//! Video Graphics Array (VGA)

use core::ptr::{addr_of, addr_of_mut};
use core::{fmt, slice};

use bitfield_struct::bitfield;
use embedded_graphics::draw_target::DrawTarget;
use embedded_graphics::geometry::{OriginDimensions, Point};
use embedded_graphics::pixelcolor::raw::ToBytes;
use embedded_graphics::pixelcolor::{Rgb565, Rgb888};
use embedded_graphics::prelude::Size;
use embedded_graphics::primitives::Rectangle;
use embedded_graphics::Pixel;

use crate::util::InlineStr;
use crate::{multiboot as mb, MBOOT_PTR, SCREEN_HEIGHT, SCREEN_WIDTH};

/// Back buffers to prevent screen flickering
static mut BUFFER: [u8; 0x800_000] = [0; 0x800_000];

/// VGA Display
pub struct Display {
    /// Address of the physical framebuffer
    addr: usize,
    width: usize,
    height: usize,
    color: ColorMode,
}

impl Display {
    pub fn info() {
        let mboot = unsafe { mb::Info::from_ptr(MBOOT_PTR as _) };
        if let Some(vbe) = mboot.vbe() {
            let ctrl = unsafe { VbeCtrlInfo::from_ptr(vbe.control_info) };
            serial!("{ctrl:x?}");
            let info = unsafe { VbeModeInfo::from_ptr(vbe.mode_info) };
            serial!("{info:x?}");
        }
    }

    pub fn new() -> Result<Self, ()> {
        // Find framebuffer
        let mboot = unsafe { mb::Info::from_ptr(MBOOT_PTR as _) };

        let fb = if let Some(fb) = mboot.framebuffer() {
            serial!("{fb:?}");
            fb.clone()
        } else if let Some(vbe) = mboot.vbe()
            && vbe.mode_info != 0
        {
            // Fallback to VBE if our old test system does not support framebuffer...
            let info = unsafe { VbeModeInfo::from_ptr(vbe.mode_info) };
            match info.framebuffer() {
                Some(fb) => fb,
                None => return Err(()),
            }
        } else {
            serial!("No framebuffer!");
            return Err(());
        };
        if (fb.width * fb.height) as usize > (SCREEN_WIDTH * SCREEN_HEIGHT) {
            serial!("FB too large");
            return Err(());
        }
        if (fb.addr + (fb.width * fb.height * 4) as u64) > u32::MAX as u64 {
            serial!("FB outside of 32bit range");
            return Err(());
        }
        let Some(mb::ColorInfo::Rgb(rgb)) = fb.color_info() else {
            serial!("No color info");
            return Err(());
        };
        let Ok(color) = ColorMode::try_from((fb.bpp, rgb)) else {
            serial!("Unsupported color mode");
            return Err(());
        };
        Ok(Self {
            addr: fb.addr as _,
            width: fb.width as _,
            height: fb.height as _,
            color,
        })
    }
    pub fn buffer<T>(&mut self) -> &mut [T] {
        let slice = unsafe { &mut *addr_of_mut!(BUFFER) };
        unsafe {
            slice::from_raw_parts_mut(slice.as_mut_ptr().cast(), slice.len() / size_of::<T>())
        }
    }
    pub fn hw_buffer(&mut self) -> &mut [u8] {
        unsafe {
            slice::from_raw_parts_mut(self.addr as *mut u8, (4 * self.width * self.height) as _)
        }
    }
    /// Copy framebuffers to screen
    pub fn render(&mut self) {
        let hw_buffer = self.hw_buffer();
        let buffer = &unsafe { &*addr_of!(BUFFER) };
        hw_buffer.copy_from_slice(&buffer[0..hw_buffer.len()]);
    }

    pub fn set(&mut self, off: usize, color: Rgb888) {
        match self.color {
            ColorMode::Rgb32 => self.buffer()[off] = color,
            ColorMode::Rgb24 => self.buffer::<[u8; 3]>()[off] = color.to_ne_bytes(),
            ColorMode::Rgb16 => self.buffer()[off] = Rgb565::from(color),
        }
    }

    pub fn fill(&mut self, off: usize, len: usize, color: Rgb888) {
        match self.color {
            ColorMode::Rgb32 => self.buffer()[off..off + len].fill(color),
            ColorMode::Rgb24 => self.buffer::<[u8; 3]>()[off..off + len].fill(color.to_ne_bytes()),
            ColorMode::Rgb16 => self.buffer()[off..off + len].fill(Rgb565::from(color)),
        }
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
enum ColorMode {
    Rgb32,
    Rgb24,
    Rgb16,
}
impl TryFrom<(u8, mb::ColorInfoRgb)> for ColorMode {
    type Error = ();

    fn try_from((bpp, mode): (u8, mb::ColorInfoRgb)) -> Result<Self, Self::Error> {
        match (bpp, mode) {
            (
                32,
                mb::ColorInfoRgb {
                    red_offset: 16,
                    red_bits: 8,
                    green_offset: 8,
                    green_bits: 8,
                    blue_offset: 0,
                    blue_bits: 8,
                },
            ) => Ok(ColorMode::Rgb32),
            (
                24,
                mb::ColorInfoRgb {
                    red_offset: 16,
                    red_bits: 8,
                    green_offset: 8,
                    green_bits: 8,
                    blue_offset: 0,
                    blue_bits: 8,
                },
            ) => Ok(ColorMode::Rgb24),
            (
                16,
                mb::ColorInfoRgb {
                    red_offset: 11,
                    red_bits: 5,
                    green_offset: 5,
                    green_bits: 6,
                    blue_offset: 0,
                    blue_bits: 5,
                },
            ) => Ok(ColorMode::Rgb16),
            _ => Err(()),
        }
    }
}

impl DrawTarget for Display {
    type Color = Rgb888;
    type Error = ();

    fn draw_iter<I>(&mut self, pixels: I) -> Result<(), Self::Error>
    where
        I: IntoIterator<Item = Pixel<Self::Color>>,
    {
        let (width, height) = (self.width, self.height);
        for Pixel(coord, color) in pixels.into_iter() {
            if 0 <= coord.x && coord.x < width as i32 && 0 <= coord.y && coord.y <= height as i32 {
                let (x, y) = (coord.x as usize, coord.y as usize);
                self.set(x + y * width, color);
            }
        }
        Ok(())
    }

    fn fill_solid(&mut self, area: &Rectangle, color: Self::Color) -> Result<(), Self::Error> {
        let (width, height) = (self.width, self.height);
        let area = area.intersection(&Rectangle::new(
            Point::zero(),
            Size::new(width as _, height as _),
        ));
        for y in area.rows() {
            self.fill(
                y as usize * width + area.top_left.x as usize,
                area.size.width as _,
                color,
            );
        }
        Ok(())
    }
}

impl OriginDimensions for Display {
    fn size(&self) -> Size {
        Size::new(self.width as _, self.height as _)
    }
}

#[repr(C, packed)]
#[derive(Debug)]
struct VbeCtrlInfo {
    signature: InlineStr<4>,
    version: u16,
    oem_string: SegOff,
    capabilities: u32,
    video_mode: SegOff,
    total_memory: u16,
    oem_software_rev: u16,
    oem_vendor_name: SegOff,
    oem_product_name: SegOff,
    oem_product_rev: SegOff,
    // reserved: [u8; 222],
    // oem_data: [u8; 256],
}
impl VbeCtrlInfo {
    unsafe fn from_ptr<'a>(ptr: u32) -> &'a Self {
        &*(ptr as *const Self)
    }
}
#[derive(Clone, Copy)]
struct SegOff {
    offset: u16,
    segment: u16,
}
impl fmt::Debug for SegOff {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{:x}:{:x}", self.offset, self.segment)
    }
}

#[derive(Debug)]
#[repr(C, packed)]
struct VbeModeInfo {
    mode_attributes: ModeAttributes,

    /// Window functions (used by all VBE revisions, but ignored here)
    _win: [u16; 7],

    /// Bytes per scan line
    pitch: u16,
    /// Horizontal resolution in pixels (GRAPHICS) or characters
    width: u16,
    /// Vertical resolution in pixels (GRAPHICS) or characters
    height: u16,

    /// Character cell width in pixels (deprecated)
    char_width: u8,
    /// Character cell height in pixels (deprecated)
    char_height: u8,
    /// Number of memory planes
    planes: u8,

    /// Bits per pixel
    bpp: u8,

    /// Number of banks
    banks: u8,

    /// Memory model type
    memory_model: MemoryModel,
    /// Bank size in KB
    bank_size: u8,
    /// Number of images
    image_pages: u8,
    /// Reserved for page function
    reserved: u8,

    // Direct Color fields (required for DIRECT_COLOR and YUV memory models)
    /// Size of direct color red mask in bits
    bits_red: u8,
    /// Bit position of lsb of red mask
    offset_red: u8,
    /// Size of direct color green mask in bits
    bits_green: u8,
    /// Bit position of lsb of green mask
    offset_green: u8,
    /// Size of direct color blue mask in bits
    bits_blue: u8,
    /// Bit position of lsb of blue mask
    offset_blue: u8,
    /// Size of direct color reserved mask in bits
    bits_rsv: u8,
    /// Bit position of lsb of reserved mask
    offset_rsv: u8,

    /// Direct color mode attributes
    /// enum DirectColorAttributes : uint8_t {
    /// 	DYNAMIC_COLOR_RAMP = 1 << 0,  ///< Programmable (otherwise fixed) color ramp
    /// 	USABLE_BITS        = 1 << 1   ///< Bits in reserved mask are usable (otherwise reserved)
    /// };
    directcolor_attributes: u8,

    // Mandatory information for VBE 2.0 and above
    /// physical address for flat memory frame buffer
    address: u32,
    /// reserved
    offscreen_memory_offset: u32,
    /// reserved
    offscreen_memory_size: u16,
}

impl VbeModeInfo {
    unsafe fn from_ptr<'a>(ptr: u32) -> &'a Self {
        &*(ptr as *const Self)
    }

    fn framebuffer(&self) -> Option<mb::FramebufferTable> {
        let attr = self.mode_attributes;
        if !attr.lfb() {
            serial!("LFB not set");
        }
        if self.address == 0 {
            serial!("No framebuffer address");
            return None;
        }
        let color_info = match self.memory_model {
            MemoryModel::TextMode => Some(mb::ColorInfo::Text),
            MemoryModel::DirectColor => Some(mb::ColorInfo::Rgb(mb::ColorInfoRgb {
                red_offset: self.offset_red,
                red_bits: self.bits_red,
                green_offset: self.offset_green,
                green_bits: self.bits_green,
                blue_offset: self.offset_blue,
                blue_bits: self.bits_blue,
            })),
            _ => None,
        };

        Some(mb::FramebufferTable::new(
            self.address as _,
            self.pitch as _,
            self.width as _,
            self.height as _,
            self.bpp,
            color_info,
        ))
    }
}

#[bitfield(u16)]
struct ModeAttributes {
    /// Text mode
    text_mode: bool,
    /// Mode supported by hardware configuration
    supported: bool,
    /// TTY Output functions supported by BIOS
    tty: bool,
    /// Color mode (otherwise monochrome)
    color: bool,
    /// Graphic mode (otherwise text)
    graphics: bool,
    /// VGA compatible
    vga: bool,
    /// VGA compatible windowed memory mode is available
    vga_paged: bool,
    /// Linear frame buffer mode is available
    lfb: bool,
    __: u8,
}

#[derive(Debug, Clone, Copy)]
#[repr(u8)]
#[allow(unused)]
enum MemoryModel {
    /// Text mode
    TextMode = 0,
    /// CGA graphics
    CGA = 1,
    /// Hercules graphics
    Hercules = 2,
    /// Planar
    Planar = 3,
    /// Packed pixel
    Packed = 4,
    /// Non-chain 4, 256 color
    NonChain4 = 5,
    /// Direct Color
    DirectColor = 6,
    /// YUV
    YUV = 7,
}