"""HTML node parser."""
from typing import TYPE_CHECKING, Any, List, Optional, Sequence

from llama_index.bridge.pydantic import Field
from llama_index.callbacks.base import CallbackManager
from llama_index.node_parser.interface import NodeParser
from llama_index.node_parser.node_utils import build_nodes_from_splits
from llama_index.schema import BaseNode, MetadataMode, TextNode
from llama_index.utils import get_tqdm_iterable

if TYPE_CHECKING:
    from bs4 import Tag

DEFAULT_TAGS = ["p", "h1", "h2", "h3", "h4", "h5", "h6", "li", "b", "i", "u", "section"]


class HTMLNodeParser(NodeParser):
    """HTML node parser.

    Splits a document into Nodes using custom HTML splitting logic.

    Args:
        include_metadata (bool): whether to include metadata in nodes
        include_prev_next_rel (bool): whether to include prev/next relationships

    """

    tags: List[str] = Field(
        default=DEFAULT_TAGS, description="HTML tags to extract text from."
    )

    @classmethod
    def from_defaults(
        cls,
        include_metadata: bool = True,
        include_prev_next_rel: bool = True,
        callback_manager: Optional[CallbackManager] = None,
        tags: Optional[List[str]] = DEFAULT_TAGS,
    ) -> "HTMLNodeParser":
        callback_manager = callback_manager or CallbackManager([])

        return cls(
            include_metadata=include_metadata,
            include_prev_next_rel=include_prev_next_rel,
            callback_manager=callback_manager,
            tags=tags,
        )

    @classmethod
    def class_name(cls) -> str:
        """Get class name."""
        return "HTMLNodeParser"

    def _parse_nodes(
        self,
        nodes: Sequence[BaseNode],
        show_progress: bool = False,
        **kwargs: Any,
    ) -> List[BaseNode]:
        all_nodes: List[BaseNode] = []
        nodes_with_progress = get_tqdm_iterable(nodes, show_progress, "Parsing nodes")

        for node in nodes_with_progress:
            nodes = self.get_nodes_from_node(node)
            all_nodes.extend(nodes)

        return all_nodes

    def get_nodes_from_node(self, node: BaseNode) -> List[TextNode]:
        """Get nodes from document."""
        try:
            from bs4 import BeautifulSoup
        except ImportError:
            raise ImportError("bs4 is required to read HTML files.")

        text = node.get_content(metadata_mode=MetadataMode.NONE)
        soup = BeautifulSoup(text, "html.parser")
        html_nodes = []
        last_tag = None
        current_section = ""

        tags = soup.find_all(self.tags)
        for tag in tags:
            tag_text = self._extract_text_from_tag(tag)
            if tag.name == last_tag or last_tag is None:
                last_tag = tag.name
                current_section += f"{tag_text.strip()}\n"
            else:
                html_nodes.append(
                    self._build_node_from_split(
                        current_section.strip(), node, {"tag": last_tag}
                    )
                )
                last_tag = tag.name
                current_section = f"{tag_text}\n"

        if current_section:
            html_nodes.append(
                self._build_node_from_split(
                    current_section.strip(), node, {"tag": last_tag}
                )
            )

        return html_nodes

    def _extract_text_from_tag(self, tag: "Tag") -> str:
        from bs4 import NavigableString

        texts = []
        for elem in tag.children:
            if isinstance(elem, NavigableString):
                if elem.strip():
                    texts.append(elem.strip())
            elif elem.name in self.tags:
                continue
            else:
                texts.append(elem.get_text().strip())
        return "\n".join(texts)

    def _build_node_from_split(
        self,
        text_split: str,
        node: BaseNode,
        metadata: dict,
    ) -> TextNode:
        """Build node from single text split."""
        node = build_nodes_from_splits([text_split], node, id_func=self.id_func)[0]

        if self.include_metadata:
            node.metadata = {**node.metadata, **metadata}

        return node
