// Copyright (c) 2016 The vulkano developers
// Licensed under the Apache License, Version 2.0
// <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT
// license <LICENSE-MIT or http://opensource.org/licenses/MIT>,
// at your option. All files in the project carrying such
// notice may not be copied, modified, or distributed except
// according to those terms.

use std::error;
use std::fmt;

use VulkanObject;
use buffer::TypedBufferAccess;
use device::Device;
use device::DeviceOwned;
use format::AcceptsPixels;
use format::Format;
use format::IncompatiblePixelsType;
use image::ImageAccess;

/// Type of operation to check.
#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
pub enum CheckCopyBufferImageTy {
    BufferToImage,
    ImageToBuffer,
}

/// Checks whether a copy buffer-image command is valid. Can check both buffer-to-image copies and
/// image-to-buffer copies.
///
/// # Panic
///
/// - Panics if the buffer and image were not created with `device`.
///
// TODO: handle compressed image formats
pub fn check_copy_buffer_image<B, I, P>(device: &Device, buffer: &B, image: &I,
                                        ty: CheckCopyBufferImageTy, image_offset: [u32; 3],
                                        image_size: [u32; 3], image_first_layer: u32,
                                        image_num_layers: u32, image_mipmap: u32)
                                        -> Result<(), CheckCopyBufferImageError>
    where I: ?Sized + ImageAccess,
          B: ?Sized + TypedBufferAccess<Content = [P]>,
          Format: AcceptsPixels<P> // TODO: use a trait on the image itself instead
{
    let buffer_inner = buffer.inner();
    let image_inner = image.inner();

    assert_eq!(buffer_inner.buffer.device().internal_object(),
               device.internal_object());
    assert_eq!(image_inner.image.device().internal_object(),
               device.internal_object());

    match ty {
        CheckCopyBufferImageTy::BufferToImage => {
            if !buffer_inner.buffer.usage_transfer_source() {
                return Err(CheckCopyBufferImageError::SourceMissingTransferUsage);
            }
            if !image_inner.image.usage_transfer_destination() {
                return Err(CheckCopyBufferImageError::DestinationMissingTransferUsage);
            }
        },
        CheckCopyBufferImageTy::ImageToBuffer => {
            if !image_inner.image.usage_transfer_source() {
                return Err(CheckCopyBufferImageError::SourceMissingTransferUsage);
            }
            if !buffer_inner.buffer.usage_transfer_destination() {
                return Err(CheckCopyBufferImageError::DestinationMissingTransferUsage);
            }
        },
    }

    if image.samples() != 1 {
        return Err(CheckCopyBufferImageError::UnexpectedMultisampled);
    }

    let image_dimensions = match image.dimensions().mipmap_dimensions(image_mipmap) {
        Some(d) => d,
        None => return Err(CheckCopyBufferImageError::ImageCoordinatesOutOfRange),
    };

    if image_first_layer + image_num_layers > image_dimensions.array_layers() {
        return Err(CheckCopyBufferImageError::ImageCoordinatesOutOfRange);
    }

    if image_offset[0] + image_size[0] > image_dimensions.width() {
        return Err(CheckCopyBufferImageError::ImageCoordinatesOutOfRange);
    }

    if image_offset[1] + image_size[1] > image_dimensions.height() {
        return Err(CheckCopyBufferImageError::ImageCoordinatesOutOfRange);
    }

    if image_offset[2] + image_size[2] > image_dimensions.depth() {
        return Err(CheckCopyBufferImageError::ImageCoordinatesOutOfRange);
    }

    image.format().ensure_accepts()?;

    {
        let num_texels = image_size[0] * image_size[1] * image_size[2] * image_num_layers;
        let required_len = num_texels as usize * image.format().rate() as usize;
        if required_len > buffer.len() {
            return Err(CheckCopyBufferImageError::BufferTooSmall {
                           required_len: required_len,
                           actual_len: buffer.len(),
                       });
        }
    }

    // TODO: check memory overlap?

    Ok(())
}

/// Error that can happen from `check_copy_buffer_image`.
#[derive(Debug, Copy, Clone)]
pub enum CheckCopyBufferImageError {
    /// The source buffer or image is missing the transfer source usage.
    SourceMissingTransferUsage,
    /// The destination buffer or image is missing the transfer destination usage.
    DestinationMissingTransferUsage,
    /// The source and destination are overlapping.
    OverlappingRanges,
    /// The image must not be multisampled.
    UnexpectedMultisampled,
    /// The image coordinates are out of range.
    ImageCoordinatesOutOfRange,
    /// The type of pixels in the buffer isn't compatible with the image format.
    WrongPixelType(IncompatiblePixelsType),
    /// The buffer is too small for the copy operation.
    BufferTooSmall {
        /// Required number of elements in the buffer.
        required_len: usize,
        /// Actual number of elements in the buffer.
        actual_len: usize,
    },
}

impl error::Error for CheckCopyBufferImageError {
    #[inline]
    fn description(&self) -> &str {
        match *self {
            CheckCopyBufferImageError::SourceMissingTransferUsage => {
                "the source buffer is missing the transfer source usage"
            },
            CheckCopyBufferImageError::DestinationMissingTransferUsage => {
                "the destination buffer is missing the transfer destination usage"
            },
            CheckCopyBufferImageError::OverlappingRanges => {
                "the source and destination are overlapping"
            },
            CheckCopyBufferImageError::UnexpectedMultisampled => {
                "the image must not be multisampled"
            },
            CheckCopyBufferImageError::ImageCoordinatesOutOfRange => {
                "the image coordinates are out of range"
            },
            CheckCopyBufferImageError::WrongPixelType(_) => {
                "the type of pixels in the buffer isn't compatible with the image format"
            },
            CheckCopyBufferImageError::BufferTooSmall { .. } => {
                "the buffer is too small for the copy operation"
            },
        }
    }

    fn cause(&self) -> Option<&error::Error> {
        match *self {
            CheckCopyBufferImageError::WrongPixelType(ref err) => {
                Some(err)
            },
            _ => None,
        }
    }
}

impl fmt::Display for CheckCopyBufferImageError {
    #[inline]
    fn fmt(&self, fmt: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        write!(fmt, "{}", error::Error::description(self))
    }
}

impl From<IncompatiblePixelsType> for CheckCopyBufferImageError {
    #[inline]
    fn from(err: IncompatiblePixelsType) -> CheckCopyBufferImageError {
        CheckCopyBufferImageError::WrongPixelType(err)
    }
}