from __future__ import annotations

import sys

import datetime
import threading
import typing as t
import unittest
from collections import Counter
from contextlib import nullcontext, contextmanager, AbstractContextManager
from itertools import chain
from pathlib import Path
from unittest.mock import patch


from io import StringIO
from sqlglot import Dialect, exp
from sqlglot.optimizer.annotate_types import annotate_types
from sqlglot.optimizer.normalize_identifiers import normalize_identifiers

from sqlmesh.core import constants as c
from sqlmesh.core.dialect import normalize_model_name, schema_
from sqlmesh.core.engine_adapter import EngineAdapter
from sqlmesh.core.macros import RuntimeStage
from sqlmesh.core.model import Model, PythonModel, SqlModel
from sqlmesh.utils import UniqueKeyDict, random_id, type_is_known, yaml
from sqlmesh.utils.date import date_dict, pandas_timestamp_to_pydatetime, to_datetime
from sqlmesh.utils.errors import ConfigError, TestError
from sqlmesh.utils.yaml import load as yaml_load
from sqlmesh.utils import Verbosity
from sqlmesh.utils.rich import df_to_table

if t.TYPE_CHECKING:
    import pandas as pd

    from sqlglot.dialects.dialect import DialectType

    Row = t.Dict[str, t.Any]


TIME_KWARG_KEYS = {
    "start",
    "end",
    "execution_time",
    "latest",
    # all built-in datetime macro var names
    *date_dict(execution_time="1970-01-01", start="1970-01-01", end="1970-01-01").keys(),
}


class ModelTest(unittest.TestCase):
    __test__ = False

    CONCURRENT_RENDER_LOCK = threading.Lock()

    def __init__(
        self,
        body: t.Dict[str, t.Any],
        test_name: str,
        model: Model,
        models: UniqueKeyDict[str, Model],
        engine_adapter: EngineAdapter,
        dialect: str | None = None,
        path: Path | None = None,
        preserve_fixtures: bool = False,
        default_catalog: str | None = None,
        concurrency: bool = False,
        verbosity: Verbosity = Verbosity.DEFAULT,
    ) -> None:
        """ModelTest encapsulates a unit test for a model.

        Args:
            body: A dictionary that contains test metadata like inputs and outputs.
            test_name: The name of the test.
            model: The model that is being tested.
            models: All models to use for expansion and mapping of physical locations.
            engine_adapter: The engine adapter to use.
            dialect: The models' dialect, used for normalization purposes.
            path: An optional path to the test definition yaml file.
            preserve_fixtures: Preserve the fixture tables in the testing database, useful for debugging.
        """
        self.body = body
        self.test_name = test_name
        self.model = model
        self.models = models
        self.engine_adapter = engine_adapter
        self.path = path
        self.preserve_fixtures = preserve_fixtures
        self.default_catalog = default_catalog
        self.dialect = dialect
        self.concurrency = concurrency
        self.verbosity = verbosity

        self._fixture_table_cache: t.Dict[str, exp.Table] = {}
        self._normalized_column_name_cache: t.Dict[str, str] = {}
        self._normalized_model_name_cache: t.Dict[t.Tuple[str, bool], str] = {}

        self._test_adapter_dialect = Dialect.get_or_raise(self.engine_adapter.dialect)

        self._validate_and_normalize_test()

        if self.engine_adapter.default_catalog:
            self._fixture_catalog: t.Optional[exp.Identifier] = normalize_identifiers(
                exp.parse_identifier(
                    self.engine_adapter.default_catalog, dialect=self._test_adapter_dialect
                ),
                dialect=self._test_adapter_dialect,
            )
        else:
            self._fixture_catalog = None

        # The test schema name is randomized to avoid concurrency issues,
        # unless a schema is provided in the unit tests's body
        self._fixture_schema = exp.parse_identifier(
            self.body.get("schema") or f"sqlmesh_test_{random_id(short=True)}"
        )
        self._qualified_fixture_schema = schema_(self._fixture_schema, self._fixture_catalog)

        self._transforms = self._test_adapter_dialect.generator_class.TRANSFORMS
        self._execution_time = str(self.body.get("vars", {}).get("execution_time") or "")

        if self._execution_time:
            # Normalizes the execution time by converting it into UTC timezone
            self._execution_time = str(to_datetime(self._execution_time))

        # When execution_time is set, we mock the CURRENT_* SQL expressions so they always return it
        if self._execution_time:
            exec_time = exp.Literal.string(self._execution_time)
            self._transforms = {
                **self._transforms,
                exp.CurrentDate: lambda self, _: self.sql(
                    exp.cast(exec_time, "date", dialect=dialect)
                ),
                exp.CurrentDatetime: lambda self, _: self.sql(
                    exp.cast(exec_time, "datetime", dialect=dialect)
                ),
                exp.CurrentTime: lambda self, _: self.sql(
                    exp.cast(exec_time, "time", dialect=dialect)
                ),
                exp.CurrentTimestamp: lambda self, _: self.sql(
                    exp.cast(exec_time, "timestamp", dialect=dialect)
                ),
            }

        super().__init__()

    def defaultTestResult(self) -> unittest.TestResult:
        from sqlmesh.core.test.result import ModelTextTestResult

        return ModelTextTestResult(stream=sys.stdout, descriptions=True, verbosity=self.verbosity)

    def shortDescription(self) -> t.Optional[str]:
        return self.body.get("description")

    def setUp(self) -> None:
        """Load all input tables"""
        import pandas as pd
        import numpy as np

        self.engine_adapter.create_schema(self._qualified_fixture_schema)

        for name, values in self.body.get("inputs", {}).items():
            all_types_are_known = False
            columns_to_known_types: t.Dict[str, exp.DataType] = {}

            model = self.models.get(name)
            if model:
                inferred_columns_to_types = model.columns_to_types or {}
                columns_to_known_types = {
                    c: t for c, t in inferred_columns_to_types.items() if type_is_known(t)
                }
                all_types_are_known = bool(inferred_columns_to_types) and (
                    len(columns_to_known_types) == len(inferred_columns_to_types)
                )

            # Types specified in the test will override the corresponding inferred ones
            columns_to_known_types.update(values.get("columns", {}))

            rows = values.get("rows")
            if not all_types_are_known and rows:
                for col, value in rows[0].items():
                    if col not in columns_to_known_types:
                        v_type = annotate_types(exp.convert(value)).type or type(value).__name__
                        v_type = exp.maybe_parse(
                            v_type, into=exp.DataType, dialect=self._test_adapter_dialect
                        )

                        if not type_is_known(v_type):
                            _raise_error(
                                f"Failed to infer the data type of column '{col}' for '{name}'. This issue can be "
                                "mitigated by casting the column in the model definition, setting its type in "
                                "external_models.yaml if it's an external model, setting the model's 'columns' property, "
                                "or setting its 'columns' mapping in the test itself",
                                self.path,
                            )

                        columns_to_known_types[col] = v_type

            if rows is None:
                query_or_df: exp.Query | pd.DataFrame = self._add_missing_columns(
                    values["query"], columns_to_known_types
                )
                if columns_to_known_types:
                    columns_to_known_types = {
                        col: columns_to_known_types[col] for col in query_or_df.named_selects
                    }
            else:
                query_or_df = self._create_df(values, columns=columns_to_known_types)

            # Convert NaN/NaT values to None if DataFrame
            if isinstance(query_or_df, pd.DataFrame):
                query_or_df = query_or_df.replace({np.nan: None})

            self.engine_adapter.create_view(
                self._test_fixture_table(name), query_or_df, columns_to_known_types
            )

    def tearDown(self) -> None:
        """Drop all fixture tables."""
        if not self.preserve_fixtures:
            self.engine_adapter.drop_schema(self._qualified_fixture_schema, cascade=True)

    def assert_equal(
        self,
        expected: pd.DataFrame,
        actual: pd.DataFrame,
        sort: bool,
        partial: t.Optional[bool] = False,
    ) -> None:
        """Compare two DataFrames"""
        import numpy as np
        import pandas as pd
        from pandas.api.types import is_object_dtype

        if partial:
            intersection = actual[actual.columns.intersection(expected.columns)]
            if len(intersection.columns) > 0:
                actual = intersection

        # Two astypes are necessary, pandas converts strings to times as NS,
        # but if the actual is US, it doesn't take effect until the 2nd try!
        actual_types = actual.dtypes.to_dict()
        expected = expected.astype(actual_types, errors="ignore").astype(
            actual_types, errors="ignore"
        )

        # The `actual` df's dtypes will almost always be pd.Timestamp for datetime values,
        # but in some scenarios (e.g., DuckDB >=0.10.2) it will be a pandas `object` type
        # containing python `datetime.xxx` values.
        #
        # Pandas `object` columns result in a noop for the `astype` call above. Because any
        # quoted YAML value is a string, we must manually convert the `expected` df string
        # values to the correct `datetime.xxx` type.
        #
        # We determine the type from a single sentinel value, but since the `actual` df is
        # coming from a database query, it is safe to assume that the column contains only
        # a single type.
        object_sentinel_values = {
            col: actual[col][0]
            for col in actual_types
            if is_object_dtype(actual_types[col]) and len(actual[col]) != 0
        }
        for col, value in object_sentinel_values.items():
            try:
                # can't use `isinstance()` here - https://stackoverflow.com/a/68743663/1707525
                if type(value) is datetime.date:
                    expected[col] = pd.to_datetime(expected[col]).dt.date
                elif type(value) is datetime.time:
                    expected[col] = pd.to_datetime(expected[col]).dt.time
                elif type(value) is datetime.datetime:
                    expected[col] = pd.to_datetime(expected[col]).dt.to_pydatetime()
            except Exception as e:
                from sqlmesh.core.console import get_console

                get_console().log_warning(
                    f"Failed to convert expected value for {col} into `datetime` "
                    f"for unit test '{str(self)}'. {str(e)}."
                )

        actual = actual.replace({np.nan: None})
        expected = expected.replace({np.nan: None})

        # We define this here to avoid a top-level import of numpy and pandas
        DATETIME_TYPES = (
            datetime.datetime,
            datetime.date,
            datetime.time,
            np.datetime64,
            pd.Timestamp,
        )

        def _to_hashable(x: t.Any) -> t.Any:
            if isinstance(x, (list, np.ndarray)):
                return tuple(_to_hashable(v) for v in x)
            if isinstance(x, dict):
                return tuple((k, _to_hashable(v)) for k, v in x.items())
            return str(x) if isinstance(x, DATETIME_TYPES) or not isinstance(x, t.Hashable) else x

        actual = actual.apply(lambda col: col.map(_to_hashable))
        expected = expected.apply(lambda col: col.map(_to_hashable))

        if sort:
            actual = actual.sort_values(by=actual.columns.to_list()).reset_index(drop=True)
            expected = expected.sort_values(by=expected.columns.to_list()).reset_index(drop=True)

        try:
            pd.testing.assert_frame_equal(
                expected,
                actual,
                check_dtype=False,
                check_datetimelike_compat=True,
                check_like=True,  # Ignore column order
            )
        except AssertionError as e:
            # There are 2 concepts at play here:
            # 1. The Exception args will contain the error message plus the diff dataframe table stringified
            #    (backwards compatibility with existing tests, possible to serialize/send over network etc)
            # 2. Each test will also transform these diff dataframes into Rich tables, which will be the ones that'll
            #    be surfaced to the user through Console for better UX (versus stringified dataframes)
            #
            # This is a bit of a hack, but it's a way to get the best of both worlds.
            args: t.List[t.Any] = []

            failed_subtest = ""

            if subtest := getattr(self, "_subtest", None):
                if cte := subtest.params.get("cte"):
                    failed_subtest = f" (CTE {cte})"

            if expected.shape != actual.shape:
                _raise_if_unexpected_columns(expected.columns, actual.columns)

                args.append("Data mismatch (rows are different)")

                missing_rows = _row_difference(expected, actual)
                if not missing_rows.empty:
                    args[0] += f"\n\nMissing rows:\n\n{missing_rows}"
                    args.append(df_to_table(f"Missing rows{failed_subtest}", missing_rows))

                unexpected_rows = _row_difference(actual, expected)

                if not unexpected_rows.empty:
                    args[0] += f"\n\nUnexpected rows:\n\n{unexpected_rows}"
                    args.append(df_to_table(f"Unexpected rows{failed_subtest}", unexpected_rows))

            else:
                diff = expected.compare(actual).rename(columns={"self": "exp", "other": "act"})

                args.append(f"Data mismatch (exp: expected, act: actual)\n\n{diff}")

                diff.rename(columns={"exp": "Expected", "act": "Actual"}, inplace=True)
                if self.verbosity == Verbosity.DEFAULT:
                    args.extend(
                        df_to_table(f"Data mismatch{failed_subtest}", df)
                        for df in _split_df_by_column_pairs(diff)
                    )
                else:
                    from pandas import DataFrame, MultiIndex

                    levels = t.cast(MultiIndex, diff.columns).levels[0]
                    for col in levels:
                        # diff[col] returns a DataFrame when columns is a MultiIndex
                        col_diff = t.cast(DataFrame, diff[col])
                        if not col_diff.empty:
                            table = df_to_table(
                                f"[bold red]Column '{col}' mismatch{failed_subtest}[/bold red]",
                                col_diff,
                            )
                            args.append(table)

            e.args = (*args,)

            raise e

    def runTest(self) -> None:
        raise NotImplementedError

    def path_relative_to(self, other: Path) -> Path | None:
        """Compute a version of this test's path relative to the `other` path"""
        return self.path.relative_to(other) if self.path else None

    @staticmethod
    def create_test(
        body: t.Dict[str, t.Any],
        test_name: str,
        models: UniqueKeyDict[str, Model],
        engine_adapter: EngineAdapter,
        dialect: str | None,
        path: Path | None,
        preserve_fixtures: bool = False,
        default_catalog: str | None = None,
        concurrency: bool = False,
        verbosity: Verbosity = Verbosity.DEFAULT,
    ) -> t.Optional[ModelTest]:
        """Create a SqlModelTest or a PythonModelTest.

        Args:
            body: A dictionary that contains test metadata like inputs and outputs.
            test_name: The name of the test.
            models: All models to use for expansion and mapping of physical locations.
            engine_adapter: The engine adapter to use.
            dialect: The models' dialect, used for normalization purposes.
            path: An optional path to the test definition yaml file.
            preserve_fixtures: Preserve the fixture tables in the testing database, useful for debugging.
        """
        name = body.get("model")
        if name is None:
            _raise_error("Missing required 'model' field", path)

        name = normalize_model_name(name, default_catalog=default_catalog, dialect=dialect)
        model = models.get(name)
        if not model:
            from sqlmesh.core.console import get_console

            get_console().log_warning(
                f"Model '{name}' was not found{' at ' + str(path) if path else ''}"
            )
            return None

        if isinstance(model, SqlModel):
            test_type: t.Type[ModelTest] = SqlModelTest
        elif isinstance(model, PythonModel):
            test_type = PythonModelTest
        else:
            _raise_error(f"Model '{name}' is an unsupported model type for testing", path)

        try:
            return test_type(
                body,
                test_name,
                t.cast(Model, model),
                models,
                engine_adapter,
                dialect,
                path,
                preserve_fixtures,
                default_catalog,
                concurrency,
                verbosity,
            )
        except Exception as e:
            raise TestError(f"Failed to create test {test_name} ({path})\n{str(e)}")

    def __str__(self) -> str:
        return f"{self.test_name} ({self.path})"

    def _validate_and_normalize_test(self) -> None:
        inputs = self.body.get("inputs")
        outputs = self.body.get("outputs", {})

        if not outputs:
            _raise_error("Incomplete test, missing outputs", self.path)

        ctes = outputs.get("ctes")
        query = outputs.get("query")
        partial = outputs.pop("partial", None)

        if ctes is None and query is None:
            _raise_error("Incomplete test, outputs must contain 'query' or 'ctes'", self.path)

        def _normalize_rows(
            values: t.List[Row] | t.Dict,
            name: str,
            partial: bool = False,
            dialect: DialectType = None,
        ) -> t.Dict:
            import pandas as pd

            if not isinstance(values, dict):
                values = {"rows": values}

            rows = values.get("rows")
            query = values.get("query")

            fmt = values.get("format")
            path = values.get("path")
            if fmt == "csv":
                csv_settings = values.get("csv_settings") or {}
                rows = pd.read_csv(path or StringIO(rows), **csv_settings).to_dict(orient="records")
            elif fmt in (None, "yaml"):
                if path:
                    input_rows = yaml_load(Path(path))
                    rows = input_rows.get("rows") if isinstance(input_rows, dict) else input_rows
            else:
                _raise_error(f"Unsupported data format '{fmt}' for '{name}'", self.path)

            if query is not None:
                if rows is not None:
                    _raise_error(
                        f"Invalid test, cannot set both 'query' and 'rows' for '{name}'", self.path
                    )

                # We parse the user-supplied query using the testing adapter dialect, but we
                # normalize its identifiers according to the model's dialect, so that, e.g.,
                # the projection names match those in its `columns_to_types` field
                values["query"] = normalize_identifiers(
                    exp.maybe_parse(query, dialect=self._test_adapter_dialect), dialect=dialect
                )
                return values

            if rows is None:
                _raise_error(f"Incomplete test, missing row data for '{name}'", self.path)

            assert isinstance(rows, list)
            values["rows"] = [
                {self._normalize_column_name(column): value for column, value in row.items()}
                for row in rows
            ]
            if partial:
                values["partial"] = True

            return values

        def _normalize_sources(
            sources: t.Dict, partial: bool = False, with_default_catalog: bool = True
        ) -> t.Dict:
            normalized_sources = {}
            for name, values in sources.items():
                normalized_name = self._normalize_model_name(
                    name, with_default_catalog=with_default_catalog
                )
                model = self.models.get(normalized_name)
                dialect = model.dialect if model else self.dialect

                normalized_sources[normalized_name] = _normalize_rows(
                    values, name, partial=partial, dialect=dialect
                )

            return normalized_sources

        normalized_model_name = self._normalize_model_name(self.body["model"])
        self.body["model"] = normalized_model_name

        if inputs:
            inputs = _normalize_sources(inputs)
            for name, values in inputs.items():
                columns = values.get("columns")
                if columns is None:
                    continue

                if not isinstance(columns, dict):
                    _raise_error(
                        f"Invalid 'columns' value for model '{name}', expected a mapping name -> type",
                        self.path,
                    )

                values["columns"] = {
                    self._normalize_column_name(c): exp.DataType.build(
                        t, dialect=self._test_adapter_dialect
                    )
                    for c, t in columns.items()
                }

            for depends_on in self.model.depends_on:
                if depends_on not in inputs:
                    _raise_error(f"Incomplete test, missing input model '{depends_on}'", self.path)

            if self.model.depends_on_self and normalized_model_name not in inputs:
                inputs[normalized_model_name] = {"rows": []}

            self.body["inputs"] = inputs

        if ctes:
            outputs["ctes"] = _normalize_sources(ctes, partial=partial, with_default_catalog=False)

        if query or query == []:
            outputs["query"] = _normalize_rows(
                query, self.model.name, partial=partial, dialect=self.model.dialect
            )

    def _test_fixture_table(self, name: str) -> exp.Table:
        table = self._fixture_table_cache.get(name)
        if not table:
            table = exp.to_table(name, dialect=self._test_adapter_dialect)

            # We change the table path below, so this ensures there are no name clashes
            table.this.set("this", "__".join(part.name for part in table.parts))

            table.set("db", self._fixture_schema.copy())
            if self._fixture_catalog:
                table.set("catalog", self._fixture_catalog.copy())

            self._fixture_table_cache[name] = table

        return table

    def _normalize_model_name(self, name: str, with_default_catalog: bool = True) -> str:
        normalized_name = self._normalized_model_name_cache.get((name, with_default_catalog))
        if normalized_name is None:
            default_catalog = self.default_catalog if with_default_catalog else None
            normalized_name = normalize_model_name(
                name, default_catalog=default_catalog, dialect=self.dialect
            )
            self._normalized_model_name_cache[(name, with_default_catalog)] = normalized_name

        return normalized_name

    def _normalize_column_name(self, name: str) -> str:
        normalized_name = self._normalized_column_name_cache.get(name)
        if normalized_name is None:
            normalized_name = normalize_identifiers(name, dialect=self.dialect).name
            self._normalized_column_name_cache[name] = normalized_name

        return normalized_name

    @contextmanager
    def _concurrent_render_context(self) -> t.Iterator[None]:
        """
        Context manager that ensures that the tests are executed safely in a concurrent environment.
        This is needed in case `execution_time` is set, as we'd then have to:
        - Freeze time through `time_machine` (not thread safe)
        - Globally patch the SQLGlot dialect so that any date/time nodes are evaluated at the `execution_time` during generation
        """
        import time_machine
        from sqlglot.generator import _DISPATCH_CACHE

        lock_ctx: AbstractContextManager = (
            self.CONCURRENT_RENDER_LOCK if self.concurrency else nullcontext()
        )
        time_ctx: AbstractContextManager = nullcontext()
        dialect_patch_ctx: AbstractContextManager = nullcontext()
        dispatch_patch_ctx: AbstractContextManager = nullcontext()

        if self._execution_time:
            generator_class = self._test_adapter_dialect.generator_class
            time_ctx = time_machine.travel(self._execution_time, tick=False)
            dialect_patch_ctx = patch.dict(generator_class.TRANSFORMS, self._transforms)

            # sqlglot caches a dispatch table per generator class, so we need to patch
            # it as well to ensure the overridden transforms are actually used
            dispatch = _DISPATCH_CACHE.get(generator_class)
            if dispatch is not None:
                dispatch_patch_ctx = patch.dict(dispatch, self._transforms)

        with lock_ctx, time_ctx, dialect_patch_ctx, dispatch_patch_ctx:
            yield

    def _execute(self, query: exp.Query | str) -> pd.DataFrame:
        """Executes the given query using the testing engine adapter and returns a DataFrame."""
        return self.engine_adapter.fetchdf(query)

    def _create_df(
        self,
        values: t.Dict[str, t.Any],
        columns: t.Optional[t.Collection] = None,
        partial: t.Optional[bool] = False,
    ) -> pd.DataFrame:
        import pandas as pd

        query = values.get("query")
        if query:
            if not partial:
                query = self._add_missing_columns(query, columns)

            return self._execute(query)

        rows = values["rows"]
        columns_str: t.Optional[t.List[str]] = None
        if columns:
            columns_str = [str(c) for c in columns]
            referenced_columns = list(dict.fromkeys(col for row in rows for col in row))
            _raise_if_unexpected_columns(columns, referenced_columns)

            if partial:
                columns_str = [c for c in columns_str if c in referenced_columns]

        return pd.DataFrame.from_records(rows, columns=columns_str)

    def _add_missing_columns(
        self, query: exp.Query, all_columns: t.Optional[t.Collection[str]] = None
    ) -> exp.Query:
        if not all_columns or query.is_star:
            return query

        query_columns = set(query.named_selects)
        missing_columns = [col for col in all_columns if col not in query_columns]
        if missing_columns:
            query.select(*[exp.null().as_(col) for col in missing_columns], copy=False)

        return query


class SqlModelTest(ModelTest):
    def test_ctes(self, ctes: t.Dict[str, exp.Expr], recursive: bool = False) -> None:
        """Run CTE queries and compare output to expected output"""
        for cte_name, values in self.body["outputs"].get("ctes", {}).items():
            with self.subTest(cte=cte_name):
                if cte_name not in ctes:
                    _raise_error(
                        f"No CTE named {cte_name} found in model {self.model.name}", self.path
                    )

                cte_query = ctes[cte_name].this

                sort = cte_query.args.get("order") is None
                partial = values.get("partial")

                cte_query = exp.select(*_projection_identifiers(cte_query)).from_(cte_name)
                for alias, cte in ctes.items():
                    cte_query = cte_query.with_(alias, cte.this, recursive=recursive)

                with self._concurrent_render_context():
                    # Similar to the model's query, we render the CTE query under the locked context
                    # so that the execution (fetchdf) can continue concurrently between the threads
                    sql = cte_query.sql(
                        self._test_adapter_dialect, pretty=self.engine_adapter._pretty_sql
                    )

                actual = self._execute(sql)
                expected = self._create_df(values, columns=cte_query.named_selects, partial=partial)

                self.assert_equal(expected, actual, sort=sort, partial=partial)

    def runTest(self) -> None:
        with self._concurrent_render_context():
            # Render the model's query and generate the SQL under the locked context so that
            # execution (fetchdf) can continue concurrently between the threads
            query = self._render_model_query()
            sql = query.sql(self._test_adapter_dialect, pretty=self.engine_adapter._pretty_sql)

        with_clause = query.args.get("with_")

        if with_clause:
            self.test_ctes(
                {
                    self._normalize_model_name(cte.alias, with_default_catalog=False): cte
                    for cte in query.ctes
                },
                recursive=with_clause.recursive,
            )

        values = self.body["outputs"].get("query")
        if values is not None:
            partial = values.get("partial")
            sort = query.args.get("order") is None

            actual = self._execute(sql)
            expected = self._create_df(values, columns=self.model.columns_to_types, partial=partial)

            self.assert_equal(expected, actual, sort=sort, partial=partial)

    def _render_model_query(self) -> exp.Query:
        variables = self.body.get("vars", {}).copy()
        time_kwargs = {key: variables.pop(key) for key in TIME_KWARG_KEYS if key in variables}

        query = self.model.render_query_or_raise(
            **time_kwargs,
            variables=variables,
            engine_adapter=self.engine_adapter,
            table_mapping={
                name: self._test_fixture_table(name).sql() for name in self.body.get("inputs", {})
            },
            runtime_stage=RuntimeStage.TESTING,
        )
        return query


class PythonModelTest(ModelTest):
    def __init__(
        self,
        body: t.Dict[str, t.Any],
        test_name: str,
        model: Model,
        models: UniqueKeyDict[str, Model],
        engine_adapter: EngineAdapter,
        dialect: str | None = None,
        path: Path | None = None,
        preserve_fixtures: bool = False,
        default_catalog: str | None = None,
        concurrency: bool = False,
        verbosity: Verbosity = Verbosity.DEFAULT,
    ) -> None:
        """PythonModelTest encapsulates a unit test for a Python model.

        Args:
            body: A dictionary that contains test metadata like inputs and outputs.
            test_name: The name of the test.
            model: The Python model that is being tested.
            models: All models to use for expansion and mapping of physical locations.
            engine_adapter: The engine adapter to use.
            dialect: The models' dialect, used for normalization purposes.
            path: An optional path to the test definition yaml file.
            preserve_fixtures: Preserve the fixture tables in the testing database, useful for debugging.
        """
        from sqlmesh.core.test.context import TestExecutionContext

        super().__init__(
            body,
            test_name,
            model,
            models,
            engine_adapter,
            dialect,
            path,
            preserve_fixtures,
            default_catalog,
            concurrency,
            verbosity,
        )

        self.context = TestExecutionContext(
            engine_adapter=engine_adapter,
            models=models,
            test=self,
            default_dialect=dialect,
            default_catalog=default_catalog,
        )

    def runTest(self) -> None:
        values = self.body["outputs"].get("query")
        if values is not None:
            partial = values.get("partial")

            actual_df = self._execute_model()
            actual_df.reset_index(drop=True, inplace=True)
            expected = self._create_df(values, columns=self.model.columns_to_types, partial=partial)

            self.assert_equal(expected, actual_df, sort=True, partial=partial)

    def _execute_model(self) -> pd.DataFrame:
        """Executes the python model and returns a DataFrame."""
        import pandas as pd

        with self._concurrent_render_context():
            variables = self.body.get("vars", {}).copy()
            time_kwargs = {key: variables.pop(key) for key in TIME_KWARG_KEYS if key in variables}
            df = next(self.model.render(context=self.context, variables=variables, **time_kwargs))

        assert not isinstance(df, exp.Expr)
        return df if isinstance(df, pd.DataFrame) else df.toPandas()


def generate_test(
    model: Model,
    input_queries: t.Dict[str, str],
    models: UniqueKeyDict[str, Model],
    engine_adapter: EngineAdapter,
    test_engine_adapter: EngineAdapter,
    project_path: Path,
    overwrite: bool = False,
    variables: t.Optional[t.Dict[str, str]] = None,
    path: t.Optional[str] = None,
    name: t.Optional[str] = None,
    include_ctes: bool = False,
) -> None:
    """Generate a unit test fixture for a given model.

    Args:
        model: The model to test.
        input_queries: Mapping of model names to queries. Each model included in this mapping
            will be populated in the test based on the results of the corresponding query.
        models: The context's models.
        engine_adapter: The target engine adapter.
        test_engine_adapter: The test engine adapter.
        project_path: The path pointing to the project's root directory.
        overwrite: Whether to overwrite the existing test in case of a file path collision.
            When set to False, an error will be raised if there is such a collision.
        variables: Key-value pairs that will define variables needed by the model.
        path: The file path corresponding to the fixture, relative to the test directory.
            By default, the fixture will be created under the test directory and the file name
            will be inferred from the test's name.
        name: The name of the test. This is inferred from the model name by default.
        include_ctes: When true, CTE fixtures will also be generated.
    """
    import numpy as np

    test_name = name or f"test_{model.view_name}"
    path = path or f"{test_name}.yaml"

    extension = path.split(".")[-1].lower()
    if extension not in ("yaml", "yml"):
        path = f"{path}.yaml"

    fixture_path = project_path / c.TESTS / path
    if not overwrite and fixture_path.exists():
        raise ConfigError(
            f"Fixture '{fixture_path}' already exists, make sure to set --overwrite if it can be safely overwritten."
        )

    # ruamel.yaml does not support pandas Timestamps, so we must convert them to python
    # datetime or datetime.date objects based on column type
    inputs = {
        dep: pandas_timestamp_to_pydatetime(
            engine_adapter.fetchdf(query).apply(lambda col: col.map(_normalize_df_value)),
            models[dep].columns_to_types,
        )
        .replace({np.nan: None})
        .to_dict(orient="records")
        for dep, query in input_queries.items()
    }
    outputs: t.Dict[str, t.Any] = {"query": {}}
    variables = variables or {}
    test_body = {"model": model.fqn, "inputs": inputs, "outputs": outputs}

    if variables:
        test_body["vars"] = variables

    test = ModelTest.create_test(
        body=test_body.copy(),
        test_name=test_name,
        models=models,
        engine_adapter=test_engine_adapter,
        dialect=model.dialect,
        path=fixture_path,
        default_catalog=model.default_catalog,
    )
    if not test:
        return

    test.setUp()

    if isinstance(model, SqlModel):
        assert isinstance(test, SqlModelTest)
        model_query = test._render_model_query()
        with_clause = model_query.args.get("with_")

        if with_clause and include_ctes:
            ctes = {}
            recursive = with_clause.recursive
            previous_ctes: t.List[exp.CTE] = []

            for cte in model_query.ctes:
                cte_query = cte.this
                cte_identifier = cte.args["alias"].this

                cte_query = exp.select(*_projection_identifiers(cte_query)).from_(cte_identifier)

                for prev in chain(previous_ctes, [cte]):
                    cte_query = cte_query.with_(
                        prev.args["alias"].this, prev.this, recursive=recursive
                    )

                cte_output = test._execute(cte_query)
                ctes[cte.alias] = (
                    pandas_timestamp_to_pydatetime(
                        df=cte_output.apply(lambda col: col.map(_normalize_df_value)),
                    )
                    .replace({np.nan: None})
                    .to_dict(orient="records")
                )

                previous_ctes.append(cte)

            if ctes:
                outputs["ctes"] = ctes

        output = test._execute(model_query)
    else:
        output = t.cast(PythonModelTest, test)._execute_model()

    outputs["query"] = (
        pandas_timestamp_to_pydatetime(
            output.apply(lambda col: col.map(_normalize_df_value)), model.columns_to_types
        )
        .replace({np.nan: None})
        .to_dict(orient="records")
    )

    test.tearDown()

    fixture_path.parent.mkdir(exist_ok=True, parents=True)
    with open(fixture_path, "w", encoding="utf-8") as file:
        yaml.dump({test_name: test_body}, file)


def _projection_identifiers(query: exp.Query) -> t.List[str | exp.Identifier]:
    identifiers: t.List[str | exp.Identifier] = []
    for select in query.selects:
        if isinstance(select, exp.Alias):
            identifiers.append(select.args["alias"])
        elif isinstance(select, exp.Column):
            identifiers.append(select.this)
        else:
            identifiers.append(select.output_name)

    return identifiers


def _raise_if_unexpected_columns(
    expected_cols: t.Collection[str], actual_cols: t.Collection[str]
) -> None:
    unique_expected_cols = set(expected_cols)
    unknown_cols = [col for col in actual_cols if col not in unique_expected_cols]

    if unknown_cols:
        expected = f"Expected column(s): {', '.join(list(expected_cols))}\n"
        unknown = f"Unknown column(s): {', '.join(unknown_cols)}"
        _raise_error(f"Detected unknown column(s)\n\n{expected}{unknown}")


def _row_difference(left: pd.DataFrame, right: pd.DataFrame) -> pd.DataFrame:
    """Returns all rows in `left` that don't appear in `right`."""
    import numpy as np
    import pandas as pd

    rows_missing_from_right = []

    # `None` replaces `np.nan` because `np.nan != np.nan` and this would affect the mapping lookup
    right_row_count: t.MutableMapping[t.Tuple, int] = Counter(
        right.replace({np.nan: None}).itertuples(index=False, name=None)
    )
    for left_row in left.replace({np.nan: None}).itertuples(index=False):
        left_row_tuple = tuple(left_row)
        if right_row_count[left_row_tuple] <= 0:
            rows_missing_from_right.append(left_row)
        else:
            right_row_count[left_row_tuple] -= 1

    return pd.DataFrame(rows_missing_from_right)


def _raise_error(msg: str, path: Path | None = None) -> None:
    if path:
        raise TestError(f"Failed to run test at {path}:\n{msg}")
    raise TestError(f"Failed to run test:\n{msg}")


def _normalize_df_value(value: t.Any) -> t.Any:
    """Normalize data in a pandas dataframe so ruamel and sqlglot can deal with it."""
    import numpy as np

    if isinstance(value, (list, np.ndarray)):
        return [_normalize_df_value(v) for v in value]
    if isinstance(value, dict):
        if "key" in value and "value" in value:
            # Maps returned by DuckDB look like: {'key': ['key1', 'key2'], 'value': [10, 20]}
            # so we convert to {'key1': 10, 'key2': 20} (TODO: handle more dialects here)
            return {k: _normalize_df_value(v) for k, v in zip(value["key"], value["value"])}
        return {k: _normalize_df_value(v) for k, v in value.items()}
    return value


def _split_df_by_column_pairs(df: pd.DataFrame, pairs_per_chunk: int = 4) -> t.List[pd.DataFrame]:
    """Split a dataframe into chunks of column pairs.

    Args:
        df: The dataframe to split
        pairs_per_chunk: Number of column pairs per chunk (default: 4)

    Returns:
        List of dataframes, each containing an even number of columns
    """
    total_columns = len(df.columns)

    # If we have fewer columns than pairs_per_chunk * 2, return the original df
    if total_columns <= pairs_per_chunk * 2:
        return [df]

    # Calculate number of chunks needed to split columns evenly
    num_chunks = (total_columns + (pairs_per_chunk * 2 - 1)) // (pairs_per_chunk * 2)

    # Calculate columns per chunk to ensure equal distribution
    # We round down to nearest even number to ensure each chunk has even columns
    columns_per_chunk = (total_columns // num_chunks) & ~1  # Round down to nearest even number
    remainder = total_columns - (columns_per_chunk * num_chunks)

    chunks = []
    start_idx = 0

    # Distribute columns evenly across chunks
    for i in range(num_chunks):
        # Add 2 columns to early chunks if there's a remainder
        # This ensures we always add pairs of columns
        extra = 2 if i < remainder // 2 else 0
        end_idx = start_idx + columns_per_chunk + extra
        chunk = df.iloc[:, start_idx:end_idx]
        chunks.append(chunk)
        start_idx = end_idx

    return chunks
