django-components/django_components/component.py

from collections import ChainMap
from typing import Any, ClassVar, Dict, Iterable, Optional, Tuple, Union

from django.core.exceptions import ImproperlyConfigured
from django.forms.widgets import Media, MediaDefiningClass
from django.template.base import NodeList, Template
from django.template.context import Context
from django.template.exceptions import TemplateSyntaxError
from django.template.loader import get_template
from django.utils.safestring import mark_safe

# Global registry var and register() function moved to separate module.
# Defining them here made little sense, since 1) component_tags.py and component.py
# rely on them equally, and 2) it made it difficult to avoid circularity in the
# way the two modules depend on one another.
from django_components.component_registry import (  # NOQA
    AlreadyRegistered,
    ComponentRegistry,
    NotRegistered,
    register,
    registry,
)
from django_components.templatetags.component_tags import (
    FILLED_SLOTS_CONTENT_CONTEXT_KEY,
    DefaultFillContent,
    FillContent,
    FilledSlotsContext,
    IfSlotFilledConditionBranchNode,
    NamedFillContent,
    SlotName,
    SlotNode,
)


class SimplifiedInterfaceMediaDefiningClass(MediaDefiningClass):
    def __new__(mcs, name, bases, attrs):
        if "Media" in attrs:
            media = attrs["Media"]

            # Allow: class Media: css = "style.css"
            if hasattr(media, "css") and isinstance(media.css, str):
                media.css = [media.css]

            # Allow: class Media: css = ["style.css"]
            if hasattr(media, "css") and isinstance(media.css, list):
                media.css = {"all": media.css}

            # Allow: class Media: css = {"all": "style.css"}
            if hasattr(media, "css") and isinstance(media.css, dict):
                for media_type, path_list in media.css.items():
                    if isinstance(path_list, str):
                        media.css[media_type] = [path_list]

            # Allow: class Media: js = "script.js"
            if hasattr(media, "js") and isinstance(media.js, str):
                media.js = [media.js]

        return super().__new__(mcs, name, bases, attrs)


class Component(metaclass=SimplifiedInterfaceMediaDefiningClass):
    # Must be set on subclass OR subclass must implement get_template_name() with
    # non-null return.
    template_name: ClassVar[str]
    media: Media

    class Media:
        css = {}
        js = []

    def __init__(
        self,
        registered_name: Optional[str] = None,
        outer_context: Optional[Context] = None,
        fill_content: Union[
            DefaultFillContent, Iterable[NamedFillContent]
        ] = (),
    ):
        self.registered_name: Optional[str] = registered_name
        self.outer_context: Context = outer_context or Context()
        self.fill_content = fill_content

    def get_context_data(self, *args, **kwargs) -> Dict[str, Any]:
        return {}

    # Can be overridden for dynamic templates
    def get_template_name(self, context) -> str:
        try:
            name = self.template_name
        except AttributeError:
            raise ImproperlyConfigured(
                f"Template name is not set for Component {type(self).__name__}. "
                f"Note: this attribute is not required if you are overriding any of "
                f"the class's `get_template*()` methods."
            )
        return name

    def get_template_string(self, context) -> str:
        ...

    def render_dependencies(self):
        """Helper function to access media.render()"""
        return self.media.render()

    def render_css_dependencies(self):
        """Render only CSS dependencies available in the media class."""
        return mark_safe("\n".join(self.media.render_css()))

    def render_js_dependencies(self):
        """Render only JS dependencies available in the media class."""
        return mark_safe("\n".join(self.media.render_js()))

    def get_template(self, context) -> Template:
        template_string = self.get_template_string(context)
        if template_string is not None:
            return Template(template_string)
        else:
            template_name = self.get_template_name(context)
            template: Template = get_template(template_name).template
            return template

    def render(self, context):
        template = self.get_template(context)
        updated_filled_slots_context: FilledSlotsContext = (
            self._process_template_and_update_filled_slot_context(
                context, template
            )
        )
        with context.update(
            {FILLED_SLOTS_CONTENT_CONTEXT_KEY: updated_filled_slots_context}
        ):
            return template.render(context)

    def _process_template_and_update_filled_slot_context(
        self, context: Context, template: Template
    ) -> FilledSlotsContext:
        fill_target2content: Dict[Optional[str], FillContent]
        if isinstance(self.fill_content, NodeList):
            fill_target2content = {None: (self.fill_content, None)}
        else:
            fill_target2content = {
                name: (nodelist, alias)
                for name, nodelist, alias in self.fill_content
            }
        slot_name2fill_content: Dict[SlotName, Optional[FillContent]] = {}
        default_slot_already_encountered: bool = False
        for node in template.nodelist.get_nodes_by_type(
            (SlotNode, IfSlotFilledConditionBranchNode)  # type: ignore
        ):
            if isinstance(node, SlotNode):
                # Give slot node knowledge of its parent template.
                node.template = template
                slot_name = node.name
                if slot_name in slot_name2fill_content:
                    raise TemplateSyntaxError(
                        f"Slot name '{slot_name}' re-used within the same template. "
                        f"Slot names must be unique."
                        f"To fix, check template '{template.name}' "
                        f"of component '{self.registered_name}'."
                    )
                content_data: Optional[
                    FillContent
                ] = None  # `None` -> unfilled
                if node.is_default:
                    if default_slot_already_encountered:
                        raise TemplateSyntaxError(
                            "Only one component slot may be marked as 'default'. "
                            f"To fix, check template '{template.name}' "
                            f"of component '{self.registered_name}'."
                        )
                    default_slot_already_encountered = True
                    content_data = fill_target2content.get(None)
                if not content_data:
                    content_data = fill_target2content.get(node.name)
                if not content_data and node.is_required:
                    raise TemplateSyntaxError(
                        f"Slot '{slot_name}' is marked as 'required' (i.e. non-optional), "
                        f"yet no fill is provided. Check template.'"
                    )
                slot_name2fill_content[slot_name] = content_data
            elif isinstance(node, IfSlotFilledConditionBranchNode):
                node.template = template
            else:
                raise RuntimeError(
                    f"Node of {type(node).__name__} does not require linking."
                )
        # Check fills
        if (
            None in fill_target2content
            and not default_slot_already_encountered
        ):
            raise TemplateSyntaxError(
                f"Component '{self.registered_name}' passed default fill content "
                f"(i.e. without explicit 'fill' tag), "
                f"even though none of its slots is marked as 'default'."
            )
        for fill_name in filter(None, fill_target2content.keys()):
            if fill_name not in slot_name2fill_content:
                raise TemplateSyntaxError(
                    f"Component '{self.registered_name}' passed fill "
                    f"that refers to undefined slot: {fill_name}"
                )
        # Return updated FILLED_SLOTS_CONTEXT map
        filled_slots_map: Dict[Tuple[SlotName, Template], FillContent] = {
            (slot_name, template): content_data
            for slot_name, content_data in slot_name2fill_content.items()
            if content_data  # (is not None)
        }
        try:
            prev_context: FilledSlotsContext = context[
                FILLED_SLOTS_CONTENT_CONTEXT_KEY
            ]
            return prev_context.new_child(filled_slots_map)
        except KeyError:
            return ChainMap(filled_slots_map)