/*
  StarForth — Steady-State Virtual Machine Runtime
  Copyright (c) 2023–2026 Robert A. James. All rights reserved.
  Licensed under the Starship License, Version 1.0 (SL-1.0).
 */

/**
 * usb_kbd.c - a USB boot-protocol keyboard's reports, as key events
 * (2026-10-14, boards/BRINGUP.md A3). See usb_kbd.h.
 *
 * A boot report says which keys are held now, not what changed: what was
 * held in the report before and is not now has been released, and the
 * other way round has been pressed. The eight modifier bits are keys too
 * (left/right Ctrl, Shift, Alt, GUI). A report whose keys are all 0x01 is
 * the keyboard's "too many keys" (ErrorRollOver) and changes nothing.
 *
 * Usage IDs (HID Usage Tables 1.12, page 7) become Linux keycodes
 * (input-event-codes.h) -- the same numbers the PS/2 and virtio keyboards
 * already give sk_key_event_poll(). Only the keys a console uses are
 * mapped; others are dropped. The keyboard does not repeat a held key:
 * held is held, and nothing here repeats it either.
 */

#include "starkernel/usb_kbd.h"

/* HID usage ID -> Linux keycode; 0 = not mapped. A full-size keyboard:
 * the main block, F1-F12, the navigation block, arrows and the keypad
 * (Captain Bob, 2026-10-14: "include caps lock, numlock, keypad and
 * arrow"). What a key means -- Caps and Num Lock as toggles, the keypad
 * as digits or navigation -- is the console's (repl.c), for every
 * keyboard alike. */
static const uint8_t usage_to_key[0x66] = {
    [0x04] = 30, [0x05] = 48, [0x06] = 46, [0x07] = 32, [0x08] = 18, /* a b c d e */
    [0x09] = 33, [0x0A] = 34, [0x0B] = 35, [0x0C] = 23, [0x0D] = 36, /* f g h i j */
    [0x0E] = 37, [0x0F] = 38, [0x10] = 50, [0x11] = 49, [0x12] = 24, /* k l m n o */
    [0x13] = 25, [0x14] = 16, [0x15] = 19, [0x16] = 31, [0x17] = 20, /* p q r s t */
    [0x18] = 22, [0x19] = 47, [0x1A] = 17, [0x1B] = 45, [0x1C] = 21, /* u v w x y */
    [0x1D] = 44,                                                      /* z */
    [0x1E] = 2,  [0x1F] = 3,  [0x20] = 4,  [0x21] = 5,  [0x22] = 6,  /* 1 2 3 4 5 */
    [0x23] = 7,  [0x24] = 8,  [0x25] = 9,  [0x26] = 10, [0x27] = 11, /* 6 7 8 9 0 */
    [0x28] = 28, [0x29] = 1,  [0x2A] = 14, [0x2B] = 15, [0x2C] = 57, /* enter esc bksp tab space */
    [0x2D] = 12, [0x2E] = 13, [0x2F] = 26, [0x30] = 27, [0x31] = 43, /* - = [ ] \ */
    [0x32] = 43, [0x33] = 39, [0x34] = 40, [0x35] = 41, [0x36] = 51, /* non-US # ; ' ` , */
    [0x37] = 52, [0x38] = 53, [0x39] = 58,                           /* . / capslock */
    [0x3A] = 59, [0x3B] = 60, [0x3C] = 61, [0x3D] = 62, [0x3E] = 63, /* F1-F5 */
    [0x3F] = 64, [0x40] = 65, [0x41] = 66, [0x42] = 67, [0x43] = 68, /* F6-F10 */
    [0x44] = 87, [0x45] = 88,                                         /* F11 F12 */
    [0x46] = 99,  [0x47] = 70,  [0x48] = 119,                         /* printscreen scrolllock pause */
    [0x49] = 110, [0x4A] = 102, [0x4B] = 104,                         /* insert home pageup */
    [0x4C] = 111, [0x4D] = 107, [0x4E] = 109,                         /* delete end pagedown */
    [0x4F] = 106, [0x50] = 105, [0x51] = 108, [0x52] = 103,           /* right left down up */
    [0x53] = 69,                                                      /* numlock */
    [0x54] = 98,  [0x55] = 55,  [0x56] = 74,  [0x57] = 78,  [0x58] = 96, /* kp/ kp* kp- kp+ kpenter */
    [0x59] = 79,  [0x5A] = 80,  [0x5B] = 81,  [0x5C] = 75,  [0x5D] = 76, /* kp1 kp2 kp3 kp4 kp5 */
    [0x5E] = 77,  [0x5F] = 71,  [0x60] = 72,  [0x61] = 73,  [0x62] = 82, /* kp6 kp7 kp8 kp9 kp0 */
    [0x63] = 83,  [0x64] = 86,  [0x65] = 127,                         /* kp. non-US\ compose(menu) */
};

/* Modifier bit n -> Linux keycode: LCtrl LShift LAlt LGUI RCtrl RShift RAlt RGUI. */
static const uint8_t modifier_key[8] = { 29, 42, 56, 125, 97, 54, 100, 126 };

#define KBD_EVENTS 64u
static struct { uint16_t keycode; uint8_t pressed; } g_events[KBD_EVENTS];
static uint32_t g_head, g_count;
/* Num Lock on to start, matching the console (repl.c). */
static uint8_t g_leds_want = USB_KBD_LED_NUM;

static void push(uint16_t keycode, int pressed)
{
    if (keycode == 0 || g_count == KBD_EVENTS) return; /* a full queue drops: nothing reads it */
    g_events[(g_head + g_count) % KBD_EVENTS].keycode = keycode;
    g_events[(g_head + g_count) % KBD_EVENTS].pressed = (uint8_t)(pressed != 0);
    g_count++;
}

static uint16_t key_for(uint8_t usage)
{
    return usage < sizeof usage_to_key ? usage_to_key[usage] : 0;
}

static int held(const uint8_t *keys, uint32_t n, uint8_t usage)
{
    uint32_t i;
    for (i = 0; i < n; i++)
        if (keys[i] == usage) return 1;
    return 0;
}

void usb_kbd_report(uint8_t prev[8], const uint8_t *report, uint32_t len)
{
    uint8_t now[8] = {0};
    uint32_t i, n;

    if (!report || len < 3) return;
    if (len > 8) len = 8;
    for (i = 0; i < len; i++) now[i] = report[i];
    if (now[2] == 0x01) return;                     /* ErrorRollOver: nothing known */

    for (i = 0; i < 8; i++) {
        uint8_t bit = (uint8_t)(1u << i);
        if ((now[0] & bit) != (prev[0] & bit)) push(modifier_key[i], (now[0] & bit) != 0);
    }
    n = 6;
    for (i = 2; i < 8; i++)                          /* released first, then pressed */
        if (prev[i] > 0x01 && !held(now + 2, n, prev[i])) push(key_for(prev[i]), 0);
    for (i = 2; i < 8; i++)
        if (now[i] > 0x01 && !held(prev + 2, n, now[i])) push(key_for(now[i]), 1);

    for (i = 0; i < 8; i++) prev[i] = now[i];
}

void usb_kbd_forget(uint8_t prev[8])
{
    static const uint8_t none[8] = {0};
    usb_kbd_report(prev, none, 8);   /* everything held, released */
}

void usb_kbd_set_leds(uint8_t leds) { g_leds_want = leds; }

uint8_t usb_kbd_leds_wanted(void) { return g_leds_want; }

int usb_kbd_pop_event(uint16_t *keycode, int *pressed)
{
    if (g_count == 0) return 0;
    *keycode = g_events[g_head].keycode;
    *pressed = g_events[g_head].pressed;
    g_head = (g_head + 1u) % KBD_EVENTS;
    g_count--;
    return 1;
}