//! This module provides an implementation of IO using the ncurses library.
const std = @import("std");
const Action = @import("../actions.zig").Action;
const ncurses = @cImport({
    @cInclude("ncurses.h");
});
const locale = @cImport({
    @cInclude("locale.h");
});

const TICK_MS = 33;

const MAIN_PANEL_WIDTH = 100;
const MAIN_PANEL_HEIGHT = 41;
const INSTRUCTION_PANEL_WIDTH = 32;
const INSTRUCTION_PANEL_HEIGHT = 39;
const MESSAGE_PANEL_WIDTH = 100;
const MESSAGE_PANEL_HEIGHT = 3;
const STATUS_PANEL_WIDTH = 32;
const STATUS_PANEL_HEIGHT = 5;
const MIN_WIDTH = MAIN_PANEL_WIDTH + INSTRUCTION_PANEL_WIDTH;
const MIN_HEIGHT = MAIN_PANEL_HEIGHT + MESSAGE_PANEL_HEIGHT;

const KEY_MOVE_UP: i32 = 'k';
const KEY_MOVE_DOWN: i32 = 'j';
const KEY_MOVE_LEFT: i32 = 'h';
const KEY_MOVE_RIGHT: i32 = 'l';
const KEY_STAIR_UP: i32 = '<';
const KEY_STAIR_DOWN: i32 = '>';
const KEY_QUIT: i32 = ncurses.KEY_F(1);

/// Provide an IO struct that manages the state of the display and user input
pub const IO = struct {
    allocator: std.mem.Allocator,
    main: ?*ncurses.WINDOW,
    inst: ?*ncurses.WINDOW,
    msgs: ?*ncurses.WINDOW,
    stat: ?*ncurses.WINDOW,
    prev_tick_time: i64,

    fn validTermSize(self: *IO) bool {
        _ = self; // should be uncallable without initialization
        return ncurses.LINES >= MIN_HEIGHT and
            ncurses.COLS >= MIN_WIDTH;
    }

    fn colorSupport(self: *IO) bool {
        _ = self; // should be uncallable without initialization
        return ncurses.has_colors();
    }

    fn createNewWin(self: *IO, height: i32, width: i32, y: i32, x: i32) ?*ncurses.WINDOW {
        _ = self; // should be uncallable without initialization
        const local_win = ncurses.newwin(height, width, y, x);
        _ = ncurses.box(local_win, 0, 0);
        _ = ncurses.wrefresh(local_win);
        return local_win;
    }

    fn formatInstruction(self: *IO, pos: i32, key: i32, description: [:0]const u8) void {
        const c_description: ?[*:0]const u8 = description.ptr;

        if (ncurses.KEY_F0 <= key and key <= ncurses.KEY_F(64)) {
            _ = ncurses.mvwprintw(self.inst, pos, 2, "F%d - %s", key - ncurses.KEY_F0, c_description);
        } else if (key < 128) {
            _ = ncurses.mvwprintw(self.inst, pos, 2, "%c - %s", key, c_description);
        } else {
            const str = std.fmt.allocPrintZ(self.allocator, "Invalid key name: {d}", .{key}) catch {
                return;
            };
            self.displayMessage(str);
            self.allocator.free(str);
        }
    }

    fn createPanels(self: *IO) void {
        self.createInstructionPanel();
        self.createMessagePanel();
        self.createStatisticsPanel();
        self.createMainPanel();
    }

    fn handleResize(self: *IO) Action {
        const lines = @as(usize, @intCast(ncurses.LINES));
        const cols = @as(usize, @intCast(ncurses.COLS));
        for (0..lines) |i| {
            for (0..cols) |j| {
                const i_32 = @as(i32, @intCast(i));
                const j_32 = @as(i32, @intCast(j));
                _ = ncurses.mvaddch(i_32, j_32, ' ');
            }
        }
        _ = ncurses.refresh();

        self.deleteWindows();

        if (!self.validTermSize()) {
            _ = ncurses.mvprintw(0, 0, "Terminal must be at least %dx%d", @as(i32, @intCast(MIN_WIDTH)), @as(i32, @intCast(MIN_HEIGHT)));
        } else {
            self.createPanels();
        }

        _ = ncurses.refresh();

        return Action.illegal;
    }

    fn displayInstructions(self: *IO) void {
        self.formatInstruction(1, KEY_MOVE_LEFT, "move left");
        self.formatInstruction(2, KEY_MOVE_DOWN, "move down");
        self.formatInstruction(3, KEY_MOVE_UP, "move up");
        self.formatInstruction(4, KEY_MOVE_RIGHT, "move right");
        self.formatInstruction(5, KEY_STAIR_DOWN, "move down staircase");
        self.formatInstruction(6, KEY_STAIR_UP, "move up staircase");
        self.formatInstruction(7, KEY_QUIT, "quit");
        _ = ncurses.wrefresh(self.inst);
    }

    /// Display a message in the message box.
    /// Takes a pre-formatted null-terminated string
    /// If the message is too wide for the box, display "Message too long" instead.
    pub fn displayMessage(self: *IO, str: [:0]const u8) void {
        if (self.msgs == null) return;

        for (1..MESSAGE_PANEL_WIDTH - 1) |i| {
            const i_32 = @as(i32, @intCast(i));
            _ = ncurses.mvwaddch(self.msgs, 1, i_32, ' ');
        }

        if (str.len > MESSAGE_PANEL_WIDTH - 2) {
            self.displayMessage("Message too long");
            return;
        }

        var buf: [MESSAGE_PANEL_WIDTH:0]u8 = undefined;
        std.mem.copyForwards(u8, &buf, str);
        buf[str.len] = 0;

        const msg: [:0]u8 = &buf;

        const c_msg: ?[*:0]const u8 = msg.ptr;
        _ = ncurses.mvwprintw(self.msgs, 1, 1, c_msg);
        _ = ncurses.wrefresh(self.msgs);
    }

    fn displayStatus(self: *IO) void {
        for (1..STATUS_PANEL_HEIGHT - 1) |i| {
            for (1..STATUS_PANEL_WIDTH - 1) |j| {
                const i_32 = @as(i32, @intCast(i));
                const j_32 = @as(i32, @intCast(j));
                _ = ncurses.mvwaddch(self.stat, i_32, j_32, ' ');
            }
        }

        // TODO: Implement

        _ = ncurses.wrefresh(self.stat);
    }

    /// An interface for user input and time processing.
    /// Waits for the end of a tick and returns a tick action.
    /// If input is given before the end of the tick, return that instead.
    pub fn waitForTick(self: *IO) Action {
        var new = std.time.milliTimestamp();

        while (new - self.prev_tick_time <= TICK_MS) {
            const action = self.processInput();
            if (action != Action.illegal) return action;

            new = std.time.milliTimestamp();
        }

        self.prev_tick_time = new;
        return Action.tick;
    }

    fn processInput(self: *IO) Action {
        const ch = ncurses.getch();

        if (!self.validTermSize()) {
            if (ch != KEY_QUIT and ch != ncurses.KEY_RESIZE) return Action.illegal;
        }

        return switch (ch) {
            KEY_MOVE_UP => Action.move_up,
            KEY_MOVE_DOWN => Action.move_down,
            KEY_MOVE_LEFT => Action.move_left,
            KEY_MOVE_RIGHT => Action.move_right,
            KEY_STAIR_DOWN => Action.down_stair,
            KEY_STAIR_UP => Action.up_stair,
            KEY_QUIT => Action.exit,
            ncurses.KEY_RESIZE => self.handleResize(),
            else => Action.illegal,
        };
    }

    fn createInstructionPanel(self: *IO) void {
        self.inst = self.createNewWin(
            INSTRUCTION_PANEL_HEIGHT,
            INSTRUCTION_PANEL_WIDTH,
            @divTrunc(ncurses.LINES - INSTRUCTION_PANEL_HEIGHT - STATUS_PANEL_HEIGHT, 2) + 1,
            @divTrunc(ncurses.COLS - MAIN_PANEL_WIDTH - INSTRUCTION_PANEL_WIDTH, 2) + MAIN_PANEL_WIDTH - 1,
        );
        if (self.inst != null) {
            self.displayInstructions();
        }
    }

    fn createMessagePanel(self: *IO) void {
        self.msgs = self.createNewWin(
            MESSAGE_PANEL_HEIGHT,
            MESSAGE_PANEL_WIDTH,
            @divTrunc(ncurses.LINES - MAIN_PANEL_HEIGHT - MESSAGE_PANEL_HEIGHT, 2) + MAIN_PANEL_HEIGHT,
            @divTrunc(ncurses.COLS - MESSAGE_PANEL_WIDTH - INSTRUCTION_PANEL_WIDTH, 2),
        );
    }

    fn createStatisticsPanel(self: *IO) void {
        self.stat = self.createNewWin(
            STATUS_PANEL_HEIGHT,
            STATUS_PANEL_WIDTH,
            @divTrunc(ncurses.LINES - INSTRUCTION_PANEL_HEIGHT - STATUS_PANEL_HEIGHT, 2) + INSTRUCTION_PANEL_HEIGHT,
            @divTrunc(ncurses.COLS - MAIN_PANEL_WIDTH - INSTRUCTION_PANEL_WIDTH, 2) + MAIN_PANEL_WIDTH - 1,
        );
    }

    fn createMainPanel(self: *IO) void {
        self.main = self.createNewWin(
            MAIN_PANEL_HEIGHT,
            MAIN_PANEL_WIDTH,
            @divTrunc(ncurses.LINES - MAIN_PANEL_HEIGHT - MESSAGE_PANEL_HEIGHT, 2) + 1,
            @divTrunc(ncurses.COLS - MAIN_PANEL_WIDTH - INSTRUCTION_PANEL_WIDTH, 2),
        );
    }

    pub fn init(allocator: std.mem.Allocator) !IO {
        _ = locale.setlocale(locale.LC_ALL, "");

        var io = IO{
            .allocator = allocator,
            .inst = null,
            .msgs = null,
            .stat = null,
            .main = null,
            .prev_tick_time = std.time.milliTimestamp(),
        };

        if (ncurses.initscr() == null) {
            return error.CursesInitFail;
        }

        if (!io.colorSupport()) {
            _ = ncurses.endwin();
            return error.NoColorSupport;
        }

        _ = ncurses.raw();
        _ = ncurses.keypad(ncurses.stdscr, true);
        _ = ncurses.noecho();
        _ = ncurses.curs_set(0);
        _ = ncurses.start_color();
        _ = ncurses.timeout(1);

        _ = ncurses.init_pair(1, ncurses.COLOR_WHITE, ncurses.COLOR_BLACK);
        _ = ncurses.init_pair(2, ncurses.COLOR_BLACK, ncurses.COLOR_RED);
        _ = ncurses.wattron(ncurses.stdscr, ncurses.COLOR_PAIR(1));
        _ = ncurses.refresh();

        if (!io.validTermSize()) {
            _ = ncurses.mvprintw(0, 0, "Terminal must be at least %dx%d", @as(i32, @intCast(MIN_WIDTH)), @as(i32, @intCast(MIN_HEIGHT)));
        } else {
            io.createPanels();
        }

        return io;
    }

    fn deleteWindows(self: *IO) void {
        _ = ncurses.delwin(self.main);
        self.main = null;
        _ = ncurses.delwin(self.inst);
        self.inst = null;
        _ = ncurses.delwin(self.msgs);
        self.msgs = null;
        _ = ncurses.delwin(self.stat);
        self.stat = null;
    }

    pub fn deinit(self: *IO) void {
        self.deleteWindows();
        _ = ncurses.endwin();
    }
};