"""Regression: recon SQL validator catches LLM-generated schema mismatches.

Bug captured: drill_down generated `SELECT district_id FROM loan` —
syntactically valid, parses, but `loan` doesn't have a `district_id` column.
We want to catch this BEFORE Postgres does, with a clear message naming
where the column actually lives.
"""

import pytest

from api.recon.types import Column, Metric, Recon, Relationship, Table
from api.recon.validate import ReconValidationError, validate_sql


def _recon() -> Recon:
    return Recon(
        schema="financial",
        tables={
            "loan": Table("loan", None, [
                Column("loan_id", "BIGINT", False),
                Column("account_id", "BIGINT", True),
                Column("amount", "BIGINT", True),
                Column("status", "TEXT", True),
            ]),
            "account": Table("account", None, [
                Column("account_id", "BIGINT", False),
                Column("district_id", "BIGINT", True),
            ]),
            "district": Table("district", None, [
                Column("district_id", "BIGINT", False),
                Column("A2", "TEXT", True),
                Column("A13", "BIGINT", True),
            ]),
        },
        metrics={},
        column_to_tables={
            "loan_id": ["loan"],
            "account_id": ["account", "loan"],
            "amount": ["loan"],
            "status": ["loan"],
            "district_id": ["account", "district"],
            "A2": ["district"],
            "A13": ["district"],
        },
        relationships=[
            Relationship("account", "district_id", "district", "district_id"),
            Relationship("loan", "account_id", "account", "account_id"),
        ],
    )


def test_valid_sql_passes():
    sql = "SELECT account_id, amount FROM loan WHERE status = 'B'"
    validate_sql(sql, _recon())


def test_valid_join_passes():
    sql = """
      SELECT d.A2, AVG(l.amount)
      FROM loan l
      JOIN account a ON l.account_id = a.account_id
      JOIN district d ON a.district_id = d.district_id
      GROUP BY d.A2
    """
    validate_sql(sql, _recon())


def test_unknown_column_on_table_raises():
    # The exact bug we hit in production: district_id picked from loan
    # without joining through account.
    sql = """
      WITH x AS (SELECT district_id, AVG(amount) FROM loan GROUP BY district_id)
      SELECT * FROM x
    """
    with pytest.raises(ReconValidationError) as exc:
        validate_sql(sql, _recon())
    msg = str(exc.value)
    assert "district_id" in msg
    # The hint should name where district_id actually lives.
    assert "account" in msg and "district" in msg


def test_misspelled_column_raises():
    sql = "SELECT amnt FROM loan"
    with pytest.raises(ReconValidationError) as exc:
        validate_sql(sql, _recon())
    assert "amnt" in str(exc.value)


def test_qualified_column_on_wrong_table_raises():
    # district.amount doesn't exist (amount is on loan).
    sql = "SELECT d.amount FROM district d"
    with pytest.raises(ReconValidationError):
        validate_sql(sql, _recon())