"""A precise failure must not be reported as a generic one.

``get_dataset_geojson`` wrapped the JSON parse, the metadata read, the CRS
resolution and the canonicalisation in one ``try``, and reported everything as
"Stored dataset is not valid JSON" with a 500. An operator whose dataset has an
unusable CRS was sent to inspect a file that parses perfectly well, and the
specific AppError the canonicaliser raised — with its own code and status —
never reached them.
"""

from __future__ import annotations

import json
from pathlib import Path
from uuid import uuid4

import pytest

from app.core.errors import AppError
from app.models import Dataset
from app.services.dataset_service import DatasetService
from app.services.vector_feature_service import VectorFeatureService


class FakeSession:
    def __init__(self, dataset: Dataset) -> None:
        self.dataset = dataset

    def get(self, _model, item_id):
        return self.dataset if item_id == self.dataset.id else None


def _dataset(tmp_path: Path, payload: str) -> Dataset:
    path = tmp_path / "features.geojson"
    path.write_text(payload, encoding="utf-8")
    return Dataset(
        id=uuid4(),
        project_id=uuid4(),
        name="features.geojson",
        dataset_type="geojson",
        source="test",
        status="ready",
        storage_path=str(path),
        crs="EPSG:4326",
    )


def test_a_valid_dataset_is_returned(tmp_path: Path) -> None:
    dataset = _dataset(
        tmp_path,
        json.dumps(
            {
                "type": "FeatureCollection",
                "features": [
                    {
                        "type": "Feature",
                        "geometry": {"type": "Point", "coordinates": [5.0, 51.0]},
                        "properties": {},
                    }
                ],
            }
        ),
    )

    result = DatasetService.get_dataset_geojson(FakeSession(dataset), dataset.id)

    assert result["type"] == "FeatureCollection"


def test_unparseable_bytes_are_reported_as_invalid_json(tmp_path: Path) -> None:
    dataset = _dataset(tmp_path, "{ not json")

    with pytest.raises(AppError) as exc_info:
        DatasetService.get_dataset_geojson(FakeSession(dataset), dataset.id)

    assert exc_info.value.code == "INVALID_GEOJSON"
    assert "JSON" in exc_info.value.message


def test_a_parseable_file_that_is_not_a_feature_collection_says_so(tmp_path: Path) -> None:
    """Valid JSON, wrong shape. Telling the operator it is not JSON sends them
    to inspect a file that parses perfectly well."""

    dataset = _dataset(tmp_path, json.dumps({"type": "Feature", "geometry": None}))

    with pytest.raises(AppError) as exc_info:
        DatasetService.get_dataset_geojson(FakeSession(dataset), dataset.id)

    assert exc_info.value.code == "INVALID_GEOJSON"
    assert "FeatureCollection" in exc_info.value.message
    # The canonicaliser's own status survives; it is a bad request, not a
    # server fault.
    assert exc_info.value.status_code == 400


def test_a_canonicalisation_failure_keeps_its_own_code(tmp_path: Path, monkeypatch) -> None:
    dataset = _dataset(tmp_path, json.dumps({"type": "FeatureCollection", "features": []}))

    def failing(*_args, **_kwargs):
        raise AppError(code="INVALID_CRS", message="Unusable source CRS", status_code=409)

    monkeypatch.setattr(VectorFeatureService, "canonicalize_geojson_payload", staticmethod(failing))

    with pytest.raises(AppError) as exc_info:
        DatasetService.get_dataset_geojson(FakeSession(dataset), dataset.id)

    assert exc_info.value.code == "INVALID_CRS"
    assert exc_info.value.status_code == 409


def test_an_unexpected_failure_still_becomes_a_server_error(tmp_path: Path, monkeypatch) -> None:
    """A genuine bug must not masquerade as a client mistake."""

    dataset = _dataset(tmp_path, json.dumps({"type": "FeatureCollection", "features": []}))

    def exploding(*_args, **_kwargs):
        raise RuntimeError("pyproj blew up")

    monkeypatch.setattr(VectorFeatureService, "canonicalize_geojson_payload", staticmethod(exploding))

    with pytest.raises(AppError) as exc_info:
        DatasetService.get_dataset_geojson(FakeSession(dataset), dataset.id)

    assert exc_info.value.status_code == 500
    assert exc_info.value.code == "DATASET_GEOJSON_UNREADABLE"