//! Encoded Buffers Implementation
//!
//! This module contains a trait used for converting byte buffers or
//! Rust strings into oniguruma char buffers to search and compile
//! with.

/// Encoded String Buffer
///
/// Represents a buffer of characters with encoding information
/// attached.
pub trait EncodedChars {
    /// Pointer to the start of the pattern
    ///
    /// This should point to the first character in the buffer,
    /// encoded as an `onig_sys` character.
    fn start_ptr(&self) -> *const onig_sys::OnigUChar;

    /// Pointer to the limit of the pattern buffer
    ///
    /// This should point just past the final character in the buffer,
    /// encoded as an `onig_sys` character.
    fn limit_ptr(&self) -> *const onig_sys::OnigUChar;

    /// The encoding of the contents of the buffer
    fn encoding(&self) -> onig_sys::OnigEncoding {
        unsafe { &mut onig_sys::OnigEncodingUTF8 }
    }

    /// The length of this buffer
    fn len(&self) -> usize;

    /// Is the buffer empty?
    fn is_empty(&self) -> bool {
        self.len() == 0
    }
}

/// Encoded Charters from a `str` Reference
impl<T> EncodedChars for T
where
    T: AsRef<str>,
{
    fn start_ptr(&self) -> *const onig_sys::OnigUChar {
        self.as_ref().as_bytes().as_ptr()
    }

    fn limit_ptr(&self) -> *const onig_sys::OnigUChar {
        let bytes = self.as_ref().as_bytes();
        bytes[bytes.len()..].as_ptr()
    }

    fn len(&self) -> usize {
        self.as_ref().len()
    }
}

/// Byte Buffer
///
/// Represents a buffer of bytes, with an encoding.
pub struct EncodedBytes<'a> {
    bytes: &'a [u8],
    enc: onig_sys::OnigEncoding,
}

impl<'a> EncodedBytes<'a> {
    /// New Buffer from Parts
    ///
    /// # Arguments
    ///
    ///  * `bytes` - The contents of the buffer
    ///  * `enc` - The encoding this buffer is in
    ///
    /// # Returns
    ///
    /// A new buffer instance
    pub fn from_parts(bytes: &'a [u8], enc: onig_sys::OnigEncoding) -> EncodedBytes<'a> {
        EncodedBytes { bytes, enc }
    }

    /// New ASCII Buffer
    ///
    /// # Arguments
    ///
    ///  * `bytes` - The ASCII encoded string
    ///
    /// # Returns
    ///
    /// A new buffer instance
    pub fn ascii(bytes: &'a [u8]) -> EncodedBytes<'a> {
        EncodedBytes {
            bytes,
            enc: unsafe { &mut onig_sys::OnigEncodingASCII },
        }
    }
}

impl<'a> EncodedChars for EncodedBytes<'a> {
    fn start_ptr(&self) -> *const onig_sys::OnigUChar {
        self.bytes.as_ptr()
    }

    fn limit_ptr(&self) -> *const onig_sys::OnigUChar {
        self.bytes[self.bytes.len()..].as_ptr()
    }

    fn encoding(&self) -> onig_sys::OnigEncoding {
        self.enc
    }

    fn len(&self) -> usize {
        self.bytes.len()
    }
}

#[cfg(test)]
pub mod tests {
    use super::*;

    #[test]
    pub fn rust_string_encoding_is_utf8() {
        let foo = "foo";
        assert_eq!(
            unsafe { &mut onig_sys::OnigEncodingUTF8 } as onig_sys::OnigEncoding,
            foo.encoding()
        );

        let bar = String::from(".*");
        assert_eq!(
            unsafe { &mut onig_sys::OnigEncodingUTF8 } as onig_sys::OnigEncoding,
            bar.encoding()
        );
    }

    #[test]
    pub fn rust_bytes_encoding_is_ascii() {
        let fizz = b"fizz";
        let buff = EncodedBytes::ascii(fizz);
        assert_eq!(
            unsafe { &mut onig_sys::OnigEncodingASCII } as onig_sys::OnigEncoding,
            buff.encoding()
        );
    }

    #[test]
    pub fn rust_string_ptr_offsets_are_valid() {
        let test_string = "hello world";
        assert_eq!(
            test_string.limit_ptr() as usize - test_string.start_ptr() as usize,
            test_string.len()
        );
    }

    #[test]
    pub fn rust_bytes_ptr_offsets_are_valid() {
        let fozz = b"foo.*bar";
        let buff = EncodedBytes::ascii(fozz);
        assert_eq!(
            buff.limit_ptr() as usize - buff.start_ptr() as usize,
            fozz.len()
        );
    }

    #[test]
    pub fn byte_buffer_create() {
        let buff = b"hello world";
        let enc_buffer =
            EncodedBytes::from_parts(buff, unsafe { &mut onig_sys::OnigEncodingASCII });
        assert_eq!(
            unsafe { &mut onig_sys::OnigEncodingASCII } as onig_sys::OnigEncoding,
            enc_buffer.encoding()
        );
        assert_eq!(
            enc_buffer.limit_ptr() as usize - enc_buffer.start_ptr() as usize,
            buff.len()
        );
    }
}