import hashlib
import os
import shutil
import tempfile
import unittest
from contextlib import nullcontext
from io import StringIO

import requests
from huggingface_hub import snapshot_download

from sglang.srt.utils import kill_process_tree
from sglang.srt.utils.model_file_verifier import compute_sha256, verify
from sglang.test.ci.ci_register import register_cuda_ci
from sglang.test.test_utils import (
    DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
    DEFAULT_URL_FOR_TEST,
    popen_launch_server,
)

register_cuda_ci(est_time=120, suite="nightly-1-gpu", nightly=True)

MODEL_NAME = "Qwen/Qwen3-0.6B"


# ======== Base Test Classes ========


class _FakeModelTestCase(unittest.TestCase):

    FAKE_FILES = {
        "model.safetensors": b"fake safetensors content " * 100,
        "config.json": b'{"model_type": "llama"}',
        "tokenizer.json": b'{"version": "1.0"}',
    }

    def setUp(self):
        self.test_dir = tempfile.mkdtemp()
        for filename, content in self.FAKE_FILES.items():
            _create_test_file(self.test_dir, filename, content)

    def tearDown(self):
        shutil.rmtree(self.test_dir, ignore_errors=True)


class _RealModelTestCase(unittest.TestCase):

    @classmethod
    def setUpClass(cls):
        cls.original_model_path = snapshot_download(MODEL_NAME)

    def setUp(self):
        self.test_dir = tempfile.mkdtemp()
        shutil.copytree(self.original_model_path, self.test_dir, dirs_exist_ok=True)

    def tearDown(self):
        shutil.rmtree(self.test_dir, ignore_errors=True)


# ======== Unit Tests ========


class TestModelFileVerifier(_FakeModelTestCase):

    def test_compute_sha256(self):
        test_file = os.path.join(self.test_dir, "test.bin")
        content = b"hello world"
        with open(test_file, "wb") as f:
            f.write(content)

        result = compute_sha256(file_path=test_file)
        expected = hashlib.sha256(content).hexdigest()
        self.assertEqual(result, expected)


# ======== HuggingFace Tests ========


class TestModelFileVerifierHF(_RealModelTestCase):

    def test_verify_with_hf_checksums_source(self):
        verify(model_path=self.test_dir, checksums_source=MODEL_NAME)


# ======== Real Model E2E Tests ========


class TestModelFileVerifierWithRealModel(_RealModelTestCase):

    def _run_server_test(self, *, corrupt_weights: bool):
        corrupted_file = None
        if corrupt_weights:
            safetensors_files = [
                f for f in os.listdir(self.test_dir) if f.endswith(".safetensors")
            ]
            self.assertTrue(len(safetensors_files) > 0, "No safetensors files found")
            corrupted_file = safetensors_files[0]
            _flip_bit_in_file(os.path.join(self.test_dir, corrupted_file))

        stdout_io, stderr_io = StringIO(), StringIO()
        ctx = self.assertRaises(Exception) if corrupt_weights else nullcontext()
        with ctx:
            process = popen_launch_server(
                model=self.test_dir,
                base_url=DEFAULT_URL_FOR_TEST,
                timeout=DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
                other_args=["--model-checksum", MODEL_NAME],
                return_stdout_stderr=(stdout_io, stderr_io),
            )

        if corrupt_weights:
            output = stdout_io.getvalue() + stderr_io.getvalue()
            self.assertIn(corrupted_file, output)
            self.assertIn("mismatch", output.lower())
        else:
            try:
                response = requests.post(
                    f"{DEFAULT_URL_FOR_TEST}/generate",
                    json={"text": "Hello", "sampling_params": {"max_new_tokens": 8}},
                )
                self.assertEqual(response.status_code, 200)
                self.assertIn("text", response.json())
            finally:
                kill_process_tree(process.pid)

    def test_server_launch_with_checksum_intact(self):
        self._run_server_test(corrupt_weights=False)

    def test_server_launch_fails_with_corrupted_weights(self):
        self._run_server_test(corrupt_weights=True)


# ======== Test Utilities ========


def _create_test_file(directory: str, filename: str, content: bytes) -> str:
    path = os.path.join(directory, filename)
    with open(path, "wb") as f:
        f.write(content)
    return path


def _flip_bit_in_file(file_path: str, byte_offset: int = 100, bit_position: int = 0):
    file_size = os.path.getsize(file_path)
    assert (
        byte_offset < file_size
    ), f"byte_offset {byte_offset} >= file_size {file_size}"

    with open(file_path, "r+b") as f:
        f.seek(byte_offset)
        original_byte = f.read(1)[0]
        f.seek(byte_offset)
        f.write(bytes([original_byte ^ (1 << bit_position)]))


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