#!/usr/bin/env python3
"""runner_evidence.py — runtime execution placement evidence (RP2/#265).

Canonical rule: THE HEAVY RUNNER IS THE DESKTOP PC, NOT THE PI.
A desktop-heavy stage executed on the Pi must NOT count as valid acceptance.

This module captures ACTUAL runtime evidence — not configuration inference:
  - hostname of the executing machine
  - runner identity (from CI env vars when present, else "local")
  - runner labels/capabilities
  - execution class (desktop-heavy / pi-lightweight)
  - stage, process id, issue, research process id, timestamp

The evidence record travels with the stage result and is validated by the
placement gate BEFORE a stage result can be accepted.
"""

from __future__ import annotations

import os
import socket
import time
from datetime import datetime, timezone

# Hostname substrings that identify the Pi fleet. Conservative: match on
# the runner name labels actually registered in Gitea, plus obvious names.
PI_IDENTIFIERS = ("rune-pi", "rune-infra-pi", "raspberry", "-pi")

# Desktop runner identity (the only valid executor for desktop-heavy stages).
DESKTOP_RUNNER_LABEL = "rune-ci-desktop"

# Stages that require desktop-heavy execution (cognition, research, coding).
DESKTOP_HEAVY_STAGES = {
    "INWARD",
    "OUTWARD",
    "APPLICABILITY",
    "INNOVATION",
    "ADVERSARIAL",
    "SYNTHESIS",
    "QUALIFY",
}

# Lightweight forge/control work that MAY legitimately run on the Pi.
PI_LIGHTWEIGHT_OPERATIONS = {
    "issue_metadata",
    "label_change",
    "artifact_metadata",
    "process_state",
    "eligibility_check",
    "state_transition",
}


def _is_pi(name: str) -> bool:
    lowered = (name or "").lower()
    return any(marker in lowered for marker in PI_IDENTIFIERS)


def capture_execution_evidence(
    stage: str,
    issue: int | None = None,
    process_id: str | None = None,
    execution_class: str = "desktop-heavy",
) -> dict:
    """Capture WHERE this stage actually ran, from runtime facts.

    Never trust configuration alone — capture the live hostname and any
    runner identity present in the environment.
    """
    hostname = socket.gethostname()
    runner_name = os.environ.get("RUNNER_NAME") or os.environ.get("GITEA_RUNNER_NAME") or ("local:" + hostname)
    runner_labels = [l.strip() for l in os.environ.get("RUNNER_LABELS", "").split(",") if l.strip()] or [runner_name]

    return {
        "runner_hostname": hostname,
        "runner_name": runner_name,
        "runner_labels": runner_labels,
        "execution_class": execution_class,
        "stage": stage,
        "process_id": process_id or f"pid:{os.getpid()}",
        "issue_id": issue,
        "research_process_id": process_id,
        "timestamp": datetime.now(timezone.utc).isoformat(),
        "monotonic": time.monotonic(),
    }


def validate_placement(evidence: dict) -> tuple[bool, list[str]]:
    """Deterministic placement gate (henxel).

    Returns (accepted, violations). A desktop-heavy stage executed on the
    Pi is REJECTED — no silent fallback, no configuration-only inference.
    """
    violations = []
    stage = evidence.get("stage", "")
    klass = evidence.get("execution_class", "desktop-heavy")

    # Evidence completeness — identity must be actually captured
    for field in ("runner_hostname", "runner_name", "runner_labels", "execution_class", "stage", "timestamp"):
        if not evidence.get(field):
            violations.append(f"placement evidence missing field: {field}")

    if klass == "desktop-heavy":
        identity = evidence.get("runner_name", "") + " " + evidence.get("runner_hostname", "")
        if _is_pi(identity) or any(_is_pi(l) for l in evidence.get("runner_labels", [])):
            violations.append(
                f"PLACEMENT VIOLATION: desktop-heavy stage '{stage}' executed on Pi "
                f"(runner={evidence.get('runner_name')}, host={evidence.get('runner_hostname')}). "
                f"Rejected as valid acceptance — the heavy runner is the desktop PC, not the Pi."
            )
        # Desktop identity = Gitea runner label (rune-ci-desktop), the Gitea
        # runner NAME (rune-desktop), or a verified local desktop execution.
        # Pi rejection above already caught Pi markers — this is the allow-side.
        labels = " ".join(evidence.get("runner_labels", []))
        if (
            DESKTOP_RUNNER_LABEL not in identity
            and "rune-desktop" not in identity
            and DESKTOP_RUNNER_LABEL not in labels
            and "local:" not in evidence.get("runner_name", "")
        ):
            violations.append(
                f"runner '{evidence.get('runner_name')}' is not '{DESKTOP_RUNNER_LABEL}' "
                f"nor the registered rune-desktop runner, and not a verified local "
                f"desktop execution"
            )
    return (len(violations) == 0, violations)


def summarize_for_artifact(evidence: dict) -> dict:
    """Strip transient fields for embedding in a stage artifact."""
    return {k: v for k, v in evidence.items() if k != "monotonic"}