from copy import deepcopy
from dataclasses import replace
from pathlib import Path

from chonkie import (
    Chunk,
    ElasticHandshake,
    FileFetcher,
    MarkdownChef,
    TextChef,
    TokenChunker,
    MarkdownDocument
)
from elasticsearch import Elasticsearch
from loguru import logger
from transformers import AutoTokenizer

from scripts.pipelines.tasks.embeddings import OllamaEmbeddings
from src.config import settings


def _get_text(element) -> str:
    for attr in ("text", "content", "markdown"):
        value = getattr(element, attr, None)
        if isinstance(value, str):
            return value
    raise AttributeError(
        f"Could not extract text from element of type {type(element).__name__}"
    )


def _merge_markdown_document(processed_doc: MarkdownDocument) -> MarkdownDocument:
    elements = []

    for chunk in processed_doc.chunks:
        elements.append(("chunk", chunk.start_index, chunk.end_index, chunk))

    for code in processed_doc.code:
        elements.append(("code", code.start_index, code.end_index, code))

    for table in processed_doc.tables:
        elements.append(("table", table.start_index, table.end_index, table))

    elements.sort(key=lambda item: (item[1], item[2]))

    merged_chunks = []
    current_chunk = None
    current_parts = []
    current_end_index = None
    current_token_count = None

    def flush():
        nonlocal current_chunk, current_parts, current_end_index, current_token_count

        if current_chunk is None:
            return

        merged_text = "\n\n".join(part for part in current_parts if part)

        merged_chunks.append(
            replace(
                current_chunk,
                text=merged_text,
                end_index=current_end_index,
                token_count=current_token_count,
            )
        )

        current_chunk = None
        current_parts = []
        current_end_index = None
        current_token_count = None

    for kind, _, _, element in elements:
        if kind == "chunk":
            flush()
            current_chunk = element
            current_parts = [_get_text(element)]
            current_end_index = element.end_index
            current_token_count = element.token_count
            continue

        if current_chunk is None:
            continue

        current_parts.append(_get_text(element))
        current_end_index = max(current_end_index, element.end_index)
        current_token_count += getattr(element, "token_count", 0)

    flush()

    fused_processed_doc = deepcopy(processed_doc)
    fused_processed_doc.chunks = merged_chunks
    fused_processed_doc.code = processed_doc.code
    fused_processed_doc.tables = processed_doc.tables

    return fused_processed_doc


def fetch_documents(docs_folder_path: str, docs_extension: list[str]) -> list[Path]:
    """
    Fetch files from a folder that match the specified extensions.

    Args:
        docs_folder_path (str): Path to the folder containing documents
        docs_extension (list[str]): List of file extensions to filter by (e.g., [".md", ".avap"])

    Returns:
        List of Paths to the fetched documents
    """
    fetcher = FileFetcher()
    docs_path = fetcher.fetch(dir=f"{settings.proj_root}/{docs_folder_path}", ext=docs_extension)
    return docs_path


def process_documents(docs_path: list[Path]) -> list[Chunk]:
    """
    Process documents by applying appropriate chefs and chunking strategies based on file type.

    Args:
        docs_path (list[Path]): List of Paths to the documents to be processed

    Returns:
        List of processed documents ready for ingestion
    """
    processed_docs = []
    custom_tokenizer = AutoTokenizer.from_pretrained(settings.hf_emb_model_name)
    chef_md = MarkdownChef(tokenizer=custom_tokenizer)
    chef_txt = TextChef()
    chunker = TokenChunker(tokenizer=custom_tokenizer)

    for doc_path in docs_path:
        doc_extension = doc_path.suffix.lower()
        
        if doc_extension == ".md":
            processed_doc = chef_md.process(doc_path)
            fused_doc = _merge_markdown_document(processed_doc)
            processed_docs.extend(fused_doc.chunks)

        elif doc_extension == ".avap":
            processed_doc = chef_txt.process(doc_path)
            chunked_doc = chunker.chunk(processed_doc.content)
            processed_docs.extend(chunked_doc)

    return processed_docs


def ingest_documents(
    chunked_docs: list[Chunk],
    es_index: str,
    es_request_timeout: int,
    es_max_retries: int,
    es_retry_on_timeout: bool,
    delete_es_index: bool,
) -> None:

    logger.info(
        f"Instantiating Elasticsearch client with URL: {settings.elasticsearch_local_url}..."
    )
    es = Elasticsearch(
        hosts=settings.elasticsearch_local_url,
        request_timeout=es_request_timeout,
        max_retries=es_max_retries,
        retry_on_timeout=es_retry_on_timeout,
    )

    if delete_es_index and es.indices.exists(index=es_index):
        logger.info(f"Deleting existing Elasticsearch index: {es_index}...")
        es.indices.delete(index=es_index)

    handshake = ElasticHandshake(
        client=es,
        index_name=es_index,
        embedding_model=OllamaEmbeddings(model=settings.ollama_emb_model_name),
    )

    logger.info(
        f"Ingesting {len(chunked_docs)} chunks into Elasticsearch index: {es_index}..."
    )
    handshake.write(chunked_docs)