#![no_std]
#![doc = include_str!("../README.md")]
extern crate alloc;

use core::fmt::{Display, Write};

/// Configurable Display implementation for slices and Vecs.
pub trait SliceDisplay<'a, T: Display> {
    #[must_use = "this does not display the slice, \
                  it returns an object that can be displayed"]
    fn display(&'a self) -> SliceDisplayImpl<'a, T>;
}

/// Helper struct for printing Vecs and slices.
#[derive(Clone, Copy)]
pub struct SliceDisplayImpl<'a, T: Display> {
    slice: &'a [T],
    terminators: (char, char),
    delimiter: char,
    should_space: bool,
}

impl<'a, T: Display> SliceDisplayImpl<'a, T> {
    /// Configures the terminators to be used for the display.
    ///
    /// # Example
    ///
    /// ```rust
    /// use slicedisplay::SliceDisplay;
    ///
    /// let hello: Vec<_> = "Hello".chars().collect();
    ///
    /// assert_eq!(hello.display().terminator('{', '}').to_string(), "{H, e, l, l, o}");
    /// ```
    pub fn terminator(self, beginning: char, ending: char) -> Self {
        Self {
            terminators: (beginning, ending),
            ..self
        }
    }

    /// Configures the delimiter to be used for the display.
    ///
    /// # Example
    ///
    /// ```rust
    /// use slicedisplay::SliceDisplay;
    ///
    /// let hello: Vec<_> = "Hello".chars().collect();
    ///
    /// assert_eq!(hello.display().delimiter(';').to_string(), "[H; e; l; l; o]");
    /// ```
    pub fn delimiter(self, delimiter: char) -> Self {
        Self { delimiter, ..self }
    }

    /// Sets whether additional spacing should be added between elements.
    ///
    /// True by default.
    ///
    /// # Example
    ///
    /// ```rust
    /// use slicedisplay::SliceDisplay;
    ///
    /// let hello: Vec<_> = "Hello".chars().collect();
    ///
    /// assert_eq!(hello.display().delimiter(';').to_string(), "[H; e; l; l; o]");
    /// assert_eq!(hello.display().delimiter(';').should_space(false).to_string(), "[H;e;l;l;o]");
    /// ```
    pub fn should_space(self, should_space: bool) -> Self {
        Self {
            should_space,
            ..self
        }
    }
}

impl<T: Display, A> SliceDisplay<'_, T> for A
where
    A: AsRef<[T]>,
{
    fn display(&self) -> SliceDisplayImpl<'_, T> {
        SliceDisplayImpl {
            slice: self.as_ref(),
            terminators: ('[', ']'),
            delimiter: ',',
            should_space: true,
        }
    }
}

impl<'a, T: Display> Display for SliceDisplayImpl<'a, T> {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        let (beginning, ending) = self.terminators;
        let delimiter = self.delimiter;
        let spacing = if self.should_space { " " } else { "" };

        f.write_char(beginning)?;
        if let Some((last, elems)) = self.slice.split_last() {
            for elem in elems {
                write!(f, "{elem}{delimiter}{spacing}")?;
            }
            write!(f, "{last}")?;
        }

        f.write_char(ending)
    }
}

#[cfg(test)]
mod tests {
    use alloc::{string::ToString, vec::Vec};

    use crate::SliceDisplay;

    extern crate alloc;

    #[test]
    fn slice_display_empty() {
        // Slighly redundant in order to ensure that we can
        // call Display on any AsRef<T>
        let empty: Vec<u8> = Vec::new();
        let empty_array: [u8; 0] = [];
        let empty_slice: &[u8] = &[];

        assert_eq!(empty.display().to_string(), "[]");
        assert_eq!(empty_array.display().to_string(), "[]");
        assert_eq!(empty_slice.display().to_string(), "[]");
    }

    #[test]
    fn slice_display_single() {
        let single = [1];
        assert_eq!(single.display().to_string(), "[1]");
    }

    #[test]
    fn slice_display_multiple() {
        let numbers = [1, 2, 3, 4, 5];
        assert_eq!(numbers.display().to_string(), "[1, 2, 3, 4, 5]");
    }

    #[test]
    fn slice_display_custom_delimiter() {
        let numbers = [1, 2, 3, 4, 5];
        assert_eq!(
            numbers.display().delimiter(';').to_string(),
            "[1; 2; 3; 4; 5]"
        );
        assert_eq!(
            numbers
                .display()
                .delimiter('-')
                .should_space(false)
                .to_string(),
            "[1-2-3-4-5]"
        );
    }

    #[test]
    fn slice_display_custom_terminators() {
        let numbers = [1, 2, 3, 4, 5];
        assert_eq!(
            numbers.display().terminator('{', '}').to_string(),
            "{1, 2, 3, 4, 5}"
        );
        assert_eq!(
            numbers
                .display()
                .terminator('{', '}')
                .should_space(false)
                .delimiter(';')
                .to_string(),
            "{1;2;3;4;5}"
        );
    }
}