//! Module for video related operations,
//! including graphics and text output.

use std::{
    ffi::{CStr, CString},
    num::NonZeroU32,
    os::raw::{c_int, c_uint},
    ptr::NonNull,
};

use crate::FileError;

/// A simple descriptor for whether a video mode is in text or graphics mode.
#[derive(Debug, Copy, Clone, PartialEq, Hash, Eq)]
pub enum VideoModeKind {
    /// Text mode, where each cell is a character or glyph.
    /// and the resolution is defined via cell matrix and font size.
    Text,
    /// Graphics mode, where the resolution is specified directly
    /// and the graphics are drawn to the screen in indexed color mode.
    Graphics,
}

/// A video mode.
///
/// This type maps to the `videomode_t` struct in the original framework.
/// Each variant is either in text mode or graphics mode.
#[derive(Debug, Copy, Clone, PartialEq, Hash, Eq)]
#[repr(u32)]
pub enum VideoMode {
    /// Text mode, 40 columns and 25 rows, 8x8 font size.
    Text40x25_8x8 = dos_like_sys::videomode_t_videomode_40x25_8x8,
    /// Text mode, 40 columns and 25 rows, 9x16 font size.
    Text40x25_9x16 = dos_like_sys::videomode_t_videomode_40x25_9x16,
    /// Text mode, 80 columns and 25 rows, 8x8 font size.
    Text80x25_8x8 = dos_like_sys::videomode_t_videomode_80x25_8x8,
    /// Text mode, 80 columns and 25 rows, 8x16 font size.
    ///
    /// This is the mode set by default.
    Text80x25_8x16 = dos_like_sys::videomode_t_videomode_80x25_8x16,
    /// Text mode, 80 columns and 25 rows, 9x16 font size.
    Text80x25_9x16 = dos_like_sys::videomode_t_videomode_80x25_9x16,
    /// Text mode, 80 columns and 43 rows, 8x8 font size.
    Text80x43_8x8 = dos_like_sys::videomode_t_videomode_80x43_8x8,
    /// Text mode, 80 columns and 50 rows, 8x8 font size.
    Text80x50_8x8 = dos_like_sys::videomode_t_videomode_80x50_8x8,
    /// Graphics mode, 320x200 pixels.
    Graphics320x200 = dos_like_sys::videomode_t_videomode_320x200,
    /// Graphics mode, 320x240 pixels.
    Graphics320x240 = dos_like_sys::videomode_t_videomode_320x240,
    /// Graphics mode, 320x400 pixels.
    Graphics320x400 = dos_like_sys::videomode_t_videomode_320x400,
    /// Graphics mode, 640x200 pixels.
    Graphics640x200 = dos_like_sys::videomode_t_videomode_640x200,
    /// Graphics mode, 640x350 pixels.
    Graphics640x350 = dos_like_sys::videomode_t_videomode_640x350,
    /// Graphics mode, 640x400 pixels.
    Graphics640x400 = dos_like_sys::videomode_t_videomode_640x400,
    /// Graphics mode, 640x480 pixels.
    Graphics640x480 = dos_like_sys::videomode_t_videomode_640x480,
}

impl VideoMode {
    /// Gets the kind of video mode this is (text or graphics).
    pub fn kind(self) -> VideoModeKind {
        match self {
            VideoMode::Text40x25_8x8
            | VideoMode::Text40x25_9x16
            | VideoMode::Text80x25_8x8
            | VideoMode::Text80x25_8x16
            | VideoMode::Text80x25_9x16
            | VideoMode::Text80x43_8x8
            | VideoMode::Text80x50_8x8 => VideoModeKind::Text,
            VideoMode::Graphics320x200
            | VideoMode::Graphics320x240
            | VideoMode::Graphics320x400
            | VideoMode::Graphics640x200
            | VideoMode::Graphics640x350
            | VideoMode::Graphics640x400
            | VideoMode::Graphics640x480 => VideoModeKind::Graphics,
        }
    }

    /// Gets whether the given video mode is in graphics mode.
    #[inline]
    pub fn is_graphics(self) -> bool {
        self.kind() == VideoModeKind::Graphics
    }

    /// Gets whether the given video mode is in text mode.
    #[inline]
    pub fn is_text(self) -> bool {
        self.kind() == VideoModeKind::Text
    }

    /// Sets the application video mode to this one.
    ///
    /// Equivalent to the module's [`set_video_mode`].
    #[inline]
    pub fn set_video_mode(self) {
        set_video_mode(self)
    }
}

/// Sets the video mode.
#[inline]
pub fn set_video_mode(mode: VideoMode) {
    unsafe {
        dos_like_sys::setvideomode(mode as c_uint);
    }
}

/// Enables or disables screen double buffering.
#[inline]
pub fn set_double_buffer(enabled: bool) {
    unsafe {
        dos_like_sys::setdoublebuffer(enabled as c_int);
    }
}

/// Obtains the screen width in pixels.
#[inline]
pub fn screen_width() -> u16 {
    unsafe { dos_like_sys::screenwidth() as u16 }
}

/// Obtains the screen height in pixels.
#[inline]
pub fn screen_height() -> u16 {
    unsafe { dos_like_sys::screenheight() as u16 }
}

/// Sets a palette color by index.
#[inline]
pub fn set_pal(index: usize, r: u8, g: u8, b: u8) {
    unsafe {
        dos_like_sys::setpal(index as c_int, r as c_int, g as c_int, b as c_int);
    }
}

/// Gets a palette color by index.
#[inline]
pub fn pal(index: usize) -> (u8, u8, u8) {
    let (mut r, mut g, mut b) = (0, 0, 0);
    unsafe {
        dos_like_sys::getpal(index as c_int, &mut r, &mut g, &mut b);
        (r as u8, g as u8, b as u8)
    }
}

// -- Graphics buffer manipulation functions
// Due to the way the original framework works,
// some operations are hard to be marked as safe by the compiler.

/// Gets a mutable slice of the current screen buffer.
///
/// Only makes sense in graphics mode.
/// The length of the slice is equal to the number of pixels on the screen.
///
/// # Safety
///
/// It is not guaranteed by the compiler
/// that the access to the screen buffer is exclusive.
/// Calling any function in this module that draws _anything_ to the screen
/// during the returned slice's lifetime
/// is _undefined behavior_.
/// It is also undefined behavior to call this function multiple times
/// without dropping the previous slices first.
///
/// However, if _double buffering_ is enabled
/// (via [`set_double_buffer`]),
/// then it is safe to call [`swap_buffers`] or [`swap_buffers_and_get`]
/// and immediately drop this slice in favor of the new buffer slice.
pub unsafe fn screen_buffer() -> &'static mut [u8] {
    // Safety: it is documented that the user
    // must not draw anything through other functions,
    // so that buffer access is truly exclusive.
    #[allow(unused_unsafe)]
    unsafe {
        let buf = dos_like_sys::screenbuffer();
        let width = dos_like_sys::screenwidth() as usize;
        let height = dos_like_sys::screenheight() as usize;
        std::slice::from_raw_parts_mut(buf, width * height)
    }
}

/// Swaps the current screen buffers
/// and returns a mutable slice of the current screen buffer.
///
/// Only makes sense in graphics mode.
///
/// # Safety
///
/// It is not guaranteed by the compiler
/// that the access to the screen buffer is exclusive.
/// Calling any function in this module that draws _anything_ to the screen
/// during the returned slice's lifetime
/// is _undefined behavior_.
///
/// Moreover, if _double buffering_ is disabled,
/// any buffer slice obtained through this function or [`screen_buffer`]
/// must be dropped _before_ this call.
/// That is,
/// it is only safe to call [`swap_buffers`] or `swap_buffers_and_get`
/// with an existing buffer slice
/// if double buffering is enabled
/// (via [`set_double_buffer`]).
/// and the other slice is immediately dropped afterwards.
///
/// # Example
///
/// ```no_run
/// # use dos_like::*;
/// set_video_mode(VideoMode::Graphics320x200);
/// set_double_buffer(true);
/// // safety: I solemnly swear that I will not draw anything through other functions
/// let mut buffer = unsafe { screen_buffer() };
///
/// loop {
///     wait_vbl();
///     // do things with buffer
///     for (i, v) in buffer.chunks_mut(320).enumerate() {
///         v.fill(i as u8);
///     }
///
///     // safety: previous buffer slice will be dropped
///     buffer = unsafe { swap_buffers_and_get() };
/// }
/// ```
pub unsafe fn swap_buffers_and_get() -> &'static mut [u8] {
    // Safety: it is documented that the user
    // must drop other buffer slices
    // and must not draw anything through other functions,
    // so that buffer access is truly exclusive and not aliased.
    #[allow(unused_unsafe)]
    unsafe {
        let buf = dos_like_sys::swapbuffers();
        let width = dos_like_sys::screenwidth() as usize;
        let height = dos_like_sys::screenheight() as usize;
        std::slice::from_raw_parts_mut(buf, width * height)
    }
}

/// Swaps the current screen buffers,
/// thus changing what to draw to the screen.
///
/// When double buffering is enabled,
/// any drawing operations are performed on the off-screen buffer,
/// so this function needs to be called
/// for the changes to be displayed.
///
/// Only makes sense in graphics mode.
///
/// For the function which also returns a slice,
/// see [`swap_buffers_and_get`].
///
/// # Example
///
/// ```no_run
/// # use dos_like::*;
/// set_video_mode(VideoMode::Graphics320x200);
/// // enable double buffering
/// set_double_buffer(true);
///
/// let mut i = 0;
/// loop {
///     // draw some things
///     line(0, 0, i, 200);
///     i += 1;
///
///     // swap!
///     swap_buffers();
/// }
/// ```
pub fn swap_buffers() {
    // safety: no slice is returned,
    // so aliased slices are not possible without calling
    // the other unsafe functions
    unsafe {
        dos_like_sys::swapbuffers();
    }
}

// -- Graphics manipulation functions

/// Blits a rectangular portion of a video data buffer to the screen.
///
/// - `x` and `y` are the target coordinates of the top-left corner
///   to blit on the screen
/// - `width` and `height` are the full dimensions of the source data
/// - `src_x` and `src_y` are the coordinates of the starting position
///   to blit from the source data
/// - `src_width` and `src_height` are the width and height to effectively blit
///   from the source data
///
/// # Panic
///
/// Panics if the given source parameters
/// are incompatible with the length of the source,
/// since this is likely a bug.
pub fn blit(
    x: i32,
    y: i32,
    source: &[u8],
    width: u16,
    height: u16,
    src_x: u16,
    src_y: u16,
    src_width: u16,
    src_height: u16,
) {
    if width as usize * height as usize > source.len() {
        panic!(
            "blit: source data ({} bytes) is too short for resolution {}x{}",
            source.len(),
            width,
            height
        );
    }

    // Safety:
    // - the source data length has been validated against `width` and `height`
    // - although a *mut pointer is passed, the impl is sure to never write to it
    unsafe {
        dos_like_sys::blit(
            x as c_int,
            y as c_int,
            source.as_ptr() as *mut _,
            width as c_int,
            height as c_int,
            src_x as c_int,
            src_y as c_int,
            src_width as c_int,
            src_height as c_int,
        );
    }
}

/// Blits a masked rectangular portion of a video data buffer to the screen,
/// skipping pixels encoded as fully transparent.
///
/// - `x` and `y` are the target coordinates of the top-left corner
///   to blit on the screen
/// - `width` and `height` are the full dimensions of the source data
/// - `src_x` and `src_y` are the coordinates of the starting position
///   to blit from the source data
/// - `src_width` and `src_height` are the width and height to effectively blit
///   from the source data
/// - `color_key` is the color to skip when blitting
///
/// # Panic
///
/// Panics if the given source parameters
/// are incompatible with the length of the source,
/// since this is likely a bug.
pub fn mask_blit(
    x: i32,
    y: i32,
    source: &[u8],
    width: u16,
    height: u16,
    src_x: u16,
    src_y: u16,
    src_width: u16,
    src_height: u16,
    color_key: u8,
) {
    if width as usize * height as usize > source.len() {
        panic!(
            "blit: source data ({} bytes) is too short for resolution {}x{}",
            source.len(),
            width,
            height
        );
    }

    // Safety:
    // - the source data length has been validated against `width` and `height`
    // - although a *mut pointer is passed, the impl is sure to never write to it
    unsafe {
        dos_like_sys::maskblit(
            x as c_int,
            y as c_int,
            source.as_ptr() as *mut _,
            width as c_int,
            height as c_int,
            src_x as c_int,
            src_y as c_int,
            src_width as c_int,
            src_height as c_int,
            color_key as c_int,
        );
    }
}

//void blit( int x, int y, unsigned char* source, int width, int height, int srcx, int srcy, int srcw, int srch );
//void maskblit( int x, int y, unsigned char* source, int width, int height, int srcx, int srcy, int srcw, int srch, int colorkey );

/// Clears the screen when in graphics mode.
#[inline]
pub fn clear_screen() {
    unsafe {
        dos_like_sys::clearscreen();
    }
}

/// Gets the color of a single pixel on the screen.
///
/// Only makes sense in graphics mode.
#[inline]
pub fn pixel(x: i32, y: i32) -> u8 {
    unsafe { dos_like_sys::getpixel(x as c_int, y as c_int) as u8 }
}

/// Puts a color on a single pixel.
///
/// Only makes sense in graphics mode.
#[inline]
pub fn put_pixel(x: u16, y: u16, color: u8) {
    unsafe {
        dos_like_sys::putpixel(x as c_int, y as c_int, color as c_int);
    }
}

/// Draws a horizonal line.
///
/// Only makes sense in graphics mode.
#[inline]
pub fn h_line(x: i32, y: i32, len: u16, color: u8) {
    unsafe {
        dos_like_sys::hline(x as c_int, y as c_int, len as c_int, color as c_int);
    }
}

/// Sets the foreground color to the given palette color index
/// for subsequent drawing operations.
///
/// Only works in graphics mode.
#[inline]
pub fn set_color(color: u8) {
    unsafe {
        dos_like_sys::setcolor(color as c_int);
    }
}

/// Gets the current foreground color by palette color index.
///
/// Returns 0 if video is not in graphics mode.
#[inline]
pub fn get_color() -> u8 {
    unsafe { dos_like_sys::getcolor() as u8 }
}

/// Draws a line on the screen from one position to another.
///
/// Only makes sense in graphics mode.
#[inline]
pub fn line(x1: i32, y1: i32, x2: i32, y2: i32) {
    unsafe {
        dos_like_sys::line(x1 as c_int, y1 as c_int, x2 as c_int, y2 as c_int);
    }
}

/// Draws a non-filled rectangle on the screen.
///
/// Only makes sense in graphics mode.
#[inline]
pub fn rectangle(x1: i32, y1: i32, width: u16, height: u16) {
    unsafe {
        dos_like_sys::rectangle(x1 as c_int, y1 as c_int, width as c_int, height as c_int);
    }
}

/// Draws a filled rectangle on the screen.
///
/// Only makes sense in graphics mode.
#[inline]
pub fn bar(x1: i32, y1: i32, width: u16, height: u16) {
    unsafe {
        dos_like_sys::bar(x1 as c_int, y1 as c_int, width as c_int, height as c_int);
    }
}

/// Draws a circle with no filling on the screen.
///
/// Only makes sense in graphics mode.
#[inline]
pub fn circle(x: i32, y: i32, r: u16) {
    unsafe {
        dos_like_sys::circle(x as c_int, y as c_int, r as c_int);
    }
}

/// Draws a filled circle on the screen.
///
/// Only makes sense in graphics mode.
#[inline]
pub fn fill_circle(x: i32, y: i32, r: u16) {
    unsafe {
        dos_like_sys::fillcircle(x as c_int, y as c_int, r as c_int);
    }
}

/// Draws a non-filled ellipse on the screen.
///
/// Only makes sense in graphics mode.
#[inline]
pub fn ellipse(x: i32, y: i32, rx: u16, ry: u16) {
    unsafe {
        dos_like_sys::ellipse(x as c_int, y as c_int, rx as c_int, ry as c_int);
    }
}

/// Draws a filled ellipse on the screen.
///
/// Only makes sense in graphics mode.
#[inline]
pub fn fill_ellipse(x: i32, y: i32, rx: u16, ry: u16) {
    unsafe {
        dos_like_sys::fillellipse(x as c_int, y as c_int, rx as c_int, ry as c_int);
    }
}

/// Draws a poly-line on the screen,
/// with the given flat list of XY coordinates in pixels.
///
/// Only makes sense in graphics mode.
///
/// # Panic
///
/// Panics if the given list of points is empty or not even.
#[inline]
pub fn draw_poly(points: &[i32]) {
    assert!(!points.is_empty() && points.len() % 2 == 0);

    // Safety: although the pointer type is *mut,
    // it never really writes via the pointer.
    unsafe {
        dos_like_sys::drawpoly(points.as_ptr() as *mut _, (points.len() / 2) as c_int);
    }
}

/// Draws a filled polygon on the screen,
/// with the given flat list of XY coordinates in pixels.
///
/// Only makes sense in graphics mode.
///
/// # Panic
///
/// Panics if the given list of points is empty or not even.
#[inline]
pub fn fill_poly(points: &[i32]) {
    assert!(!points.is_empty() && points.len() % 2 == 0);

    // Safety: although the pointer type is *mut,
    // it never really writes via the pointer.
    unsafe {
        dos_like_sys::fillpoly(points.as_ptr() as *mut _, (points.len() / 2) as c_int);
    }
}

/// Flood fills the screen from the given position.
///
/// Only makes sense in graphics mode.
pub fn flood_fill(x: i32, y: i32) {
    unsafe {
        dos_like_sys::floodfill(x as c_int, y as c_int);
    }
}

/// Flood fills the screen from the given position
/// with the given color as boundary.
///
/// Only makes sense in graphics mode.
pub fn boundary_fill(x: i32, y: i32, boundary: u8) {
    unsafe {
        dos_like_sys::boundaryfill(x as c_int, y as c_int, boundary as c_int);
    }
}

/// Blits a text to the screen at the given position.
///
/// XY coordinates are in pixels.
///
/// Only makes sense in graphics mode.
pub fn out_text_xy(x: i32, y: i32, text: impl AsRef<[u8]>) {
    let text = CString::new(text.as_ref()).unwrap();

    unsafe {
        dos_like_sys::outtextxy(x as c_int, y as c_int, text.as_ptr() as *const _);
    }
}

/// Blits a text to the screen at the given position,
/// wrapping around before it goes beyond the width specified.
///
/// XY coordinates and width are in pixels.
///
/// Only makes sense in graphics mode.
pub fn wrap_text_xy(x: i32, y: i32, text: impl AsRef<[u8]>, width: u16) {
    let text = CString::new(text.as_ref()).unwrap();

    unsafe {
        dos_like_sys::wraptextxy(
            x as c_int,
            y as c_int,
            text.as_ptr() as *const _,
            width as c_int,
        );
    }
}

/// Blits a text to the screen centered at the given position.
///
/// XY coordinates and width are in pixels.
///
/// Only makes sense in graphics mode.
pub fn center_text_xy(x: i32, y: i32, text: impl AsRef<[u8]>, width: u16) {
    let text = CString::new(text.as_ref()).unwrap();

    unsafe {
        dos_like_sys::centertextxy(
            x as c_int,
            y as c_int,
            text.as_ptr() as *const _,
            width as c_int,
        );
    }
}

// -- Image reading

/// An image loaded from a file.
#[derive(Debug)]
pub struct Image {
    /// The color palette of the image.
    palette: [u8; 768],
    /// The real size of the palette
    palette_count: u32,
    /// The width of the image.
    width: u32,
    /// The height of the image.
    height: u32,
    /// Pointer to the indexed pixel data.
    data: NonNull<u8>,
}

unsafe impl Send for Image {}
unsafe impl Sync for Image {}

impl Image {
    pub fn width(&self) -> u32 {
        self.width
    }

    pub fn height(&self) -> u32 {
        self.height
    }

    /// Gets the image data as a slice of bytes,
    /// each byte representing a pixel indexed by the image's palette.
    pub fn data(&self) -> &[u8] {
        unsafe {
            std::slice::from_raw_parts(
                self.data.as_ptr(),
                self.width as usize * self.height as usize,
            )
        }
    }

    /// Gets the image data as a mutable slice of bytes,
    /// each byte representing a pixel indexed by the image's palette.
    pub fn data_mut(&mut self) -> &mut [u8] {
        unsafe {
            std::slice::from_raw_parts_mut(
                self.data.as_ptr(),
                self.width as usize * self.height as usize,
            )
        }
    }

    /// Gets the number of pixel colors in the palette.
    /// The full size of the palette is `palette_count * 3` bytes.
    pub fn palette_count(&self) -> u32 {
        self.palette_count
    }

    /// Gets the image's color palette as a slice of bytes, in RGB
    /// (8 bits per channel).
    pub fn palette(&self) -> &[u8] {
        &self.palette[..self.palette_count as usize * 3]
    }

    /// Gets the image's color palette as a mutable slice of bytes, in RGB
    /// (8 bits per channel).
    pub fn palette_mut(&mut self) -> &mut [u8] {
        &mut self.palette[..self.palette_count as usize]
    }

    /// Gets the image's color palette as a reference to the underlying array,
    /// in RGB (8 bits per channel).
    ///
    /// The maximum expected size of any palette is 768 bytes
    /// (256 colors * 3 bytes per color).
    /// Note that the real palette used might be smaller than
    /// the full size of the array,
    /// see [`palette`][self::Image::palette] for an accurate slice.
    pub fn raw_palette(&self) -> &[u8; 768] {
        &self.palette
    }
}

/// Loads an image from a GIF file.
pub fn load_gif(path: impl AsRef<str>) -> Result<Image, FileError> {
    let filename = CString::new(path.as_ref()).map_err(|_| FileError::BadFilePath)?;
    let mut width = 0;
    let mut height = 0;
    let mut palcount = 0;
    let mut palette = [0; 768];

    unsafe {
        let data = dos_like_sys::loadgif(
            filename.as_ptr(),
            &mut width,
            &mut height,
            &mut palcount,
            palette.as_mut_ptr(),
        );

        if let Some(data) = NonNull::new(data) {
            Ok(Image {
                width: width as u32,
                height: height as u32,
                palette_count: palcount as u32,
                palette,
                data,
            })
        } else {
            Err(FileError::FileNotFound)
        }
    }
}

// -- Font manipulation functions --

/// A font identifier.
///
/// Use [`install_user_font`] to obtain a font,
/// or take one of the associated constants for the default fonts.
#[derive(Debug, Copy, Clone, PartialEq, Hash, Eq)]
#[repr(transparent)]
pub struct Font(NonZeroU32);

impl Font {
    /// The default 8x8 font.
    pub const DEFAULT_8X8: Font = Font(
        // safety: definitely not 0
        unsafe { NonZeroU32::new_unchecked(dos_like_sys::DEFAULT_FONT_8X8) },
    );

    /// The default 8x16 font.
    pub const DEFAULT_8X16: Font = Font(
        // safety: definitely not 0
        unsafe { NonZeroU32::new_unchecked(dos_like_sys::DEFAULT_FONT_8X16) },
    );

    /// The default 9x16 font.
    pub const DEFAULT_9X16: Font = Font(
        // safety: definitely not 0
        unsafe { NonZeroU32::new_unchecked(dos_like_sys::DEFAULT_FONT_9X16) },
    );

    /// Installs a font from a .fnt file
    ///
    /// This is the same as the module's [`install_user_font`] function.
    pub fn install_user_font(filename: impl AsRef<str>) -> Result<Self, FileError> {
        install_user_font(filename)
    }

    /// Obtains a font identifier by its internal index.
    ///
    /// This operation does not check whether the font really exists.
    #[inline]
    pub fn from_id(id: u32) -> Option<Font> {
        Self::from_raw_id(id as c_int)
    }

    #[inline]
    fn from_raw_id(id: c_int) -> Option<Font> {
        NonZeroU32::new(id as u32).map(Font)
    }

    #[inline]
    fn to_id(self) -> c_int {
        self.0.get() as c_int
    }
}

/// Installs a font from a .fnt file.
///
/// Returns the identifier of the font.
pub fn install_user_font(filename: impl AsRef<str>) -> Result<Font, FileError> {
    let filename = CString::new(filename.as_ref()).map_err(|_| FileError::BadFilePath)?;

    unsafe {
        let font_id = dos_like_sys::installuserfont(filename.as_ptr() as *const _);

        Font::from_id(font_id as u32).ok_or(FileError::FileNotFound)
    }
}

/// Sets the font and style of upcoming text blit operations.
///
/// This is only available in graphics mode with a font loaded.
/// The operations is ignored if `FontId` does not correspond to a valid font.
#[inline]
pub fn set_text_style(font: Font, bold: bool, italic: bool, underline: bool) {
    unsafe {
        dos_like_sys::settextstyle(
            font.to_id(),
            bold as c_int,
            italic as c_int,
            underline as c_int,
        );
    }
}

// --- Pure text mode functions ---

/// Writes a string to the screen, at the current cursor position.
///
/// Does nothing unless the video is in text mode.
///
/// This is equivalent to creating a [`CString`](std::ffi::CString)
/// (so that it is null terminated)
/// and calling [`put_cstr`].
///
/// # Panics
///
/// Panics if the given string cannot be converted to be printed to the screen.
/// Always check for null characters (`\0`) in the string
/// before calling this function.
#[inline]
pub fn put_str(string: impl AsRef<str>) {
    let text = CString::new(string.as_ref()).unwrap();
    put_cstr(&text)
}

/// Writes a C string to the screen, at the current cursor position.
///
/// Requires a valid, null terminated C-style string,
/// but does not require a new string to be allocated.
///
/// Does nothing unless the video is in text mode.
#[inline]
pub fn put_cstr(text: impl AsRef<CStr>) {
    unsafe {
        dos_like_sys::cputs(text.as_ref().as_ptr() as *const _);
    }
}

/// Sets the color of the text.
///
/// Only works in text mode.
#[inline]
pub fn text_color(color: u32) {
    unsafe {
        dos_like_sys::textcolor(color as c_int);
    }
}

/// Sets the background color of the text by palette color index.
///
/// Only works in text mode.
#[inline]
pub fn text_background(color: u8) {
    unsafe {
        dos_like_sys::textbackground(color as c_int);
    }
}

/// Moves the cursor to the specified position.
///
/// Only works in text mode.
#[inline]
pub fn goto_xy(x: u16, y: u16) {
    unsafe {
        dos_like_sys::gotoxy(x as c_int, y as c_int);
    }
}

/// Gets the cursor's current X position.
///
/// Returns 0 if the video is not in text mode.
#[inline]
pub fn where_x() -> u16 {
    unsafe { dos_like_sys::wherex().max(0) as u16 }
}

/// Gets the cursor's current Y position.
///
/// Returns 0 if the video is not in text mode.
#[inline]
pub fn where_y() -> u16 {
    unsafe { dos_like_sys::wherex().max(0) as u16 }
}

/// Clears the screen when in text mode.
pub fn clr_scr() {
    unsafe {
        dos_like_sys::clrscr();
    }
}

/// Enables the blinking text cursor.
///
/// The cursor is visible to the user by default.
///
/// Only works in text mode.
#[inline]
pub fn curs_on() {
    unsafe {
        dos_like_sys::curson();
    }
}

/// Hides the text cursor.
///
/// Only works in text mode.
#[inline]
pub fn curs_off() {
    unsafe {
        dos_like_sys::cursoff();
    }
}