import os
import re
import string
from importlib.util import find_spec
from pathlib import Path
from shutil import copy2, copystat, ignore_patterns, move
from stat import S_IWUSR as OWNER_WRITE_PERMISSION

import scrapy
from scrapy.commands import ScrapyCommand
from scrapy.exceptions import UsageError
from scrapy.utils.template import render_templatefile, string_camelcase

TEMPLATES_TO_RENDER = (
    ("scrapy.cfg",),
    ("${project_name}", "settings.py.tmpl"),
    ("${project_name}", "items.py.tmpl"),
    ("${project_name}", "pipelines.py.tmpl"),
    ("${project_name}", "middlewares.py.tmpl"),
)

IGNORE = ignore_patterns("*.pyc", "__pycache__", ".svn")


def _make_writable(path):
    current_permissions = os.stat(path).st_mode
    os.chmod(path, current_permissions | OWNER_WRITE_PERMISSION)


class Command(ScrapyCommand):

    requires_project = False
    default_settings = {"LOG_ENABLED": False, "SPIDER_LOADER_WARN_ONLY": True}

    def syntax(self):
        return "<project_name> [project_dir]"

    def short_desc(self):
        return "Create new project"

    def _is_valid_name(self, project_name):
        def _module_exists(module_name):
            spec = find_spec(module_name)
            return spec is not None and spec.loader is not None

        if not re.search(r"^[_a-zA-Z]\w*$", project_name):
            print(
                "Error: Project names must begin with a letter and contain"
                " only\nletters, numbers and underscores"
            )
        elif _module_exists(project_name):
            print(f"Error: Module {project_name!r} already exists")
        else:
            return True
        return False

    def _copytree(self, src: Path, dst: Path):
        """
        Since the original function always creates the directory, to resolve
        the issue a new function had to be created. It's a simple copy and
        was reduced for this case.

        More info at:
        https://github.com/scrapy/scrapy/pull/2005
        """
        ignore = IGNORE
        names = [x.name for x in src.iterdir()]
        ignored_names = ignore(src, names)

        if not dst.exists():
            dst.mkdir(parents=True)

        for name in names:
            if name in ignored_names:
                continue

            srcname = src / name
            dstname = dst / name
            if srcname.is_dir():
                self._copytree(srcname, dstname)
            else:
                copy2(srcname, dstname)
                _make_writable(dstname)

        copystat(src, dst)
        _make_writable(dst)

    def run(self, args, opts):
        if len(args) not in (1, 2):
            raise UsageError()

        project_name = args[0]

        if len(args) == 2:
            project_dir = Path(args[1])
        else:
            project_dir = Path(args[0])

        if (project_dir / "scrapy.cfg").exists():
            self.exitcode = 1
            print(f"Error: scrapy.cfg already exists in {project_dir.resolve()}")
            return

        if not self._is_valid_name(project_name):
            self.exitcode = 1
            return

        self._copytree(Path(self.templates_dir), project_dir.resolve())
        move(project_dir / "module", project_dir / project_name)
        for paths in TEMPLATES_TO_RENDER:
            tplfile = Path(
                project_dir,
                *(
                    string.Template(s).substitute(project_name=project_name)
                    for s in paths
                ),
            )
            render_templatefile(
                tplfile,
                project_name=project_name,
                ProjectName=string_camelcase(project_name),
            )
        print(
            f"New Scrapy project '{project_name}', using template directory "
            f"'{self.templates_dir}', created in:"
        )
        print(f"    {project_dir.resolve()}\n")
        print("You can start your first spider with:")
        print(f"    cd {project_dir}")
        print("    scrapy genspider example example.com")

    @property
    def templates_dir(self) -> str:
        return str(
            Path(
                self.settings["TEMPLATES_DIR"] or Path(scrapy.__path__[0], "templates"),
                "project",
            )
        )
