//! Framebuffer

use alloc::string::String;
use core::fmt;
use lazy_static::lazy_static;
use log::*;
use spin::Mutex;
use crate::fs::vga::{fb_var_screeninfo, fb_bitfield};

/// Framebuffer information
#[repr(C)]
#[derive(Debug, Clone, Copy)]
pub struct FramebufferInfo {
    /// visible width
    pub xres: u32,
    /// visible height
    pub yres: u32,
    /// virtual width
    pub xres_virtual: u32,
    /// virtual height
    pub yres_virtual: u32,
    /// virtual offset x
    pub xoffset: u32,
    /// virtual offset y
    pub yoffset: u32,

    /// bits per pixel
    pub depth: u32,
    /// bytes per line
    pub pitch: u32,

    /// bus address, starts from 0xC0000000/0x40000000
    /// (see https://github.com/raspberrypi/firmware/wiki/Accessing-mailboxes)
    pub bus_addr: u32,
    /// screen buffer size
    pub screen_size: u32,
}

#[repr(u32)]
#[derive(Debug, Clone, Copy)]
pub enum ColorDepth {
    ColorDepth8 = 8,
    ColorDepth16 = 16,
    ColorDepth24 = 24,
    ColorDepth32 = 32,
}
use self::ColorDepth::*;

#[repr(u32)]
#[derive(Debug, Clone, Copy)]
pub enum ColorConfig {
    RGB332,
    RGB565,
    BGRA8888,
    VgaPalette,
}
use self::ColorConfig::*;

pub type FramebufferResult = Result<(FramebufferInfo, ColorConfig, usize), String>;

#[repr(C)]
union ColorBuffer {
    base_addr: usize,
    buf8: &'static mut [u8],
    buf16: &'static mut [u16],
    buf32: &'static mut [u32],
}

impl ColorBuffer {
    fn new(color_depth: ColorDepth, base_addr: usize, size: usize) -> ColorBuffer {
        unsafe {
            match color_depth {
                ColorDepth8 => ColorBuffer {
                    buf8: core::slice::from_raw_parts_mut(base_addr as *mut u8, size),
                },
                ColorDepth16 => ColorBuffer {
                    buf16: core::slice::from_raw_parts_mut(base_addr as *mut u16, size / 2),
                },
                ColorDepth24 => ColorBuffer {
                    buf8: core::slice::from_raw_parts_mut(base_addr as *mut u8, size),
                },
                ColorDepth32 => ColorBuffer {
                    buf32: core::slice::from_raw_parts_mut(base_addr as *mut u32, size / 4),
                },
            }
        }
    }

    #[inline]
    fn read8(&self, index: u32) -> u8 {
        unsafe { self.buf8[index as usize] }
    }

    #[inline]
    fn read16(&self, index: u32) -> u16 {
        unsafe { self.buf16[index as usize] }
    }

    #[inline]
    fn read32(&self, index: u32) -> u32 {
        unsafe { self.buf32[index as usize] }
    }

    #[inline]
    fn write8(&mut self, index: u32, pixel: u8) {
        unsafe { self.buf8[index as usize] = pixel }
    }

    #[inline]
    fn write16(&mut self, index: u32, pixel: u16) {
        unsafe { self.buf16[index as usize] = pixel }
    }

    #[inline]
    fn write24(&mut self, index: u32, pixel: u32) {
        let index = index * 3;
        unsafe { self.buf8[2 + index as usize] = (pixel >> 16) as u8 }
        unsafe { self.buf8[1 + index as usize] = (pixel >> 8) as u8 }
        unsafe { self.buf8[index as usize] = pixel as u8 }
    }

    #[inline]
    fn write32(&mut self, index: u32, pixel: u32) {
        unsafe { self.buf32[index as usize] = pixel }
    }
}

/// Frambuffer structure
pub struct Framebuffer {
    pub fb_info: FramebufferInfo,
    pub color_depth: ColorDepth,
    pub color_config: ColorConfig,
    buf: ColorBuffer,
}

impl fmt::Debug for Framebuffer {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        let mut f = f.debug_struct("Framebuffer");
        f.field("fb_info", &self.fb_info);
        f.field("color_depth", &self.color_depth);
        f.field("color_config", &self.color_config);
        f.field("base_addr", unsafe { &self.buf.base_addr });
        f.finish()
    }
}

impl Framebuffer {
    fn new(width: u32, height: u32, depth: u32) -> Result<Framebuffer, String> {
        let probed_info = super::probe_fb_info(width, height, depth);

        match probed_info {
            Ok((info, config, addr)) => {
                let color_depth = match info.depth {
                    8 => ColorDepth8,
                    16 => ColorDepth16,
                    32 => ColorDepth32,
                    24 => ColorDepth24,
                    _ => Err(format!("unsupported color depth {}", info.depth))?,
                };
                Ok(Framebuffer {
                    buf: ColorBuffer::new(color_depth, addr, info.screen_size as usize),
                    color_config: config,
                    color_depth,
                    fb_info: info,
                })
            }
            Err(e) => Err(e)?,
        }
    }

    #[inline]
    pub fn base_addr(&self) -> usize {
        unsafe { self.buf.base_addr }
    }

    #[inline]
    pub fn bus_addr(&self) -> usize {
        self.fb_info.bus_addr as usize
    }

    /// Read pixel at `(x, y)`.
    #[inline]
    pub fn read(&self, x: u32, y: u32) -> u32 {
        match self.color_depth {
            ColorDepth8 => self.buf.read8(y * self.fb_info.xres + x) as u32,
            ColorDepth16 => self.buf.read16(y * self.fb_info.xres + x) as u32,
            ColorDepth24 => self.buf.read16(y * self.fb_info.xres + x) as u32, // TODO
            ColorDepth32 => self.buf.read32(y * self.fb_info.xres + x),
        }
    }

    /// Write pixel at `(x, y)`.
    #[inline]
    pub fn write(&mut self, x: u32, y: u32, pixel: u32) {
        match self.color_depth {
            ColorDepth8 => self.buf.write8(y * self.fb_info.xres + x, pixel as u8),
            ColorDepth16 => self.buf.write16(y * self.fb_info.xres + x, pixel as u16),
            ColorDepth24 => self.buf.write24(y * self.fb_info.xres + x, pixel),
            ColorDepth32 => self.buf.write32(y * self.fb_info.xres + x, pixel),
        }
    }

    /// Copy buffer `[src_off .. src_off + size]` to `[dst_off .. dst_off + size]`.
    /// `dst_off`, `src_off` and `size` must be aligned with `usize`.
    pub fn copy(&mut self, dst_off: usize, src_off: usize, size: usize) {
        const USIZE: usize = core::mem::size_of::<usize>();
        let mut dst = self.base_addr() + dst_off;
        let mut src = self.base_addr() + src_off;
        let src_end = src + size;
        while src < src_end {
            unsafe { *(dst as *mut usize) = *(src as *mut usize) }
            dst += USIZE;
            src += USIZE;
        }
    }

    /// Fill buffer `[offset .. offset + size]` with `pixel`.
    /// `offset` and `size` must be aligned with `usize`.
    pub fn fill(&mut self, offset: usize, size: usize, pixel: u32) {
        const USIZE: usize = core::mem::size_of::<usize>();
        let mut value: usize = 0;
        let repeat = USIZE * 8 / self.fb_info.depth as usize;
        let mask = ((1u64 << self.fb_info.depth) - 1) as usize;
        for _i in 0..repeat {
            value <<= self.fb_info.depth;
            value += pixel as usize & mask;
        }

        let mut start = self.base_addr() + offset;
        let end = start + size;
        while start < end {
            unsafe { *(start as *mut usize) = value }
            start += USIZE;
        }
    }

    /// Fill the entire buffer with `0`.
    pub fn clear(&mut self) {
        self.fill(0, self.fb_info.screen_size as usize, 0);
    }

    pub fn fill_var_screeninfo(&self, var_info : &mut fb_var_screeninfo) {
        var_info.xres = self.fb_info.xres;
        var_info.yres = self.fb_info.yres;
        var_info.xres_virtual = self.fb_info.xres_virtual;
        var_info.yres_virtual = self.fb_info.yres_virtual;
        var_info.xoffset = self.fb_info.xoffset;
        var_info.yoffset = self.fb_info.yoffset;
        var_info.bits_per_pixel = self.fb_info.depth;
    }
}

lazy_static! {
    pub static ref FRAME_BUFFER: Mutex<Option<Framebuffer>> = Mutex::new(None);
}

/// Initialize framebuffer
pub fn init() {
    match Framebuffer::new(0, 0, 0) {
        Ok(fb) => {
            info!("framebuffer: init end\n{:#x?}", fb);
            *FRAME_BUFFER.lock() = Some(fb);
        }
        Err(err) => warn!("framebuffer init failed: {}", err),
    }
}