"""Tests for Prometheus metrics exposed by the OCR service.

Each test that asserts on a counter/gauge value uses a fresh CollectorRegistry
(see decision #3 on issue #652) to keep the metrics isolated between tests.
"""

from unittest.mock import AsyncMock, patch

import pytest
from httpx import ASGITransport, AsyncClient
from PIL import Image
from prometheus_client import CollectorRegistry

from main import app
from metrics import build_metrics


@pytest.fixture
def fresh_metrics(monkeypatch):
    """Replace the module-level `main.metrics` with one bound to a fresh registry."""
    registry = CollectorRegistry()
    test_metrics = build_metrics(registry)
    monkeypatch.setattr("main.metrics", test_metrics)
    return test_metrics


@pytest.mark.asyncio
async def test_metrics_endpoint_returns_200():
    """`GET /metrics` returns 200 with Prometheus exposition content."""
    with patch("main.kraken_engine.load_models"), \
         patch("main.load_spell_checker"):
        async with AsyncClient(transport=ASGITransport(app=app), base_url="http://test") as client:
            response = await client.get("/metrics")

    assert response.status_code == 200
    assert "text/plain" in response.headers.get("content-type", "")


@pytest.mark.asyncio
async def test_metrics_includes_http_request_metrics_after_ocr_call():
    """After a request to /ocr, `/metrics` exposes auto-instrumented http_* metrics."""
    mock_images = [Image.new("RGB", (100, 100))]
    mock_blocks = [{"pageNumber": 1, "x": 0.0, "y": 0.0, "width": 1.0, "height": 1.0,
                    "polygon": None, "text": "hi", "words": []}]

    with patch("main.kraken_engine.load_models"), \
         patch("main.load_spell_checker"), \
         patch("main._download_and_convert_pdf", new_callable=AsyncMock, return_value=mock_images), \
         patch("main.preprocess_page", side_effect=lambda img: img), \
         patch("main.surya_engine.extract_blocks", return_value=mock_blocks):
        async with AsyncClient(transport=ASGITransport(app=app), base_url="http://test") as client:
            # Models need to be loaded for /ocr to accept requests; force the flag.
            import main as main_module
            main_module._models_ready = True
            try:
                ocr_response = await client.post("/ocr", json={
                    "pdfUrl": "http://minio/doc.pdf",
                    "scriptType": "TYPEWRITER",
                    "language": "de",
                })
                assert ocr_response.status_code == 200, ocr_response.text

                metrics_response = await client.get("/metrics")
            finally:
                main_module._models_ready = False

    body = metrics_response.text
    assert "http_requests_total" in body
    assert "http_request_duration_seconds" in body


def test_build_metrics_registers_all_custom_metrics_on_given_registry():
    """`build_metrics` returns an OcrMetrics bound to the supplied registry."""
    registry = CollectorRegistry()
    metrics = build_metrics(registry)

    metric_names = {m.name for m in registry.collect()}
    expected = {
        "ocr_jobs",
        "ocr_pages",
        "ocr_skipped_pages",
        "ocr_words",
        "ocr_illegible_words",
        "ocr_processing_seconds",
        "ocr_training_runs",
        "ocr_model_accuracy",
        "ocr_models_ready",
    }
    assert expected <= metric_names, f"missing: {expected - metric_names}"

    # A second registry yields a separate container — no shared state.
    other_metrics = build_metrics(CollectorRegistry())
    assert metrics is not other_metrics