from __future__ import annotations

"""Orchestrate the OSM station/track import and load pipeline."""

import argparse
import sys
from dataclasses import dataclass
from pathlib import Path
from typing import Callable, Sequence

from backend.app.core.osm_config import DEFAULT_REGIONS
from backend.scripts import (
    stations_import,
    stations_load,
    tracks_import,
    tracks_load,
)


@dataclass(slots=True)
class Stage:
    label: str
    runner: Callable[[list[str] | None], int]
    args: list[str]
    input_path: Path | None = None
    output_path: Path | None = None


def build_argument_parser() -> argparse.ArgumentParser:
    parser = argparse.ArgumentParser(
        description="Run the station and track import/load workflow in sequence.",
    )
    parser.add_argument(
        "--region",
        choices=[region.name for region in DEFAULT_REGIONS] + ["all"],
        default="all",
        help="Region selector forwarded to the import scripts (default: all).",
    )
    parser.add_argument(
        "--output-dir",
        type=Path,
        default=Path("data"),
        help="Directory where intermediate JSON payloads are stored (default: data/).",
    )
    parser.add_argument(
        "--stations-json",
        type=Path,
        help="Existing station JSON file to load; defaults to <output-dir>/osm_stations.json.",
    )
    parser.add_argument(
        "--tracks-json",
        type=Path,
        help="Existing track JSON file to load; defaults to <output-dir>/osm_tracks.json.",
    )
    parser.add_argument(
        "--skip-station-import",
        action="store_true",
        help="Skip the station import step (expects --stations-json to point to data).",
    )
    parser.add_argument(
        "--skip-station-load",
        action="store_true",
        help="Skip loading stations into PostGIS.",
    )
    parser.add_argument(
        "--skip-track-import",
        action="store_true",
        help="Skip the track import step (expects --tracks-json to point to data).",
    )
    parser.add_argument(
        "--skip-track-load",
        action="store_true",
        help="Skip loading tracks into PostGIS.",
    )
    parser.add_argument(
        "--dry-run",
        action="store_true",
        help="Print the planned stages without invoking Overpass or mutating the database.",
    )
    parser.add_argument(
        "--commit",
        dest="commit",
        action="store_true",
        default=True,
        help="Commit database changes produced by the load steps (default).",
    )
    parser.add_argument(
        "--no-commit",
        dest="commit",
        action="store_false",
        help="Rollback database changes after load steps (dry run).",
    )
    return parser


def _build_stage_plan(args: argparse.Namespace) -> list[Stage]:
    station_json = args.stations_json or args.output_dir / "osm_stations.json"
    track_json = args.tracks_json or args.output_dir / "osm_tracks.json"

    stages: list[Stage] = []

    if not args.skip_station_import:
        stages.append(
            Stage(
                label="Import stations",
                runner=stations_import.main,
                args=["--output", str(station_json), "--region", args.region],
                output_path=station_json,
            )
        )

    if not args.skip_station_load:
        load_args = [str(station_json)]
        if not args.commit:
            load_args.append("--no-commit")
        stages.append(
            Stage(
                label="Load stations",
                runner=stations_load.main,
                args=load_args,
                input_path=station_json,
            )
        )

    if not args.skip_track_import:
        stages.append(
            Stage(
                label="Import tracks",
                runner=tracks_import.main,
                args=["--output", str(track_json), "--region", args.region],
                output_path=track_json,
            )
        )

    if not args.skip_track_load:
        load_args = [str(track_json)]
        if not args.commit:
            load_args.append("--no-commit")
        stages.append(
            Stage(
                label="Load tracks",
                runner=tracks_load.main,
                args=load_args,
                input_path=track_json,
            )
        )

    return stages


def _describe_plan(stages: Sequence[Stage]) -> None:
    if not stages:
        print("No stages selected; nothing to do.")
        return

    print("Selected stages:")
    for stage in stages:
        detail = " ".join(stage.args) if stage.args else "<no args>"
        print(f"  - {stage.label}: {detail}")


def _execute_stage(stage: Stage) -> None:
    print(f"\n>>> {stage.label}")

    if stage.output_path is not None:
        stage.output_path.parent.mkdir(parents=True, exist_ok=True)

    if stage.input_path is not None and not stage.input_path.exists():
        raise RuntimeError(
            f"Expected input file {stage.input_path} for {stage.label}; run the import step first or provide an existing file."
        )

    try:
        exit_code = stage.runner(stage.args)
    except SystemExit as exc:  # argparse.error exits via SystemExit
        exit_code = int(exc.code or 0)

    if exit_code:
        raise RuntimeError(f"{stage.label} failed with exit code {exit_code}.")


def main(argv: list[str] | None = None) -> int:
    parser = build_argument_parser()
    args = parser.parse_args(argv)

    stages = _build_stage_plan(args)

    if args.dry_run:
        print("Dry run: the following stages would run in order.")
        _describe_plan(stages)
        return 0

    for stage in stages:
        _execute_stage(stage)

    print("\nOSM refresh pipeline completed successfully.")
    return 0


if __name__ == "__main__":
    sys.exit(main())