use crate::instance::Instance;
use crate::prelude::*;
use crate::vk;
use crate::RawPtr;
use std::error::Error;
use std::ffi::CStr;
use std::fmt;
use std::mem;
use std::os::raw::c_char;
use std::os::raw::c_void;
use std::ptr;

/// Holds a custom type `L` to load symbols from (usually a handle to a `dlopen`ed library),
/// the [`vkGetInstanceProcAddr`][vk::StaticFn::get_instance_proc_addr()] loader function from
/// this library (in [`vk::StaticFn`]), and Vulkan's "entry point" functions (resolved with `NULL`
/// `instance`) as listed in [`vkGetInstanceProcAddr`'s description].
///
/// [`vkGetInstanceProcAddr`'s description]: https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/vkGetInstanceProcAddr.html#_description
#[derive(Clone)]
pub struct EntryCustom<L> {
    static_fn: vk::StaticFn,
    entry_fn_1_0: vk::EntryFnV1_0,
    entry_fn_1_1: vk::EntryFnV1_1,
    entry_fn_1_2: vk::EntryFnV1_2,
    lib: L,
}

/// Vulkan core 1.0
#[allow(non_camel_case_types)]
impl<L> EntryCustom<L> {
    pub fn new_custom<Load>(
        mut lib: L,
        mut load: Load,
    ) -> std::result::Result<Self, MissingEntryPoint>
    where
        Load: FnMut(&mut L, &::std::ffi::CStr) -> *const c_void,
    {
        // Bypass the normal StaticFn::load so we can return an error
        let static_fn = vk::StaticFn::load_checked(|name| load(&mut lib, name))?;
        let load_fn = |name: &std::ffi::CStr| unsafe {
            mem::transmute(static_fn.get_instance_proc_addr(vk::Instance::null(), name.as_ptr()))
        };
        let entry_fn_1_0 = vk::EntryFnV1_0::load(load_fn);
        let entry_fn_1_1 = vk::EntryFnV1_1::load(load_fn);
        let entry_fn_1_2 = vk::EntryFnV1_2::load(load_fn);

        Ok(EntryCustom {
            static_fn,
            entry_fn_1_0,
            entry_fn_1_1,
            entry_fn_1_2,
            lib,
        })
    }

    pub fn fp_v1_0(&self) -> &vk::EntryFnV1_0 {
        &self.entry_fn_1_0
    }

    pub fn static_fn(&self) -> &vk::StaticFn {
        &self.static_fn
    }

    #[doc = "<https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/vkEnumerateInstanceVersion.html>"]
    /// ```no_run
    /// # use ash::{Entry, vk};
    /// # fn main() -> Result<(), Box<dyn std::error::Error>> {
    /// let entry = unsafe { Entry::new() }?;
    /// match entry.try_enumerate_instance_version()? {
    ///     // Vulkan 1.1+
    ///     Some(version) => {
    ///         let major = vk::version_major(version);
    ///         let minor = vk::version_minor(version);
    ///         let patch = vk::version_patch(version);
    ///     },
    ///     // Vulkan 1.0
    ///     None => {},
    /// }
    /// # Ok(()) }
    /// ```
    pub fn try_enumerate_instance_version(&self) -> VkResult<Option<u32>> {
        unsafe {
            let mut api_version = 0;
            let enumerate_instance_version: Option<vk::PFN_vkEnumerateInstanceVersion> = {
                let name = b"vkEnumerateInstanceVersion\0".as_ptr() as *const _;
                mem::transmute(
                    self.static_fn
                        .get_instance_proc_addr(vk::Instance::null(), name),
                )
            };
            if let Some(enumerate_instance_version) = enumerate_instance_version {
                (enumerate_instance_version)(&mut api_version)
                    .result_with_success(Some(api_version))
            } else {
                Ok(None)
            }
        }
    }

    #[doc = "<https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/vkCreateInstance.html>"]
    ///
    /// # Safety
    /// In order for the created [`Instance`] to be valid for the duration of its
    /// usage, the [`Entry`](Self) this was called on must be dropped later than the
    /// resulting [`Instance`].
    pub unsafe fn create_instance(
        &self,
        create_info: &vk::InstanceCreateInfo,
        allocation_callbacks: Option<&vk::AllocationCallbacks>,
    ) -> Result<Instance, InstanceError> {
        let mut instance = mem::zeroed();
        self.entry_fn_1_0
            .create_instance(
                create_info,
                allocation_callbacks.as_raw_ptr(),
                &mut instance,
            )
            .result()
            .map_err(InstanceError::VkError)?;
        Ok(Instance::load(&self.static_fn, instance))
    }

    #[doc = "<https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/vkEnumerateInstanceLayerProperties.html>"]
    pub fn enumerate_instance_layer_properties(&self) -> VkResult<Vec<vk::LayerProperties>> {
        unsafe {
            read_into_uninitialized_vector(|count, data| {
                self.entry_fn_1_0
                    .enumerate_instance_layer_properties(count, data)
            })
        }
    }

    #[doc = "<https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/vkEnumerateInstanceExtensionProperties.html>"]
    pub fn enumerate_instance_extension_properties(
        &self,
    ) -> VkResult<Vec<vk::ExtensionProperties>> {
        unsafe {
            read_into_uninitialized_vector(|count, data| {
                self.entry_fn_1_0
                    .enumerate_instance_extension_properties(ptr::null(), count, data)
            })
        }
    }

    #[doc = "<https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/vkGetInstanceProcAddr.html>"]
    pub unsafe fn get_instance_proc_addr(
        &self,
        instance: vk::Instance,
        p_name: *const c_char,
    ) -> vk::PFN_vkVoidFunction {
        self.static_fn.get_instance_proc_addr(instance, p_name)
    }
}

/// Vulkan core 1.1
#[allow(non_camel_case_types)]
impl<L> EntryCustom<L> {
    pub fn fp_v1_1(&self) -> &vk::EntryFnV1_1 {
        &self.entry_fn_1_1
    }

    #[deprecated = "This function is unavailable and therefore panics on Vulkan 1.0, please use `try_enumerate_instance_version` instead"]
    #[doc = "<https://www.khronos.org/registry/vulkan/specs/1.2-extensions/man/html/vkEnumerateInstanceVersion.html>"]
    ///
    /// Please use [`Self::try_enumerate_instance_version`] instead.
    pub fn enumerate_instance_version(&self) -> VkResult<u32> {
        unsafe {
            let mut api_version = 0;
            self.entry_fn_1_1
                .enumerate_instance_version(&mut api_version)
                .result_with_success(api_version)
        }
    }
}

/// Vulkan core 1.2
#[allow(non_camel_case_types)]
impl<L> EntryCustom<L> {
    pub fn fp_v1_2(&self) -> &vk::EntryFnV1_2 {
        &self.entry_fn_1_2
    }
}

#[derive(Clone, Debug)]
pub enum InstanceError {
    LoadError(Vec<&'static str>),
    VkError(vk::Result),
}

impl fmt::Display for InstanceError {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            InstanceError::LoadError(e) => write!(f, "{}", e.join("; ")),
            InstanceError::VkError(e) => write!(f, "{}", e),
        }
    }
}

impl Error for InstanceError {}

impl vk::StaticFn {
    pub fn load_checked<F>(mut _f: F) -> Result<Self, MissingEntryPoint>
    where
        F: FnMut(&::std::ffi::CStr) -> *const c_void,
    {
        // TODO: Make this a &'static CStr once CStr::from_bytes_with_nul_unchecked is const
        static ENTRY_POINT: &[u8] = b"vkGetInstanceProcAddr\0";

        Ok(vk::StaticFn {
            get_instance_proc_addr: unsafe {
                let cname = CStr::from_bytes_with_nul_unchecked(ENTRY_POINT);
                let val = _f(cname);
                if val.is_null() {
                    return Err(MissingEntryPoint);
                } else {
                    ::std::mem::transmute(val)
                }
            },
        })
    }
}

#[derive(Clone, Debug)]
pub struct MissingEntryPoint;
impl std::fmt::Display for MissingEntryPoint {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::result::Result<(), std::fmt::Error> {
        write!(f, "Cannot load `vkGetInstanceProcAddr` symbol from library")
    }
}
impl std::error::Error for MissingEntryPoint {}