// Copyright 2022 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use crate::{
    description::Description,
    matcher::{Matcher, MatcherBase, MatcherResult},
};
use std::fmt::Debug;

/// Matches a container containing all of the items in the given container
/// `subset`.
///
/// The element type `ElementT` must implement `PartialEq` to allow element
/// comparison.
///
/// `ActualT` and `ExpectedT` can each be any container which implements
/// `IntoIterator`. For instance, `ActualT` and `ExpectedT` can be a
/// common container like `&Vec`, arrays or slices. They need not be the same
/// container type.
///
/// ```
/// # use googletest::prelude::*;
/// # use std::collections::HashSet;
/// # fn should_pass_1() -> Result<()> {
/// let value = vec![1, 2, 3];
/// verify_that!(value, superset_of([&1, &2]))?;  // Passes
/// let array_value = [1, 2, 3];
/// verify_that!(array_value, superset_of([1, 2]))?;  // Passes
/// #     Ok(())
/// # }
/// # fn should_fail() -> Result<()> {
/// # let value = vec![1, 2, 3];
/// verify_that!(value, superset_of([&1, &2, &4]))?;  // Fails: 4 is not in the subset
/// #     Ok(())
/// # }
/// # should_pass_1().unwrap();
/// # should_fail().unwrap_err();
///
/// # fn should_pass_2() -> Result<()> {
/// let value: HashSet<i32> = [1, 2, 3].into();
/// verify_that!(value, superset_of([&1, &2, &3]))?;  // Passes
/// #     Ok(())
/// # }
/// # should_pass_2().unwrap();
/// ```
///
/// Item multiplicity in both the actual and expected containers is ignored:
///
/// ```
/// # use googletest::prelude::*;
/// # fn should_pass() -> Result<()> {
/// let value: Vec<i32> = vec![0, 0, 1];
/// verify_that!(value, superset_of([&0, &1]))?;  // Passes
/// verify_that!(value, superset_of([&0, &1, &1]))?;  // Passes
/// #     Ok(())
/// # }
/// # should_pass().unwrap();
/// ```
///
/// A note on performance: This matcher uses a naive algorithm with a worst-case
/// runtime proportional to the *product* of the sizes of the actual and
/// expected containers as well as the time to check equality of each pair of
/// items. It should not be used on especially large containers.
pub fn superset_of<ExpectedT>(subset: ExpectedT) -> SupersetOfMatcher<ExpectedT> {
    SupersetOfMatcher { subset }
}

#[derive(MatcherBase)]
pub struct SupersetOfMatcher<ExpectedT> {
    subset: ExpectedT,
}

impl<ElementT: Debug + Copy + PartialEq, ActualT: Debug + Copy, ExpectedT: Debug> Matcher<ActualT>
    for SupersetOfMatcher<ExpectedT>
where
    ActualT: IntoIterator<Item = ElementT>,
    for<'a> &'a ExpectedT: IntoIterator<Item = &'a ElementT>,
{
    fn matches(&self, actual: ActualT) -> MatcherResult {
        for expected_item in &self.subset {
            if actual_is_missing(actual, expected_item) {
                return MatcherResult::NoMatch;
            }
        }
        MatcherResult::Match
    }

    fn explain_match(&self, actual: ActualT) -> Description {
        let missing_items: Vec<_> = self
            .subset
            .into_iter()
            .filter(|expected_item| actual_is_missing(actual, *expected_item))
            .map(|expected_item| format!("{expected_item:#?}"))
            .collect();
        match missing_items.len() {
            0 => "whose no element is missing".into(),
            1 => format!("whose element {} is missing", &missing_items[0]).into(),
            _ => format!("whose elements {} are missing", missing_items.join(", ")).into(),
        }
    }

    fn describe(&self, matcher_result: MatcherResult) -> Description {
        match matcher_result {
            MatcherResult::Match => format!("is a superset of {:#?}", self.subset).into(),
            MatcherResult::NoMatch => format!("isn't a superset of {:#?}", self.subset).into(),
        }
    }
}

fn actual_is_missing<ElementT: PartialEq, ActualT>(actual: ActualT, needle: &ElementT) -> bool
where
    ActualT: IntoIterator<Item = ElementT>,
{
    !actual.into_iter().any(|item| &item == needle)
}
#[cfg(test)]
mod tests {
    use crate::prelude::*;
    use indoc::indoc;
    use std::collections::HashSet;

    #[test]
    fn superset_of_matches_empty_vec() -> Result<()> {
        let value: Vec<i32> = vec![];
        verify_that!(value, superset_of([]))
    }

    #[test]
    fn superset_of_matches_vec_with_one_element() -> Result<()> {
        let value = vec![1];
        verify_that!(value, superset_of([&1]))
    }

    #[test]
    fn superset_of_matches_vec_with_two_items() -> Result<()> {
        let value = vec![1, 2];
        verify_that!(value, superset_of([&1, &2]))
    }

    #[test]
    fn superset_of_matches_vec_when_actual_has_excess_element() -> Result<()> {
        let value = vec![1, 2, 3];
        verify_that!(value, superset_of([&1, &2]))
    }

    #[test]
    fn superset_of_matches_vec_when_actual_has_excess_element_first() -> Result<()> {
        let value = vec![3, 1, 2];
        verify_that!(value, superset_of([&1, &2]))
    }

    #[test]
    fn superset_of_matches_slice_with_one_element() -> Result<()> {
        let value = &[1];
        verify_that!(value, superset_of([&1]))
    }

    #[test]
    fn superset_of_matches_hash_set_with_one_element() -> Result<()> {
        let value: HashSet<i32> = [1].into();
        verify_that!(value, superset_of([&1]))
    }

    #[test]
    fn superset_of_does_not_match_when_first_element_does_not_match() -> Result<()> {
        let value = vec![0];
        verify_that!(value, not(superset_of([&1])))
    }

    #[test]
    fn superset_of_does_not_match_when_second_element_does_not_match() -> Result<()> {
        let value = vec![2];
        verify_that!(value, not(superset_of([&2, &0])))
    }

    #[test]
    fn superset_of_shows_correct_message_when_first_item_does_not_match() -> Result<()> {
        let result = verify_that!(vec![0, 2, 3], superset_of([&1, &2, &3]));

        verify_that!(
            result,
            err(displays_as(contains_substring(indoc!(
                "
                    Value of: vec![0, 2, 3]
                    Expected: is a superset of [
                        1,
                        2,
                        3,
                    ]
                    Actual: [0, 2, 3],
                      whose element 1 is missing
                "
            ))))
        )
    }

    #[test]
    fn superset_of_shows_correct_message_when_second_item_does_not_match() -> Result<()> {
        let result = verify_that!(vec![1, 0, 3], superset_of([&1, &2, &3]));

        verify_that!(
            result,
            err(displays_as(contains_substring(indoc!(
                "
                    Value of: vec![1, 0, 3]
                    Expected: is a superset of [
                        1,
                        2,
                        3,
                    ]
                    Actual: [1, 0, 3],
                      whose element 2 is missing
                "
            ))))
        )
    }

    #[test]
    fn superset_of_shows_correct_message_when_first_two_items_do_not_match() -> Result<()> {
        let result = verify_that!(vec![0, 0, 3], superset_of([&1, &2, &3]));

        verify_that!(
            result,
            err(displays_as(contains_substring(indoc!(
                "
                    Value of: vec![0, 0, 3]
                    Expected: is a superset of [
                        1,
                        2,
                        3,
                    ]
                    Actual: [0, 0, 3],
                      whose elements 1, 2 are missing
                "
            ))))
        )
    }
}