"""Service for processing documents and ingesting to vector store."""

from langchain.text_splitter import RecursiveCharacterTextSplitter
from langchain_core.documents import Document as LangChainDocument
from src.db.postgres.vector_store import get_vector_store
from src.storage.az_blob.az_blob import blob_storage
from src.db.postgres.models import Document as DBDocument
from sqlalchemy.ext.asyncio import AsyncSession
from src.middlewares.logging import get_logger
from typing import List
from datetime import datetime, timezone, timedelta
import sys
import docx
import pytesseract
from pdf2image import convert_from_bytes
from io import BytesIO

_JAKARTA_TZ = timezone(timedelta(hours=7))

logger = get_logger("knowledge_processing")


class KnowledgeProcessingService:
    """Service for processing documents and ingesting to vector store."""

    def __init__(self):
        self.text_splitter = RecursiveCharacterTextSplitter(
            chunk_size=1000,
            chunk_overlap=200,
            length_function=len
        )

    async def process_document(self, db_doc: DBDocument, db: AsyncSession) -> int:
        """Process document and ingest to vector store.

        Returns:
            Number of chunks ingested
        """
        try:
            logger.info(f"Processing document {db_doc.id}")
            content = await blob_storage.download_file(db_doc.blob_name)

            if db_doc.file_type == "pdf":
                documents = await self._build_pdf_documents(content, db_doc)
            else:
                text = self._extract_text(content, db_doc.file_type)
                if not text.strip():
                    raise ValueError("No text extracted from document")
                chunks = self.text_splitter.split_text(text)
                documents = [
                    LangChainDocument(
                        page_content=chunk,
                        metadata={
                            "user_id": db_doc.user_id,
                            "source_type": "document",
                            "updated_at": datetime.now(_JAKARTA_TZ).isoformat(),
                            "data": {
                                "document_id": db_doc.id,
                                "filename": db_doc.filename,
                                "file_type": db_doc.file_type,
                                "chunk_index": i,
                            },
                        }
                    )
                    for i, chunk in enumerate(chunks)
                ]

            if not documents:
                raise ValueError("No text extracted from document")

            vector_store = get_vector_store()
            await vector_store.aadd_documents(documents)

            logger.info(f"Processed {db_doc.id}: {len(documents)} chunks ingested")
            return len(documents)

        except Exception as e:
            logger.error(f"Failed to process document {db_doc.id}", error=str(e))
            raise

    async def _build_pdf_documents(
        self, content: bytes, db_doc: DBDocument
    ) -> List[LangChainDocument]:
        """Build LangChain documents from PDF with page_label metadata using Tesseract OCR."""
        documents: List[LangChainDocument] = []

        poppler_path = None
        if sys.platform == "win32":
            pytesseract.pytesseract.tesseract_cmd = r"./software/Tesseract-OCR/tesseract.exe"
            poppler_path = "./software/poppler-24.08.0/Library/bin"

        images = convert_from_bytes(content, poppler_path=poppler_path)
        logger.info(f"Tesseract OCR: converting {len(images)} pages")

        for page_num, image in enumerate(images, start=1):
            page_text = pytesseract.image_to_string(image)
            if not page_text.strip():
                continue
            for chunk in self.text_splitter.split_text(page_text):
                documents.append(LangChainDocument(
                    page_content=chunk,
                    metadata={
                        "user_id": db_doc.user_id,
                        "source_type": "document",
                        "updated_at": datetime.now(_JAKARTA_TZ).isoformat(),
                        "data": {
                            "document_id": db_doc.id,
                            "filename": db_doc.filename,
                            "file_type": db_doc.file_type,
                            "chunk_index": len(documents),
                            "page_label": page_num,
                        },
                    }
                ))

        return documents

    def _extract_text(self, content: bytes, file_type: str) -> str:
        """Extract text from DOCX or TXT content."""
        if file_type == "docx":
            doc = docx.Document(BytesIO(content))
            return "\n".join(p.text for p in doc.paragraphs)
        elif file_type == "txt":
            return content.decode("utf-8")
        else:
            raise ValueError(f"Unsupported file type: {file_type}")


knowledge_processor = KnowledgeProcessingService()