount of
                    caller's funds.
    @param _value The amount of tokens `_spender` is allowed to spend.
    @return bool Success
    """
    self._approve(msg.sender, _spender, _value)
    return True

@internal
def _approve(_owner: address, _spender: address, _value: uint256):
    self.allowance[_owner][_spender] = _value

    log Approval(_owner, _spender, _value)

allowance: public(HashMap[address, HashMap[address, uint256]])

event Approval:
    owner: indexed(address)
    spender: indexed(address)
    value: uint256

allowance: public(HashMap[address, HashMap[address, uint256]])

@external
def increaseAllowance(_spender: address, _add_value: uint256) -> bool:
    """
    @notice Increase the allowance granted to `_spender`.
    @dev This function will never overflow, and instead will bound
        allowance to max_value(uint256). This has the potential to grant an
        infinite approval.
    @param _spender The account to increase the allowance of.
    @param _add_value The amount to increase the allowance by.
    @return bool Success
    """
    cached_allowance: uint256 = self.allowance[msg.sender][_spender]
    allowance: uint256 = unsafe_add(cached_allowance, _add_value)

    if allowance < cached_allowance:  # <-------------- Check for an overflow.
        allowance = max_value(uint256)

    if allowance != cached_allowance:
        self._approve(msg.sender, _spender, allowance)

    return True    

@internal
def _approve(_owner: address, _spender: address, _value: uint256):
    self.allowance[_owner][_spender] = _value

    log Approval(_owner, _spender, _value)

event Approval:
    owner: indexed(address)
    spender: indexed(address)
    value: uint256

allowance: public(HashMap[address, HashMap[address, uint256]])

@external
def decreaseAllowance(_spender: address, _sub_value: uint256) -> bool:
    """
    @notice Decrease the allowance granted to `_spender`.
    @dev This function will never underflow, and instead will bound
        allowance to 0.
    @param _spender The account to decrease the allowance of.
    @param _sub_value The amount to decrease the allowance by.
    @return bool Success.
    """
    cached_allowance: uint256 = self.allowance[msg.sender][_spender]
    allowance: uint256 = unsafe_sub(cached_allowance, _sub_value)

    if cached_allowance < allowance:  # <------------- Check for an underflow.
        allowance = 0

    if allowance != cached_allowance:
        self._approve(msg.sender, _spender, allowance)

    return True    

@internal
def _approve(_owner: address, _spender: address, _value: uint256):
    self.allowance[_owner][_spender] = _value

    log Approval(_owner, _spender, _value)

event Approval:
    owner: indexed(address)
    spender: indexed(address)
    value: uint256

@external
def permit(
    _owner: address,
    _spender: address,
    _value: uint256,
    _deadline: uint256,
    _v: uint8,
    _r: bytes32,
    _s: bytes32,
) -> bool:
    """
    @notice Permit `_spender` to spend up to `_value` amount of `_owner`'s
            tokens via a signature.
    @dev In the event of a chain fork, replay attacks are prevented as
        domain separator is recalculated. However, this is only if the
        resulting chains update their chainId.
    @param _owner The account which generated the signature and is granting an
                allowance.
    @param _spender The account which will be granted an allowance.
    @param _value The approval amount.
    @param _deadline The deadline by which the signature must be submitted.
    @param _v The last byte of the ECDSA signature.
    @param _r The first 32 bytes of the ECDSA signature.
    @param _s The second 32 bytes of the ECDSA signature.
    @return bool Success.
    """
    assert _owner != empty(address)  # dev: invalid owner
    assert block.timestamp <= _deadline  # dev: permit expired

    nonce: uint256 = self.nonces[_owner]
    digest: bytes32 = keccak256(
        concat(
            b"\x19\x01",
            self._domain_separator(),
            keccak256(
                _abi_encode(
                    EIP2612_TYPEHASH, _owner, _spender, _value, nonce, _deadline
                )
            ),
        )
    )
    assert ecrecover(digest, _v, _r, _s) == _owner  # dev: invalid signature

    self.nonces[_owner] = unsafe_add(nonce, 1)  # <-- Unsafe add is safe here.
    self._approve(_owner, _spender, _value)
    return True  

@internal
def _approve(_owner: address, _spender: address, _value: uint256):
    self.allowance[_owner][_spender] = _value

    log Approval(_owner, _spender, _value)