import glob
import io
import os
import sys
import importlib.metadata
import argparse
import traceback
import contextlib
from io import StringIO
import json
import subprocess
import re
import tempfile
import email.parser
import pathlib
import zipfile

from pyproject_requirements_txt import convert_requirements_txt


# Some valid Python version specifiers are not supported.
# Allow only the forms we know we can handle.
VERSION_RE = re.compile(r'[a-zA-Z0-9.-]+(\.\*)?')


class EndPass(Exception):
    """End current pass of generating requirements"""


# nb: we don't use functools.partial to be able to use pytest's capsys
# see https://github.com/pytest-dev/pytest/issues/8900
def print_err(*args, **kwargs):
    kwargs.setdefault('file', sys.stderr)
    print(*args, **kwargs)


try:
    from packaging.requirements import Requirement, InvalidRequirement
    from packaging.utils import canonicalize_name
except ImportError as e:
    print_err('Import error:', e)
    # already echoed by the %pyproject_buildrequires macro
    sys.exit(0)

# uses packaging, needs to be imported after packaging is verified to be present
from pyproject_convert import convert


@contextlib.contextmanager
def hook_call():
    captured_out = StringIO()
    with contextlib.redirect_stdout(captured_out):
        yield
    for line in captured_out.getvalue().splitlines():
        print_err('HOOK STDOUT:', line)


def guess_reason_for_invalid_requirement(requirement_str):
    if ':' in requirement_str:
        message = (
            'It might be an URL. '
            '%pyproject_buildrequires cannot handle all URL-based requirements. '
            'Add PackageName@ (see PEP 508) to the URL to at least require any version of PackageName.'
        )
        if '@' in requirement_str:
            message += ' (but note that URLs might not work well with other features)'
        return message
    if '/' in requirement_str:
        return (
            'It might be a local path. '
            '%pyproject_buildrequires cannot handle local paths as requirements. '
            'Use an URL with PackageName@ (see PEP 508) to at least require any version of PackageName.'
        )
    # No more ideas
    return None


class Requirements:
    """Requirement printer"""
    def __init__(self, get_installed_version, extras=None,
                 generate_extras=False, python3_pkgversion='3'):
        self.get_installed_version = get_installed_version
        self.extras = set()

        if extras:
            for extra in extras:
                self.add_extras(*extra.split(','))

        self.missing_requirements = False

        self.generate_extras = generate_extras
        self.python3_pkgversion = python3_pkgversion

    def add_extras(self, *extras):
        self.extras |= set(e.strip() for e in extras)

    @property
    def marker_envs(self):
        if self.extras:
            return [{'extra': e} for e in sorted(self.extras)]
        return [{'extra': ''}]

    def evaluate_all_environamnets(self, requirement):
        for marker_env in self.marker_envs:
            if requirement.marker.evaluate(environment=marker_env):
                return True
        return False

    def add(self, requirement_str, *, source=None):
        """Output a Python-style requirement string as RPM dep"""
        print_err(f'Handling {requirement_str} from {source}')

        try:
            requirement = Requirement(requirement_str)
        except InvalidRequirement:
            hint = guess_reason_for_invalid_requirement(requirement_str)
            message = f'Requirement {requirement_str!r} from {source} is invalid.'
            if hint:
                message += f' Hint: {hint}'
            raise ValueError(message)

        if requirement.url:
            print_err(
                f'WARNING: Simplifying {requirement_str!r} to {requirement.name!r}.'
            )

        name = canonicalize_name(requirement.name)
        if (requirement.marker is not None and
                not self.evaluate_all_environamnets(requirement)):
            print_err(f'Ignoring alien requirement:', requirement_str)
            return

        # We need to always accept pre-releases as satisfying the requirement
        # Otherwise e.g. installed cffi version 1.15.0rc2 won't even satisfy the requirement for "cffi"
        # https://bugzilla.redhat.com/show_bug.cgi?id=2014639#c3
        requirement.specifier.prereleases = True

        try:
            # TODO: check if requirements with extras are satisfied
            installed = self.get_installed_version(requirement.name)
        except importlib.metadata.PackageNotFoundError:
            print_err(f'Requirement not satisfied: {requirement_str}')
            installed = None
        if installed and installed in requirement.specifier:
            print_err(f'Requirement satisfied: {requirement_str}')
            print_err(f'   (installed: {requirement.name} {installed})')
            if requirement.extras:
                print_err(f'   (extras are currently not checked)')
        else:
            self.missing_requirements = True

        if self.generate_extras:
            extra_names = [f'{name}[{extra.lower()}]' for extra in sorted(requirement.extras)]
        else:
            extra_names = []

        for name in [name] + extra_names:
            together = []
            for specifier in sorted(
                requirement.specifier,
                key=lambda s: (s.operator, s.version),
            ):
                if not VERSION_RE.fullmatch(str(specifier.version)):
                    raise ValueError(
                        f'Unknown character in version: {specifier.version}. '
                        + '(This might be a bug in pyproject-rpm-macros.)',
                    )
                together.append(convert(python3dist(name, python3_pkgversion=self.python3_pkgversion),
                                        specifier.operator, specifier.version))
            if len(together) == 0:
                print(python3dist(name,
                                  python3_pkgversion=self.python3_pkgversion))
            elif len(together) == 1:
                print(together[0])
            else:
                print(f"({' with '.join(together)})")

    def check(self, *, source=None):
        """End current pass if any unsatisfied dependencies were output"""
        if self.missing_requirements:
            print_err(f'Exiting dependency generation pass: {source}')
            raise EndPass(source)

    def extend(self, requirement_strs, **kwargs):
        """add() several requirements"""
        for req_str in requirement_strs:
            self.add(req_str, **kwargs)


def get_backend(requirements):
    try:
        f = open('pyproject.toml')
    except FileNotFoundError:
        pyproject_data = {}
    else:
        try:
            # lazy import toml here, not needed without pyproject.toml
            import toml
        except ImportError as e:
            print_err('Import error:', e)
            # already echoed by the %pyproject_buildrequires macro
            sys.exit(0)
        with f:
            pyproject_data = toml.load(f)

    buildsystem_data = pyproject_data.get('build-system', {})
    requirements.extend(
        buildsystem_data.get('requires', ()),
        source='build-system.requires',
    )

    backend_name = buildsystem_data.get('build-backend')
    if not backend_name:
        # https://www.python.org/dev/peps/pep-0517/:
        # If the pyproject.toml file is absent, or the build-backend key is
        # missing, the source tree is not using this specification, and tools
        # should revert to the legacy behaviour of running setup.py
        # (either directly, or by implicitly invoking the [following] backend).
        # If setup.py is also not present program will mimick pip's behavior
        # and end with an error.
        if not os.path.exists('setup.py'):
            raise FileNotFoundError('File "setup.py" not found for legacy project.')
        backend_name = 'setuptools.build_meta:__legacy__'

        # Note: For projects without pyproject.toml, this was already echoed
        # by the %pyproject_buildrequires macro, but this also handles cases
        # with pyproject.toml without a specified build backend.
        # If the default requirements change, also change them in the macro!
        requirements.add('setuptools >= 40.8', source='default build backend')
        requirements.add('wheel', source='default build backend')

    requirements.check(source='build backend')

    backend_path = buildsystem_data.get('backend-path')
    if backend_path:
        # PEP 517 example shows the path as a list, but some projects don't follow that
        if isinstance(backend_path, str):
            backend_path = [backend_path]
        sys.path = backend_path + sys.path

    module_name, _, object_name = backend_name.partition(":")
    backend_module = importlib.import_module(module_name)

    if object_name:
        return getattr(backend_module, object_name)

    return backend_module


def generate_build_requirements(backend, requirements):
    get_requires = getattr(backend, 'get_requires_for_build_wheel', None)
    if get_requires:
        with hook_call():
            new_reqs = get_requires()
        requirements.extend(new_reqs, source='get_requires_for_build_wheel')
        requirements.check(source='get_requires_for_build_wheel')


def requires_from_metadata_file(metadata_file):
    message = email.parser.Parser().parse(metadata_file, headersonly=True)
    return {k: message.get_all(k, ()) for k in ('Requires', 'Requires-Dist')}


def generate_run_requirements_hook(backend, requirements):
    hook_name = 'prepare_metadata_for_build_wheel'
    prepare_metadata = getattr(backend, hook_name, None)
    if not prepare_metadata:
        raise ValueError(
            'The build backend cannot provide build metadata '
            '(incl. runtime requirements) before build. '
            'Use the provisional -w flag to build the wheel and parse the metadata from it, '
            'or use the -R flag not to generate runtime dependencies.'
        )
    with hook_call():
        dir_basename = prepare_metadata('.')
    with open(dir_basename + '/METADATA') as metadata_file:
        for key, requires in requires_from_metadata_file(metadata_file).items():
            requirements.extend(requires, source=f'hook generated metadata: {key}')


def find_built_wheel(wheeldir):
    wheels = glob.glob(os.path.join(wheeldir, '*.whl'))
    if not wheels:
        return None
    if len(wheels) > 1:
        raise RuntimeError('Found multiple wheels in %{_pyproject_wheeldir}, '
                           'this is not supported with %pyproject_buildrequires -w.')
    return wheels[0]


def generate_run_requirements_wheel(backend, requirements, wheeldir):
    # Reuse the wheel from the previous round of %pyproject_buildrequires (if it exists)
    wheel = find_built_wheel(wheeldir)
    if not wheel:
        import pyproject_wheel
        returncode = pyproject_wheel.build_wheel(wheeldir=wheeldir, stdout=sys.stderr)
        if returncode != 0:
            raise RuntimeError('Failed to build the wheel for %pyproject_buildrequires -w.')
        wheel = find_built_wheel(wheeldir)
    if not wheel:
        raise RuntimeError('Cannot locate the built wheel for %pyproject_buildrequires -w.')

    print_err(f'Reading metadata from {wheel}')
    with zipfile.ZipFile(wheel) as wheelfile:
        for name in wheelfile.namelist():
            if name.count('/') == 1 and name.endswith('.dist-info/METADATA'):
                with io.TextIOWrapper(wheelfile.open(name), encoding='utf-8') as metadata_file:
                    for key, requires in requires_from_metadata_file(metadata_file).items():
                        requirements.extend(requires, source=f'built wheel metadata: {key}')
                break
        else:
            raise RuntimeError('Could not find *.dist-info/METADATA in built wheel.')


def generate_run_requirements(backend, requirements, *, build_wheel, wheeldir):
    if build_wheel:
        generate_run_requirements_wheel(backend, requirements, wheeldir)
    else:
        generate_run_requirements_hook(backend, requirements)


def generate_tox_requirements(toxenv, requirements):
    toxenv = ','.join(toxenv)
    requirements.add('tox-current-env >= 0.0.6', source='tox itself')
    requirements.check(source='tox itself')
    with tempfile.NamedTemporaryFile('r') as deps, \
        tempfile.NamedTemporaryFile('r') as extras, \
            tempfile.NamedTemporaryFile('r') as provision:
        r = subprocess.run(
            [sys.executable, '-m', 'tox',
             '--print-deps-to', deps.name,
             '--print-extras-to', extras.name,
             '--no-provision', provision.name,
             '-q', '-r', '-e', toxenv],
            check=False,
            encoding='utf-8',
            stdout=subprocess.PIPE,
            stderr=subprocess.STDOUT,
        )
        if r.stdout:
            print_err(r.stdout, end='')

        provision_content = provision.read()
        if provision_content and r.returncode != 0:
            provision_requires = json.loads(provision_content)
            if 'minversion' in provision_requires:
                requirements.add(f'tox >= {provision_requires["minversion"]}',
                                 source='tox provision (minversion)')
            if 'requires' in provision_requires:
                requirements.extend(provision_requires["requires"],
                                    source='tox provision (requires)')
            requirements.check(source='tox provision')  # this terminates the script
            raise RuntimeError(
                'Dependencies requested by tox provisioning appear installed, '
                'but tox disagreed.')
        else:
            r.check_returncode()

        deplines = deps.read().splitlines()
        packages = convert_requirements_txt(deplines)
        requirements.add_extras(*extras.read().splitlines())
        requirements.extend(packages,
                            source=f'tox --print-deps-only: {toxenv}')


def python3dist(name, op=None, version=None, python3_pkgversion="3"):
    prefix = f"python{python3_pkgversion}dist"

    if op is None:
        if version is not None:
            raise AssertionError('op and version go together')
        return f'{prefix}({name})'
    else:
        return f'{prefix}({name}) {op} {version}'


def generate_requires(
    *, include_runtime=False, build_wheel=False, wheeldir=None, toxenv=None, extras=None,
    get_installed_version=importlib.metadata.version,  # for dep injection
    generate_extras=False, python3_pkgversion="3", requirement_files=None, use_build_system=True
):
    """Generate the BuildRequires for the project in the current directory

    This is the main Python entry point.
    """
    requirements = Requirements(
        get_installed_version, extras=extras or [],
        generate_extras=generate_extras,
        python3_pkgversion=python3_pkgversion
    )

    try:
        if (include_runtime or toxenv) and not use_build_system:
            raise ValueError('-N option cannot be used in combination with -r, -e, -t, -x options')
        if requirement_files:
            for req_file in requirement_files:
                requirements.extend(
                    convert_requirements_txt(req_file, pathlib.Path(req_file.name)),
                    source=f'requirements file {req_file.name}'
                )
            requirements.check(source='all requirements files')
        if use_build_system:
            backend = get_backend(requirements)
            generate_build_requirements(backend, requirements)
        if toxenv:
            include_runtime = True
            generate_tox_requirements(toxenv, requirements)
        if include_runtime:
            generate_run_requirements(backend, requirements, build_wheel=build_wheel, wheeldir=wheeldir)
    except EndPass:
        return


def main(argv):
    parser = argparse.ArgumentParser(
        description='Generate BuildRequires for a Python project.'
    )
    parser.add_argument(
        '-r', '--runtime', action='store_true', default=True,
        help='Generate run-time requirements (default, disable with -R)',
    )
    parser.add_argument(
        '-w', '--wheel', action='store_true', default=False,
        help=('Generate run-time requirements by building the wheel '
              '(useful for build backends without the prepare_metadata_for_build_wheel hook)'),
    )
    parser.add_argument(
        '--wheeldir', metavar='PATH', default=None,
        help='The directory with wheel, used when -w.',
    )
    parser.add_argument(
        '-R', '--no-runtime', action='store_false', dest='runtime',
        help="Don't generate run-time requirements (implied by -N)",
    )
    parser.add_argument(
        '-e', '--toxenv', metavar='TOXENVS', action='append',
        help=('specify tox environments (comma separated and/or repeated)'
              '(implies --tox)'),
    )
    parser.add_argument(
        '-t', '--tox', action='store_true',
        help=('generate test tequirements from tox environment '
              '(implies --runtime)'),
    )
    parser.add_argument(
        '-x', '--extras', metavar='EXTRAS', action='append',
        help='comma separated list of "extras" for runtime requirements '
             '(e.g. -x testing,feature-x) (implies --runtime, can be repeated)',
    )
    parser.add_argument(
        '--generate-extras', action='store_true',
        help='Generate build requirements on Python Extras',
    )
    parser.add_argument(
        '-p', '--python3_pkgversion', metavar='PYTHON3_PKGVERSION',
        default="3", help=('Python version for pythonXdist()'
                           'or pythonX.Ydist() requirements'),
    )
    parser.add_argument(
        '-N', '--no-use-build-system', dest='use_build_system',
        action='store_false', help='Use -N to indicate that project does not use any build system',
    )
    parser.add_argument(
       'requirement_files', nargs='*', type=argparse.FileType('r'),
        help=('Add buildrequires from file'),
    )

    args = parser.parse_args(argv)

    if not args.use_build_system:
        args.runtime = False

    if args.wheel:
        if not args.wheeldir:
            raise ValueError('--wheeldir must be set when -w.')

    if args.toxenv:
        args.tox = True

    if args.tox:
        args.runtime = True
        if not args.toxenv:
            _default = f'py{sys.version_info.major}{sys.version_info.minor}'
            args.toxenv = [os.getenv('RPM_TOXENV', _default)]

    if args.extras:
        args.runtime = True

    try:
        generate_requires(
            include_runtime=args.runtime,
            build_wheel=args.wheel,
            wheeldir=args.wheeldir,
            toxenv=args.toxenv,
            extras=args.extras,
            generate_extras=args.generate_extras,
            python3_pkgversion=args.python3_pkgversion,
            requirement_files=args.requirement_files,
            use_build_system=args.use_build_system,
        )
    except Exception:
        # Log the traceback explicitly (it's useful debug info)
        traceback.print_exc()
        exit(1)


if __name__ == '__main__':
    main(sys.argv[1:])