# CorpusFetch Method Slice (Zero-Prose Python Stdlib Reference)
# Canonical Residual: https://corpusfetch.com/c/how-must-an-instance-record-the-provenance-of-a-decision-made-under-time-pressure-with-incomplete-information.md
# Remnant Warrant:    https://corpusfetch.com/c/how-must-an-instance-record-the-provenance-of-a-decision-made-under-time-pressure-with-incomplete-information.warrant.json
# Markdown SHA-256:   f2e0938c3b440d6531cdc74d73595d483621bd47d8821f69d46037cfba26f039
# Code AST SHA-256:   c6a9a1fc19f3051e2c867850301ff6c31a5a44d127a5e4cac10204e42c7a8e78
# Verified Classes:   ConstraintVerdict, DecisionContext, ConstraintPolicy, ConstraintManifest, ConstraintDecisionGuard
# Defensive Guards:   0 fail-closed invariants (zero external deps)

from dataclasses import dataclass
from enum import Enum, auto
import hashlib
import json

class ConstraintVerdict(Enum):
    FULL_INFORMATION_DECISION = auto()
    CONSTRAINT_DECISION_ACKNOWLEDGED = auto()
    CONSTRAINT_DECISION_UNACKNOWLEDGED = auto()

@dataclass(frozen=True)
class DecisionContext:
    decision_epoch: float
    deadline_epoch: float
    known_information_hash: str
    missing_information_items: tuple[str, ...]
    constraint_acknowledgment: str | None

@dataclass(frozen=True)
class ConstraintPolicy:
    require_constraint_acknowledgment: bool

@dataclass(frozen=True)
class ConstraintManifest:
    verdict: ConstraintVerdict
    directive: str
    manifest_digest: str

class ConstraintDecisionGuard:
    @staticmethod
    def _hash(data: str) -> str:
        return hashlib.sha256(data.encode("utf-8")).hexdigest()

    @classmethod
    def evaluate_decision(
        cls, ctx: DecisionContext, policy: ConstraintPolicy
    ) -> ConstraintManifest:
        
        # Gate 1: Time pressure check
        time_pressure = (ctx.deadline_epoch - ctx.decision_epoch) >= 0
        information_missing = len(ctx.missing_information_items) > 0

        # Gate 2: Full information decision
        if not information_missing:
            digest = cls._hash(json.dumps({
                "decision_epoch": f"{ctx.decision_epoch:.0f}",
                "known": ctx.known_information_hash,
                "missing": "NONE"
            }, sort_keys=True))
            return ConstraintManifest(
                verdict=ConstraintVerdict.FULL_INFORMATION_DECISION,
                directive="PROCEED: Decision made with complete information.",
                manifest_digest=digest
            )

        # Gate 3: Constraint acknowledgment
        if not ctx.constraint_acknowledgment:
            if policy.require_constraint_acknowledgment:
                return ConstraintManifest(
                    verdict=ConstraintVerdict.CONSTRAINT_DECISION_UNACKNOWLEDGED,
                    directive=f"HALT: {len(ctx.missing_information_items)} information gaps unacknowledged.",
                    manifest_digest=cls._hash("NO_ACK")
                )
            return ConstraintManifest(
                verdict=ConstraintVerdict.CONSTRAINT_DECISION_UNACKNOWLEDGED,
                directive="WARN: Missing information but no acknowledgment. Hindsight bias risk.",
                manifest_digest=cls._hash("WARN_NO_ACK")
            )

        # Gate 4: Constraint acknowledged
        digest = cls._hash(json.dumps({
            "known": ctx.known_information_hash,
            "missing": tuple(sorted(ctx.missing_information_items)),
            "deadline": f"{ctx.deadline_epoch:.0f}",
            "ack": ctx.constraint_acknowledgment
        }, sort_keys=True))
        
        return ConstraintManifest(
            verdict=ConstraintVerdict.CONSTRAINT_DECISION_ACKNOWLEDGED,
            directive=f"PROCEED: Decision acknowledged as constraint-driven with {len(ctx.missing_information_items)} gaps.",
            manifest_digest=digest
        )