//! WinApi related logic for terminal manipulation.

use crossterm_winapi::{Console, Coord, Handle, ScreenBuffer, Size};

use crate::{cursor, terminal::ClearType, utils::Result, ErrorKind};

/// Exits the current application.
pub fn exit() {
    ::std::process::exit(256);
}

/// Returns the terminal size `(columns, rows)`.
///
/// The top left cell is represented `1,1`.
pub fn size() -> Result<(u16, u16)> {
    let terminal_size = ScreenBuffer::current()?.info()?.terminal_size();
    // windows starts counting at 0, unix at 1, add one to replicated unix behaviour.
    Ok((
        (terminal_size.width + 1) as u16,
        (terminal_size.height + 1) as u16,
    ))
}

pub(crate) fn clear(clear_type: ClearType) -> Result<()> {
    let screen_buffer = ScreenBuffer::current()?;
    let csbi = screen_buffer.info()?;

    let pos = csbi.cursor_pos();
    let buffer_size = csbi.buffer_size();
    let current_attribute = csbi.attributes();

    match clear_type {
        ClearType::All => {
            clear_entire_screen(buffer_size, current_attribute)?;
        }
        ClearType::FromCursorDown => clear_after_cursor(pos, buffer_size, current_attribute)?,
        ClearType::FromCursorUp => clear_before_cursor(pos, buffer_size, current_attribute)?,
        ClearType::CurrentLine => clear_current_line(pos, buffer_size, current_attribute)?,
        ClearType::UntilNewLine => clear_until_line(pos, buffer_size, current_attribute)?,
    };
    Ok(())
}

pub(crate) fn scroll_up(row_count: u16) -> Result<()> {
    let csbi = ScreenBuffer::current()?;
    let mut window = csbi.info()?.terminal_window();

    // check whether the window is too close to the screen buffer top
    let count = row_count as i16;
    if window.top >= count {
        window.top -= count; // move top down
        window.bottom -= count; // move bottom down

        Console::output()?.set_console_info(true, window)?;
    }
    Ok(())
}

pub(crate) fn scroll_down(row_count: u16) -> Result<()> {
    let screen_buffer = ScreenBuffer::current()?;
    let csbi = screen_buffer.info()?;
    let mut window = csbi.terminal_window();
    let buffer_size = csbi.buffer_size();

    // check whether the window is too close to the screen buffer top
    let count = row_count as i16;
    if window.bottom < buffer_size.height - count {
        window.top += count; // move top down
        window.bottom += count; // move bottom down

        Console::output()?.set_console_info(true, window)?;
    }
    Ok(())
}

/// Set the current terminal size
pub(crate) fn set_size(width: u16, height: u16) -> Result<()> {
    if width <= 1 {
        return Err(ErrorKind::ResizingTerminalFailure(String::from(
            "Cannot set the terminal width lower than 1.",
        )));
    }

    if height <= 1 {
        return Err(ErrorKind::ResizingTerminalFailure(String::from(
            "Cannot set the terminal height lower then 1.",
        )));
    }

    // get the position of the current console window
    let screen_buffer = ScreenBuffer::current()?;
    let console = Console::from(screen_buffer.handle().clone());
    let csbi = screen_buffer.info()?;

    let current_size = csbi.buffer_size();
    let window = csbi.terminal_window();

    let mut new_size = Size::new(current_size.width, current_size.height);

    // If the buffer is smaller than this new window size, resize the
    // buffer to be large enough.  Include window position.
    let mut resize_buffer = false;

    let width = width as i16;
    if current_size.width < window.left + width {
        if window.left >= i16::max_value() - width {
            return Err(ErrorKind::ResizingTerminalFailure(String::from(
                "Argument out of range when setting terminal width.",
            )));
        }

        new_size.width = window.left + width;
        resize_buffer = true;
    }
    let height = height as i16;
    if current_size.height < window.top + height {
        if window.top >= i16::max_value() - height {
            return Err(ErrorKind::ResizingTerminalFailure(String::from(
                "Argument out of range when setting terminal height.",
            )));
        }

        new_size.height = window.top + height;
        resize_buffer = true;
    }

    if resize_buffer
        && screen_buffer
            .set_size(new_size.width - 1, new_size.height - 1)
            .is_err()
    {
        return Err(ErrorKind::ResizingTerminalFailure(String::from(
            "Something went wrong when setting screen buffer size.",
        )));
    }

    let mut window = window;

    // preserve the position, but change the size.
    window.bottom = window.top + height - 1;
    window.right = window.left + width - 1;
    console.set_console_info(true, window)?;

    // if we resized the buffer, un-resize it.
    if resize_buffer
        && screen_buffer
            .set_size(current_size.width - 1, current_size.height - 1)
            .is_err()
    {
        return Err(ErrorKind::ResizingTerminalFailure(String::from(
            "Something went wrong when setting screen buffer size.",
        )));
    }

    let bounds = console.largest_window_size();

    if width > bounds.x {
        return Err(ErrorKind::ResizingTerminalFailure(format!(
            "Argument width: {} out of range when setting terminal width.",
            width
        )));
    }
    if height > bounds.y {
        return Err(ErrorKind::ResizingTerminalFailure(format!(
            "Argument height: {} out of range when setting terminal height.",
            width
        )));
    }

    Ok(())
}

fn clear_after_cursor(location: Coord, buffer_size: Size, current_attribute: u16) -> Result<()> {
    let (mut x, mut y) = (location.x, location.y);

    // if cursor position is at the outer right position
    if x as i16 > buffer_size.width {
        y += 1;
        x = 0;
    }

    // location where to start clearing
    let start_location = Coord::new(x, y);

    // get sum cells before cursor
    let cells_to_write = buffer_size.width as u32 * buffer_size.height as u32;

    clear_winapi(start_location, cells_to_write, current_attribute)
}

fn clear_before_cursor(location: Coord, buffer_size: Size, current_attribute: u16) -> Result<()> {
    let (xpos, ypos) = (location.x, location.y);

    // one cell after cursor position
    let x = 0;
    // one at row of cursor position
    let y = 0;

    // location where to start clearing
    let start_location = Coord::new(x, y);

    // get sum cells before cursor
    let cells_to_write = (buffer_size.width as u32 * ypos as u32) + (xpos as u32 + 1);

    // clear everything before cursor position
    clear_winapi(start_location, cells_to_write, current_attribute)
}

fn clear_entire_screen(buffer_size: Size, current_attribute: u16) -> Result<()> {
    // get sum cells before cursor
    let cells_to_write = buffer_size.width as u32 * buffer_size.height as u32;

    // location where to start clearing
    let start_location = Coord::new(0, 0);

    // clear the entire screen
    clear_winapi(start_location, cells_to_write, current_attribute)?;

    // put the cursor back at cell 0,0
    cursor::sys::move_to(0, 0)?;
    Ok(())
}

fn clear_current_line(location: Coord, buffer_size: Size, current_attribute: u16) -> Result<()> {
    // location where to start clearing
    let start_location = Coord::new(0, location.y);

    // get sum cells before cursor
    let cells_to_write = buffer_size.width as u32;

    // clear the whole current line
    clear_winapi(start_location, cells_to_write, current_attribute)?;

    // put the cursor back at cell 1 on current row
    cursor::sys::move_to(0, location.y as u16)?;
    Ok(())
}

fn clear_until_line(location: Coord, buffer_size: Size, current_attribute: u16) -> Result<()> {
    let (x, y) = (location.x, location.y);

    // location where to start clearing
    let start_location = Coord::new(x, y);

    // get sum cells before cursor
    let cells_to_write = (buffer_size.width - x as i16) as u32;

    // clear until the current line
    clear_winapi(start_location, cells_to_write, current_attribute)?;

    // put the cursor back at original cursor position before we did the clearing
    cursor::sys::move_to(x as u16, y as u16)?;
    Ok(())
}

fn clear_winapi(start_location: Coord, cells_to_write: u32, current_attribute: u16) -> Result<()> {
    let console = Console::from(Handle::current_out_handle()?);
    console.fill_whit_character(start_location, cells_to_write, ' ')?;
    console.fill_whit_attribute(start_location, cells_to_write, current_attribute)?;
    Ok(())
}

#[cfg(test)]
mod tests {
    use crossterm_winapi::ScreenBuffer;

    use super::{scroll_down, scroll_up, set_size, size};

    #[test]
    fn test_resize_winapi() {
        let (width, height) = size().unwrap();

        set_size(30, 30).unwrap();
        assert_eq!((30, 30), size().unwrap());

        // reset to previous size
        set_size(width, height).unwrap();
        assert_eq!((width, height), size().unwrap());
    }

    // Test is disabled, because it's failing on Travis CI
    #[test]
    #[ignore]
    fn test_scroll_down_winapi() {
        let current_window = ScreenBuffer::current()
            .unwrap()
            .info()
            .unwrap()
            .terminal_window();

        scroll_down(2).unwrap();

        let new_window = ScreenBuffer::current()
            .unwrap()
            .info()
            .unwrap()
            .terminal_window();

        assert_eq!(new_window.top, current_window.top + 2);
        assert_eq!(new_window.bottom, current_window.bottom + 2);
    }

    // Test is disabled, because it's failing on Travis CI
    #[test]
    #[ignore]
    fn test_scroll_up_winapi() {
        // move the terminal buffer down before moving it up
        test_scroll_down_winapi();

        let current_window = ScreenBuffer::current()
            .unwrap()
            .info()
            .unwrap()
            .terminal_window();

        scroll_up(2).unwrap();

        let new_window = ScreenBuffer::current()
            .unwrap()
            .info()
            .unwrap()
            .terminal_window();

        assert_eq!(new_window.top, current_window.top - 2);
        assert_eq!(new_window.bottom, current_window.bottom - 2);
    }
}
