"""Templates utility functions for Sphinx.
"""

import os
from functools import partial
from os import path
from typing import Callable, Dict, List, Tuple, Union

from jinja2 import TemplateNotFound
from jinja2.environment import Environment
from jinja2.loaders import BaseLoader
from jinja2.sandbox import SandboxedEnvironment

from sphinx import package_dir
from sphinx.jinja2glue import SphinxFileSystemLoader
from sphinx.locale import get_translator
from sphinx.util import rst, texescape


class BaseRenderer:
    def __init__(self, loader: BaseLoader = None) -> None:
        self.env = SandboxedEnvironment(loader=loader, extensions=['jinja2.ext.i18n'])
        self.env.filters['repr'] = repr
        self.env.install_gettext_translations(get_translator())

    def render(self, template_name: str, context: Dict) -> str:
        return self.env.get_template(template_name).render(context)

    def render_string(self, source: str, context: Dict) -> str:
        return self.env.from_string(source).render(context)


class FileRenderer(BaseRenderer):
    def __init__(self, search_path: Union[str, List[str]]) -> None:
        if isinstance(search_path, str):
            search_path = [search_path]
        else:
            # filter "None" paths
            search_path = list(filter(None, search_path))

        loader = SphinxFileSystemLoader(search_path)
        super().__init__(loader)

    @classmethod
    def render_from_file(cls, filename: str, context: Dict) -> str:
        dirname = os.path.dirname(filename)
        basename = os.path.basename(filename)
        return cls(dirname).render(basename, context)


class SphinxRenderer(FileRenderer):
    def __init__(self, template_path: Union[str, List[str]] = None) -> None:
        if template_path is None:
            template_path = os.path.join(package_dir, 'templates')
        super().__init__(template_path)

    @classmethod
    def render_from_file(cls, filename: str, context: Dict) -> str:
        return FileRenderer.render_from_file(filename, context)


class LaTeXRenderer(SphinxRenderer):
    def __init__(self, template_path: str = None, latex_engine: str = None) -> None:
        if template_path is None:
            template_path = os.path.join(package_dir, 'templates', 'latex')
        super().__init__(template_path)

        # use texescape as escape filter
        escape = partial(texescape.escape, latex_engine=latex_engine)
        self.env.filters['e'] = escape
        self.env.filters['escape'] = escape
        self.env.filters['eabbr'] = texescape.escape_abbr

        # use JSP/eRuby like tagging instead because curly bracket; the default
        # tagging of jinja2 is not good for LaTeX sources.
        self.env.variable_start_string = '<%='
        self.env.variable_end_string = '%>'
        self.env.block_start_string = '<%'
        self.env.block_end_string = '%>'
        self.env.comment_start_string = '<#'
        self.env.comment_end_string = '#>'


class ReSTRenderer(SphinxRenderer):
    def __init__(self, template_path: Union[str, List[str]] = None, language: str = None) -> None:  # NOQA
        super().__init__(template_path)

        # add language to environment
        self.env.extend(language=language)

        # use texescape as escape filter
        self.env.filters['e'] = rst.escape
        self.env.filters['escape'] = rst.escape
        self.env.filters['heading'] = rst.heading


class SphinxTemplateLoader(BaseLoader):
    """A loader supporting template inheritance"""

    def __init__(self, confdir: str, templates_paths: List[str],
                 system_templates_paths: List[str]) -> None:
        self.loaders = []
        self.sysloaders = []

        for templates_path in templates_paths:
            loader = SphinxFileSystemLoader(path.join(confdir, templates_path))
            self.loaders.append(loader)

        for templates_path in system_templates_paths:
            loader = SphinxFileSystemLoader(templates_path)
            self.loaders.append(loader)
            self.sysloaders.append(loader)

    def get_source(self, environment: Environment, template: str) -> Tuple[str, str, Callable]:
        if template.startswith('!'):
            # search a template from ``system_templates_paths``
            loaders = self.sysloaders
            template = template[1:]
        else:
            loaders = self.loaders

        for loader in loaders:
            try:
                return loader.get_source(environment, template)
            except TemplateNotFound:
                pass
        raise TemplateNotFound(template)