// 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.

//! Cache the pipeline objects to disk for faster reloads.
//!
//! A pipeline cache is an opaque type that allow you to cache your graphics and compute
//! pipelines on the disk.
//!
//! You can create either an empty cache or a cache from some initial data. Whenever you create a
//! graphics or compute pipeline, you have the possibility to pass a reference to that cache.
//! TODO: ^ that's not the case yet
//! The Vulkan implementation will then look in the cache for an existing entry, or add one if it
//! doesn't exist.
//!
//! Once that is done, you can extract the data from the cache and store it. See the documentation
//! of [`get_data`](struct.PipelineCache.html#method.get_data) for example of how to store the data
//! on the disk, and [`with_data`](struct.PipelineCache.html#method.with_data) for how to reload it.
//!

use std::mem::MaybeUninit;
use std::ptr;
use std::sync::Arc;

use device::Device;

use OomError;
use VulkanObject;
use check_errors;
use vk;

/// Opaque cache that contains pipeline objects.
///
/// See [the documentation of the module](index.html) for more info.
pub struct PipelineCache {
    device: Arc<Device>,
    cache: vk::PipelineCache,
}

impl PipelineCache {
    /// Builds a new pipeline cache from existing data. The data must have been previously obtained
    /// with [`get_data`](#method.get_data).
    ///
    /// The data passed to this function will most likely be blindly trusted by the Vulkan
    /// implementation. Therefore you can easily crash your application or the system by passing
    /// wrong data. Hence why this function is unsafe.
    ///
    /// # Example
    ///
    /// This example loads a cache from a file, if it exists.
    /// See [`get_data`](#method.get_data) for how to store the data in a file.
    /// TODO: there's a header in the cached data that must be checked ; talk about this
    ///
    /// ```
    /// # use std::sync::Arc;
    /// # use vulkano::device::Device;
    /// use std::fs::File;
    /// use std::io::Read;
    /// use vulkano::pipeline::cache::PipelineCache;
    /// # let device: Arc<Device> = return;
    ///
    /// let data = {
    ///     let file = File::open("pipeline_cache.bin");
    ///     if let Ok(mut file) = file {
    ///         let mut data = Vec::new();
    ///         if let Ok(_) = file.read_to_end(&mut data) {
    ///             Some(data)
    ///         } else { None }
    ///     } else { None }
    /// };
    ///
    /// let cache = if let Some(data) = data {
    ///     // This is unsafe because there is no way to be sure that the file contains valid data.
    ///     unsafe { PipelineCache::with_data(device.clone(), &data).unwrap() }
    /// } else {
    ///     PipelineCache::empty(device.clone()).unwrap()
    /// };
    /// ```
    #[inline]
    pub unsafe fn with_data(device: Arc<Device>, initial_data: &[u8])
                            -> Result<Arc<PipelineCache>, OomError> {
        PipelineCache::new_impl(device, Some(initial_data))
    }

    /// Builds a new empty pipeline cache.
    ///
    /// # Example
    ///
    /// ```
    /// # use std::sync::Arc;
    /// # use vulkano::device::Device;
    /// use vulkano::pipeline::cache::PipelineCache;
    /// # let device: Arc<Device> = return;
    /// let cache = PipelineCache::empty(device.clone()).unwrap();
    /// ```
    #[inline]
    pub fn empty(device: Arc<Device>) -> Result<Arc<PipelineCache>, OomError> {
        unsafe { PipelineCache::new_impl(device, None) }
    }

    // Actual implementation of the constructor.
    unsafe fn new_impl(device: Arc<Device>, initial_data: Option<&[u8]>)
                       -> Result<Arc<PipelineCache>, OomError> {
        let vk = device.pointers();

        let cache = {
            let infos = vk::PipelineCacheCreateInfo {
                sType: vk::STRUCTURE_TYPE_PIPELINE_CACHE_CREATE_INFO,
                pNext: ptr::null(),
                flags: 0, // reserved
                initialDataSize: initial_data.map(|d| d.len()).unwrap_or(0),
                pInitialData: initial_data
                    .map(|d| d.as_ptr() as *const _)
                    .unwrap_or(ptr::null()),
            };

            let mut output = MaybeUninit::uninit();
            check_errors(vk.CreatePipelineCache(device.internal_object(),
                                                &infos,
                                                ptr::null(),
                                                output.as_mut_ptr()))?;
            output.assume_init()
        };

        Ok(Arc::new(PipelineCache {
                        device: device.clone(),
                        cache: cache,
                    }))
    }

    /// Merges other pipeline caches into this one.
    ///
    /// It is `self` that is modified here. The pipeline caches passed as parameter are untouched.
    ///
    /// # Panic
    ///
    /// - Panics if `self` is included in the list of other pipelines.
    ///
    // FIXME: vkMergePipelineCaches is not thread safe for the destination cache
    // TODO: write example
    pub fn merge<'a, I>(&self, pipelines: I) -> Result<(), OomError>
        where I: IntoIterator<Item = &'a &'a Arc<PipelineCache>>
    {
        unsafe {
            let vk = self.device.pointers();

            let pipelines = pipelines
                .into_iter()
                .map(|pipeline| {
                         assert!(&***pipeline as *const _ != &*self as *const _);
                         pipeline.cache
                     })
                .collect::<Vec<_>>();

            check_errors(vk.MergePipelineCaches(self.device.internal_object(),
                                                self.cache,
                                                pipelines.len() as u32,
                                                pipelines.as_ptr()))?;

            Ok(())
        }
    }

    /// Obtains the data from the cache.
    ///
    /// This data can be stored and then reloaded and passed to `PipelineCache::with_data`.
    ///
    /// # Example
    ///
    /// This example stores the data of a pipeline cache on the disk.
    /// See [`with_data`](#method.with_data) for how to reload it.
    ///
    /// ```
    /// use std::fs;
    /// use std::fs::File;
    /// use std::io::Write;
    /// # use std::sync::Arc;
    /// # use vulkano::pipeline::cache::PipelineCache;
    ///
    /// # let cache: Arc<PipelineCache> = return;
    /// // If an error happens (eg. no permission for the file) we simply skip storing the cache.
    /// if let Ok(data) = cache.get_data() {
    ///     if let Ok(mut file) = File::create("pipeline_cache.bin.tmp") {
    ///         if let Ok(_) = file.write_all(&data) {
    ///             let _ = fs::rename("pipeline_cache.bin.tmp", "pipeline_cache.bin");
    ///         } else {
    ///             let _ = fs::remove_file("pipeline_cache.bin.tmp");
    ///         }
    ///     }
    /// }
    /// ```
    pub fn get_data(&self) -> Result<Vec<u8>, OomError> {
        unsafe {
            let vk = self.device.pointers();

            let mut num = 0;
            check_errors(vk.GetPipelineCacheData(self.device.internal_object(),
                                                 self.cache,
                                                 &mut num,
                                                 ptr::null_mut()))?;

            let mut data: Vec<u8> = Vec::with_capacity(num as usize);
            check_errors(vk.GetPipelineCacheData(self.device.internal_object(),
                                                 self.cache,
                                                 &mut num,
                                                 data.as_mut_ptr() as *mut _))?;
            data.set_len(num as usize);

            Ok(data)
        }
    }
}

unsafe impl VulkanObject for PipelineCache {
    type Object = vk::PipelineCache;

    const TYPE: vk::ObjectType = vk::OBJECT_TYPE_PIPELINE_CACHE;

    #[inline]
    fn internal_object(&self) -> vk::PipelineCache {
        self.cache
    }
}

impl Drop for PipelineCache {
    #[inline]
    fn drop(&mut self) {
        unsafe {
            let vk = self.device.pointers();
            vk.DestroyPipelineCache(self.device.internal_object(), self.cache, ptr::null());
        }
    }
}

#[cfg(test)]
mod tests {
    use pipeline::cache::PipelineCache;

    #[test]
    fn merge_self_forbidden() {
        let (device, queue) = gfx_dev_and_queue!();
        let pipeline = PipelineCache::empty(device).unwrap();
        assert_should_panic!({
                                 pipeline.merge(&[&pipeline]).unwrap();
                             });
    }
}