import contextlib
import multiprocessing
import os
import subprocess
import tempfile

HEADERS: str = """
#include <bits/stdc++.h>
"""


def check_correctness(candidate, reference, cpp_type, task_id, completion_id):
    """
    Evaluates the functional correctness of a completion by running the test
    suite provided in the problem.

    :param completion_id: an optional completion ID so we can match
        the results later even if execution finishes asynchronously.
    """

    manager = multiprocessing.Manager()

    result = dict(
        task_id=task_id,
        completion_id=completion_id,
    )

    if cpp_type == "base":
        base_run_result = manager.list()
        process_case(
            unsafe_execute_cpp,
            candidate,
            reference["tests"],
            base_run_result,
            "c++17",
        )
        base_run_result = base_run_result[0]
        base_run_passed = base_run_result == "passed"
        base_run_compiled = (
            base_run_result == "passed"
            or base_run_result.startswith("failed: runtime error:")
        )
        result = {
            **result,
            **dict(
                base_run_passed=base_run_passed,
                base_run_compiled=base_run_compiled,
                base_run_result=base_run_result,
            ),
        }
    elif cpp_type == "sfinae":
        sfinae_run_result = manager.list()
        process_case(
            unsafe_execute_cpp,
            candidate,
            reference["tests"],
            sfinae_run_result,
            "c++17",
        )
        sfinae_constrain_result = manager.list()
        process_case(
            invalid_compile_cpp,
            candidate,
            reference["invalids"],
            sfinae_constrain_result,
            "c++17",
        )
        sfinae_run_result = sfinae_run_result[0]
        sfinae_constrain_result = sfinae_constrain_result[0]
        sfinae_run_passed = sfinae_run_result == "passed"
        sfinae_run_compiled = sfinae_run_passed or sfinae_run_result.startswith(
            "failed: runtime error:"
        )
        sfinae_constrain_passed = (
            sfinae_constrain_result == "passed" and sfinae_run_compiled
        )
        result = {
            **result,
            **dict(
                sfinae_run_passed=sfinae_run_passed,
                sfinae_run_compiled=sfinae_run_compiled,
                sfinae_run_result=sfinae_run_result,
                sfinae_constrain_passed=sfinae_constrain_passed,
                sfinae_constrain_result=sfinae_constrain_result,
            ),
        }
    elif cpp_type == "concepts":
        concepts_run_result = manager.list()
        process_case(
            unsafe_execute_cpp,
            candidate,
            reference["tests"],
            concepts_run_result,
            "c++20",
        )
        concepts_constrain_result = manager.list()
        process_case(
            invalid_compile_cpp,
            candidate,
            reference["invalids"],
            concepts_constrain_result,
            "c++20",
        )
        concepts_run_result = concepts_run_result[0]
        concepts_constrain_result = concepts_constrain_result[0]
        concepts_run_passed = concepts_run_result == "passed"
        concepts_run_compiled = (
            concepts_run_passed
            or concepts_run_result.startswith("failed: runtime error:")
        )
        concepts_constrain_passed = (
            concepts_constrain_result == "passed" and concepts_run_compiled
        )
        result = {
            **result,
            **dict(
                concepts_run_passed=concepts_run_passed,
                concepts_run_compiled=concepts_run_compiled,
                concepts_run_result=concepts_run_result,
                concepts_constrain_passed=concepts_constrain_passed,
                concepts_constrain_result=concepts_constrain_result,
            ),
        }
    else:
        raise ValueError(f"Unknown cpp_type: {cpp_type}")

    return result


def process_case(target, candidate, reference, result, cppstd):
    timeout = 60

    p = multiprocessing.Process(
        target=target,
        args=(candidate, reference, result, timeout, cppstd),
    )

    p.start()
    p.join(timeout=timeout + 5)
    if p.is_alive():
        p.kill()

    if not result:
        result.append("timed out")


def unsafe_execute_cpp(candidate, reference, result, timeout, cppstd):
    with create_tempdir():
        code = "\n".join([HEADERS, candidate, reference])
        open(f"test.cpp", "w").write(code)

        cpp_compiler = os.getenv("GENERICIFY_CLANG")
        compilation_result = subprocess.run(
            [cpp_compiler, f"-std={cppstd}", "test.cpp"],
            timeout=timeout,
            capture_output=True,
        )
        if compilation_result.returncode != 0:
            if compilation_result.stderr:
                err = compilation_result.stderr.decode()
            else:
                err = compilation_result.stdout.decode()
            result.append(f"failed: compilation error: {err}")
        else:
            try:
                exec_result = subprocess.run(
                    ["./a.out"], timeout=timeout, capture_output=True
                )

                if exec_result.returncode == 0:
                    result.append("passed")
                else:
                    if exec_result.stderr:
                        try:
                            err = exec_result.stderr.decode()
                        except:
                            err = exec_result.stderr
                    else:
                        try:
                            err = exec_result.stdout.decode()
                        except:
                            err = exec_result.stdout
                    result.append(f"failed: runtime error: {err}")

            except subprocess.TimeoutExpired as e:
                result.append("timed out")


def invalid_compile_cpp(candidate, reference, result, timeout, cppstd):
    with create_tempdir():
        code = "\n".join([HEADERS, candidate, reference])
        open(f"invalid.cpp", "w").write(code)

        cpp_compiler = os.getenv("GENERICIFY_CLANG")
        compilation_result = subprocess.run(
            [cpp_compiler, f"-std={cppstd}", "invalid.cpp"],
            timeout=timeout,
            capture_output=True,
        )

        if compilation_result.stderr:
            err = compilation_result.stderr.decode()
        else:
            err = compilation_result.stdout.decode()

        if compilation_result.returncode != 1:
            result.append(f"failed: compilation succeeded: {err}")
        else:
            if "note: candidate template ignored" in err:
                result.append("passed")
            else:
                result.append("failed: improperly constrained: {err}")


@contextlib.contextmanager
def create_tempdir():
    with tempfile.TemporaryDirectory() as dirname:
        with chdir(dirname):
            yield dirname


@contextlib.contextmanager
def chdir(root):
    if root == ".":
        yield
        return
    cwd = os.getcwd()
    os.chdir(root)
    try:
        yield
    except BaseException as exc:
        raise exc
    finally:
        os.chdir(cwd)