use std::char;
use std::io;
use std::marker::PhantomData;
use std::sync::atomic::{AtomicBool, Ordering};

use crate::bindings;
use crate::util;

pub const KEY_TAB: i32 = bindings::KEY_TAB as i32;
pub const KEY_LF: i32 = bindings::KEY_LF as i32;
pub const KEY_CR: i32 = bindings::KEY_CR as i32;
pub const KEY_ESC: i32 = bindings::KEY_ESC as i32;
pub const KEY_BACKSPACE: i32 = bindings::KEY_BACKSPACE as i32;

pub const KEY_RIGHT: i32 = bindings::KEY_RIGHT as i32;
pub const KEY_UP: i32 = bindings::KEY_UP as i32;
pub const KEY_LEFT: i32 = bindings::KEY_LEFT as i32;
pub const KEY_DOWN: i32 = bindings::KEY_DOWN as i32;
pub const KEY_PAGEUP: i32 = bindings::KEY_PAGEUP as i32;
pub const KEY_PAGEDOWN: i32 = bindings::KEY_PAGEDOWN as i32;
pub const KEY_DELETE: i32 = bindings::KEY_DELETE as i32;
pub const KEY_SHIFTTAB: i32 = bindings::KEY_SHIFTTAB as i32;

/// Modifier combinator.
pub const KEY_CTRL: i32 = bindings::KEY_CTRL as i32;
/// Modifier combinator.
pub const KEY_SHIFT: i32 = bindings::KEY_SHIFT as i32;
/// Modifier combinator.
pub const KEY_ALT: i32 = bindings::KEY_ALT as i32;
/// Modifier combinator.
pub const KEY_CTRLALT: i32 = bindings::KEY_CTRLALT as i32;
/// Modifier combinator.
pub const KEY_CTRLSHIFT: i32 = bindings::KEY_CTRLSHIFT as i32;

/// A style descriptor for a cell on the screen.
#[derive(Debug, Copy, Clone)]
pub struct Style {
    /// The foreground color; valid values are 0, 1, ..., 7 (the eight ANSI
    /// colors) and 9 (the default color).
    pub fg: u8,

    /// The background color; valid values are 0, 1, ..., 7 (the eight ANSI
    /// colors) and 9 (the default color).
    pub bg: u8,

    /// Whether the character in the cell should be printed bold. If this is
    /// enabled, the terminal generally uses the bright version of the
    /// foreground color instead of the normal version. Therefore, there are
    /// effectively 16, not 8, foreground colors (in addition to the default
    /// color, 9).
    pub bold: bool,

    /// Whether to display an underline.
    pub ul: bool
}

/// RAII struct for keyboard-input initialization
///
/// Only one instance of this struct can be active at a time. Attempting to
/// create a second instance will panic.
pub struct Keyboard {
    _phantom: PhantomData<*mut u8>,
}

static KEYBOARD_REFCOUNT: AtomicBool = AtomicBool::new(false);

impl Keyboard {
    /// Grab the keyboard, i.e. enable raw mode.
    ///
    /// This disables automatic printing of typed characters (echo), and allows
    /// reading a single character even when a newline has not yet been
    /// entered.
    ///
    /// If `nosigkeys` is true, interrupt keycodes like ctrl-C, ctrl-\ and
    /// ctrl-Z will no longer be handled by the shell but will be available to
    /// be read using `get_key()` just like the other keys.
    pub fn grab(nosigkeys: bool) -> Self {
        let prev = KEYBOARD_REFCOUNT.compare_and_swap(
                        false, true, Ordering::SeqCst);
        if prev {
            panic!("Can only hold one Keyboard struct at a time!");
        }

        unsafe { bindings::initkeyboard(nosigkeys); }
        Self { _phantom: PhantomData }
    }

    /// Explicitly release the keyboard.
    ///
    /// This prevents further use of the Keyboard functionality and
    /// simultaneously forces its lifetime to extend until this call, delaying
    /// deinitialization of the keyboard until this call.
    pub fn end(self) {}

    // None on EOF, otherwise a combination of the KEY_* constants
    pub fn get_key(&self) -> io::Result<Option<i32>> {
        match unsafe { bindings::tgetkey() } {
            -2 => Err(io::Error::last_os_error()),
            -1 => Ok(None),
            value => Ok(Some(value)),
        }
    }

    pub fn get_line(&self) -> Option<String> {
        let ptr = unsafe { bindings::tgetline() };
        if ptr.is_null() {
            None
        } else {
            unsafe { Some(util::string_from_utf8_charp(ptr)) }
        }
    }
}

impl Drop for Keyboard {
    fn drop(&mut self) {
        let prev = KEYBOARD_REFCOUNT.compare_and_swap(
                        true, false, Ordering::SeqCst);
        if !prev {
            panic!("Internal: No Keyboard was held on Drop of a Keyboard?");
        }

        unsafe { bindings::endkeyboard(); }
    }
}

/// RAII struct for screen-drawing initialization
///
/// Only one instance of this struct can be active at a time. Attempting to
/// create a second instance will panic.
pub struct Screen<'a> {
    _keyboard: &'a Keyboard,
}

static SCREEN_REFCOUNT: AtomicBool = AtomicBool::new(false);

impl<'a> Screen<'a> {
    /// Grab the screen, i.e. switch to the alternative screen and allocate draw
    /// buffers.
    ///
    /// This function takes and stores a Keyboard reference to ensure that the
    /// keyboard is initialized while the screen is grabbed.
    pub fn grab<'b: 'a>(keyboard: &'b Keyboard) -> Self {
        let prev = SCREEN_REFCOUNT.compare_and_swap(
                        false, true, Ordering::SeqCst);
        if prev {
            panic!("Can only hold one Screen struct at a time!");
        }

        unsafe { bindings::initscreen(); }
        Self { _keyboard: keyboard }
    }

    pub fn end(self) {}

    /// Install ctrl-L redraw handler.
    ///
    /// If the argument is true, then upon reading ctrl-L in
    /// `Keyboard::get_key()`, a full redraw is issued, and the the call blocks
    /// for the next key. Note that if the user only types ctrl-L, this means
    /// that `get_key` may block while you don't expect it.
    pub fn install_cl_handler(&self, install: bool) {
        unsafe { bindings::installCLhandler(install); }
    }

    /// Install redraw handler.
    ///
    /// The argument indicates whether the redraw is a full redraw. The handler
    /// is called before the redraw is performed. Please do not trigger redraws
    /// from within the handler.
    pub fn on_redraw(&self, handler: extern "C" fn(full_redraw: bool)) {
        unsafe { bindings::installredrawhandler(Some(handler)); }
    }

    pub fn clear(&self) {
        unsafe { bindings::clearscreen(); }
    }

    /// Update style state.
    ///
    /// This modifies the style for the characters printed from now on. Note
    /// that this does not write anything to the terminal.
    pub fn set_style(&self, style: Style) {
        let sty = bindings::Style {
            fg: style.fg as i32,
            bg: style.bg as i32,
            bold: style.bold,
            ul: style.ul,
        };
        unsafe { bindings::setstyle(&sty as *const bindings::Style); }
    }

    /// Update partial style state. see `set_style()`.
    pub fn set_fg(&self, fg: u8) {
        unsafe { bindings::setfg(fg as i32); }
    }

    /// Update partial style state. see `set_style()`.
    pub fn set_bg(&self, bg: u8) {
        unsafe { bindings::setbg(bg as i32); }
    }

    /// Update partial style state. see `set_style()`.
    pub fn set_bold(&self, bold: bool) {
        unsafe { bindings::setbold(bold); }
    }

    /// Update partial style state. see `set_style()`.
    pub fn set_ul(&self, ul: bool) {
        unsafe { bindings::setul(ul); }
    }

    pub fn putc(&self, c: char) {
        unsafe { bindings::tputc(c as i32); }
    }

    /// Newlines ('\n') return to the column on which printing started.
    pub fn print(&self, s: &str) {
        unsafe { bindings::tprint(s.as_bytes().as_ptr() as *const i8); }
    }

    pub fn fill_rect(&self, lefttop: (u32, u32), size: (u32, u32), c: char) {
        unsafe { bindings::fillrect(
                    lefttop.0 as i32, lefttop.1 as i32,
                    size.0 as i32, size.1 as i32,
                    c as i32); }
    }

    pub fn redraw(&self) {
        unsafe { bindings::redraw(); }
    }

    pub fn redraw_full(&self) {
        unsafe { bindings::redrawfull(); }
    }

    /// Scrolls a rectangle on the screen by a signed number of lines.
    pub fn scroll_term(&self, lefttop: (u32, u32), size: (u32, u32), amount: i32) {
        unsafe { bindings::scrollterm(
                    lefttop.0 as i32, lefttop.1 as i32,
                    size.0 as i32, size.1 as i32,
                    amount); }
    }

    pub fn get_buffer_char(&self, pos: (u32, u32)) -> char {
        unsafe {
            char::from_u32(
                bindings::getbufferchar(pos.0 as i32, pos.1 as i32) as u32
            ).unwrap()
        }
    }

    /// Updates state; does not actually move the cursor yet (use `redraw()`).
    pub fn move_to(&self, pos: (u32, u32)) {
        unsafe { bindings::moveto(pos.0 as i32, pos.1 as i32); }
    }

    /// Save the (internal) cursor position on a stack.
    pub fn push_cursor(&self) {
        unsafe { bindings::pushcursor(); }
    }

    /// Pop the (internal) cursor position from the stack.
    pub fn pop_cursor(&self) {
        unsafe { bindings::popcursor(); }
    }

    /// Takes effect immediately!
    pub fn cursor_visible(&self, visible: bool) {
        unsafe { bindings::cursorvisible(visible); }
    }
}

impl<'a> Drop for Screen<'a> {
    fn drop(&mut self) {
        let prev = SCREEN_REFCOUNT.compare_and_swap(
                        true, false, Ordering::SeqCst);
        if !prev {
            panic!("Internal: No Screen was held on Drop of a Screen?");
        }

        unsafe { bindings::endscreen(); }
    }
}

pub fn get_term_size() -> (u32, u32) {
    let sz = unsafe { bindings::gettermsize() };
    (sz.w as u32, sz.h as u32)
}

pub fn bel() {
    unsafe { bindings::bel(); }
}