"""Deterministic incident workflow. Author: Sandeep Belgavi. Synthetic only."""
from dataclasses import dataclass

@dataclass(frozen=True)
class Checkpoint:
    incident: str
    stage: str = "new"
    category: str = ""
    evidence: str = ""

def advance(state, classifier, inventory):
    if not isinstance(state, Checkpoint) or not state.incident:
        raise ValueError("incident checkpoint required")
    if state.stage == "new":
        category = classifier(state.incident)
        if category not in {"latency", "availability"}:
            raise ValueError("unsupported classification")
        return Checkpoint(state.incident, "classified", category)
    if state.stage == "classified":
        if state.category not in {"latency", "availability"}:
            raise ValueError("invalid stored category")
        value = inventory.get(state.category)
        if not isinstance(value, str) or not value:
            raise ValueError("evidence missing")
        return Checkpoint(state.incident, "collected", state.category, value)
    if state.stage in {"collected", "ready"}:
        if state.category not in {"latency", "availability"} or not state.evidence:
            raise ValueError("incomplete checkpoint")
        return Checkpoint(state.incident, "ready", state.category, state.evidence)
    raise ValueError("unknown stage")

if __name__ == "__main__":
    state = Checkpoint("INC-42")
    for _ in range(3):
        state = advance(state, lambda _: "latency", {"latency": "fixture:L1"})
    print(f"stage={state.stage} category={state.category} evidence={state.evidence}")