"""Read RDF files."""

from pathlib import Path
from typing import Dict, List, Optional

from llama_index.readers.base import BaseReader
from llama_index.readers.schema.base import Document


class RDFReader(BaseReader):
    """RDF reader."""

    def __init__(
        self,
        *args: Any,
        **kwargs: Any,
    ) -> None:
        """Initialize loader."""
        
        super().__init__(*args, **kwargs)
        
        from rdflib import Graph, URIRef
        from rdflib.namespace import RDFS, RDF

    def fetch_labels(self, uri: URIRef, graph: Graph, lang: str):
        """Fetch all labels of a URI by language."""

        return list(filter(
            lambda x: x.language in [lang, None], 
            graph.objects(uri, RDFS.label)))

    def fetch_label_in_graphs(self, uri: URIRef, lang: str = 'en'):
        """Fetch one label of a URI by language from the local or global graph."""

        labels = self.fetch_labels(uri, self.g_local, lang)
        if len(labels) > 0:
            return labels[0].value
        
        labels = self.fetch_labels(uri, self.g_global, lang)
        if len(labels) > 0:
            return labels[0].value
        
        raise Exception(f"Label not found for: {uri}")
        
    def load_data(
        self, file: Path, extra_info: Optional[Dict] = None
    ) -> List[Document]:
        """Parse file."""

        lang = extra_info['lang'] if extra_info is not None else 'en'

        self.g_local = Graph()
        self.g_local.parse(file)

        self.g_global = Graph()
        self.g_global.parse(str(RDF))
        self.g_global.parse(str(RDFS))

        text_list = []

        for s, p, o in self.g_local:
            if p == RDFS.label:
                continue
            triple = f"<{self.fetch_label_in_graphs(s, lang=lang)}> " \
                     f"<{self.fetch_label_in_graphs(p, lang=lang)}> " \
                     f"<{self.fetch_label_in_graphs(o, lang=lang)}>"
            text_list.append(triple)

        text = "\n".join(text_list)

        return [Document(text, extra_info=extra_info)]