import os

import pandas as pd

from .config import REQUIRED_COLUMNS


def cargar_mensajes(path):
    ext = os.path.splitext(path)[1].lower()
    if ext == ".csv":
        df = pd.read_csv(path, dtype=str)
    elif ext in [".xls", ".xlsx"]:
        df = pd.read_excel(path, dtype=str)
    else:
        raise ValueError("Formato no soportado. Usa .csv o .xlsx")

    df.columns = [column.strip() for column in df.columns]
    missing = REQUIRED_COLUMNS - set(df.columns)
    if missing:
        raise ValueError(f"Columnas faltantes en '{path}': {missing}")

    df["tipo"] = df["tipo"].str.strip().str.lower()
    return df[df["tipo"].isin(["contacto", "grupo"])].reset_index(drop=True)