'''
Support for Python packaging operations.
'''

import base64
import distutils.util
import hashlib
import io
import os
import platform
import shutil
import site
import subprocess
import sys
import tarfile
import time
import zipfile


class Package:
    '''
    Helper for Python packaging operations.

    Our constructor takes a definition of a Python package similar to that
    passed to distutils.core.setup() or setuptools.setup() - name, version,
    summary etc, plus callbacks for build, clean and sdist filenames.

    We then provide methods that can be used to implement a Python package's
    PEP-517 backend and/or minimal setup.py support for use with a legacy
    (pre-PEP-517) pip.

    A PEP-517 backend can be implemented with:

        import pipcl
        import subprocess

        def build():
            subprocess.check_call('cc -shared -fPIC -o foo.so foo.c')
            return ['foo.py', 'foo.so']

        def sdist():
            return ['foo.py', 'foo.c', 'pyproject.toml', ...]

        p = pipcl.Package('foo', '1.2.3', fn_build=build, fsdist=sdist, ...)

        def build_wheel(wheel_directory, config_settings=None, metadata_directory=None):
            return p.build_wheel(wheel_directory, config_settings, metadata_directory)

        def build_sdist(sdist_directory, config_settings=None):
            return p.build_sdist(sdist_directory, config_settings)

    Work as a setup.py script by appending:

        import sys
        if __name__ == '__main__':
            p.handle_argv(sys.argv)

    '''
    def __init__(self,
            name,
            version,
            root=None,
            summary = None,
            description = None,
            classifiers = None,
            author = None,
            author_email = None,
            url_docs = None,
            url_home = None,
            url_source = None,
            url_tracker = None,
            keywords = None,
            platform = None,
            license_files = None,
            fn_build = None,
            fn_clean = None,
            fn_sdist = None,
            ):
        '''
        name
            A string, the name of the Python package.
        version
            A string containing only 0-9 and '.'.
        root:
            Root of package, defaults to current directory.
        summary
            A string.
        description
            A string.
        classifiers
            A list of strings.
        url_home
        url_source
        url_docs
        url_tracker
            A string containing a URL.
        keywords
            A string containing space-separated keywords.
        platform
            A string, used in metainfo.
        license_files
            List of string names of license files.
        fn_build
            A function taking no args that builds the package.

            Should return a list of items; each item should be a tuple of two
            strings (from_, to_) or a single string <path> which is treated as
            the tuple (path, path).

            <from_> should be the path to a file; if a relative path it is
            assumed to be relative to <root>. <to_> identifies what the file
            should be called within a wheel or when installing.

            If we are building a wheel (e.g. 'bdist_wheel' in the argv passed
            to self.handle_argv() or PEP-517 pip calls self.build_wheel()), we
            copy file <from_> to <to_> inside the wheel archive.

            If we are installing (e.g. 'install' command in the argv passed to
            self.handle_argv()), we copy <from_> to <sitepackages>/<to_>, where
            <sitepackages> is the first item in site.getsitepackages()[] that
            exists.
        fn_clean
            A function taking a single arg <all_> that cleans generated files.
            <all_> is true iff --all is in argv.

            Can also returns a list of files/directories to be deleted.
            Relative paths are interpreted as relative to <root>. Paths are
            asserted to be within <root>.
        fn_sdist
            A function taking no args that returns a list of paths, e.g.
            using pipcl.git_items(), for files that should be copied into the
            sdist. Relative paths are interpreted as relative to <root>. It is
            an error if a path does not exist or is not a file.
        '''
        self.name = name
        self.version = version
        self.root_sep = os.path.abspath(root if root else os.getcwd()) + os.sep
        self.summary = summary
        self.description = description
        self.classifiers = classifiers
        self.author = author
        self.author_email  = author_email
        self.url_docs = url_docs
        self.url_home  = url_home
        self.url_source = url_source
        self.url_tracker = url_tracker
        self.keywords = keywords
        self.platform = platform
        self.license_files = license_files
        self.fn_build = fn_build
        self.fn_clean = fn_clean
        self.fn_sdist = fn_sdist


    def build_wheel(self, wheel_directory, config_settings=None, metadata_directory=None):
        '''
        Helper for implementing a PEP-517 backend's build_wheel() function.

        Also called by handle_argv() to handle the 'bdist_wheel' command.

        Returns leafname of generated wheel within <wheel_directory>.
        '''
        _log('build_wheel():'
                f' wheel_directory={wheel_directory}'
                f' config_settings={config_settings}'
                f' metadata_directory={metadata_directory}'
                )

        # Find platform tag used in wheel filename, as described in
        # PEP-0425. E.g. 'openbsd_6_8_amd64', 'win_amd64' or 'win32'.
        #
        tag_platform = distutils.util.get_platform().replace('-', '_').replace('.', '_')

        # Get two-digit python version, e.g. 3.8 for python-3.8.6.
        #
        tag_python = ''.join(platform.python_version().split('.')[:2])

        # Final tag is, for example, 'cp39-none-win32', 'cp39-none-win_amd64'
        # or 'cp38-none-openbsd_6_8_amd64'.
        #
        tag = f'cp{tag_python}-none-{tag_platform}'

        path = f'{wheel_directory}/{self.name}-{self.version}-{tag}.whl'

        # Do a build and get list of files to copy into the wheel.
        #
        items = []
        if self.fn_build:
            _log(f'calling self.fn_build={self.fn_build}')
            items = self.fn_build()

        _log(f'build_wheel(): Writing wheel {path} ...')
        os.makedirs(wheel_directory, exist_ok=True)
        record = _Record()
        with zipfile.ZipFile(path, 'w') as z:

            def add_file(from_, to_):
                z.write(from_, to_)
                record.add_file(from_, to_)

            def add_str(content, to_):
                z.writestr(to_, content)
                record.add_content(content, to_)

            # Add the files returned by fn_build().
            #
            for item in items:
                (from_abs, from_rel), (to_abs, to_rel) = self._fromto(item)
                add_file(from_abs, to_rel)

            dist_info_path = f'{self.name}-{self.version}.dist-info'
            # Add <name>-<version>.dist-info/WHEEL.
            #
            add_str(
                    f'Wheel-Version: 1.0\n'
                    f'Generator: bdist_wheel\n'
                    f'Root-Is-Purelib: false\n'
                    f'Tag: {tag}\n'
                    ,
                    f'{dist_info_path}/WHEEL',
                    )
            # Add <name>-<version>.dist-info/METADATA.
            #
            add_str(self._metainfo(), f'{dist_info_path}/METADATA')
            if self.license_files:
                for license_file in self.license_files:
                    (from_abs, from_to), (to_abs, to_rel) = self._fromto(license_file)
                    add_file(from_abs, f'{dist_info_path}/{to_rel}')

            # Update <name>-<version>.dist-info/RECORD. This must be last.
            #
            z.writestr(f'{dist_info_path}/RECORD', record.get())

        _log( f'build_wheel(): Have created wheel: {path}')
        return os.path.basename(path)


    def build_sdist(self, sdist_directory, config_settings=None):
        '''
        Helper for implementing a PEP-517 backend's build_sdist() function.

        [Though as of 2021-03-24 pip doesn't actually seem to ever call the
        backend's build_sdist() function?]

        Also called by handle_argv() to handle the 'sdist' command.

        Returns leafname of generated archive within <sdist_directory>.
        '''
        paths = []
        if self.fn_sdist:
            paths = self.fn_sdist()

        manifest = []
        def add(tar, name, contents):
            '''
            Adds item called <name> to tarfile.TarInfo <tar>, containing
            <contents>. If contents is a string, it is encoded using utf8.
            '''
            if isinstance(contents, str):
                contents = contents.encode('utf8')
            ti = tarfile.TarInfo(name)
            ti.size = len(contents)
            ti.mtime = time.time()
            tar.addfile(ti, io.BytesIO(contents))

        os.makedirs(sdist_directory, exist_ok=True)
        tarpath = f'{sdist_directory}/{self.name}-{self.version}.tar.gz'
        _log(f'build_sdist(): Writing sdist {tarpath} ...')
        with tarfile.open(tarpath, 'w:gz') as tar:
            for path in paths:
                path_abs, path_rel = self._path_relative_to_root( path)
                if path_abs.startswith(f'{os.path.abspath(sdist_directory)}/'):
                    # Ignore files inside <sdist_directory>.
                    assert 0, f'Path is inside sdist_directory={sdist_directory}: {path_abs!r}'
                if not os.path.exists(path_abs):
                    assert 0, f'Path does not exist: {path_abs!r}'
                if not os.path.isfile(path_abs):
                    assert 0, f'Path is not a file: {path_abs!r}'
                #log(f'path={path}')
                tar.add( path_abs, f'{self.name}-{self.version}/{path_rel}', recursive=False)
                manifest.append(path_rel)
            add(tar, f'{self.name}-{self.version}/PKG-INFO', self._metainfo())

            # It doesn't look like MANIFEST or setup.cfg are required?
            #
            if 0:
                # Add manifest:
                add(tar, f'{self.name}-{self.version}/MANIFEST', '\n'.join(manifest))

            if 0:
                # add setup.cfg
                setup_cfg = ''
                setup_cfg += '[bdist_wheel]\n'
                setup_cfg += 'universal = 1\n'
                setup_cfg += '\n'
                setup_cfg += '[flake8]\n'
                setup_cfg += 'max-line-length = 100\n'
                setup_cfg += 'ignore = F821\n'
                setup_cfg += '\n'
                setup_cfg += '[metadata]\n'
                setup_cfg += 'license_file = LICENSE\n'
                setup_cfg += '\n'
                setup_cfg += '[tool:pytest]\n'
                setup_cfg += 'minversion = 2.2.0\n'
                setup_cfg += '\n'
                setup_cfg += '[egg_info]\n'
                setup_cfg += 'tag_build = \n'
                setup_cfg += 'tag_date = 0\n'
                add(tar, f'{self.name}-{self.version}/setup.cfg', setup_cfg)

        _log( f'build_sdist(): Have created sdist: {tarpath}')
        return os.path.basename(tarpath)


    def argv_clean(self, all_):
        '''
        Called by handle_argv().
        '''
        if not self.fn_clean:
            return
        paths = self.fn_clean(all_)
        if paths:
            if isinstance(paths, str):
                paths = paths,
            for path in paths:
                path = os.path.abspath(path)
                assert path.startswith(self.root_sep), \
                        f'path={path!r} does not start with root={self.root_sep!r}'
                _log(f'Removing: {path}')
                shutil.rmtree(path, ignore_errors=True)


    def argv_install(self, record_path):
        '''
        Called by handle_argv().
        '''
        items = []
        if self.fn_build:
            items = self.fn_build()

        # We install to the first item in site.getsitepackages()[] that exists.
        #
        sitepackages_all = site.getsitepackages()
        for p in sitepackages_all:
            if os.path.exists(p):
                sitepackages = p
                break
        else:
            text = 'No item exists in site.getsitepackages():\n'
            for i in sitepackages_all:
                text += f'    {i}\n'
            raise Exception(text)

        record = _Record() if record_path else None
        for item in items:
            (from_abs, from_rel), (to_abs, to_rel) = self._fromto(item)
            to_path = f'{sitepackages}/{to_rel}'
            _log(f'copying from {from_abs} to {to_path}')
            shutil.copy2( from_abs, f'{to_path}')
            if record:
                # Could maybe use relative path of to_path from sitepackages/.
                record.add_file(from_abs, to_path)

        if record:
            with open(record_path, 'w') as f:
                f.write(record.get())

        _log(f'argv_install(): Finished.')


    def argv_dist_info(self, egg_base):
        '''
        Called by handle_argv(). There doesn't seem to be any documentation
        for 'setup.py dist_info', but it appears to be like egg_info except it
        writes to a slightly different directory.
        '''
        self._write_info(f'{egg_base}/{self.name}.dist-info')


    def argv_egg_info(self, egg_base):
        '''
        Called by handle_argv().
        '''
        if egg_base is None:
            egg_base = '.'
        self._write_info(f'{egg_base}/.egg-info')


    def _write_info(self, dirpath=None):
        '''
        Writes egg/dist info to files in directory <dirpath> or self.root_sep
        if None.
        '''
        if dirpath is None:
            dirpath = self.root_sep
        _log(f'_write_info(): creating files in directory {dirpath}')
        os.mkdir(dirpath)
        with open(os.path.join(dirpath, 'PKG-INFO'), 'w') as f:
            f.write(self._metainfo())

        # These don't seem to be required?
        #
        #with open(os.path.join(dirpath, 'SOURCES.txt', 'w') as f:
        #    pass
        #with open(os.path.join(dirpath, 'dependency_links.txt', 'w') as f:
        #    pass
        #with open(os.path.join(dirpath, 'top_level.txt', 'w') as f:
        #    f.write(f'{self.name}\n')
        #with open(os.path.join(dirpath, 'METADATA', 'w') as f:
        #    f.write(self._metainfo())


    def handle_argv(self, argv):
        '''
        Handles old-style (pre PEP-517) command line passed by old releases of pip to a
        setup.py script.

        We only handle those args that seem to be used by pre-PEP-517 pip.
        '''
        #_log(f'handle_argv(): argv: {argv}')

        class ArgsRaise:
            pass

        class Args:
            '''
            Iterates over argv items.
            '''
            def __init__( self, argv):
                self.items = iter( argv)
            def next( self, eof=ArgsRaise):
                '''
                Returns next arg. If no more args, we return <eof> or raise an
                exception if <eof> is ArgsRaise.
                '''
                try:
                    return next( self.items)
                except StopIteration:
                    if eof is ArgsRaise:
                        raise Exception('Not enough args')
                    return eof

        command = None
        opt_all = None
        opt_dist_dir = 'dist'
        opt_egg_base = None
        opt_install_headers = None
        opt_python_tag = None
        opt_record = None

        args = Args(argv[1:])

        while 1:
            arg = args.next(None)
            if arg is None:
                break

            elif arg in ('-h', '--help', '--help-commands'):
                _log(
                        'Options:\n'
                        '    bdist_wheel\n'
                        '        Creates a wheel called\n'
                        '        <dist-dir>/<name>-<version>-<details>.whl, where\n'
                        '        <dist-dir> is "dist" or as specified by --dist-dir,\n'
                        '        and <details> encodes ABI and platform etc.\n'
                        '    clean\n'
                        '        Cleans build files.\n'
                        '    egg_info\n'
                        '        Creates files in <egg-base>/.egg-info/, where\n'
                        '        <egg-base> is as specified with --egg-base.\n'
                        '    install\n'
                        '        Installs into location from Python\'s\n'
                        '        site.getsitepackages() array. Writes installation\n'
                        '        information to <record> if --record\n'
                        '        was specified.\n'
                        '    sdist\n'
                        '        Make a source distribution:\n'
                        '            <dist-dir>/<name>-<version>.tar.gz\n'
                        '    dist_info\n'
                        '        Like <egg_info> but creates files in\n'
                        '        <egg-base>/<name>.dist-info/\n'
                        '    --dist-dir | -d <dist-dir>\n'
                        '        Default is "dist".\n'
                        '    --egg-base <egg-base>\n'
                        '        Used by "egg_info".\n'
                        '    --record <record>\n'
                        '        Used by "install".\n'
                        '    --single-version-externally-managed\n'
                        '        Ignored.\n'
                        '    --compile\n'
                        '        Ignored.\n'
                        '    --install-headers <directory>\n'
                        '        Ignored.\n'
                        )
                return

            elif arg in ('bdist_wheel', 'clean', 'egg_info', 'install', 'sdist', 'dist_info'):
                assert command is None, 'Two commands specified: {command} and {arg}.'
                command = arg

            elif arg == '--all':
                opt_all = True

            elif arg == '--compile':
                pass

            elif arg == '--dist-dir' or arg == '-d':
                opt_dist_dir = args.next()

            elif arg == '--egg-base':
                opt_egg_base = args.next()

            elif arg == '--install-headers':
                opt_install_headers = args.next()

            elif arg == '--python-tag':
                opt_python_tag = args.next()

            elif arg == '--record':
                opt_record = args.next()

            elif arg == '--single-version-externally-managed':
                pass

            else:
               raise Exception(f'Unrecognised arg: {arg}')

        if not command:
            return

        _log(f'handle_argv(): Handling command={command}')
        if 0:   pass
        elif command == 'bdist_wheel':  self.build_wheel(opt_dist_dir)
        elif command == 'clean':        self.argv_clean(opt_all)
        elif command == 'dist_info':    self.argv_dist_info(opt_egg_base)
        elif command == 'egg_info':     self.argv_egg_info(opt_egg_base)
        elif command == 'install':      self.argv_install(opt_record)
        elif command == 'sdist':        self.build_sdist(opt_dist_dir)
        else:
            assert 0, f'Unrecognised command: {command}'

        _log(f'handle_argv(): Finished handling command={command}')


    def __str__(self):
        return ('{'
            f'name={self.name!r}'
            f' version={self.version!r}'
            f' root_sep={self.root_sep!r}'
            f' summary={self.summary!r}'
            f' description={self.description!r}'
            f' classifiers={self.classifiers!r}'
            f' author={self.author!r}'
            f' author_email ={self.author_email!r}'
            f' url_docs={self.url_docs!r}'
            f' url_home ={self.url_home!r}'
            f' url_source={self.url_source!r}'
            f' url_tracker={self.url_tracker!r}'
            f' keywords={self.keywords!r}'
            f' platform={self.platform!r}'
            f' license_files={self.license_files!r}'
            f' fn_build={self.fn_build!r}'
            f' fn_sdist={self.fn_sdist!r}'
            f' fn_clean={self.fn_clean!r}'
            '}'
            )


    def _metainfo(self):
        '''
        Returns text for .egg-info/PKG-INFO file, or PKG-INFO in an sdist
        tar.gz file, or ...dist-info/METADATA in a wheel.
        '''
        # 2021-04-30: Have been unable to get multiline content working on
        # test.pypi.org so we currently put the description as the body after
        # all the other headers.
        #
        ret = ['']
        def add(key, value):
            if value is not None:
                assert '\n' not in value, f'key={key} value contains newline: {value!r}'
                ret[0] += f'{key}: {value}\n'
        add('Metadata-Version', '1.2')
        add('Name', self.name)
        add('Version', self.version)
        add('Summary', self.summary)
        #add('Description', self.description)
        add('Home-page', self.url_home)
        add('Platform', self.platform)
        add('Author', self.author)
        add('Author-email', self.author_email)
        if self.url_source:  add('Home-page', f'Source, {self.url_source}')
        if self.url_docs:    add('Home-page', f'Source, {self.url_docs}')
        if self.url_tracker: add('Home-page', f'Source, {self.url_tracker}')
        if self.keywords:
            add('Keywords', self.keywords)
        if self.classifiers:
            classifiers2 = self.classifiers
            if isinstance(classifiers2, str):
                classifiers2 = classifiers2.split('\n')
            for c in classifiers2:
                add('Classifier', c)
        ret = ret[0]

        # Append description as the body
        if self.description:
            ret += '\n' # Empty line separates headers from body.
            ret += self.description.strip()
            ret += '\n'
        return ret

    def _path_relative_to_root(self, path):
        '''
        Returns (path_abs, path_rel), where <path_abs> is absolute path and
        <path_rel> is relative to self.root_sep.

        Interprets <path> as relative to self.root_sep if not absolute.

        We use os.path.realpath() to resolve any links.

        Assert-fails if path is not within self.root_sep.
        '''
        if os.path.isabs(path):
            p = path
        else:
            p = os.path.join(self.root_sep, path)
        p = os.path.realpath(os.path.abspath(p))
        assert p.startswith(self.root_sep), f'Path not within root={self.root_sep}: {path}'
        p_rel = os.path.relpath(p, self.root_sep)
        return p, p_rel

    def _fromto(self, p):
        '''
        Returns ((from_abs, from_rel), (to_abs, to_rel)).

        If <p> is a string we convert to (p, p). Otherwise we assert that
        <p> is a tuple of two strings. Non-absolute paths are assumed to be
        relative to self.root_sep.

        from_abs and to_abs are absolute paths, asserted to be within
        self.root_sep.

        from_rel and to_rel are derived from the _abs paths and are relative to
        self.root_sep.
        '''
        ret = None
        if isinstance(p, str):
            ret = p, p
        elif isinstance(p, tuple) and len(p) == 2:
            from_, to_ = p
            if isinstance(from_, str) and isinstance(to_, str):
                ret = from_, to_
        assert ret, 'p should be str or (str, str), but is: {p}'
        from_, to_ = ret
        return self._path_relative_to_root(from_), self._path_relative_to_root(to_)


# Functions that might be useful.
#

def git_items( directory, submodules=False):
    '''
    Helper for pipcl.Package's fn_sdist() callback.

    Returns list of paths for all files known to git within <directory>. Each
    path is relative to <directory>.

    <directory> must be somewhere within a git checkout.

    We run a 'git ls-files' command internally.
    '''
    command = 'cd ' + directory + ' && git ls-files'
    if submodules:
        command += ' --recurse-submodules'
    text = subprocess.check_output( command, shell=True)
    ret = []
    for path in text.decode('utf8').strip().split( '\n'):
        path2 = os.path.join(directory, path)
        # Sometimes git ls-files seems to list empty/non-existant directories
        # within submodules.
        #
        if not os.path.exists(path2):
            _log(f'*** Ignoring git ls-files item that does not exist: {path2}')
        elif os.path.isdir(path2):
            _log(f'*** Ignoring git ls-files item that is actually a directory: {path2}')
        else:
            ret.append(path)
    return ret


def parse_pkg_info(path):
    '''
    Parses a PKJG-INFO file, each line is '<key>: <value>\n'. Returns a dict.
    '''
    ret = dict()
    with open(path) as f:
        for line in f:
            s = line.find(': ')
            if s >= 0 and line.endswith('\n'):
                k = line[:s]
                v = line[s+2:-1]
                ret[k] = v
    return ret


# Implementation helpers.
#

def _log(text=''):
    '''
    Logs lines with prefix.
    '''
    for line in text.split('\n'):
        print(f'pipcl.py: {line}')
    sys.stdout.flush()


class _Record:
    '''
    Internal - builds up text suitable for writing to a RECORD item, e.g.
    within a wheel.
    '''
    def __init__(self):
        self.text = ''

    def add_content(self, content, to_):
        if isinstance(content, str):
            content = content.encode('latin1')
        h = hashlib.sha256(content)
        digest = h.digest()
        digest = base64.urlsafe_b64encode(digest)
        self.text += f'{to_},sha256={digest},{len(content)}\n'

    def add_file(self, from_, to_):
        with open(from_, 'rb') as f:
            content = f.read()
        self.add_content(content, to_)

    def get(self):
        return self.text
