from sklearn.pipeline import Pipeline
from sklearn.feature_extraction.text import TfidfVectorizer
from sklearn.linear_model import LogisticRegression

def build_tfidf_model():
    model = Pipeline([
        ("tfidf", TfidfVectorizer(
            max_features=20000,
            ngram_range=(1, 2),
            stop_words="english"
        )),
        ("clf", LogisticRegression(
            max_iter=1000,
            class_weight="balanced"
        ))
    ])
    return model