#!/usr/bin/env python3
"""Common test generation classes and main function.

These are used both by generate_psa_tests.py and generate_bignum_tests.py.
"""

# Copyright The Mbed TLS Contributors
# SPDX-License-Identifier: Apache-2.0
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import argparse
import os
import posixpath
import re

from abc import ABCMeta, abstractmethod
from typing import Callable, Dict, Iterable, List, Type, TypeVar

from mbedtls_dev import build_tree
from mbedtls_dev import test_case

T = TypeVar('T') #pylint: disable=invalid-name


class BaseTarget(metaclass=ABCMeta):
    """Base target for test case generation.

    Attributes:
        count: Counter for test cases from this class.
        case_description: Short description of the test case. This may be
            automatically generated using the class, or manually set.
        target_basename: Basename of file to write generated tests to. This
            should be specified in a child class of BaseTarget.
        test_function: Test function which the class generates cases for.
        test_name: A common name or description of the test function. This can
            be the function's name, or a short summary of its purpose.
    """
    count = 0
    case_description = ""
    target_basename = ""
    test_function = ""
    test_name = ""

    def __init__(self) -> None:
        type(self).count += 1

    @abstractmethod
    def arguments(self) -> List[str]:
        """Get the list of arguments for the test case.

        Override this method to provide the list of arguments required for
        generating the test_function.

        Returns:
            List of arguments required for the test function.
        """
        pass

    def description(self) -> str:
        """Create a test description.

        Creates a description of the test case, including a name for the test
        function, and describing the specific test case. This should inform a
        reader of the purpose of the case. The case description may be
        generated in the class, or provided manually as needed.

        Returns:
            Description for the test case.
        """
        return "{} #{} {}".format(self.test_name, self.count, self.case_description)


    def create_test_case(self) -> test_case.TestCase:
        """Generate TestCase from the current object."""
        tc = test_case.TestCase()
        tc.set_description(self.description())
        tc.set_function(self.test_function)
        tc.set_arguments(self.arguments())

        return tc

    @classmethod
    def generate_tests(cls):
        """Generate test cases for the target subclasses.

        During generation, each class will iterate over any subclasses, calling
        this method in each.
        In abstract classes, no tests will be generated, as there is no
        function to generate tests for.
        In classes which do implement a test function, this should be overridden
        and a means to use `create_test_case()` should be added.
        """
        for subclass in sorted(cls.__subclasses__(), key=lambda c: c.__name__):
            yield from subclass.generate_tests()


class TestGenerator:
    """Generate test data."""
    def __init__(self, options) -> None:
        self.test_suite_directory = self.get_option(options, 'directory',
                                                    'tests/suites')

    @staticmethod
    def get_option(options, name: str, default: T) -> T:
        value = getattr(options, name, None)
        return default if value is None else value

    def filename_for(self, basename: str) -> str:
        """The location of the data file with the specified base name."""
        return posixpath.join(self.test_suite_directory, basename + '.data')

    def write_test_data_file(self, basename: str,
                             test_cases: Iterable[test_case.TestCase]) -> None:
        """Write the test cases to a .data file.

        The output file is ``basename + '.data'`` in the test suite directory.
        """
        filename = self.filename_for(basename)
        test_case.write_data_file(filename, test_cases)

    # Note that targets whose names contain 'test_format' have their content
    # validated by `abi_check.py`.
    TARGETS = {} # type: Dict[str, Callable[..., test_case.TestCase]]

    def generate_target(self, name: str, *target_args) -> None:
        """Generate cases and write to data file for a target.

        For target callables which require arguments, override this function
        and pass these arguments using super() (see PSATestGenerator).
        """
        test_cases = self.TARGETS[name](*target_args)
        self.write_test_data_file(name, test_cases)

def main(args, generator_class: Type[TestGenerator] = TestGenerator):
    """Command line entry point."""
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument('--list', action='store_true',
                        help='List available targets and exit')
    parser.add_argument('--list-for-cmake', action='store_true',
                        help='Print \';\'-separated list of available targets and exit')
    parser.add_argument('--directory', metavar='DIR',
                        help='Output directory (default: tests/suites)')
    parser.add_argument('targets', nargs='*', metavar='TARGET',
                        help='Target file to generate (default: all; "-": none)')
    options = parser.parse_args(args)
    build_tree.chdir_to_root()
    generator = generator_class(options)
    if options.list:
        for name in sorted(generator.TARGETS):
            print(generator.filename_for(name))
        return
    # List in a cmake list format (i.e. ';'-separated)
    if options.list_for_cmake:
        print(';'.join(generator.filename_for(name)
                       for name in sorted(generator.TARGETS)), end='')
        return
    if options.targets:
        # Allow "-" as a special case so you can run
        # ``generate_xxx_tests.py - $targets`` and it works uniformly whether
        # ``$targets`` is empty or not.
        options.targets = [os.path.basename(re.sub(r'\.data\Z', r'', target))
                           for target in options.targets
                           if target != '-']
    else:
        options.targets = sorted(generator.TARGETS)
    for target in options.targets:
        generator.generate_target(target)