from __future__ import annotations

import json
from urllib.parse import urlparse

from sqlalchemy import select
from sqlalchemy.orm import Session

from app.config import settings
from app.models import Dataset, Source
from app.pipeline.download import materialize_source
from app.pipeline.osm_pbf import _raw_format
from app.pipeline.osm_replication import fetch_replication_state
from app.pipeline.utils import sha256_file


def run_osm_diff_source(session: Session, source: Source) -> Dataset:
    """Commit an OSM change file as a raw update artifact.

    Applying the diff to an authoritative OSM base extract is a separate step;
    this importer deliberately records the file without treating it as a
    complete visual route layer.
    """
    if _looks_like_update_directory(source.url):
        return _commit_update_directory_state(session, source)

    raw_path = materialize_source(source)
    raw_hash = sha256_file(raw_path)
    existing = session.scalar(
        select(Dataset)
        .where(Dataset.source_id == source.id, Dataset.kind == "osm_diff_raw", Dataset.sha256 == raw_hash)
        .order_by(Dataset.id.desc())
    )
    if existing is not None:
        return existing

    dataset = Dataset(
        source_id=source.id,
        kind="osm_diff_raw",
        local_path=str(raw_path),
        sha256=raw_hash,
        is_active=False,
        status="committed",
        metadata_json=json.dumps(
            {
                "stage": "raw_osm_diff",
                "raw_format": _raw_format(raw_path),
                "source_url": source.url,
            },
            indent=2,
        ),
    )
    session.add(dataset)
    session.flush()
    return dataset


def _commit_update_directory_state(session: Session, source: Source) -> Dataset:
    state = fetch_replication_state(source.url, timeout=settings.osm_diff_state_timeout_seconds)
    source_dir = settings.data_dir / "sources" / f"source_{source.id}"
    source_dir.mkdir(parents=True, exist_ok=True)
    state_path = source_dir / f"state_{state.sequence_number}.txt"
    state_path.write_text(
        "\n".join(f"{key}={value}" for key, value in sorted(state.raw.items())) + "\n",
        encoding="utf-8",
    )
    state_hash = sha256_file(state_path)
    existing = session.scalar(
        select(Dataset)
        .where(Dataset.source_id == source.id, Dataset.kind == "osm_diff_state", Dataset.sha256 == state_hash)
        .order_by(Dataset.id.desc())
    )
    if existing is not None:
        return existing
    dataset = Dataset(
        source_id=source.id,
        kind="osm_diff_state",
        local_path=str(state_path),
        sha256=state_hash,
        is_active=False,
        status="committed",
        metadata_json=json.dumps(
            {
                "stage": "osm_diff_state",
                "updates_url": source.url,
                "sequence_number": state.sequence_number,
                "timestamp": state.timestamp,
                "state": state.raw,
            },
            indent=2,
        ),
    )
    session.add(dataset)
    session.flush()
    return dataset


def _looks_like_update_directory(url: str) -> bool:
    lower_path = urlparse(url).path.lower()
    return lower_path.endswith("-updates") or lower_path.endswith("-updates/")