html.py

"""HTML Exporter class"""

# Copyright (c) Jupyter Development Team.
# Distributed under the terms of the Modified BSD License.

import base64
import json
import mimetypes
import os
from pathlib import Path
from typing import Any, Dict, Optional, Tuple

import jinja2
import markupsafe
from bs4 import BeautifulSoup
from jupyter_core.paths import jupyter_path
from traitlets import Bool, Unicode, default, validate
from traitlets.config import Config

if tuple(int(x) for x in jinja2.__version__.split(".")[:3]) < (3, 0, 0):
    from jinja2 import contextfilter  # type:ignore[attr-defined]
else:
    from jinja2 import pass_context as contextfilter

from jinja2.loaders import split_template_path
from nbformat import NotebookNode

from nbconvert.filters.highlight import Highlight2HTML
from nbconvert.filters.markdown_mistune import IPythonRenderer, MarkdownWithMath
from nbconvert.filters.widgetsdatatypefilter import WidgetsDataTypeFilter
from nbconvert.utils.iso639_1 import iso639_1

from .templateexporter import TemplateExporter


def find_lab_theme(theme_name):
    """
    Find a JupyterLab theme location by name.

    Parameters
    ----------
    theme_name : str
        The name of the labextension theme you want to find.

    Raises
    ------
    ValueError
        If the theme was not found, or if it was not specific enough.

    Returns
    -------
    theme_name: str
        Full theme name (with scope, if any)
    labextension_path : Path
        The path to the found labextension on the system.
    """
    paths = jupyter_path("labextensions")

    matching_themes = []
    theme_path = None
    for path in paths:
        for dirpath, dirnames, filenames in os.walk(path):
            # If it's a federated labextension that contains themes
            if "package.json" in filenames and "themes" in dirnames:
                # TODO Find the theme name in the JS code instead?
                # TODO Find if it's a light or dark theme?
                with open(Path(dirpath) / "package.json", encoding="utf-8") as fobj:
                    labext_name = json.loads(fobj.read())["name"]

                if labext_name == theme_name or theme_name in labext_name.split("/"):
                    matching_themes.append(labext_name)

                    full_theme_name = labext_name
                    theme_path = Path(dirpath) / "themes" / labext_name

    if len(matching_themes) == 0:
        msg = f'Could not find lab theme "{theme_name}"'
        raise ValueError(msg)

    if len(matching_themes) > 1:
        msg = (
            f'Found multiple themes matching "{theme_name}": {matching_themes}. '
            "Please be more specific about which theme you want to use."
        )
        raise ValueError(msg)

    return full_theme_name, theme_path


class HTMLExporter(TemplateExporter):
    """
    Exports a basic HTML document.  This exporter assists with the export of
    HTML.  Inherit from it if you are writing your own HTML template and need
    custom preprocessors/filters.  If you don't need custom preprocessors/
    filters, just change the 'template_file' config option.
    """

    export_from_notebook = "HTML"

    anchor_link_text = Unicode("¶", help="The text used as the text for anchor links.").tag(
        config=True
    )

    exclude_anchor_links = Bool(False, help="If anchor links should be included or not.").tag(
        config=True
    )

    require_js_url = Unicode(
        "https://cdnjs.cloudflare.com/ajax/libs/require.js/2.1.10/require.min.js",
        help="""
        URL to load require.js from.

        Defaults to loading from cdnjs.
        """,
    ).tag(config=True)

    mathjax_url = Unicode(
        "https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.7/latest.js?config=TeX-AMS_CHTML-full,Safe",
        help="""
        URL to load Mathjax from.

        Defaults to loading from cdnjs.
        """,
    ).tag(config=True)

    mermaid_js_url = Unicode(
        "https://cdnjs.cloudflare.com/ajax/libs/mermaid/10.5.0/mermaid.esm.min.mjs",
        help="""
        URL to load MermaidJS from.

        Defaults to loading from cdnjs.
        """,
    )

    jquery_url = Unicode(
        "https://cdnjs.cloudflare.com/ajax/libs/jquery/2.0.3/jquery.min.js",
        help="""
        URL to load jQuery from.

        Defaults to loading from cdnjs.
        """,
    ).tag(config=True)

    jupyter_widgets_base_url = Unicode(
        "https://unpkg.com/", help="URL base for Jupyter widgets"
    ).tag(config=True)

    widget_renderer_url = Unicode("", help="Full URL for Jupyter widgets").tag(config=True)

    html_manager_semver_range = Unicode(
        "*", help="Semver range for Jupyter widgets HTML manager"
    ).tag(config=True)

    @default("file_extension")
    def _file_extension_default(self):
        return ".html"

    @default("template_name")
    def _template_name_default(self):
        return "lab"

    theme = Unicode(
        "light",
        help="Template specific theme(e.g. the name of a JupyterLab CSS theme distributed as prebuilt extension for the lab template)",
    ).tag(config=True)

    sanitize_html = Bool(
        False,
        help=(
            "Whether the HTML in Markdown cells and cell outputs should be sanitized."
            "This should be set to True by nbviewer or similar tools."
        ),
    ).tag(config=True)

    embed_images = Bool(
        False, help="Whether or not to embed images as base64 in markdown cells."
    ).tag(config=True)

    output_mimetype = "text/html"

    @property
    def default_config(self):
        c = Config(
            {
                "NbConvertBase": {
                    "display_data_priority": [
                        "application/vnd.jupyter.widget-view+json",
                        "application/javascript",
                        "text/html",
                        "text/markdown",
                        "image/svg+xml",
                        "text/vnd.mermaid",
                        "text/latex",
                        "image/png",
                        "image/jpeg",
                        "text/plain",
                    ]
                },
                "HighlightMagicsPreprocessor": {"enabled": True},
            }
        )
        if super().default_config:
            c2 = super().default_config.copy()
            c2.merge(c)
            c = c2
        return c

    language_code = Unicode(
        "en", help="Language code of the content, should be one of the ISO639-1"
    ).tag(config=True)

    @validate("language_code")
    def _valid_language_code(self, proposal):
        if self.language_code not in iso639_1:
            self.log.warning(
                f'"{self.language_code}" is not an ISO 639-1 language code. '
                'It has been replaced by the default value "en".'
            )
            return proposal["trait"].default_value
        return proposal["value"]

    @contextfilter
    def markdown2html(self, context, source):
        """Markdown to HTML filter respecting the anchor_link_text setting"""
        cell = context.get("cell", {})
        attachments = cell.get("attachments", {})
        path = context.get("resources", {}).get("metadata", {}).get("path", "")

        renderer = IPythonRenderer(
            escape=False,
            attachments=attachments,
            embed_images=self.embed_images,
            path=path,
            anchor_link_text=self.anchor_link_text,
            exclude_anchor_links=self.exclude_anchor_links,
        )
        return MarkdownWithMath(renderer=renderer).render(source)

    def default_filters(self):
        """Get the default filters."""
        yield from super().default_filters()
        yield ("markdown2html", self.markdown2html)

    def from_notebook_node(  # type:ignore[explicit-override, override]
        self, nb: NotebookNode, resources: Optional[Dict[str, Any]] = None, **kw: Any
    ) -> Tuple[str, Dict[str, Any]]:
        """Convert from notebook node."""
        langinfo = nb.metadata.get("language_info", {})
        lexer = langinfo.get("pygments_lexer", langinfo.get("name", None))
        highlight_code = self.filters.get(
            "highlight_code", Highlight2HTML(pygments_lexer=lexer, parent=self)
        )

        filter_data_type = WidgetsDataTypeFilter(
            notebook_metadata=self._nb_metadata, parent=self, resources=resources
        )

        self.register_filter("highlight_code", highlight_code)
        self.register_filter("filter_data_type", filter_data_type)
        html, resources = super().from_notebook_node(nb, resources, **kw)
        soup = BeautifulSoup(html, features="html.parser")
        # Add image's alternative text
        missing_alt = 0
        for elem in soup.select("img:not([alt])"):
            elem.attrs["alt"] = "No description has been provided for this image"
            missing_alt += 1
        if missing_alt:
            self.log.warning(f"Alternative text is missing on {missing_alt} image(s).")
        # Set input and output focusable
        for elem in soup.select(".jp-Notebook div.jp-Cell-inputWrapper"):
            elem.attrs["tabindex"] = "0"
        for elem in soup.select(".jp-Notebook div.jp-OutputArea-output"):
            elem.attrs["tabindex"] = "0"

        return str(soup), resources

    def _init_resources(self, resources):  # noqa
        def resources_include_css(name):
            env = self.environment
            code = """<style type="text/css">\n%s</style>""" % (env.loader.get_source(env, name)[0])
            return markupsafe.Markup(code)

        def resources_include_lab_theme(name):
            # Try to find the theme with the given name, looking through the labextensions
            _, theme_path = find_lab_theme(name)

            with open(theme_path / "index.css") as file:
                data = file.read()

            # Embed assets (fonts, images...)
            for asset in os.listdir(theme_path):
                local_url = f"url({Path(asset).as_posix()})"

                if local_url in data:
                    mime_type = mimetypes.guess_type(asset)[0]

                    # Replace asset url by a base64 dataurl
                    with open(theme_path / asset, "rb") as assetfile:
                        base64_data = base64.b64encode(assetfile.read())
                        base64_str = base64_data.replace(b"\n", b"").decode("ascii")

                        data = data.replace(local_url, f"url(data:{mime_type};base64,{base64_str})")

            code = """<style type="text/css">\n%s</style>""" % data
            return markupsafe.Markup(code)

        def resources_include_js(name):
            """Get the resources include JS for a name."""
            env = self.environment
            code = """<script>\n%s</script>""" % (env.loader.get_source(env, name)[0])
            return markupsafe.Markup(code)

        def resources_include_url(name):
            """Get the resources include url for a name."""
            env = self.environment
            mime_type, encoding = mimetypes.guess_type(name)
            try:
                # we try to load via the jinja loader, but that tries to load
                # as (encoded) text
                data = env.loader.get_source(env, name)[0].encode("utf8")
            except UnicodeDecodeError:
                # if that fails (for instance a binary file, png or ttf)
                # we mimic jinja2
                pieces = split_template_path(name)
                for searchpath in self.template_paths:
                    filename = os.path.join(searchpath, *pieces)
                    if os.path.exists(filename):
                        with open(filename, "rb") as f:
                            data = f.read()
                            break
                else:
                    msg = f"No file {name!r} found in {searchpath!r}"
                    raise ValueError(msg)
            data = base64.b64encode(data)
            data = data.replace(b"\n", b"").decode("ascii")
            src = f"data:{mime_type};base64,{data}"
            return markupsafe.Markup(src)

        resources = super()._init_resources(resources)
        resources["theme"] = self.theme
        resources["include_css"] = resources_include_css
        resources["include_lab_theme"] = resources_include_lab_theme
        resources["include_js"] = resources_include_js
        resources["include_url"] = resources_include_url
        resources["require_js_url"] = self.require_js_url
        resources["mathjax_url"] = self.mathjax_url
        resources["mermaid_js_url"] = self.mermaid_js_url
        resources["jquery_url"] = self.jquery_url
        resources["jupyter_widgets_base_url"] = self.jupyter_widgets_base_url
        resources["widget_renderer_url"] = self.widget_renderer_url
        resources["html_manager_semver_range"] = self.html_manager_semver_range
        resources["should_sanitize_html"] = self.sanitize_html
        resources["language_code"] = self.language_code
        return resources