How to compare POSIXTime to POSIXTimeRange?

[juliusfrost]

I am implementing the vesting contract in plutus-pioneers-program, and I need to compare the posix time provided in the datum is within the valid range specified in the script context. I have some skeleton code below:

from eopsin.prelude import *


@dataclass()
class VestingParams(PlutusData):
    beneficiary: PubKeyHash
    deadline: POSIXTime


def signed_by_beneficiary(datum: VestingParams, context: ScriptContext) -> bool:
    return datum.beneficiary in context.tx_info.signatories


def deadline_reached(datum: VestingParams, context: ScriptContext) -> bool:
    deadline: POSIXTime = datum.deadline
    valid_range: POSIXTimeRange = context.tx_info.valid_range
    # comparison logic here
    return False


def validator(datum: VestingParams, redeemer: None, context: ScriptContext) -> bool:
    assert signed_by_beneficiary(datum, context), "beneficiary's signature missing"
    assert deadline_reached(datum, context), "deadline not reached"
    return True

Looking at the prelude, POSIXTimeRange has LowerBoundPOSIXTime and UpperBoundPOSIXTime which both have ExtendedPOSIXTime = Union[NegInfPOSIXTime, FinitePOSIXTime, PosInfPOSIXTime]. But because I can't distinguish union types in eopsin due to isinstance not being implemented, I can't create my own comparison logic in my script. Do I need to wait until the isinstance implementation finished?

[juliusfrost]

Okay I found that isinstance is implemented in the condition of if isinstance(data, Union) where data is a Union type
https://github.com/ImperatorLang/eopsin/blob/cee2aa9bb2910732f283ff9ac69e870a94024770/eopsin/type_inference.py#L222-L262

So I made an unoptimized implementation of the contains comparison:

def contains(time: POSIXTime, time_range: POSIXTimeRange) -> bool:
    # Lower bound
    lower_comparison = False
    lower_bound_limit = time_range.lower_bound.limit
    lower_bound_closed = time_range.lower_bound.closed
    if isinstance(lower_bound_limit, FinitePOSIXTime):
        lower_time = lower_bound_limit.time
        if isinstance(lower_bound_closed, TrueData):
            lower_comparison = lower_time <= time
        else:
            lower_comparison = lower_time < time
    if isinstance(lower_bound_limit, NegInfPOSIXTime):
        lower_comparison = True
    # Upper bound
    upper_comparison = False
    upper_bound_limit = time_range.upper_bound.limit
    upper_bound_closed = time_range.upper_bound.closed
    if isinstance(upper_bound_limit, FinitePOSIXTime):
        upper_time = upper_bound_limit.time
        if isinstance(upper_bound_closed, TrueData):
            upper_comparison = time <= upper_time
        else:
            upper_comparison = time < upper_time
    if isinstance(upper_bound_limit, PosInfPOSIXTime):
        upper_comparison = True
    return lower_comparison and upper_comparison

[nielstron]

Thats the way :) See also this reference implementation in the simple/native script emulator

https://github.com/ImperatorLang/eopsin/blob/example/simple_scripts/examples/smart_contracts/simple_script.py#L75

[nielstron]

Maybe we can include the function in the stdlib, there will likely be more people that need it.

[juliusfrost]

@nielstron Agreed. That would be very useful!