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// SPDX-FileCopyrightText: 2024 Markus Haug (Korrat)
//
// SPDX-License-Identifier: Apache-2.0
// SPDX-License-Identifier: MIT

//! This crate provides helpers for working with Nullables as described by James Shore in [Testing without Mocks].
//!
//! [Testing without Mocks]: https://www.jamesshore.com/v2/projects/nullables/testing-without-mocks

extern crate alloc;

pub use nullable_utils_macros::*;

/// `NulledResponses` helps with implementing [Configurable Responses] for Nullable types.
///
/// [Configurable Responses]: https://www.jamesshore.com/v2/projects/nullables/testing-without-mocks#configurable-responses
#[derive(Clone, Debug)]
// TODO exchange this for an implementation using boxed iterators?
pub enum NulledResponses<T> {
    /// Repeat a single response forever.
    Repeating(T),
    /// Return a sequence of responses, panicking when the sequence runs out.
    Sequence(alloc::vec::Vec<T>),
}

impl<T> NulledResponses<T> {
    /// Backmap can be used to convert between `NulledResponses` for different types.
    ///
    /// For example, a high-level infrastructure wrapper can use this to convert its own response configuration into a
    /// response configuration for an embedded lower-level infrastructure wrapper.
    pub fn backmap<U>(self, mut mapper: impl FnMut(T) -> U) -> NulledResponses<U> {
        match self {
            Self::Repeating(response) => NulledResponses::Repeating(mapper(response)),
            Self::Sequence(responses) => {
                NulledResponses::Sequence(responses.into_iter().map(mapper).collect())
            }
        }
    }
}

impl<T> NulledResponses<T>
where
    T: Clone,
{
    /// Gets the next response.
    ///
    /// # Panics
    ///
    /// Panics if this object was configured with a finite sequence of responses and that sequence has been exhausted.
    pub fn get(&mut self) -> T {
        match self {
            Self::Repeating(response) => response.clone(),
            Self::Sequence(responses) => responses.pop().expect("not enough responses configured"),
        }
    }
}

impl<T, const N: usize> From<[T; N]> for NulledResponses<T> {
    fn from(value: [T; N]) -> Self {
        Self::from(Vec::from(value))
    }
}

impl<T> From<&[T]> for NulledResponses<T>
where
    T: Clone,
{
    fn from(value: &[T]) -> Self {
        Self::from(Vec::from(value))
    }
}

impl<T> From<T> for NulledResponses<T>
where
    T: Clone,
{
    fn from(value: T) -> Self {
        Self::Repeating(value)
    }
}

impl<T> From<Vec<T>> for NulledResponses<T> {
    fn from(mut value: Vec<T>) -> Self {
        value.reverse();
        Self::Sequence(value)
    }
}