"""
Document processing utilities for the RAG service.
Handles text chunking and extraction from various file formats.
"""

import logging
import subprocess
import tempfile
from pathlib import Path
from typing import List

logger = logging.getLogger("moxie-rag.processor")

# Approximate chars per token for multilingual text
CHARS_PER_TOKEN = 4


def chunk_text(
    text: str,
    chunk_size: int = 500,
    overlap: int = 50,
) -> List[str]:
    """
    Split text into chunks of approximately chunk_size tokens with overlap.
    """
    char_size = chunk_size * CHARS_PER_TOKEN
    char_overlap = overlap * CHARS_PER_TOKEN

    text = text.strip()
    if not text:
        return []

    if len(text) <= char_size:
        return [text]

    chunks = []
    start = 0

    while start < len(text):
        end = start + char_size

        if end < len(text):
            window = text[start:end]
            best_break = -1
            for separator in ["\n\n", ".\n", ". ", "?\n", "? ", "!\n", "! ", "\n", ", ", " "]:
                pos = window.rfind(separator)
                if pos > char_size // 2:
                    best_break = pos + len(separator)
                    break
            if best_break > 0:
                end = start + best_break

        chunk = text[start:end].strip()
        if chunk:
            chunks.append(chunk)

        next_start = end - char_overlap
        if next_start <= start:
            next_start = end
        start = next_start

    return chunks


def extract_text_from_pdf(file_path: str) -> str:
    """Extract text from a PDF file using pdfplumber."""
    import pdfplumber

    text_parts = []
    with pdfplumber.open(file_path) as pdf:
        for i, page in enumerate(pdf.pages):
            page_text = page.extract_text()
            if page_text:
                text_parts.append(page_text)
            else:
                logger.debug(f"Page {i + 1}: no text extracted")

    result = "\n\n".join(text_parts)
    logger.info(f"Extracted {len(result)} chars from PDF ({len(text_parts)} pages)")
    return result


def extract_text_from_docx(file_path: str) -> str:
    """Extract text from a DOCX file using python-docx."""
    from docx import Document

    doc = Document(file_path)
    paragraphs = [p.text for p in doc.paragraphs if p.text.strip()]
    result = "\n\n".join(paragraphs)
    logger.info(f"Extracted {len(result)} chars from DOCX ({len(paragraphs)} paragraphs)")
    return result


def extract_text_from_excel(file_path: str) -> str:
    """Extract text from Excel files (.xlsx, .xls) using openpyxl/pandas."""
    import pandas as pd

    text_parts = []
    xls = pd.ExcelFile(file_path)

    for sheet_name in xls.sheet_names:
        df = pd.read_excel(file_path, sheet_name=sheet_name)
        if df.empty:
            continue

        text_parts.append(f"--- Sheet: {sheet_name} ---")

        # Include column headers
        headers = " | ".join(str(c) for c in df.columns)
        text_parts.append(f"Columns: {headers}")

        # Convert rows to readable text
        for idx, row in df.iterrows():
            row_text = " | ".join(
                f"{col}: {val}" for col, val in row.items()
                if pd.notna(val) and str(val).strip()
            )
            if row_text:
                text_parts.append(row_text)

    result = "\n".join(text_parts)
    logger.info(f"Extracted {len(result)} chars from Excel ({len(xls.sheet_names)} sheets)")
    return result


def extract_audio_from_video(video_path: str) -> str:
    """Extract audio track from video file using ffmpeg. Returns path to wav file."""
    audio_path = tempfile.mktemp(suffix=".wav")
    try:
        subprocess.run(
            [
                "ffmpeg", "-i", video_path,
                "-vn", "-acodec", "pcm_s16le",
                "-ar", "16000", "-ac", "1",
                "-y", audio_path,
            ],
            capture_output=True,
            check=True,
            timeout=600,
        )
        logger.info(f"Extracted audio from video to {audio_path}")
        return audio_path
    except subprocess.CalledProcessError as e:
        logger.error(f"ffmpeg failed: {e.stderr.decode()}")
        raise ValueError(f"Could not extract audio from video: {e.stderr.decode()[:200]}")


def extract_text_from_file(file_path: str, filename: str) -> str:
    """
    Extract text from a file based on its extension.

    Supported: .pdf, .docx, .doc, .txt, .md, .csv, .json, .html, .xlsx, .xls
    """
    ext = Path(filename).suffix.lower()

    if ext == ".pdf":
        return extract_text_from_pdf(file_path)
    elif ext in (".docx", ".doc"):
        return extract_text_from_docx(file_path)
    elif ext in (".xlsx", ".xls"):
        return extract_text_from_excel(file_path)
    elif ext in (".txt", ".md", ".csv", ".json", ".html", ".xml", ".rst"):
        with open(file_path, "r", encoding="utf-8", errors="ignore") as f:
            content = f.read()
        logger.info(f"Read {len(content)} chars from {ext} file")
        return content
    else:
        raise ValueError(f"Unsupported file type: {ext}")