/*
 * btui.h
 * Copyright 2020 Bruce Hill
 * Released under the MIT License
 *
 * This file defines some Text User Interface (TUI) functionality.
 */

#ifndef __BTUI_H__
#define __BTUI_H__

#include <signal.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <termios.h>
#include <time.h>
#include <unistd.h>

#define BTUI_VERSION 5

// Terminal escape sequences:
#define T_WRAP        "7"
#define T_SHOW_CURSOR "25"
#define T_MOUSE_XY    "1000"
#define T_MOUSE_CELL  "1002"
#define T_MOUSE_SGR   "1006"
#define T_ALT_SCREEN  "1049"
#define T_ON(opt)  "\033[?" opt "h"
#define T_OFF(opt) "\033[?" opt "l"

// Maximum time in milliseconds between double clicks
#ifndef BTUI_DOUBLECLICK_THRESHOLD
#define BTUI_DOUBLECLICK_THRESHOLD 200
#endif

// Keyboard modifiers:
#define MOD_BITSHIFT  9
#define MOD_META   (1 << (MOD_BITSHIFT + 0))
#define MOD_CTRL   (1 << (MOD_BITSHIFT + 1))
#define MOD_ALT    (1 << (MOD_BITSHIFT + 2))
#define MOD_SHIFT  (1 << (MOD_BITSHIFT + 3))

typedef enum {
    BTUI_MODE_UNINITIALIZED = 0,
    BTUI_MODE_NORMAL,
    BTUI_MODE_TUI,
} btui_mode_t;

typedef enum {
    // ASCII chars:
    KEY_CTRL_AT = 0x00, KEY_CTRL_A, KEY_CTRL_B, KEY_CTRL_C, KEY_CTRL_D,
    KEY_CTRL_E, KEY_CTRL_F, KEY_CTRL_G, KEY_CTRL_H, KEY_CTRL_I, KEY_CTRL_J,
    KEY_CTRL_K, KEY_CTRL_L, KEY_CTRL_M, KEY_CTRL_N, KEY_CTRL_O, KEY_CTRL_P,
    KEY_CTRL_Q, KEY_CTRL_R, KEY_CTRL_S, KEY_CTRL_T, KEY_CTRL_U, KEY_CTRL_V,
    KEY_CTRL_W, KEY_CTRL_X, KEY_CTRL_Y, KEY_CTRL_Z,
    KEY_CTRL_LSQ_BRACKET, KEY_CTRL_BACKSLASH, KEY_CTRL_RSQ_BRACKET,
    KEY_CTRL_CARET, KEY_CTRL_UNDERSCORE, KEY_SPACE,
    // Printable chars would be here
    KEY_BACKSPACE2 = 0x7F,

    // Non-ascii multi-byte keys:
    KEY_F0, KEY_F1, KEY_F2, KEY_F3, KEY_F4, KEY_F5, KEY_F6, KEY_F7, KEY_F8,
    KEY_F9, KEY_F10, KEY_F11, KEY_F12,
    KEY_INSERT, KEY_DELETE, KEY_HOME, KEY_END, KEY_PGUP, KEY_PGDN,
    KEY_ARROW_UP, KEY_ARROW_DOWN, KEY_ARROW_LEFT, KEY_ARROW_RIGHT,
    MOUSE_LEFT_PRESS, MOUSE_RIGHT_PRESS, MOUSE_MIDDLE_PRESS,
    MOUSE_LEFT_DRAG, MOUSE_RIGHT_DRAG, MOUSE_MIDDLE_DRAG,
    MOUSE_LEFT_RELEASE, MOUSE_RIGHT_RELEASE, MOUSE_MIDDLE_RELEASE,
    MOUSE_LEFT_DOUBLE, MOUSE_RIGHT_DOUBLE, MOUSE_MIDDLE_DOUBLE,
    MOUSE_WHEEL_RELEASE, MOUSE_WHEEL_PRESS,
    // Special:
    RESIZE_EVENT,
} btui_key_t;

typedef enum {
    CURSOR_DEFAULT            = 0,
    CURSOR_BLINKING_BLOCK     = 1,
    CURSOR_STEADY_BLOCK       = 2,
    CURSOR_BLINKING_UNDERLINE = 3,
    CURSOR_STEADY_UNDERLINE   = 4,
    CURSOR_BLINKING_BAR       = 5,
    CURSOR_STEADY_BAR         = 6,
} cursor_t;

// Overlapping key codes:
const btui_key_t KEY_CTRL_BACKTICK  = KEY_CTRL_AT;
const btui_key_t KEY_CTRL_2         = KEY_CTRL_AT;
const btui_key_t KEY_CTRL_SPACE     = KEY_CTRL_AT;
const btui_key_t KEY_BACKSPACE      = KEY_CTRL_H;
const btui_key_t KEY_TAB            = KEY_CTRL_I;
const btui_key_t KEY_ENTER          = KEY_CTRL_M;
const btui_key_t KEY_ESC            = KEY_CTRL_LSQ_BRACKET;
const btui_key_t KEY_CTRL_3         = KEY_CTRL_LSQ_BRACKET;
const btui_key_t KEY_CTRL_4         = KEY_CTRL_BACKSLASH;
const btui_key_t KEY_CTRL_5         = KEY_CTRL_RSQ_BRACKET;
const btui_key_t KEY_CTRL_TILDE     = KEY_CTRL_CARET;
const btui_key_t KEY_CTRL_6         = KEY_CTRL_CARET;
const btui_key_t KEY_CTRL_7         = KEY_CTRL_UNDERSCORE;
const btui_key_t KEY_CTRL_SLASH     = KEY_CTRL_UNDERSCORE;
const btui_key_t KEY_CTRL_8         = KEY_BACKSPACE2;

typedef enum {
    BTUI_CLEAR_SCREEN = 0,
    BTUI_CLEAR_ABOVE  = 1,
    BTUI_CLEAR_BELOW  = 2,
    BTUI_CLEAR_LINE   = 3,
    BTUI_CLEAR_LEFT   = 4,
    BTUI_CLEAR_RIGHT  = 5,
} btui_clear_t;

// Text attributes:
typedef uint64_t attr_t;
const attr_t BTUI_NORMAL               = 1ul << 0;
const attr_t BTUI_BOLD                 = 1ul << 1;
const attr_t BTUI_FAINT                = 1ul << 2;
const attr_t BTUI_ITALIC               = 1ul << 3;
const attr_t BTUI_UNDERLINE            = 1ul << 4;
const attr_t BTUI_BLINK_SLOW           = 1ul << 5;
const attr_t BTUI_BLINK_FAST           = 1ul << 6;
const attr_t BTUI_REVERSE              = 1ul << 7;
const attr_t BTUI_CONCEAL              = 1ul << 8;
const attr_t BTUI_STRIKETHROUGH        = 1ul << 9;
// 10-19: alternative fonts
const attr_t BTUI_FRAKTUR              = 1ul << 20;
const attr_t BTUI_DOUBLE_UNDERLINE     = 1ul << 21;
const attr_t BTUI_NO_BOLD_OR_FAINT     = 1ul << 22;
const attr_t BTUI_NO_ITALIC_OR_FRAKTUR = 1ul << 23;
const attr_t BTUI_NO_UNDERLINE         = 1ul << 24;
const attr_t BTUI_NO_BLINK             = 1ul << 25;
// 26: reserved
const attr_t BTUI_NO_REVERSE           = 1ul << 27;
const attr_t BTUI_NO_CONCEAL           = 1ul << 28;
const attr_t BTUI_NO_STRIKETHROUGH     = 1ul << 29;
const attr_t BTUI_FG_BLACK             = 1ul << 30;
const attr_t BTUI_FG_RED               = 1ul << 31;
const attr_t BTUI_FG_GREEN             = 1ul << 32;
const attr_t BTUI_FG_YELLOW            = 1ul << 33;
const attr_t BTUI_FG_BLUE              = 1ul << 34;
const attr_t BTUI_FG_MAGENTA           = 1ul << 35;
const attr_t BTUI_FG_CYAN              = 1ul << 36;
const attr_t BTUI_FG_WHITE             = 1ul << 37;
// 38: 256/24bit color
const attr_t BTUI_FG_NORMAL            = 1ul << 39;
const attr_t BTUI_BG_BLACK             = 1ul << 40;
const attr_t BTUI_BG_RED               = 1ul << 41;
const attr_t BTUI_BG_GREEN             = 1ul << 42;
const attr_t BTUI_BG_YELLOW            = 1ul << 43;
const attr_t BTUI_BG_BLUE              = 1ul << 44;
const attr_t BTUI_BG_MAGENTA           = 1ul << 45;
const attr_t BTUI_BG_CYAN              = 1ul << 46;
const attr_t BTUI_BG_WHITE             = 1ul << 47;
// 48: 256/24bit color
const attr_t BTUI_BG_NORMAL            = 1ul << 49;
// 50: Inverse of 26 (reserved)
const attr_t BTUI_FRAMED               = 1ul << 51;
const attr_t BTUI_ENCIRCLED            = 1ul << 52;
const attr_t BTUI_OVERLINED            = 1ul << 53;
const attr_t BTUI_NO_FRAMED_OR_ENCIRCLED = 1ul << 54;
const attr_t BTUI_NO_OVERLINED         = 1ul << 55;
// 56-59: reserved
// 60-65: Ideogram stuff


// BTUI object:
typedef struct {
    FILE *in, *out;
    int width, height;
    int size_changed;
    btui_mode_t mode;
} btui_t;

// Key Names:
typedef struct {
    int key;
    const char *name;
} keyname_t;


// Public API:
int     btui_clear(btui_t *bt, int mode);
void    btui_disable(btui_t *bt);
void    btui_draw_linebox(btui_t *bt, int x, int y, int w, int h);
void    btui_draw_shadow(btui_t *bt, int x, int y, int w, int h);
btui_t* btui_create(btui_mode_t mode);
#define btui_enable() btui_create(BTUI_MODE_TUI)
void    btui_fill_box(btui_t *bt, int x, int y, int w, int h);
int     btui_flush(btui_t *bt);
void    btui_force_close(btui_t *bt);
int     btui_getkey(btui_t *bt, int timeout, int *mouse_x, int *mouse_y);
int     btui_hide_cursor(btui_t *bt);
char    *btui_keyname(int key, char *buf);
int     btui_keynamed(const char *name);
int     btui_move_cursor(btui_t *bt, int x, int y);
#define btui_printf(bt, ...) fprintf((bt)->out, __VA_ARGS__)
int     btui_puts(btui_t *bt, const char *s);
int     btui_scroll(btui_t *bt, int firstline, int lastline, int scroll_amount);
int     btui_set_attributes(btui_t *bt, attr_t attrs);
int     btui_set_bg(btui_t *bt, unsigned char r, unsigned char g, unsigned char b);
int     btui_set_bg_hex(btui_t *bt, int hex);
int     btui_set_cursor(btui_t *bt, cursor_t cur);
int     btui_set_fg(btui_t *bt, unsigned char r, unsigned char g, unsigned char b);
int     btui_set_fg_hex(btui_t *bt, int hex);
void    btui_set_mode(btui_t *bt, btui_mode_t mode);
int     btui_show_cursor(btui_t *bt);
int     btui_suspend(btui_t *bt);


// File-local variables:
static btui_t current_bt = {.in = NULL, .out = NULL, .mode = BTUI_MODE_UNINITIALIZED};

// The names of keys that don't render well:
static keyname_t key_names[] = {
    {KEY_SPACE, "Space"}, {KEY_BACKSPACE2, "Backspace"},
    {KEY_INSERT, "Insert"}, {KEY_DELETE, "Delete"},
    {KEY_TAB, "Tab"}, {KEY_ENTER, "Enter"}, {KEY_ENTER, "Return"},
    {KEY_HOME, "Home"}, {KEY_END, "End"},
    {KEY_PGUP, "PgUp"}, {KEY_PGUP, "Page Up"},
    {KEY_PGDN, "PgDn"}, {KEY_PGDN, "Page Down"},
    {KEY_ARROW_UP, "Up"}, {KEY_ARROW_DOWN, "Down"}, {KEY_ARROW_LEFT, "Left"}, {KEY_ARROW_RIGHT, "Right"},
    {MOUSE_LEFT_PRESS, "Left press"}, {MOUSE_RIGHT_PRESS, "Right press"}, {MOUSE_MIDDLE_PRESS, "Middle press"},
    {MOUSE_LEFT_DRAG, "Left drag"}, {MOUSE_RIGHT_DRAG, "Right drag"}, {MOUSE_MIDDLE_DRAG, "Middle drag"},
    {MOUSE_LEFT_RELEASE, "Left release"}, {MOUSE_RIGHT_RELEASE, "Right release"}, {MOUSE_MIDDLE_RELEASE, "Middle release"},
    {MOUSE_LEFT_RELEASE, "Left up"}, {MOUSE_RIGHT_RELEASE, "Right up"}, {MOUSE_MIDDLE_RELEASE, "Middle up"},
    {MOUSE_LEFT_RELEASE, "Left click"}, {MOUSE_RIGHT_RELEASE, "Right click"}, {MOUSE_MIDDLE_RELEASE, "Middle click"},
    {MOUSE_LEFT_DOUBLE, "Double left click"}, {MOUSE_RIGHT_DOUBLE, "Double right click"}, {MOUSE_MIDDLE_DOUBLE, "Double middle click"},
    {MOUSE_WHEEL_RELEASE, "Mouse wheel up"}, {MOUSE_WHEEL_PRESS, "Mouse wheel down"},
    {KEY_ESC, "Esc"}, {KEY_ESC, "Escape"},
    {KEY_CTRL_A, "Ctrl-a"}, {KEY_CTRL_B, "Ctrl-b"}, {KEY_CTRL_C, "Ctrl-c"},
    {KEY_CTRL_D, "Ctrl-d"}, {KEY_CTRL_E, "Ctrl-e"}, {KEY_CTRL_F, "Ctrl-f"},
    {KEY_CTRL_G, "Ctrl-g"}, {KEY_CTRL_H, "Ctrl-h"}, {KEY_CTRL_I, "Ctrl-i"},
    {KEY_CTRL_J, "Ctrl-j"}, {KEY_CTRL_K, "Ctrl-k"}, {KEY_CTRL_L, "Ctrl-l"},
    {KEY_CTRL_M, "Ctrl-m"}, {KEY_CTRL_N, "Ctrl-n"}, {KEY_CTRL_O, "Ctrl-o"},
    {KEY_CTRL_P, "Ctrl-p"}, {KEY_CTRL_Q, "Ctrl-q"}, {KEY_CTRL_R, "Ctrl-r"},
    {KEY_CTRL_S, "Ctrl-s"}, {KEY_CTRL_T, "Ctrl-t"}, {KEY_CTRL_U, "Ctrl-u"},
    {KEY_CTRL_V, "Ctrl-v"}, {KEY_CTRL_W, "Ctrl-w"}, {KEY_CTRL_X, "Ctrl-x"},
    {KEY_CTRL_Y, "Ctrl-y"}, {KEY_CTRL_Z, "Ctrl-z"},
    {KEY_CTRL_TILDE, "Ctrl-~"}, {KEY_CTRL_BACKSLASH, "Ctrl-\\"},
    {KEY_CTRL_LSQ_BRACKET, "Ctrl-]"}, {KEY_CTRL_RSQ_BRACKET, "Ctrl-]"},
    {KEY_CTRL_UNDERSCORE, "Ctrl-_"}, {KEY_CTRL_SLASH, "Ctrl-/"},
    {KEY_CTRL_AT, "Ctrl-@"}, {KEY_CTRL_CARET, "Ctrl-^"},
    {KEY_CTRL_BACKTICK, "Ctrl-`"},
    {KEY_CTRL_2, "Ctrl-2"}, {KEY_CTRL_3, "Ctrl-3"}, {KEY_CTRL_4, "Ctrl-4"},
    {KEY_CTRL_5, "Ctrl-5"}, {KEY_CTRL_6, "Ctrl-6"}, {KEY_CTRL_7, "Ctrl-7"},
    {KEY_CTRL_5, "Ctrl-8"}, {KEY_CTRL_6, "Ctrl-9"},
    {KEY_F1, "F1"}, {KEY_F2, "F2"}, {KEY_F3, "F3"}, {KEY_F4, "F4"}, {KEY_F5, "F5"},
    {KEY_F6, "F6"}, {KEY_F7, "F7"}, {KEY_F8, "F8"}, {KEY_F9, "F9"}, {KEY_F10, "F10"},
    {KEY_F11, "F11"}, {KEY_F12, "F12"},
    {RESIZE_EVENT, "Resize"},
};

// This is the default termios for normal terminal behavior and the text-user-interface one:
static struct termios normal_termios, tui_termios;

// File-local functions:

/* 
 * Read and return the next character from the file descriptor, or -1 if no
 * character is available. (Helper method for nextnum() and btui_getkey())
 */
static inline int nextchar(int fd)
{
    char c;
    return read(fd, &c, 1) == 1 ? c : -1;
}

/*
 * Given a file descriptor, parse an integer value, updating *c to hold the
 * next character after the integer value. Return the parsed integer value.
 * (Helper method for btui_getkey())
 */
static inline int nextnum(int fd, int *c)
{
    int n;
    *c = nextchar(fd);
    for (n = 0; '0' <= *c && *c <= '9'; *c = nextchar(fd))
        n = 10*n + (*c - '0');
    return n;
}

/*
 * Reset the terminal back to its normal state.
 */
static void btui_cleanup(void)
{
    if (!current_bt.out) return;
    tcsetattr(fileno(current_bt.out), TCSANOW, &normal_termios);
    btui_set_cursor(&current_bt, CURSOR_DEFAULT);
    btui_set_mode(&current_bt, BTUI_MODE_UNINITIALIZED);
    fflush(current_bt.out);
    fclose(current_bt.in);
    fclose(current_bt.out);
    memset(&current_bt, 0, sizeof(btui_t));
}

/*
 * Reset the terminal back to its normal state and raise the given signal.
 * (This is used as a signal handler that gracefully exits without gunking up
 * the terminal)
 */
static void btui_cleanup_and_raise(int sig)
{
    btui_mode_t mode = current_bt.mode;
    btui_cleanup();
    raise(sig);
    // This code will only ever be run if sig is SIGTSTP/SIGSTOP, otherwise, raise() won't return:
    btui_create(mode);
    struct sigaction sa = {.sa_handler = &btui_cleanup_and_raise, .sa_flags = (int)(SA_NODEFER | SA_RESETHAND)};
    sigaction(sig, &sa, NULL);
}

/*
 * A signal handler used to update BTUI's internal window size values when a
 * SIGWINCH event occurs.
 */
static void update_term_size(int sig)
{
    (void)sig;
    struct winsize winsize;
    ioctl(STDIN_FILENO, TIOCGWINSZ, &winsize);
    if (winsize.ws_col != current_bt.width || winsize.ws_row != current_bt.height) {
        current_bt.width = winsize.ws_col;
        current_bt.height = winsize.ws_row;
        current_bt.size_changed = 1;
    }
}

// Public API functions:

/*
 * Clear all or part of the screen. `mode` should be one of:
 *   BTUI_CLEAR_(BELOW|ABOVE|SCREEN|RIGHT|LEFT|LINE)
 */
int btui_clear(btui_t *bt, int mode)
{
    switch (mode) {
        case BTUI_CLEAR_BELOW:  return fputs("\033[J", bt->out);
        case BTUI_CLEAR_ABOVE:  return fputs("\033[1J", bt->out);
        case BTUI_CLEAR_SCREEN: return fputs("\033[2J", bt->out);
        case BTUI_CLEAR_RIGHT:  return fputs("\033[K", bt->out);
        case BTUI_CLEAR_LEFT:   return fputs("\033[1K", bt->out);
        case BTUI_CLEAR_LINE:   return fputs("\033[2K", bt->out);
        default:                return -1;
    }
}

/*
 * Disable TUI mode (return to the normal terminal with the normal terminal
 * input handling).
 */
void btui_disable(btui_t *bt)
{
    (void)bt;
    btui_cleanup();
}

/*
 * Draw a box using the special box-drawing characters at the given x,y
 * position with the given width,height.
 */
void btui_draw_linebox(btui_t *bt, int x, int y, int w, int h)
{
    btui_move_cursor(bt, x-1, y-1);
    // Top row
    fputs("\033(0l", bt->out);
    for (int i = 0; i < w; i++)
       fputc('q', bt->out);
    fputc('k', bt->out);
    // Side walls
    for (int i = 0; i < h; i++) {
        btui_move_cursor(bt, x-1, y + i);
        fputc('x', bt->out);
        btui_move_cursor(bt, x + w, y + i);
        fputc('x', bt->out);
    }
    // Bottom row
    btui_move_cursor(bt, x-1, y + h);
    fputc('m', bt->out);
    for (int i = 0; i < w; i++)
       fputc('q', bt->out);
    fputs("j\033(B", bt->out);
}

/*
 * Draw a shadow to the bottom right of the given box coordinates.
 */
void btui_draw_shadow(btui_t *bt, int x, int y, int w, int h)
{
    fputs("\033(0", bt->out);
    for (int i = 0; i < h-1; i++) {
        btui_move_cursor(bt, x + w, y + 1 + i);
        fputc('a', bt->out);
    }
    btui_move_cursor(bt, x + 1, y + h);
    for (int i = 0; i < w; i++) {
        fputc('a', bt->out);
    }
    fputs("\033(B", bt->out);
}

/*
 * Enable TUI mode for this terminal and return a pointer to the BTUI struct
 * that should be passed to future API calls.
 */
btui_t *btui_create(btui_mode_t mode)
{
    FILE *in = fopen("/dev/tty", "r");
    if (!in) return NULL;
    FILE *out = fopen("/dev/tty", "w");
    if (!out) {
        fclose(in);
        return NULL;
    }

    if (tcgetattr(fileno(in), &normal_termios)
      || tcgetattr(fileno(in), &tui_termios)
      || (cfmakeraw(&tui_termios),
         tcsetattr(fileno(out), TCSANOW, &tui_termios))) {
        fclose(in);
        fclose(out);
        return NULL;
    }

    current_bt.in = in;
    current_bt.out = out;
    current_bt.mode = BTUI_MODE_NORMAL;
    atexit(btui_cleanup);

    struct sigaction sa_winch = {.sa_handler = &update_term_size};
    sigaction(SIGWINCH, &sa_winch, NULL);
    int signals[] = {SIGTERM, SIGINT, SIGXCPU, SIGXFSZ, SIGVTALRM, SIGPROF, SIGSEGV, SIGTSTP, SIGPIPE};
    struct sigaction sa = {.sa_handler = &btui_cleanup_and_raise, .sa_flags = (int)(SA_NODEFER | SA_RESETHAND)};
    for (size_t i = 0; i < sizeof(signals)/sizeof(signals[0]); i++)
        sigaction(signals[i], &sa, NULL);

    update_term_size(SIGWINCH);
    current_bt.size_changed = 0;
    btui_set_mode(&current_bt, mode);
    return &current_bt;
}

/*
 * Set the display mode of BTUI
 */
void btui_set_mode(btui_t *bt, btui_mode_t mode)
{
    if (mode == bt->mode) return;
    switch (mode) {
        case BTUI_MODE_NORMAL: case BTUI_MODE_UNINITIALIZED:
            if (bt->mode == BTUI_MODE_TUI)
                fputs(T_OFF(T_ALT_SCREEN), bt->out);
            fputs(T_ON(T_SHOW_CURSOR ";" T_WRAP) T_OFF(T_MOUSE_XY ";" T_MOUSE_CELL ";" T_MOUSE_SGR) "\033[0m", bt->out);
            break;
        case BTUI_MODE_TUI:
            fputs(T_OFF(T_SHOW_CURSOR ";" T_WRAP)  T_ON(T_ALT_SCREEN ";" T_MOUSE_XY ";" T_MOUSE_CELL ";" T_MOUSE_SGR), bt->out);
            break;
        default: break;
    }
    fflush(bt->out);
    bt->mode = mode;
}

/*
 * Fill the given rectangular area (x,y coordinates and width,height) with
 * spaces.
 */
void btui_fill_box(btui_t *bt, int x, int y, int w, int h)
{
    int left = x, bottom = y + h;
    for ( ; y < bottom; y++) {
        x = left;
        btui_move_cursor(bt, x, y);
        for ( ; x < left + w; x++) {
            fputc(' ', bt->out);
        }
    }
}

/*
 * Flush BTUI's output.
 */
int btui_flush(btui_t *bt)
{
    return fflush(bt->out);
}

/*
 * Close BTUI files and prevent cleaning up (useful for fork/exec)
 */
void btui_force_close(btui_t *bt)
{
    if (!bt->out) return;
    fclose(bt->in);
    fclose(bt->out);
    memset(bt, 0, sizeof(btui_t));
}

/*
 * Get one key of input from the given file. Returns -1 on failure.
 * If mouse_x or mouse_y are non-null and a mouse event occurs, they will be
 * set to the position of the mouse (0-indexed).
 */
int btui_getkey(btui_t *bt, int timeout, int *mouse_x, int *mouse_y)
{
    int new_vmin = timeout < 0 ? 1 : 0, new_vtime = timeout < 0 ? 0 : timeout;
    if (new_vmin != tui_termios.c_cc[VMIN] || new_vtime != tui_termios.c_cc[VTIME]) {
        tui_termios.c_cc[VMIN] = new_vmin;
        tui_termios.c_cc[VTIME] = new_vtime;
        if (tcsetattr(fileno(bt->out), TCSANOW, &tui_termios) == -1)
            return -1;
    }

    if (mouse_x) *mouse_x = -1;
    if (mouse_y) *mouse_y = -1;
    int fd = fileno(bt->in);
    int numcode = 0, modifiers = 0;
    int c = nextchar(fd);
    if (c == '\x1b') {
        goto escape;
    } else if (c == -1 && bt->size_changed) {
        bt->size_changed = 0;
        return RESIZE_EVENT;
    }

    return c;

  escape:
    c = nextchar(fd);
    // Actual escape key:
    if (c < 0)
        return KEY_ESC;

    switch (c) {
        case '\x1b': return KEY_ESC;
        case '[': c = nextchar(fd); goto CSI_start;
        case 'P': goto DCS;
        case 'O': goto SS3;
        default: return MOD_ALT | c;
    }

  CSI_start:
    if (c == -1)
        return MOD_ALT | '[';

    switch (c) {
        case 'A': return modifiers | KEY_ARROW_UP;
        case 'B': return modifiers | KEY_ARROW_DOWN;
        case 'C': return modifiers | KEY_ARROW_RIGHT;
        case 'D': return modifiers | KEY_ARROW_LEFT;
        case 'F': return modifiers | KEY_END;
        case 'H': return modifiers | KEY_HOME;
        case 'J': return numcode == 2 ? (MOD_SHIFT | KEY_HOME) : -1;
        case 'K': return MOD_SHIFT | KEY_END;
        case 'M': return MOD_CTRL | KEY_DELETE;
        case 'P': return modifiers | (numcode == 1 ? KEY_F1 : KEY_DELETE);
        case 'Q': return numcode == 1 ? (modifiers | KEY_F2) : -1;
        case 'R': return numcode == 1 ? (modifiers | KEY_F3) : -1;
        case 'S': return numcode == 1 ? (modifiers | KEY_F4) : -1;
        case 'Z': return MOD_SHIFT | modifiers | (int)KEY_TAB;
        case '~':
            switch (numcode) {
                case 1: return modifiers | KEY_HOME;
                case 2: return modifiers | KEY_INSERT;
                case 3: return modifiers | KEY_DELETE;
                case 4: return modifiers | KEY_END;
                case 5: return modifiers | KEY_PGUP;
                case 6: return modifiers | KEY_PGDN;
                case 7: return modifiers | KEY_HOME;
                case 8: return modifiers | KEY_END;
                case 10: return modifiers | KEY_F0;
                case 11: return modifiers | KEY_F1;
                case 12: return modifiers | KEY_F2;
                case 13: return modifiers | KEY_F3;
                case 14: return modifiers | KEY_F4;
                case 15: return modifiers | KEY_F5;
                case 17: return modifiers | KEY_F6;
                case 18: return modifiers | KEY_F7;
                case 19: return modifiers | KEY_F8;
                case 20: return modifiers | KEY_F9;
                case 21: return modifiers | KEY_F10;
                case 23: return modifiers | KEY_F11;
                case 24: return modifiers | KEY_F12;
                default: break;
            }
            return -1;
        case '<': { // Mouse clicks
            int buttons = nextnum(fd, &c);
            if (c != ';') return -1;
            int x = nextnum(fd, &c);
            if (c != ';') return -1;
            int y = nextnum(fd, &c);
            if (c != 'm' && c != 'M') return -1;

            if (mouse_x) *mouse_x = x - 1;
            if (mouse_y) *mouse_y = y - 1;

            if (buttons & 4) modifiers |= MOD_SHIFT;
            if (buttons & 8) modifiers |= MOD_META;
            if (buttons & 16) modifiers |= MOD_CTRL;
            int key = -1;
            switch (buttons & ~(4|8|16)) {
                case 0: key = c == 'm' ? MOUSE_LEFT_RELEASE : MOUSE_LEFT_PRESS; break;
                case 1: key = c == 'm' ? MOUSE_MIDDLE_RELEASE : MOUSE_MIDDLE_PRESS; break;
                case 2: key = c == 'm' ? MOUSE_RIGHT_RELEASE : MOUSE_RIGHT_PRESS; break;
                case 32: key = MOUSE_LEFT_DRAG; break;
                case 33: key = MOUSE_MIDDLE_DRAG; break;
                case 34: key = MOUSE_RIGHT_DRAG; break;
                case 64: key = MOUSE_WHEEL_RELEASE; break;
                case 65: key = MOUSE_WHEEL_PRESS; break;
                default: return -1;
            }
            if (key == MOUSE_LEFT_RELEASE || key == MOUSE_RIGHT_RELEASE || key == MOUSE_MIDDLE_RELEASE) {
                static int lastclick = -1;
                static struct timespec lastclicktime = {0, 0};
                struct timespec clicktime;
                clock_gettime(CLOCK_MONOTONIC, &clicktime);
                if (key == lastclick) {
                    double dt_ms = 1e3*(double)(clicktime.tv_sec - lastclicktime.tv_sec)
                        + 1e-6*(double)(clicktime.tv_nsec - lastclicktime.tv_nsec);
                    if (dt_ms < BTUI_DOUBLECLICK_THRESHOLD) {
                        switch (key) {
                            case MOUSE_LEFT_RELEASE: key = MOUSE_LEFT_DOUBLE; break;
                            case MOUSE_RIGHT_RELEASE: key = MOUSE_RIGHT_DOUBLE; break;
                            case MOUSE_MIDDLE_RELEASE: key = MOUSE_MIDDLE_DOUBLE; break;
                            default: break;
                        }
                    }
                }
                lastclicktime = clicktime;
                lastclick = key;
            }
            return modifiers | key;
        }
        default:
            if ('0' <= c && c <= '9') {
                // Ps prefix
                for (numcode = 0; '0' <= c && c <= '9'; c = nextchar(fd))
                    numcode = 10*numcode + (c - '0');
                if (c == ';') {
                    modifiers = nextnum(fd, &c);
                    modifiers = (modifiers >> 1) << MOD_BITSHIFT;
                }
                goto CSI_start;
            }
    }
    return -1;

  DCS:
    return -1;

  SS3:
    switch (nextchar(fd)) {
        case 'P': return KEY_F1;
        case 'Q': return KEY_F2;
        case 'R': return KEY_F3;
        case 'S': return KEY_F4;
        default: break;
    }
    return -1;
}

/*
 * Populate `buf` with the name of a key.
 */
char *btui_keyname(int key, char *buf)
{
    if (key == -1) return buf + sprintf(buf, "<none>");
    if (key & MOD_META) buf = stpcpy(buf, "Super-");
    if (key & MOD_CTRL) buf = stpcpy(buf, "Ctrl-");
    if (key & MOD_ALT) buf = stpcpy(buf, "Alt-");
    if (key & MOD_SHIFT) buf = stpcpy(buf, "Shift-");
    key &= ~(MOD_META | MOD_CTRL | MOD_ALT | MOD_SHIFT);
    for (size_t i = 0; i < sizeof(key_names)/sizeof(key_names[0]); i++) {
        if (key_names[i].key == key) {
            return stpcpy(buf, key_names[i].name);
        }
    }
    if (' ' < key && key <= '~')
        return buf + sprintf(buf, "%c", key);
    else
        return buf + sprintf(buf, "\\x%02X", (unsigned int)key);
}

/*
 * Return the key with the given name, if one exists, otherwise -1.
 * (i.e. btui_keynamed("Space") == ' ', btui_keynamed("x") == 'x', btui_keynamed("F1") == KEY_F1, btui_keynamed("???") == -1)
 */
int btui_keynamed(const char *name)
{
    int modifiers = 0;
    static const struct { const char *prefix; int modifier; } modnames[] = {
        {"Super-", MOD_META}, {"Ctrl-", MOD_CTRL}, {"Alt-", MOD_ALT}, {"Shift-", MOD_SHIFT}
    };
  check_names:
    for (size_t i = 0; i < sizeof(key_names)/sizeof(key_names[0]); i++) {
        if (strcmp(key_names[i].name, name) == 0)
            return modifiers | key_names[i].key;
    }
    for (size_t i = 0; i < sizeof(modnames)/sizeof(modnames[0]); i++) {
        if (strncmp(name, modnames[i].prefix, strlen(modnames[i].prefix)) == 0) {
            modifiers |= modnames[i].modifier;
            name += strlen(modnames[i].prefix);
            goto check_names;
        }
    }
    return strlen(name) == 1 ? name[0] : -1;
}

/*
 * Move the terminal's cursor to the given x,y coordinates.
 */
int btui_move_cursor(btui_t *bt, int x, int y)
{
    return fprintf(bt->out, "\033[%d;%dH", y+1, x+1);
}

/*
 * Hide the terminal cursor.
 */
int btui_hide_cursor(btui_t *bt)
{
    return fputs(T_OFF(T_SHOW_CURSOR), bt->out);
}

/*
 * Output a string to the terminal.
 */
int btui_puts(btui_t *bt, const char *s)
{
    int ret = fputs(s, bt->out);
    return ret;
}

/*
 * Scroll the given screen region by the given amount. This is much faster than
 * redrawing many lines.
 */
int btui_scroll(btui_t *bt, int firstline, int lastline, int scroll_amount)
{
    if (scroll_amount > 0) {
        return fprintf(bt->out, "\033[%d;%dr\033[%dS\033[r",
                       firstline+1, lastline+1, scroll_amount);
    } else if (scroll_amount < 0) {
        return fprintf(bt->out, "\033[%d;%dr\033[%dT\033[r",
                       firstline+1, lastline+1, -scroll_amount);
    }
    return 0;
}

/*
 * Set the given text attributes on the terminal output.
 */
int btui_set_attributes(btui_t *bt, attr_t attrs)
{
    int printed = fputs("\033[", bt->out);
    for (int i = 0; i < 64; i++) {
        if (attrs & (1ul << i)) {
            attrs ^= (1ul << i);
            if (attrs)
                printed += fprintf(bt->out, "%d;", i);
            else
                printed += fprintf(bt->out, "%d", i);
        }
    }
    printed += fputs("m", bt->out);
    return printed;
}

/*
 * Set the terminal text background color to the given RGB value.
 */
int btui_set_bg(btui_t *bt, unsigned char r, unsigned char g, unsigned char b)
{
    return fprintf(bt->out, "\033[48;2;%d;%d;%dm", r, g, b);
}

/*
 * Set the terminal text background color to the given hexidecimal value.
 */
int btui_set_bg_hex(btui_t *bt, int hex)
{
    return fprintf(bt->out, "\033[48;2;%d;%d;%dm",
                   (hex >> 16) & 0xFF, (hex >> 8) & 0xFF, hex & 0xFF);
}

/*
 * Set the cursor shape.
 */
int btui_set_cursor(btui_t *bt, cursor_t cur)
{
    return fprintf(bt->out, "\033[%u q", cur);
}

/*
 * Set the terminal text foreground color to the given RGB value.
 */
int btui_set_fg(btui_t *bt, unsigned char r, unsigned char g, unsigned char b)
{
    return fprintf(bt->out, "\033[38;2;%d;%d;%dm", r, g, b);
}

/*
 * Set the terminal text foreground color to the given hexidecimal value.
 */
int btui_set_fg_hex(btui_t *bt, int hex)
{
    return fprintf(bt->out, "\033[38;2;%d;%d;%dm",
                   (hex >> 16) & 0xFF, (hex >> 8) & 0xFF, hex & 0xFF);
}

/*
 * Show the terminal cursor.
 */
int btui_show_cursor(btui_t *bt)
{
    return fputs(T_ON(T_SHOW_CURSOR), bt->out);
}

/*
 * Suspend the current application. This will leave TUI mode and typically drop
 * to the console. Normally, this would be caused by Ctrl-z, but BTUI
 * intercepts Ctrl-z and requires you to handle it manually.
 */
int btui_suspend(btui_t *bt)
{
    (void)bt;
    return kill(getpid(), SIGTSTP);
}

#endif
// vim: ts=4 sw=0 et cino=L2,l1,(0,W4,m1