"""Reference Data Registry (Missão 5, Fase 1): the NEW admin-approved ingestion workflow, separate
from central/app/datasets/service.py's existing auto-activate methods (untouched, still used by the
9 pre-existing dataset kinds). A dataset registered here lands as DRAFT and only becomes VIGENTE
(superseding the previous VIGENTE of the same kind) after an explicit ADMIN approval of the diff -
"Nenhuma versão de dataset vira 'vigente' sem aprovação ADMIN do diff" (mission rule).
"""
from __future__ import annotations

from datetime import datetime, timezone

from sqlalchemy import select, update

from .models import Dataset

STATUSES = ("DRAFT", "APPROVED", "VIGENTE", "OBSOLETO", "REJECTED")


class RegistryError(Exception):
    pass


def register_draft(session, *, kind: str, provider: str, source_url: str, sha256: str, version_label: str,
                   act: str = "", valid_from: str | None = None, valid_to: str | None = None, record_count: int = 0,
                   parse_errors: dict | None = None, licence_terms: str | None = None, raw_file_path: str | None = None,
                   file_size_bytes: int | None = None, submitted_by: str | None = None) -> Dataset:
    """Registers a new dataset submission as DRAFT. If this exact (provider, sha256) already exists
    under ANY status, returns it unchanged (idempotent re-submission of an unchanged official file -
    e.g. re-downloading the same official NCM table produces byte-identical content) instead of
    creating a duplicate row (the (provider, sha256) constraint would refuse it anyway)."""
    existing = session.scalar(select(Dataset).where(Dataset.provider == provider, Dataset.sha256 == sha256))
    if existing:
        return existing
    dataset = Dataset(kind=kind, provider=provider, sha256=sha256, version_label=version_label, act=act, source_url=source_url,
                      downloaded_at=datetime.now(timezone.utc), status="DRAFT", record_count=record_count, licence_terms=licence_terms,
                      valid_from=valid_from, valid_to=valid_to, file_size_bytes=file_size_bytes, raw_file_path=raw_file_path,
                      parse_errors=parse_errors or {}, submitted_by=submitted_by)
    session.add(dataset)
    session.commit()
    return dataset


def diff_against_vigente(session, dataset: Dataset) -> dict:
    """A summary an ADMIN reviews before approving: what the current VIGENTE of the same kind looks
    like vs this DRAFT - never the row-by-row content (that lives in the kind-specific entry tables),
    just the registry-level facts that matter for an approval decision."""
    current = session.scalar(select(Dataset).where(Dataset.kind == dataset.kind, Dataset.status == "VIGENTE"))
    return {
        "kind": dataset.kind,
        "draft": {"id": dataset.id, "version_label": dataset.version_label, "sha256": dataset.sha256, "record_count": dataset.record_count,
                  "valid_from": dataset.valid_from, "valid_to": dataset.valid_to, "parse_errors": dataset.parse_errors},
        "current_vigente": None if current is None else {"id": current.id, "version_label": current.version_label, "sha256": current.sha256,
                                                          "record_count": current.record_count, "valid_from": current.valid_from, "valid_to": current.valid_to},
        "record_count_delta": None if current is None else dataset.record_count - current.record_count,
        "is_first_version": current is None,
        "sha256_unchanged": current is not None and current.sha256 == dataset.sha256,
    }


def approve_draft(session, dataset_id: int, *, admin_name: str) -> Dataset:
    """DRAFT -> VIGENTE, superseding the previous VIGENTE of the same kind (OBSOLETO, never deleted).
    Refuses a dataset that isn't DRAFT, and refuses a dataset with recorded parse errors (must be
    re-submitted clean - an ADMIN cannot approve past a known parsing problem)."""
    dataset = session.get(Dataset, dataset_id)
    if dataset is None:
        raise RegistryError("dataset not found")
    if dataset.status != "DRAFT":
        raise RegistryError(f"only a DRAFT dataset can be approved (current status: {dataset.status})")
    if dataset.parse_errors:
        raise RegistryError("dataset has recorded parse errors - re-submit a clean version")
    session.execute(update(Dataset).where(Dataset.kind == dataset.kind, Dataset.status == "VIGENTE").values(status="OBSOLETO"))
    dataset.status = "VIGENTE"
    dataset.approved_by = admin_name
    dataset.approved_at = datetime.now(timezone.utc)
    session.commit()
    return dataset


def reject_draft(session, dataset_id: int, *, admin_name: str) -> Dataset:
    dataset = session.get(Dataset, dataset_id)
    if dataset is None:
        raise RegistryError("dataset not found")
    if dataset.status != "DRAFT":
        raise RegistryError(f"only a DRAFT dataset can be rejected (current status: {dataset.status})")
    dataset.status = "REJECTED"
    dataset.approved_by = admin_name
    dataset.approved_at = datetime.now(timezone.utc)
    session.commit()
    return dataset


def list_registry(session) -> list[Dataset]:
    return list(session.scalars(select(Dataset).where(Dataset.status.in_(STATUSES)).order_by(Dataset.kind, Dataset.downloaded_at.desc())))