"""Verifier node — the VERIFY-stage LangGraph node (design §3.3, §3.3.2 P3).

The verifier reads the authenticated CI results for a task's candidate diff and
either advances it to a draft PR or loops it back to the builders. The single
load-bearing rule from §3.3.2 boundary #4 is enforced structurally here:

    **The verifier *agent* cannot declare success.** Pass/fail is owned by the
    pure-code gate (:mod:`agent_team.ci_gate`) over the authenticated,
    patch-independent CI conclusion. The LLM verifier only ever reads *failures*
    to propose the next fix.

So this node calls :func:`agent_team.ci_gate.evaluate_ci_gate` for the decision
and consults an (optional, injectable) LLM **only** on a FAIL/BLOCK to author a
fix hint for the builders. The LLM is never asked whether the task passed.

State contract (mirrors :class:`agent_team.task_model.PipelineState`):

* reads  ``candidate_diff``, ``diff_hash`` (ledger hash), ``ci_results``;
* writes ``status``, ``current_phase``, ``review_verdicts`` (appends the gate
  verdict), and ``ci_results`` (annotated with the gate decision for
  provenance).

Transitions (the §3.3 "Stability + autonomy bounds" — the verifier must pass or
the task loops/holds, never ships):

* gate PASS  -> :class:`~agent_team.task_model.Phase.DONE`,
  :class:`~agent_team.task_model.TaskStatus.DONE` (verifier produced a draft PR).
* gate FAIL  -> :class:`~agent_team.task_model.Phase.BUILD`,
  :class:`~agent_team.task_model.TaskStatus.ACTIVE` (loop back to builders),
  unless the per-task build-loop budget is spent, in which case it PARKs.
* gate BLOCK -> :class:`~agent_team.task_model.Phase.PARKED`,
  :class:`~agent_team.task_model.TaskStatus.PARKED` — an ALARM-worthy trust
  violation (denylist hit, hash mismatch, ambiguous conclusion) is never auto-
  retried; it parks for human + GPT cross-review.

This module imports the committed foundation contracts verbatim and redefines
none of them. The LLM seam is injectable (mirroring
:func:`agent_team.billing.set_invoker`) so the node is pure-function testable
with no SDK or network.
"""

from __future__ import annotations

from dataclasses import dataclass
from datetime import datetime, timezone
from typing import Any, Callable, Mapping

from agent_team.ci_gate import GateDecision, GateResult, evaluate_ci_gate
from agent_team.task_model import Phase, PipelineState, TaskStatus

__all__ = [
    "DEFAULT_MAX_BUILD_LOOPS",
    "VerifierConfig",
    "set_fix_advisor",
    "verifier_node",
]

# Default cap on build<->verify loops before a still-failing task parks rather
# than spinning (§3.3 bound #6 "N failed build loops"). Configurable per task
# via :class:`VerifierConfig`.
DEFAULT_MAX_BUILD_LOOPS: int = 3


@dataclass
class VerifierConfig:
    """Per-invocation knobs for the verifier node (§3.3, §3.3.2).

    ``expected_run_id`` keys the gate to the exact CI run the verifier
    dispatched for this diff (a stale/substituted run id is a BLOCK).
    ``allowed_scope`` is the task's declared-scope path prefixes for the
    denylist boundary. ``max_build_loops`` caps build<->verify retries before
    the task parks. ``build_loops`` is the loops already consumed for this task
    (the coordinator threads it through state).
    """

    expected_run_id: str
    allowed_scope: list[str] | None = None
    max_build_loops: int = DEFAULT_MAX_BUILD_LOOPS
    build_loops: int = 0


# Fix-advisor seam: signature (gate_result, state) -> str. Consulted ONLY on a
# gate FAIL/BLOCK to author a fix hint for the builders from the *failure*
# details. Never consulted on PASS — the gate, not the LLM, owns success. The
# default returns no hint so an un-wired environment degrades to "loop back with
# no extra guidance" rather than crashing.
FixAdvisor = Callable[[GateResult, Mapping[str, Any]], str]


def _null_advisor(gate_result: GateResult, state: Mapping[str, Any]) -> str:
    return ""


_fix_advisor: FixAdvisor = _null_advisor


def set_fix_advisor(advisor: FixAdvisor) -> None:
    """Bind the LLM fix-advisor consulted on a gate FAIL/BLOCK.

    Leaves call this once at startup with an implementation that reads the gate
    failure reasons + the CI logs and authors a next-fix hint for the builders.
    Keeping it injectable keeps this node dependency-free and unit-testable, and
    structurally enforces that the advisor is only ever invoked on failure (this
    module never calls it on a PASS).
    """
    global _fix_advisor
    _fix_advisor = advisor


def _utc_now_iso() -> str:
    return datetime.now(timezone.utc).isoformat()


def _verdict(
    gate_result: GateResult,
    *,
    next_phase: Phase,
    build_loops: int,
    fix_hint: str = "",
) -> dict[str, Any]:
    """Build the review-verdict record appended to ``review_verdicts``."""
    return {
        "stage": "verify",
        "decision": gate_result.decision.value,
        "reasons": list(gate_result.reasons),
        "run_id": gate_result.run_id,
        "diff_hash": gate_result.diff_hash,
        "ci_conclusion": gate_result.ci_conclusion,
        "next_phase": next_phase.value,
        "build_loops": build_loops,
        "fix_hint": fix_hint,
        "at": _utc_now_iso(),
    }


def verifier_node(
    state: PipelineState,
    config: VerifierConfig,
) -> PipelineState:
    """Run the VERIFY stage: gate the CI result, decide the next phase.

    Pure function of ``state`` + ``config`` (the gate does no I/O; the optional
    fix-advisor is the only outbound call, and only on failure). Returns a
    **partial** :class:`PipelineState` update (``total=False``) carrying the new
    ``status``/``current_phase``, an appended ``review_verdicts`` entry, and a
    gate-annotated ``ci_results`` for provenance — the LangGraph reducer merges
    it into the durable thread state.

    Decision flow (§3.3.2 boundary #4 + §3.3 autonomy bounds):

    1. Call :func:`agent_team.ci_gate.evaluate_ci_gate` with the candidate diff,
       the ledger hash (``diff_hash``), the authenticated ``ci_results``, the
       ``expected_run_id``, and the task's ``allowed_scope``.
    2. PASS  -> advance to DONE (draft PR). The advisor is NOT consulted.
    3. FAIL  -> consult the fix-advisor for a hint, then loop back to BUILD —
       unless ``build_loops`` has reached ``max_build_loops``, in which case
       PARK (a task that keeps failing must hold, never ship: §3.3 bound #3/#6).
    4. BLOCK -> PARK + (advisor hint) for human + GPT cross-review. A trust
       violation is never auto-retried.
    """
    candidate_diff = state.get("candidate_diff")
    ledger_hash = state.get("diff_hash")
    ci_results = state.get("ci_results")

    if not isinstance(candidate_diff, str):
        # No diff to verify is itself a refuse-to-proceed: park for a human
        # rather than declaring anything. (A builder must have produced a diff
        # before VERIFY runs.)
        gate_result = GateResult(
            decision=GateDecision.BLOCK,
            reasons=["no candidate_diff present in state to verify"],
            run_id=config.expected_run_id,
            diff_hash=ledger_hash,
            ci_conclusion=None,
        )
    else:
        gate_result = evaluate_ci_gate(
            candidate_diff=candidate_diff,
            ledger_hash=ledger_hash,
            ci_result=ci_results,
            expected_run_id=config.expected_run_id,
            allowed_scope=config.allowed_scope,
        )

    annotated_ci = dict(ci_results) if isinstance(ci_results, Mapping) else {}
    annotated_ci["gate_decision"] = gate_result.decision.value
    annotated_ci["gate_reasons"] = list(gate_result.reasons)

    if gate_result.decision is GateDecision.PASS:
        verdict = _verdict(
            gate_result, next_phase=Phase.DONE, build_loops=config.build_loops
        )
        return {
            "status": TaskStatus.DONE.value,
            "current_phase": Phase.DONE.value,
            "review_verdicts": [verdict],
            "ci_results": annotated_ci,
            "updated_at": verdict["at"],
        }

    # Every non-PASS path consults the fix-advisor on the *failure* details.
    # This is the only place the LLM is touched, and it never decides success.
    fix_hint = _fix_advisor(gate_result, state)

    if gate_result.decision is GateDecision.FAIL:
        next_loops = config.build_loops + 1
        if next_loops >= config.max_build_loops:
            # Exhausted the build-loop budget: hold rather than spin (§3.3 #6).
            verdict = _verdict(
                gate_result,
                next_phase=Phase.PARKED,
                build_loops=next_loops,
                fix_hint=fix_hint,
            )
            verdict["reasons"].append(
                f"max build loops ({config.max_build_loops}) reached; parking"
            )
            return {
                "status": TaskStatus.PARKED.value,
                "current_phase": Phase.PARKED.value,
                "review_verdicts": [verdict],
                "ci_results": annotated_ci,
                "updated_at": verdict["at"],
            }
        verdict = _verdict(
            gate_result,
            next_phase=Phase.BUILD,
            build_loops=next_loops,
            fix_hint=fix_hint,
        )
        return {
            "status": TaskStatus.ACTIVE.value,
            "current_phase": Phase.BUILD.value,
            "review_verdicts": [verdict],
            "ci_results": annotated_ci,
            "updated_at": verdict["at"],
        }

    # GateDecision.BLOCK — trust violation. Park for human + GPT cross-review;
    # never auto-retried, never shipped.
    verdict = _verdict(
        gate_result,
        next_phase=Phase.PARKED,
        build_loops=config.build_loops,
        fix_hint=fix_hint,
    )
    return {
        "status": TaskStatus.PARKED.value,
        "current_phase": Phase.PARKED.value,
        "review_verdicts": [verdict],
        "ci_results": annotated_ci,
        "updated_at": verdict["at"],
    }