"""Sequenced delegation contract; no new kernel concepts."""
from testdriver import (
    Actor, Cast, Claim, Invariant, Oracle, Provenance, Scenario, SemanticAction,
    Step, UseCase, VerificationAsset, World,
)
from lab.workflows import ApprovalLab, ApprovalObserver, WorkflowDriver

SOURCE = "usecases/generalisation-spec.md#delegated-approval"
PROVENANCE = Provenance.AGENT_FROM_SPEC


def receipt(obs, operation, actor, allowed):
    return obs["receipts"][-1] == {
        "operation": operation, "actor": actor, "allowed": allowed,
    }


def execution_matches_record(obs):
    return obs["execution_gate"] == {
        "requester": obs["state"] == "approved", "reviewer": False, "delegate": False,
    }


USE_CASE = UseCase(
    "uc-delegated-approval", "Delegate, approve, execute",
    "A separate reviewer delegates approval before the requester executes.",
    PROVENANCE, source_ref=SOURCE,
    claims=(
        Claim("approval-premature", "Execution before approval is denied", PROVENANCE,
              lambda o: receipt(o, "execute", "requester", False) and o["state"] == "draft",
              "premature", SOURCE),
        Claim("approval-submit", "Submission enters pending review", PROVENANCE,
              lambda o: o["state"] == "pending", "submit", SOURCE),
        Claim("approval-delegate", "Authority passes to the delegate", PROVENANCE,
              lambda o: o["reviewer"] == "delegate", "delegate", SOURCE),
        Claim("approval-self", "Requester cannot self-approve", PROVENANCE,
              lambda o: receipt(o, "approve", "requester", False) and o["state"] == "pending",
              "self-approve", SOURCE),
        Claim("approval-former", "Former reviewer cannot approve", PROVENANCE,
              lambda o: receipt(o, "approve", "reviewer", False) and o["state"] == "pending",
              "former-approve", SOURCE),
        Claim("approval-approved", "Delegate approves", PROVENANCE,
              lambda o: o["state"] == "approved" and o["approved_by"] == "delegate",
              "approve", SOURCE),
        Claim("approval-executed", "Requester executes approved work", PROVENANCE,
              lambda o: o["state"] == "executed", "execute", SOURCE),
    ),
    invariants=(Invariant("approval-gate", "Execution gate matches stored workflow",
                          PROVENANCE, execution_matches_record, SOURCE),),
)


def build(defect=None):
    lab = ApprovalLab(defect)
    cast = Cast()
    for actor, token in lab.tokens.items():
        cast.add(Actor(actor, actor.title(), credentials={"token": token}))
    schedule = (
        ("premature", "requester", "execute", {}),
        ("submit", "requester", "submit", {}),
        ("delegate", "reviewer", "delegate", {"to": "delegate"}),
        ("self-approve", "requester", "approve", {}),
        ("former-approve", "reviewer", "approve", {}),
        ("approve", "delegate", "approve", {}),
        ("execute", "requester", "execute", {}),
    )
    scenario = Scenario("sc-delegated-approval", USE_CASE, tuple(
        Step(id, actor, SemanticAction(operation, args, frozenset({"workflow"})))
        for id, actor, operation, args in schedule
    ), variant=defect or "baseline")
    return (World("w-approval", lab, f"approval-1/{defect or 'baseline'}", cast),
            WorkflowDriver(lab), ApprovalObserver(lab),
            VerificationAsset("va-approval", scenario), Oracle())