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use std::ops::Deref;

mod bindings;
#[cfg(test)]
mod test;

#[allow(non_snake_case)]
pub fn WebPEncodeLosslessRGB(rgb: &[u8], width: usize, height: usize) -> Result<Bytes, Error> {
    unsafe {
        if !(1..=16383).contains(&width) || !(1..=16383).contains(&height) {
            return Err(Error::LimitExceeded);
        }
        if rgb.len() < width * height * 3 {
            return Err(Error::TooFewPixels);
        }
        let mut ptr = std::ptr::null_mut();
        let len = bindings::WebPEncodeLosslessRGB(
            rgb.as_ptr(),
            width as _,
            height as _,
            (width * 3) as _,
            &mut ptr,
        );
        if len == 0 {
            return Err(Error::Unknown);
        }
        if ptr.is_null() {
            return Err(Error::NullPointer);
        }
        Ok(Bytes { ptr, len })
    }
}

#[allow(non_snake_case)]
pub fn WebPEncodeLosslessRGBA(rgba: &[u8], width: usize, height: usize) -> Result<Bytes, Error> {
    unsafe {
        if !(1..=16383).contains(&width) || !(1..=16383).contains(&height) {
            return Err(Error::LimitExceeded);
        }
        if rgba.len() < width * height * 4 {
            return Err(Error::TooFewPixels);
        }
        let mut ptr = std::ptr::null_mut();
        let len = bindings::WebPEncodeLosslessRGBA(
            rgba.as_ptr(),
            width as _,
            height as _,
            (width * 4) as _,
            &mut ptr,
        );
        if len == 0 {
            return Err(Error::Unknown);
        }
        if ptr.is_null() {
            return Err(Error::NullPointer);
        }
        Ok(Bytes { ptr, len })
    }
}

#[derive(thiserror::Error, Debug)]
pub enum Error {
    #[error("unknown")]
    Unknown,
    #[error("null pointer")]
    NullPointer,
    #[error("limit exceeded")]
    LimitExceeded,
    #[error("too few pixels")]
    TooFewPixels,
}

pub struct Bytes {
    ptr: *mut u8,
    len: usize,
}

unsafe impl Send for Bytes {}

impl Deref for Bytes {
    type Target = [u8];

    fn deref(&self) -> &Self::Target {
        unsafe { std::slice::from_raw_parts(self.ptr, self.len) }
    }
}

impl Drop for Bytes {
    fn drop(&mut self) {
        unsafe {
            bindings::WebPFree(self.ptr as _);
        }
    }
}