use std::os::fd::{AsRawFd, OwnedFd, RawFd};
use std::ffi::{OsString, c_void};
use libc;
use crate::gpu::i915::DrmDeviceNode;

use super::native;
use super::get_drm_version;
use std::fs;
use std::fs::File;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum EngineClass {
    Render, Copy, Video, VideoEnhance, Compute, Invalid
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct EngineClassInstance {
    pub engine_class: EngineClass,
    pub engine_instance: u16,
}

pub type EngineInfoFlags = u64;

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct EngineInfo {
    pub engine: EngineClassInstance,
    pub logical_instance: u16,
    pub flags: EngineInfoFlags,
    pub capabilities: u64,
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct DrmGemHandle {
    pub handle: u32,
}

fn engine_class_from_u16(engine_class: u16) -> EngineClass {
    match engine_class {
        0 => EngineClass::Render,
        1 => EngineClass::Copy,
        2 => EngineClass::Video,
        3 => EngineClass::VideoEnhance,
        4 => EngineClass::Compute,
        _ => EngineClass::Invalid,
    }
}

fn engine_class_instance_from_native(engine_class_instance: native::i915_engine_class_instance) -> EngineClassInstance {
    EngineClassInstance {
        engine_class: engine_class_from_u16(engine_class_instance.engine_class),
        engine_instance: engine_class_instance.engine_instance,
    }
}

fn engine_info_from_native(engine_info: native::drm_i915_engine_info) -> EngineInfo {
    EngineInfo {
        engine: engine_class_instance_from_native(engine_info.engine),
        logical_instance: engine_info.logical_instance,
        flags: engine_info.flags,
        capabilities: engine_info.capabilities,
    }
}

impl EngineInfo {
    pub fn to_native(&self) -> native::drm_i915_engine_info {
        native::drm_i915_engine_info {
            engine: native::i915_engine_class_instance {
                engine_class: match self.engine.engine_class {
                    EngineClass::Render => 0,
                    EngineClass::Copy => 1,
                    EngineClass::Video => 2,
                    EngineClass::VideoEnhance => 3,
                    EngineClass::Compute => 4,
                    EngineClass::Invalid => 0xFFFF,
                },
                engine_instance: self.engine.engine_instance,
            },
            logical_instance: self.logical_instance,
            flags: self.flags,
            capabilities: self.capabilities,
            rsvd0: 0,
            rsvd1: [0; 3],
            rsvd2: [0; 3],
        }
    }
    pub fn from_native(engine_info: native::drm_i915_engine_info) -> EngineInfo {
        engine_info_from_native(engine_info)
    }
}

pub unsafe fn do_query<T>(fd: RawFd, query_id: u32) -> Option<*mut T> {
    let mut query_item = native::drm_i915_query_item {
        query_id: query_id as u64,
        length: 0,
        data_ptr: core::ptr::null_mut::<c_void>() as u64,
        flags: 0,
    };
    let mut query = native::drm_i915_query {
        items_ptr: (&mut query_item) as *mut native::drm_i915_query_item as u64,
        num_items: 1,
        flags: 0,
    };
    let res = libc::ioctl(fd.as_raw_fd(), native::DRM_IOCTL_I915_QUERY, &mut query);
    if res != 0 {
        return None;
    }
    let result_info = libc::malloc(query_item.length as usize)
        as *mut T;
    libc::memset(result_info as *mut c_void, 0, query_item.length as usize);
    query_item.data_ptr = result_info as u64;
    let res = libc::ioctl(fd.as_raw_fd(), native::DRM_IOCTL_I915_QUERY, &mut query);
    if res != 0 {
        return None;
    }
    Some(result_info)
}

pub fn get_engines(fd: RawFd) -> Option<Vec<EngineInfo>> {
    unsafe {
        let engine_data = 
            do_query::<native::drm_i915_query_engine_info>(fd, 
                native::DRM_I915_QUERY_ENGINE_INFO)?
            .as_mut().unwrap();
        let engines = engine_data.engines.as_mut_slice(engine_data.num_engines as usize);
        let mut engines_res: Vec<EngineInfo> = Vec::new();
        for i in 0..engine_data.num_engines {
            let engine = EngineInfo::from_native(engines[i as usize]);
            engines_res.push(engine);            
        }
        Some(engines_res)
    }
}

pub fn get_param(fd: RawFd, param_id: i32) -> Option<i32> {
    unsafe {
        let mut value: i32 = 0;
        let mut param = native::drm_i915_getparam {
            param: param_id,
            value: &mut value as *mut i32
        };
        let res = libc::ioctl(fd, native::DRM_IOCTL_I915_GETPARAM, &mut param);
        if res != 0 {
            return None;
        }
        Some(value)
    }
}

pub fn get_context_param(fd: RawFd, context_id: u32, param_id: u32) -> Option<u64> {
    unsafe {
        let mut param = native::drm_i915_gem_context_param {
            ctx_id: context_id,
            param: param_id as u64,
            value: 0,
            size: 0,
        };
        let res = libc::ioctl(fd, native::DRM_IOCTL_I915_GEM_CONTEXT_GETPARAM, &mut param);
        if res != 0 {
            return None;
        }
        Some(param.value)
    }
}

pub fn make_gem(fd: RawFd, size: u64) -> Option<DrmGemHandle> {
    unsafe {
        let mut create = native::drm_i915_gem_create {
            size: size,
            handle: 0,
            pad: 0,
        };
        let res = libc::ioctl(fd, native::DRM_IOCTL_I915_GEM_CREATE, &mut create);
        if res != 0 {
            return None;
        }
        let handle = DrmGemHandle {
            handle: create.handle,
        };
        Some(handle)
    }
}

pub fn close_gem(fd: RawFd, handle: DrmGemHandle) -> Result<(), i32> {
    unsafe {
        let mut close = native::drm_gem_close {
            handle: handle.handle,
            pad: 0,
        };
        let res = libc::ioctl(fd, native::DRM_IOCTL_GEM_CLOSE, &mut close);
        if res != 0 {
            return Err(res);
        }
        Ok(())
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum GemIoctlError {
    InvalidHandle,
    PermissionDenied,
    Unknown(i32),
}

pub fn gem_has_tiling(fd: RawFd, handle: DrmGemHandle) -> Result<bool, GemIoctlError> {
    unsafe {
        let mut tiling = native::drm_i915_gem_set_tiling {
            handle: handle.handle,
            tiling_mode: 0,
            stride: 0,
            swizzle_mode: 0,
        };
        let res = libc::ioctl(fd, native::DRM_IOCTL_I915_GEM_SET_TILING, &mut tiling);
        match -res {
            0 => Ok(true),
            libc::ENOENT => Err(GemIoctlError::InvalidHandle),
            libc::EPERM => Err(GemIoctlError::PermissionDenied),
            libc::EINVAL => Ok(false),
            _ => Err(GemIoctlError::Unknown(res)),
        }
    }
}

pub fn gem_is_valid(fd: RawFd, handle: DrmGemHandle) -> Result<bool, GemIoctlError> {
    let res = gem_has_tiling(fd, handle);
    if res.is_ok() && res.unwrap() {
        return Ok(true);
    }

    // For some reason the kernel returns -EPERM instead of -ENOENT when the handle is invalid...
    if res.is_err() && res.unwrap_err() == GemIoctlError::PermissionDenied {
        return Ok(false);
    }

    return Err(res.unwrap_err());
}

pub fn find_node() -> Option<DrmDeviceNode> {
    let inodes = fs::read_dir("/dev/dri").ok()?;
    for inode in inodes {
        let inode = inode.ok()?;
        let path = inode.path();
        let path = path.to_str()?;
        if path.starts_with("/dev/dri/renderD") {
            let file = File::open(path).unwrap();
            let dev = get_drm_version(file.as_raw_fd());
            if dev.is_some() && dev.unwrap().name.to_str().unwrap() == "i915" {
                return Some(DrmDeviceNode {
                    fd: OwnedFd::from(file),
                    path: Some(OsString::from(path)),
                });
            }
        }
    }
    None
}

pub fn find_fd() -> Option<OwnedFd> {
    return find_node().map(|node| node.fd);
}