"""Read-only validation of recovered campaign authorization evidence."""

from __future__ import annotations

import hashlib
import json
from pathlib import Path
import stat
from typing import Any


class RecoveryEvidenceError(RuntimeError):
    pass


def _digest(path: Path) -> str:
    h = hashlib.sha256()
    with path.open("rb") as stream:
        for block in iter(lambda: stream.read(1024 * 1024), b""):
            h.update(block)
    return h.hexdigest()


def _secure_json(path: Path) -> dict[str, Any]:
    if path.is_symlink() or not path.is_file():
        raise RecoveryEvidenceError("RECOVERY_EVIDENCE_MISSING")
    info = path.stat(follow_symlinks=False)
    if info.st_uid != 0 or stat.S_IMODE(info.st_mode) & 0o022:
        raise RecoveryEvidenceError("RECOVERY_EVIDENCE_PERMISSIONS")
    try:
        value = json.loads(path.read_text(encoding="utf-8"))
    except (OSError, UnicodeDecodeError, json.JSONDecodeError) as exc:
        raise RecoveryEvidenceError("RECOVERY_EVIDENCE_INVALID") from exc
    if not isinstance(value, dict):
        raise RecoveryEvidenceError("RECOVERY_EVIDENCE_OBJECT_REQUIRED")
    return value


def load_recovered_authorization(path: str | Path) -> dict[str, Any]:
    """Verify the recovery receipt, sidecar, and all referenced immutable files."""
    receipt_path = Path(path)
    receipt = _secure_json(receipt_path)
    sidecar = receipt_path.with_suffix(receipt_path.suffix + ".sha256")
    if sidecar.is_symlink() or not sidecar.is_file():
        raise RecoveryEvidenceError("RECOVERY_DIGEST_SIDECAR_MISSING")
    expected = sidecar.read_text(encoding="ascii").split()[0]
    actual = _digest(receipt_path)
    if expected != actual:
        raise RecoveryEvidenceError("RECOVERY_DIGEST_MISMATCH")
    required = {
        "schema",
        "campaign_id",
        "original_event_id",
        "original_authorization_digest",
        "signed_grant_id",
        "signed_grant_digest",
        "task_id",
        "repository",
        "original_base_oid",
        "branch",
        "expected_branch_oid",
        "recovered_from_existing_evidence",
        "new_owner_interaction",
        "recovery_state",
        "production_side_effect_executed",
        "global_writes_enabled",
        "grant_consumed",
        "owner_authorization_consumed",
        "original_receipts_immutable",
        "recovered_at",
        "evidence_files",
    }
    if set(receipt) != required or receipt["schema"] != "aios.owner-authorization-recovery.v1":
        raise RecoveryEvidenceError("RECOVERY_SCHEMA_INVALID")
    if receipt["recovered_from_existing_evidence"] is not True or receipt["new_owner_interaction"] is not False:
        raise RecoveryEvidenceError("RECOVERY_NOT_APPEND_ONLY")
    if receipt["production_side_effect_executed"] is not False or receipt["global_writes_enabled"] is not False:
        raise RecoveryEvidenceError("RECOVERY_SCOPE_INVALID")
    if receipt["recovery_state"] != "RECOVERED_PENDING_CONTINUATION_LEASE":
        raise RecoveryEvidenceError("RECOVERY_STATE_INVALID")
    evidence = receipt["evidence_files"]
    if not isinstance(evidence, list) or not evidence:
        raise RecoveryEvidenceError("RECOVERY_EVIDENCE_LIST_INVALID")
    for item in evidence:
        if not isinstance(item, dict) or set(item) != {"path", "sha256"}:
            raise RecoveryEvidenceError("RECOVERY_EVIDENCE_ENTRY_INVALID")
        target = Path(item["path"])
        if _digest(target) != item["sha256"]:
            raise RecoveryEvidenceError("RECOVERY_EVIDENCE_DIGEST_MISMATCH")
    return {
        "schema": receipt["schema"],
        "state": receipt["recovery_state"],
        "campaign_id": receipt["campaign_id"],
        "original_event_id": receipt["original_event_id"],
        "original_authorization_digest": receipt["original_authorization_digest"],
        "signed_grant_id": receipt["signed_grant_id"],
        "task_id": receipt["task_id"],
        "repository": receipt["repository"],
        "original_base_oid": receipt["original_base_oid"],
        "branch": receipt["branch"],
        "expected_branch_oid": receipt["expected_branch_oid"],
        "digest": actual,
        "new_owner_interaction": False,
    }