from __future__ import annotations

import hashlib
import math
from pathlib import Path
import unittest

from app.main import run_system_xml_simulation


FIXTURE_PATH = (
    Path(__file__).resolve().parent
    / "fixtures"
    / "high_stiffness_explicit_rk45.xml"
)
ORIGINAL_XML_SHA256 = (
    "27048a99da0a21922d75785b760c3b5d04be3349b8aef6fbfedfd811d87ef1d5"
)


def short_explicit_rk45_xml() -> bytes:
    original = FIXTURE_PATH.read_bytes()
    canonical = original.replace(b"\r\n", b"\n").rstrip(b"\n")
    if hashlib.sha256(canonical).hexdigest() != ORIGINAL_XML_SHA256:
        raise AssertionError("The high-stiffness RK45 fixture differs from the user XML.")
    if original.count(b'tStop="10"') != 1:
        raise AssertionError("Expected one original simulation stop time.")
    if original.count(b'sampleStep="0.02"') != 1:
        raise AssertionError("Expected one original simulation sample step.")
    return original.replace(
        b'tStop="10"',
        b'tStop="0.005"',
        1,
    ).replace(
        b'sampleStep="0.02"',
        b'sampleStep="0.001"',
        1,
    )


class HighStiffnessExplicitRk45RegressionTests(unittest.TestCase):
    def test_short_user_model_crosses_the_early_stiff_limit_event(self) -> None:
        result = run_system_xml_simulation(
            short_explicit_rk45_xml(),
            cancel_check=lambda: False,
        )

        self.assertTrue(result["success"], result["message"])
        self.assertEqual(result["status"], "completed")
        self.assertFalse(result["partial"])
        self.assertEqual(result["simulatedUntil"], 0.005)
        self.assertNotIn("provided bounds", result["message"])

        integration = result["diagnostics"]["integration"]
        totals = integration["totals"]
        self.assertEqual(integration["method"], "RK45")
        self.assertGreaterEqual(totals["stateTransitionCount"], 1)
        self.assertGreaterEqual(totals["solverStartCount"], 2)

        series = result["series"]
        times = series["time"]
        self.assertEqual(times[0], 0.0)
        self.assertEqual(times[-1], 0.005)
        self.assertTrue(
            all(first < second for first, second in zip(times, times[1:]))
        )
        self.assertTrue(any(0.0 < time < 0.001 for time in times))
        for values in series.values():
            self.assertEqual(len(values), len(times))
            self.assertTrue(all(math.isfinite(value) for value in values))


if __name__ == "__main__":
    unittest.main()