// Copyright 2023 Google LLC
// Copyright 2026 Bradford Hovinen <bradford@hovinen.me>
//
// 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::{Describable, Matcher, MatcherResult},
};
use std::fmt::Debug;

/// Matches a byte sequence which is a UTF-8 encoded string matched by `inner`.
///
/// The matcher reports no match if either the string is not UTF-8 encoded or if
/// `inner` does not match on the decoded string.
///
/// The input may be a slice `&[u8]` or a `Vec` of bytes.
///
/// ```
/// # use test_that::prelude::*;
/// # fn should_pass() -> TestResult<()> {
/// let bytes: &[u8] = "A string".as_bytes();
/// verify_that!(bytes, is_utf8_string(eq("A string")))?; // Passes
/// let bytes: Vec<u8> = "A string".as_bytes().to_vec();
/// verify_that!(bytes, is_utf8_string(eq("A string")))?; // Passes
/// #     Ok(())
/// # }
/// # fn should_fail_1() -> TestResult<()> {
/// # let bytes: &[u8] = "A string".as_bytes();
/// verify_that!(bytes, is_utf8_string(eq("Another string")))?; // Fails (inner matcher does not match)
/// #     Ok(())
/// # }
/// # fn should_fail_2() -> TestResult<()> {
/// let bytes: Vec<u8> = vec![255, 64, 128, 32];
/// verify_that!(bytes, is_utf8_string(anything()))?; // Fails (not UTF-8 encoded)
/// #     Ok(())
/// # }
/// # should_pass().unwrap();
/// # should_fail_1().unwrap_err();
/// # should_fail_2().unwrap_err();
/// ```
pub fn is_utf8_string<InnerMatcherT>(
    inner: InnerMatcherT,
) -> __internal::IsEncodedStringMatcher<InnerMatcherT>
where
    InnerMatcherT: Matcher<String>,
{
    __internal::IsEncodedStringMatcher { inner }
}

pub mod __internal {
    use super::*;

    #[doc(hidden)]
    pub struct IsEncodedStringMatcher<InnerMatcherT> {
        pub(super) inner: InnerMatcherT,
    }

    impl<'a, ActualT: AsRef<[u8]> + Debug + 'a, InnerMatcherT: Matcher<String>> Matcher<ActualT>
        for IsEncodedStringMatcher<InnerMatcherT>
    {
        fn matches(&self, actual: &ActualT) -> MatcherResult {
            String::from_utf8(actual.as_ref().to_vec())
                .map(|s| self.inner.matches(&s))
                .unwrap_or(MatcherResult::NoMatch)
        }

        fn explain_match(&self, actual: &ActualT) -> Description {
            match String::from_utf8(actual.as_ref().to_vec()) {
                Ok(s) => {
                    format!(
                        "which is a UTF-8 encoded string {}",
                        self.inner.explain_match(&s)
                    )
                    .into()
                }
                Err(e) => format!("which is not a UTF-8 encoded string: {e}").into(),
            }
        }
    }

    impl<InnerMatcherT: Describable> Describable for IsEncodedStringMatcher<InnerMatcherT> {
        fn describe(&self, matcher_result: MatcherResult) -> Description {
            match matcher_result {
                MatcherResult::Match => format!(
                    "is a UTF-8 encoded string which {}",
                    self.inner.describe(MatcherResult::Match)
                )
                .into(),
                MatcherResult::NoMatch => format!(
                    "is not a UTF-8 encoded string which {}",
                    self.inner.describe(MatcherResult::Match)
                )
                .into(),
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use crate::matcher::{Describable as _, MatcherResult};
    use crate::prelude::*;

    #[test]
    fn matches_string_as_byte_slice() -> TestResult<()> {
        verify_that!("A string".as_bytes(), is_utf8_string(eq("A string")))
    }

    #[test]
    fn matches_string_as_byte_vec() -> TestResult<()> {
        verify_that!("A string".as_bytes().to_vec(), is_utf8_string(eq("A string")))
    }

    #[test]
    fn matches_string_with_utf_8_encoded_sequences() -> TestResult<()> {
        verify_that!("äöüÄÖÜ".as_bytes().to_vec(), is_utf8_string(eq("äöüÄÖÜ")))
    }

    #[test]
    fn does_not_match_non_equal_string() -> TestResult<()> {
        verify_that!("äöüÄÖÜ".as_bytes().to_vec(), not(is_utf8_string(eq("A string"))))
    }

    #[test]
    fn does_not_match_non_utf_8_encoded_byte_sequence() -> TestResult<()> {
        verify_that!(&[192, 64, 255, 32], not(is_utf8_string(eq("A string"))))
    }

    #[test]
    fn has_correct_description_in_matched_case() -> TestResult<()> {
        let matcher = is_utf8_string(eq("A string"));

        verify_that!(
            matcher.describe(MatcherResult::Match),
            displays_as(eq("is a UTF-8 encoded string which is equal to \"A string\""))
        )
    }

    #[test]
    fn has_correct_description_in_not_matched_case() -> TestResult<()> {
        let matcher = is_utf8_string(eq("A string"));

        verify_that!(
            matcher.describe(MatcherResult::NoMatch),
            displays_as(eq("is not a UTF-8 encoded string which is equal to \"A string\""))
        )
    }

    #[test]
    fn has_correct_explanation_in_matched_case() -> TestResult<()> {
        let explanation = is_utf8_string(eq("A string")).explain_match(&"A string".as_bytes());

        verify_that!(
            explanation,
            displays_as(eq("which is a UTF-8 encoded string which is equal to \"A string\""))
        )
    }

    #[test]
    fn has_correct_explanation_when_byte_array_is_not_utf8_encoded() -> TestResult<()> {
        let explanation = is_utf8_string(eq("A string")).explain_match(&&[192, 128, 0, 64]);

        verify_that!(explanation, displays_as(starts_with("which is not a UTF-8 encoded string: ")))
    }

    #[test]
    fn has_correct_explanation_when_inner_matcher_does_not_match() -> TestResult<()> {
        let explanation =
            is_utf8_string(eq("A string")).explain_match(&"Another string".as_bytes());

        verify_that!(
            explanation,
            displays_as(eq("which is a UTF-8 encoded string which isn't equal to \"A string\""))
        )
    }
}
