"""distutils.command.build_scripts

Implements the Distutils 'build_scripts' command."""

import os
import re
import tokenize
from distutils import sysconfig
from distutils._log import log
from stat import ST_MODE

from .._modified import newer
from ..core import Command
from ..util import convert_path

shebang_pattern = re.compile('^#!.*python[0-9.]*([ \t].*)?$')
"""
Pattern matching a Python interpreter indicated in first line of a script.
"""

# for Setuptools compatibility
first_line_re = shebang_pattern


class build_scripts(Command):
    description = "\"build\" scripts (copy and fixup #! line)"

    user_options = [
        ('build-dir=', 'd', "directory to \"build\" (copy) to"),
        ('force', 'f', "forcibly build everything (ignore file timestamps"),
        ('executable=', 'e', "specify final destination interpreter path"),
    ]

    boolean_options = ['force']

    def initialize_options(self):
        self.build_dir = None
        self.scripts = None
        self.force = None
        self.executable = None

    def finalize_options(self):
        self.set_undefined_options(
            'build',
            ('build_scripts', 'build_dir'),
            ('force', 'force'),
            ('executable', 'executable'),
        )
        self.scripts = self.distribution.scripts

    def get_source_files(self):
        return self.scripts

    def run(self):
        if not self.scripts:
            return
        self.copy_scripts()

    def copy_scripts(self):
        """
        Copy each script listed in ``self.scripts``.

        If a script is marked as a Python script (first line matches
        'shebang_pattern', i.e. starts with ``#!`` and contains
        "python"), then adjust in the copy the first line to refer to
        the current Python interpreter.
        """
        self.mkpath(self.build_dir)
        outfiles = []
        updated_files = []
        for script in self.scripts:
            self._copy_script(script, outfiles, updated_files)

        self._change_modes(outfiles)

        return outfiles, updated_files

    def _copy_script(self, script, outfiles, updated_files):  # noqa: C901
        shebang_match = None
        script = convert_path(script)
        outfile = os.path.join(self.build_dir, os.path.basename(script))
        outfiles.append(outfile)

        if not self.force and not newer(script, outfile):
            log.debug("not copying %s (up-to-date)", script)
            return

        # Always open the file, but ignore failures in dry-run mode
        # in order to attempt to copy directly.
        try:
            f = tokenize.open(script)
        except OSError:
            if not self.dry_run:
                raise
            f = None
        else:
            first_line = f.readline()
            if not first_line:
                self.warn(f"{script} is an empty file (skipping)")
                return

            shebang_match = shebang_pattern.match(first_line)

        updated_files.append(outfile)
        if shebang_match:
            log.info("copying and adjusting %s -> %s", script, self.build_dir)
            if not self.dry_run:
                if not sysconfig.python_build:
                    executable = self.executable
                else:
                    executable = os.path.join(
                        sysconfig.get_config_var("BINDIR"),
                        "python{}{}".format(
                            sysconfig.get_config_var("VERSION"),
                            sysconfig.get_config_var("EXE"),
                        ),
                    )
                post_interp = shebang_match.group(1) or ''
                shebang = "#!" + executable + post_interp + "\n"
                self._validate_shebang(shebang, f.encoding)
                with open(outfile, "w", encoding=f.encoding) as outf:
                    outf.write(shebang)
                    outf.writelines(f.readlines())
            if f:
                f.close()
        else:
            if f:
                f.close()
            self.copy_file(script, outfile)

    def _change_modes(self, outfiles):
        if os.name != 'posix':
            return

        for file in outfiles:
            self._change_mode(file)

    def _change_mode(self, file):
        if self.dry_run:
            log.info("changing mode of %s", file)
            return

        oldmode = os.stat(file)[ST_MODE] & 0o7777
        newmode = (oldmode | 0o555) & 0o7777
        if newmode != oldmode:
            log.info("changing mode of %s from %o to %o", file, oldmode, newmode)
            os.chmod(file, newmode)

    @staticmethod
    def _validate_shebang(shebang, encoding):
        # Python parser starts to read a script using UTF-8 until
        # it gets a #coding:xxx cookie. The shebang has to be the
        # first line of a file, the #coding:xxx cookie cannot be
        # written before. So the shebang has to be encodable to
        # UTF-8.
        try:
            shebang.encode('utf-8')
        except UnicodeEncodeError:
            raise ValueError(f"The shebang ({shebang!r}) is not encodable to utf-8")

        # If the script is encoded to a custom encoding (use a
        # #coding:xxx cookie), the shebang has to be encodable to
        # the script encoding too.
        try:
            shebang.encode(encoding)
        except UnicodeEncodeError:
            raise ValueError(
                f"The shebang ({shebang!r}) is not encodable "
                f"to the script encoding ({encoding})"
            )