use winapi::um::wincodec::{IWICImagingFactory, IWICBitmapDecoder, IWICBitmapSource, WICPixelFormatGUID};
use winapi::shared::winerror::S_OK;
use crate::win32::image_decoder as img;
use crate::{NwgError, Bitmap};
use std::{ptr, mem};


/**
    A image decoder. Can load an extended number of image file format from a filename, from a file handle, or from a stream.

    ImageDecoder do not take any parameter to build, but it still provides a builder API to match the other component of NWG.
    You can also use "ImageDecoder::new" to avoid the builder API.

    There's not much reason to have more than 1 image decoder per application.

    Images loaded from a decoder cannot be used as-is by an image frame. They must first be converted to a bitmap resource.

    ```rust
    use native_windows_gui as nwg;
    fn open_image(decoder: &nwg::ImageDecoder) -> Result<nwg::ImageData, nwg::NwgError> {
        decoder
            .from_filename("corn.png")?
            .frame(0)
    }
    ```

    ```rust
    use native_windows_gui as nwg;
    fn build_image_decode(decode: &mut nwg::ImageDecoder) -> Result<(), nwg::NwgError> {
        nwg::ImageDecoder::builder()
            .build(decode)
    }
    ```
*/
pub struct ImageDecoder {
    pub factory: *mut IWICImagingFactory,
}

impl ImageDecoder {
    pub fn new() -> Result<ImageDecoder, NwgError> {
        let factory = unsafe { img::create_image_factory() }?;
        Ok(ImageDecoder { factory })
    }

    pub fn builder() -> ImageDecoderBuilder {
        ImageDecoderBuilder {
        }
    }

    /**
        Try to read an image from a file path.
        The file type can be any of the native WIC codecs (https://docs.microsoft.com/en-us/windows/win32/wic/native-wic-codecs)

        * If there is an error during the decoding, returns a NwgError.
        * If the image decoder was not initialized, this method panics

        This method returns a ImageSource object
    */
    pub fn from_filename<'a>(&self, path: &'a str) -> Result<ImageSource, NwgError> {
        if self.factory.is_null() {
            panic!("ImageDecoder is not yet bound to a winapi object");
        }

        let decoder = unsafe { img::create_decoder_from_file(&*self.factory, path) }?;

        Ok(ImageSource { decoder })
    }

    /**
        Build an image from a stream of data.
        The file type can be any of the native WIC codecs (https://docs.microsoft.com/en-us/windows/win32/wic/native-wic-codecs)

        * If there is an error during the decoding, returns a NwgError.
        * If the image decoder was not initialized, this method panics

        This method copies the bytes and returns a ImageSource object
    */
    pub fn from_stream(&self, stream: &[u8]) -> Result<ImageSource, NwgError> {
        if self.factory.is_null() {
            panic!("ImageDecoder is not yet bound to a winapi object");
        }

        let decoder = unsafe { img::create_decoder_from_stream(&*self.factory, stream) }?;

        Ok(ImageSource { decoder })
    }

    /**
        Resize an image, returning the new resized image. The pixel format might change.
    */
    pub fn resize_image(&self, image: &ImageData, new_size: [u32;2]) -> Result<ImageData, NwgError> {
        unsafe { img::resize_bitmap(&*self.factory, image, new_size) }
    }

}


/**
    Represents a image data source in read only mode.
*/
pub struct ImageSource {
    pub decoder: *mut IWICBitmapDecoder
}

impl ImageSource {

    /**
        Return the number of frame in the image. For most format (ex: PNG), this will be 1.
        It might be more than 1 in animated image formats (such as GIFs).
    */
    pub fn frame_count(&self) -> u32 {
        let mut frame_count = 0;
        unsafe { (&*self.decoder).GetFrameCount(&mut frame_count); }
        frame_count
    }

    /**
        Return the image data of the requested frame in a ImageData object.
    */
    pub fn frame(&self, index: u32) -> Result<ImageData, NwgError> {
        let mut bitmap = ptr::null_mut();
        let hr = unsafe { (&*self.decoder).GetFrame(index, &mut bitmap) };
        match hr {
            S_OK => Ok(ImageData { frame: bitmap as *mut IWICBitmapSource }),
            err => Err(NwgError::image_decoder(err, "Could not read image frame"))
        }
    }

    /*  Retrieves the container format of the image source. 

        See https://docs.microsoft.com/en-us/windows/win32/wic/-wic-guids-clsids#container-formats
    */
    pub fn container_format(&self) -> ContainerFormat {
        use ContainerFormat::*;
        let mut container = unsafe { mem::zeroed() };
        unsafe { (&*self.decoder).GetContainerFormat(&mut container) };

        // Just use the first field of the GUID because the winapi type does no implement EQ

        match container.Data1 {
            0xf3ff6d0d => Adng,
            0xaf1d87e => Bmp,
            0x1b7cfaf4 => Png,
            0xa3a860c4 => Ico,
            0x19e4a5aa => Jpeg,
            0x163bcc30 => Tiff,
            0x1f8a5601 => Gif,
            0x57a37caa => Wmp,
            _ => Unknown
        }

    }

}


/**
    Represents a source of pixel that can be read, but cannot be written back to.
*/
pub struct ImageData {
    pub frame: *mut IWICBitmapSource
}

impl ImageData {

    /// Retrieves the sampling rate between pixels and physical world measurements.

    pub fn resolution(&self) -> (f64, f64) {
        let (mut rx, mut ry) = (0.0, 0.0);
        unsafe { (&*self.frame).GetResolution(&mut rx, &mut ry) };
        (rx, ry)
    }  
    
    /// Retrieves the pixel width and height of the bitmap.

    pub fn size(&self) -> (u32, u32) {
        let (mut sx, mut sy) = (0, 0);
        unsafe { (&*self.frame).GetSize(&mut sx, &mut sy) };
        (sx, sy)
    }

    /*  Retrieves the pixel format of the bitmap source. Returns a GUID, Match it to the GUID defined in the link below:

        See https://docs.microsoft.com/en-us/windows/win32/wic/-wic-codec-native-pixel-formats#undefined-pixel-formats
    */
    pub fn pixel_format(&self) -> WICPixelFormatGUID {
        let mut fmt = unsafe { mem::zeroed() };
        unsafe { (&*self.frame).GetPixelFormat(&mut fmt) };
        fmt
    }

    /**
        Copy the frame pixels into a buffer.

        Parameters:
            pixel_size: defines the size of a pixel in bytes. In a typical RGBA image, this would be 4 (1 byte for each component).
                        If unsure, use the pixel_format.

        May return an error if the pixel data could not be read
    */
    pub fn pixels(&self, pixel_size: u32) -> Result<Vec<u8>, NwgError> {
        let (w, h) = self.size();
        let scanline = w * pixel_size;
        let buffer_size = (w * h * pixel_size) as usize;
        let mut buffer: Vec<u8> = Vec::with_capacity(buffer_size);
        
        let hr = unsafe {
            buffer.set_len(buffer_size);
            (&*self.frame).CopyPixels(ptr::null(), scanline, buffer_size as u32, buffer.as_mut_ptr())
        };

        match hr {
            S_OK => Ok(buffer),
            err => Err(NwgError::image_decoder(err, "Could not read image pixels"))
        }
    }

    /**
        Copy a region of the frames pixel into a buffer.

        Parameters:
            offset: The [x,y] offset at which the region begins
            size: The [width, height] size of the region
            pixel_size: defines the size of a pixel in bytes. In a typical RGBA image, this would be 4 (1 byte for each component).
                        If unsure, use the pixel_format.

        May return an error if the pixel data could not be read
    */
    pub fn region_pixels(&self, offset: [i32;2], size: [i32;2], pixel_size: u32) -> Result<Vec<u8>, NwgError> {
        use winapi::um::wincodec::WICRect;

        let [x, y] = offset;
        let [w, h] = size;
        let scanline = (w as u32) * pixel_size;
        let buffer_size = (scanline * (h as u32)) as usize;
        let mut buffer: Vec<u8> = Vec::with_capacity(buffer_size);

        let region = WICRect { X: x, Y: y, Width: w, Height: h };
        
        let hr = unsafe {
            buffer.set_len(buffer_size);
            (&*self.frame).CopyPixels(&region, scanline, buffer_size as u32, buffer.as_mut_ptr())
        };

        match hr {
            S_OK => Ok(buffer),
            err => Err(NwgError::image_decoder(err, "Could not read image pixels"))
        }
    }

    /**
        Create a bitmap resource the the image data. This resource can then be used in the other NWG component.
        The bitmap returned is considered "owned".
    */
    pub fn as_bitmap(&self) -> Result<Bitmap, NwgError> {
        unsafe { img::create_bitmap_from_wic(self) }
    }

}

/// A list of container format implemented in WIC

#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub enum ContainerFormat {
    Unknown,
    Adng,
    Bmp,
    Png,
    Ico,
    Jpeg,
    Tiff,
    Gif,
    Wmp,
}

//

// IMPL

//


impl Default for ImageDecoder {
    fn default() -> ImageDecoder {
        ImageDecoder {
            factory: ptr::null_mut()
        }
    }
}

impl Drop for ImageDecoder {
    fn drop(&mut self) {
        if !self.factory.is_null() {
            unsafe { (&*self.factory).Release(); }
        }
    }
}

impl Drop for ImageSource {
    fn drop(&mut self) {
        unsafe { (&*self.decoder).Release(); }
    }
}

impl Drop for ImageData {
    fn drop(&mut self) {
        unsafe { (&*self.frame).Release(); }
    }
}


/**
    A blank builder for the image decoder
*/
pub struct ImageDecoderBuilder {
}

impl ImageDecoderBuilder {
    pub fn build(self, out: &mut ImageDecoder) -> Result<(), NwgError> {
        let factory = unsafe { img::create_image_factory() }?;
        *out = ImageDecoder { factory };
        Ok(())
    }
}