from datetime import datetime

from app.schemas import Transaction
from app.services import generate_insights


def _txn(ts: str, category: str, amount: float) -> Transaction:
    return Transaction(
        timestamp=datetime.fromisoformat(ts),
        category=category,
        amount=amount,
        currency="INR",
    )


def test_generate_insights_detects_increase():
    txns = [
        _txn("2025-09-05T00:00:00", "Groceries", 100),
        _txn("2025-10-05T00:00:00", "Groceries", 130),
        _txn("2025-11-05T00:00:00", "Groceries", 200),
    ]
    insights, months = generate_insights(txns)
    assert insights, "Expected at least one insight"
    assert any("increased" in insight.message for insight in insights)
    assert months, "Expected evaluated months to be returned"


def test_generate_insights_handles_new_user():
    insights, months = generate_insights([])
    assert months == []
    assert insights[0].message.startswith("Add a few expenses")