import io
import pandas as pd
from PyPDF2 import PdfReader

def read_pdf(file_bytes: bytes) -> str:
    """
    Extracts text from a PDF file provided as bytes.
    """
    try:
        reader = PdfReader(io.BytesIO(file_bytes))
        text = ""
        for page in reader.pages:
            text += page.extract_text() or ""
        return text.strip()
    except Exception as e:
        return f"[ERROR] Failed to read PDF: {e}"

def read_csv(file_bytes: bytes) -> str:
    """
    Reads the first few rows of a CSV file provided as bytes.
    """
    try:
        df = pd.read_csv(io.BytesIO(file_bytes))
        return df.head(10).to_string(index=False)
    except Exception as e:
        return f"[ERROR] Failed to read CSV: {e}"

def read_txt(file_bytes: bytes) -> str:
    """
    Reads a plain text file provided as bytes.
    """
    try:
        return file_bytes.decode('utf-8').strip()
    except UnicodeDecodeError:
        return file_bytes.decode('latin1', errors='ignore').strip()
    except Exception as e:
        return f"[ERROR] Failed to read TXT: {e}"