"""``explicit-c2`` — independent dual-compile of a candidate (``docs/02`` §7).

The one implemented subcommand, ``dual-compile``, runs the C2 compiler over a
single candidate described by a JSON file: it builds the two pinned model
clients (proposer = Qwen3.5-9B, verifier = Gemma-4-12B-it) from the resource
manifest, sends the §7.1 independent request to each, and reconciles their
outputs through the §7.2/§7.3 gate. The two ``compiled_program`` records and the
:class:`C2Outcome` are written to ``--output``.

Model calls go through the real :class:`HfModelClient`, which is **gated and
never fakes a response**: when a pinned snapshot is absent, LFS-pointer-only,
or the accelerator/``transformers`` stack is missing, it raises
:class:`ModelUnavailable`. The CLI surfaces that as exit code ``2`` with a
``BLOCKED`` notice — the candidate is skipped, never substituted (runbook:
blocked → skip, never replace). A successful dual-compile exits ``0``; a bad
candidate/config exits ``1``.

Candidate sourcing at scale (selecting ChartQA-H / MMK12 / MMR1-RL / MMMU rows
and building their worlds) is the P11 assembler; this driver consumes one
candidate from disk so the gate is exercisable end-to-end before P11 lands.
"""

from __future__ import annotations

import argparse
import json
import sys
from pathlib import Path
from typing import Any

from ..c2 import C2Candidate, C2Compiler, ModelUnavailable
from ..c2.client import HfModelClient
from ..config import ConfigError, load_resources
from ..hashing import choices_sha256, question_sha256
from ..paths import repo_root
from ..resources import plan
from ._stub import dispatch

_PROG = "explicit-c2"

_SUBCOMMANDS = {
    "dual-compile": "Run the §7 independent dual-compile over one candidate (P4).",
}


# Roles pinned in ``configs/resources.yaml`` (ADR-0002).
_PROPOSER_ROLE = "program_proposer"
_VERIFIER_ROLE = "independent_program_verifier"


def _utc_now() -> str:
    from datetime import UTC, datetime

    return datetime.now(tz=UTC).strftime("%Y-%m-%dT%H:%M:%SZ")


def _load_resources(path: Path) -> Any:
    try:
        return load_resources(path)
    except (ConfigError, FileNotFoundError) as exc:
        print(f"{_PROG} dual-compile: resources load failed: {exc}", file=sys.stderr)
        raise _Handled(1) from exc


class _Handled(Exception):
    """Internal signal that a nonzero exit has already been printed."""

    def __init__(self, code: int) -> None:
        super().__init__()
        self.code = code


def _model_client(resources: Any, role: str, resources_path: Path) -> HfModelClient:
    """Build the :class:`HfModelClient` for the manifest entry with ``role``.

    Raises :class:`_Handled(1)` if no entry (or more than one) carries the role.
    """
    matches = [ref for ref in plan(resources) if ref.kind == "model" and ref.role == role]
    if not matches:
        disabled_role = f"disabled_future_c2_{role}"
        disabled = [
            entry
            for entry in resources.models.values()
            if getattr(entry, "role", None) == disabled_role
        ]
        if disabled:
            print(
                f"{_PROG} dual-compile: BLOCKED — {role!r} is disabled for the v1 release",
                file=sys.stderr,
            )
            raise _Handled(2)
        print(
            f"{_PROG} dual-compile: no model with role {role!r} in {resources_path}",
            file=sys.stderr,
        )
        raise _Handled(1)
    if len(matches) > 1:
        print(
            f"{_PROG} dual-compile: multiple models with role {role!r}; expected exactly one",
            file=sys.stderr,
        )
        raise _Handled(1)
    ref = matches[0]
    return HfModelClient(
        logical_name=ref.logical_name,
        repo_id=ref.repo_id,
        revision=ref.revision,
        local_path=ref.local_path,
    )


def _load_candidate(path: Path) -> C2Candidate:
    """Parse a candidate JSON file into a :class:`C2Candidate`.

    The file carries ``base_id``, ``dsl``, ``question_text``, ``choices``
    (``[{key, text}, ...]``), ``image_sha256``, and ``world``. The question/
    choices hashes are computed from the text when not supplied, so the caller
    cannot accidentally desync them.
    """
    try:
        raw = json.loads(path.read_text(encoding="utf-8"))
    except (OSError, json.JSONDecodeError) as exc:
        print(f"{_PROG} dual-compile: cannot read candidate {path}: {exc}", file=sys.stderr)
        raise _Handled(1) from exc
    if not isinstance(raw, dict):
        print(f"{_PROG} dual-compile: candidate must be a JSON object: {path}", file=sys.stderr)
        raise _Handled(1)

    base_id = raw.get("base_id")
    dsl = raw.get("dsl")
    question_text = raw.get("question_text")
    choices_raw = raw.get("choices")
    world = raw.get("world")
    if not (isinstance(base_id, str) and isinstance(dsl, str) and isinstance(question_text, str)):
        print(
            f"{_PROG} dual-compile: candidate needs string base_id, dsl, question_text: {path}",
            file=sys.stderr,
        )
        raise _Handled(1)
    if dsl not in ("plotqa_dsl_v1", "geometry_dsl_v1", "table_dsl_v1"):
        print(f"{_PROG} dual-compile: unknown dsl {dsl!r}: {path}", file=sys.stderr)
        raise _Handled(1)
    if not isinstance(choices_raw, list) or not isinstance(world, dict):
        print(
            f"{_PROG} dual-compile: candidate needs list 'choices' and object 'world': {path}",
            file=sys.stderr,
        )
        raise _Handled(1)

    choices: tuple[tuple[str, str], ...] = tuple(
        (str(c["key"]), str(c["text"])) for c in choices_raw
    )
    q_sha = raw.get("question_sha256") or question_sha256(question_text)
    c_sha = raw.get("choices_sha256") or choices_sha256([{"key": k, "text": t} for k, t in choices])
    return C2Candidate(
        base_id=base_id,
        dsl=dsl,  # type: ignore[arg-type]
        question_sha256=q_sha,
        choices_sha256=c_sha,
        question_text=question_text,
        choices=choices,
        image_sha256=str(raw.get("image_sha256", "")),
        world=world,
    )


def _outcome_to_json(outcome: Any) -> dict[str, Any]:
    """Serialize a :class:`C2Outcome` to a JSON-safe dict."""
    return {
        "state": outcome.state,
        "accepted": outcome.accepted,
        "reason": outcome.reason,
        "canonical_hash_proposer": outcome.canonical_hash_proposer,
        "canonical_hash_verifier": outcome.canonical_hash_verifier,
        "full_answer_proposer": list(outcome.full_answer_proposer)
        if outcome.full_answer_proposer is not None
        else None,
        "full_answer_verifier": list(outcome.full_answer_verifier)
        if outcome.full_answer_verifier is not None
        else None,
        "mutation_evidence": [
            {
                "leaf": e.leaf,
                "kind": e.kind,
                "description": e.description,
                "proposer_status": e.proposer_status,
                "proposer_answer": e.proposer_answer,
                "verifier_status": e.verifier_status,
                "verifier_answer": e.verifier_answer,
                "agree": e.agree,
            }
            for e in outcome.mutation_evidence
        ],
        "proposer_record": outcome.proposer_record,
        "verifier_record": outcome.verifier_record,
    }


def cmd_dual_compile(argv: list[str]) -> int:
    parser = argparse.ArgumentParser(prog=f"{_PROG} dual-compile")
    parser.add_argument(
        "--candidate", type=Path, required=True, help="candidate JSON file (§7.1 evidence)."
    )
    parser.add_argument(
        "--resources",
        type=Path,
        default=repo_root() / "configs" / "resources.yaml",
    )
    parser.add_argument("--output", type=Path, required=True, help="output JSON path.")
    parser.add_argument("--seed", type=int, default=0, help="deterministic mutation-suite seed.")
    args = parser.parse_args(argv)

    try:
        resources = _load_resources(args.resources)
        candidate = _load_candidate(args.candidate)
        proposer = _model_client(resources, _PROPOSER_ROLE, args.resources)
        verifier = _model_client(resources, _VERIFIER_ROLE, args.resources)
    except _Handled as exc:
        return exc.code

    compiler = C2Compiler(proposer=proposer, verifier=verifier)
    try:
        outcome = compiler.compile(candidate, seed=args.seed)
    except ModelUnavailable as exc:
        # Blocked → skip, never substitute (runbook). Surface as exit 2, not a
        # faked success and not a silent empty output.
        print(f"{_PROG} dual-compile: BLOCKED — model unavailable: {exc}", file=sys.stderr)
        return 2

    payload = {
        "schema_version": 1,
        "produced_at": _utc_now(),
        "candidate_base_id": candidate.base_id,
        "seed": args.seed,
        "outcome": _outcome_to_json(outcome),
    }
    args.output.parent.mkdir(parents=True, exist_ok=True)
    args.output.write_text(json.dumps(payload, indent=2, sort_keys=True), encoding="utf-8")
    print(
        json.dumps(
            {"state": outcome.state, "accepted": outcome.accepted, "output": str(args.output)},
            sort_keys=True,
        )
    )
    return 0


_IMPLEMENTATIONS = {
    "dual-compile": cmd_dual_compile,
}


def main(argv: list[str] | None = None) -> int:
    # When invoked as a console entry point, ``argv`` is ``None`` and the real
    # arguments live on ``sys.argv``. Fall back to those (rather than the empty
    # list the stub dispatcher treats as "no subcommand") so the ``explicit-c2``
    # script is genuinely usable — never a faked success.
    if argv is None:
        argv = sys.argv[1:]
    return dispatch(_PROG, argv, _SUBCOMMANDS, _IMPLEMENTATIONS)


if __name__ == "__main__":
    raise SystemExit(main())