# Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
# SPDX-License-Identifier: Apache-2.0

"""Module for comparison criteria."""

from abc import ABC, abstractmethod
from pydoc import locate


class CriteriaException(Exception):
    """Exception returned by failure of check criteria."""


# pylint: disable=R0903
class CriteriaFactory:
    """Comparison criteria factory class."""

    @classmethod
    def get(cls, criteria_cls_name) -> "ComparisonCriteria":
        """`criteria_cls_name` must be a valid criteria class name."""
        return locate(f"framework.stats.criteria.{criteria_cls_name}")


# pylint: disable=R0903
class ComparisonCriteria(ABC):
    """Comparison criteria between results and targets."""

    def __init__(self, name: str, baseline: dict):
        """Initialize the comparison criteria.

        Baseline expected schema:
        ```
        {
            "type": "object",
            "properties": {
                "target": number,
            },
            "required": ["target"]
        }
        ```
        """
        self._baseline = baseline
        self._name = name

    @abstractmethod
    def check(self, actual):
        """Compare the target and the actual."""

    @property
    def name(self):
        """Return criteria name."""
        return self._name

    @property
    def target(self):
        """Return criteria target."""
        if self._baseline is None:
            raise CriteriaException("Baseline data not defined.")

        target = self._baseline.get("target")
        if target is None:
            raise CriteriaException("Baseline target not defined.")

        return target

    @property
    def baseline(self) -> dict:
        """Return the baseline."""
        return self._baseline

    def fail_msg(self, actual):
        """Return the default fail message."""
        return self.name + f" failed. Target: '{self.target} vs Actual: " f"'{actual}'."


# pylint: disable=R0903
class GreaterThan(ComparisonCriteria):
    """Greater than comparison criteria."""

    def __init__(self, baseline: dict):
        """Initialize the criteria."""
        super().__init__("GreaterThan", baseline)

    def check(self, actual):
        """Compare the target and the actual."""
        if actual < self.target:
            raise CriteriaException(self.fail_msg(actual))


# pylint: disable=R0903
class LowerThan(ComparisonCriteria):
    """Lower than comparison criteria."""

    def __init__(self, baseline: dict):
        """Initialize the criteria."""
        super().__init__("LowerThan", baseline)

    def check(self, actual):
        """Compare the target and the actual."""
        if actual > self.target:
            raise CriteriaException(self.fail_msg(actual))


# pylint: disable=R0903
class EqualWith(ComparisonCriteria):
    """Equal with comparison criteria.

    Baseline expected schema:
    ```
    {
        "type": "object",
        "properties": {
            "target": number,
            "delta": number
        },
        "required": ["target", "delta"]
    }
    ```
    """

    def __init__(self, baseline: dict):
        """Initialize the criteria."""
        super().__init__("EqualWith", baseline)

    @property
    def delta(self):
        """Return the `delta` field of the baseline."""
        if self._baseline is None:
            raise CriteriaException("Baseline data not defined.")

        delta = self._baseline.get("delta")
        if delta is None:
            raise CriteriaException("Baseline delta not defined.")
        return delta

    def fail_msg(self, actual):
        """Return the `EqualWith` failure message."""
        return (
            self.name + f" failed. Target: '{self.target} +- "
            f"{self.delta}' vs Actual: '{actual}'."
        )

    def check(self, actual):
        """Compare the target and the actual."""
        if abs(self.target - actual) > self.delta:
            raise CriteriaException(self.fail_msg(actual))