// Copyright 2021-2023 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

/**
 * @file caps_word.c
 * @brief Caps Word implementation
 *
 * For full documentation, see
 * <https://getreuer.info/posts/keyboards/caps-word>
 */

#include "caps_word.h"

#pragma message \
    "Caps Word is now a core QMK feature! To use it, update your QMK set up and see https://docs.qmk.fm/features/caps_word"

#if !defined(IS_QK_MOD_TAP)
// Attempt to detect out-of-date QMK installation, which would fail with
// implicit-function-declaration errors in the code below.
#error "caps_word: QMK version is too old to build. Please update QMK."
#else

// Many keyboards enable the Command feature, which by default is also activated
// by Left Shift + Right Shift. It can be configured to use a different key
// combination by defining IS_COMMAND(). We make a non-fatal warning if Command
// is enabled but IS_COMMAND() is *not* defined.
#if defined(COMMAND_ENABLE) && !defined(IS_COMMAND)
#pragma message \
    "Caps Word and Command should not be enabled at the same time, since both use the Left Shift + Right Shift key combination. Please disable Command, or ensure that `IS_COMMAND` is not set to (get_mods() == MOD_MASK_SHIFT)."
#endif  // defined(COMMAND_ENABLE) && !defined(IS_COMMAND)

static bool caps_word_active = false;

#if CAPS_WORD_IDLE_TIMEOUT > 0
#if CAPS_WORD_IDLE_TIMEOUT < 100 || CAPS_WORD_IDLE_TIMEOUT > 30000
// Constrain timeout to a sensible range. With the 16-bit timer, the longest
// representable timeout is 32768 ms, rounded here to 30000 ms = half a minute.
#error "caps_word: CAPS_WORD_IDLE_TIMEOUT must be between 100 and 30000 ms"
#endif

static uint16_t idle_timer = 0;

void caps_word_task(void) {
  if (caps_word_active && timer_expired(timer_read(), idle_timer)) {
    caps_word_off();
  }
}
#endif  // CAPS_WORD_IDLE_TIMEOUT > 0

#ifdef CAPS_WORD_INVERT_ON_SHIFT
static uint8_t held_mods = 0;

static bool handle_shift(uint16_t keycode, keyrecord_t* record) {
#ifndef NO_ACTION_TAPPING
  switch (keycode) {
    case QK_MOD_TAP ... QK_MOD_TAP_MAX:
      if (record->tap.count == 0) {  // Mod-tap key is held.
        switch (QK_MOD_TAP_GET_MODS(keycode)) {
          case MOD_LSFT:
            keycode = KC_LSFT;
            break;
          case MOD_RSFT:
            keycode = KC_RSFT;
            break;
        }
      }
  }
#endif  // NO_ACTION_TAPPING

  if (keycode == KC_LSFT || keycode == KC_RSFT) {
    const uint8_t mod = MOD_BIT(keycode);

    if (is_caps_word_on()) {
      if (record->event.pressed) {
        held_mods |= mod;
      } else {
        held_mods &= ~mod;
      }
      return false;
    } else if ((held_mods & mod) != 0) {
      held_mods &= ~mod;
      del_mods(mod);
      return record->event.pressed;
    }
  }

  return true;
}
#endif  // CAPS_WORD_INVERT_ON_SHIFT

bool process_caps_word(uint16_t keycode, keyrecord_t* record) {
#ifdef CAPS_WORD_TOGGLE_KEY
  if (keycode == CW_TOGG) {  // Pressing CW_TOGG toggles Caps Word.
    if (record->event.pressed) {
      caps_word_toggle();
    }
    return false;
  }
#endif  // CAPS_WORD_TOGGLE_KEY
#ifdef CAPS_WORD_INVERT_ON_SHIFT
  if (!handle_shift(keycode, record)) {
    return false;
  }
#endif  // CAPS_WORD_INVERT_ON_SHIFT

#ifndef NO_ACTION_ONESHOT
  const uint8_t mods = get_mods() | get_oneshot_mods();
#else
  const uint8_t mods = get_mods();
#endif  // NO_ACTION_ONESHOT

  if (!caps_word_active) {
    // Pressing both shift keys at the same time enables caps word.
    if (mods == MOD_MASK_SHIFT) {
      caps_word_on();
      return false;
    }
    return true;
  } else {
#if CAPS_WORD_IDLE_TIMEOUT > 0
    idle_timer = record->event.time + CAPS_WORD_IDLE_TIMEOUT;
#endif  // CAPS_WORD_IDLE_TIMEOUT > 0
  }

  if (!record->event.pressed) {
    return true;
  }

  if (!(mods & ~(MOD_MASK_SHIFT | MOD_BIT(KC_RALT)))) {
    switch (keycode) {
      // Ignore MO, TO, TG, TT, and OSL layer switch keys.
      case QK_MOMENTARY ... QK_MOMENTARY_MAX:
      case QK_TO ... QK_TO_MAX:
      case QK_TOGGLE_LAYER ... QK_TOGGLE_LAYER_MAX:
      case QK_LAYER_TAP_TOGGLE ... QK_LAYER_TAP_TOGGLE_MAX:
      case QK_ONE_SHOT_LAYER ... QK_ONE_SHOT_LAYER_MAX:
      // Ignore AltGr.
      case KC_RALT:
      case OSM(MOD_RALT):
        return true;

#ifndef NO_ACTION_TAPPING
      case QK_MOD_TAP ... QK_MOD_TAP_MAX:
        if (record->tap.count == 0) {  // Mod-tap key is held.
          // Corresponding to how mods are handled above:
          // * For shift mods, pass KC_LSFT or KC_RSFT to caps_word_press_user()
          //   to determine whether to continue Caps Word.
          // * For Shift + AltGr (MOD_RSFT | MOD_RALT), pass RSFT(KC_RALT).
          // * AltGr (MOD_RALT) is ignored.
          // * Otherwise stop Caps Word.
          const uint8_t mods = QK_MOD_TAP_GET_MODS(keycode);
          switch (mods) {
            case MOD_LSFT:
              keycode = KC_LSFT;
              break;
            case MOD_RSFT:
              keycode = KC_RSFT;
              break;
            case MOD_RSFT | MOD_RALT:
              keycode = RSFT(KC_RALT);
              break;
            default:
              if (mods != MOD_RALT) {
                caps_word_off();
#ifdef CAPS_WORD_INVERT_ON_SHIFT
                add_mods(held_mods);
#endif  // CAPS_WORD_INVERT_ON_SHIFT
              }
              return true;
          }
        } else {
          keycode = QK_MOD_TAP_GET_TAP_KEYCODE(keycode);
        }
        break;

#ifndef NO_ACTION_LAYER
      case QK_LAYER_TAP ... QK_LAYER_TAP_MAX:
#endif  // NO_ACTION_LAYER
        if (record->tap.count == 0) {
          return true;
        }
        keycode = QK_LAYER_TAP_GET_TAP_KEYCODE(keycode);
        break;
#endif  // NO_ACTION_TAPPING

#ifdef SWAP_HANDS_ENABLE
      case QK_SWAP_HANDS ... QK_SWAP_HANDS_MAX:
        if (IS_SWAP_HANDS_KEYCODE(keycode) || record->tap.count == 0) {
          return true;
        }
        keycode = QK_SWAP_HANDS_GET_TAP_KEYCODE(keycode);
        break;
#endif  // SWAP_HANDS_ENABLE
    }

    clear_weak_mods();
    if (caps_word_press_user(keycode)) {
#ifdef CAPS_WORD_INVERT_ON_SHIFT
      if (held_mods) {
        set_weak_mods(get_weak_mods() ^ MOD_BIT(KC_LSFT));
      }
#endif  // CAPS_WORD_INVERT_ON_SHIFT
      send_keyboard_report();
      return true;
    }
  }

  caps_word_off();
#ifdef CAPS_WORD_INVERT_ON_SHIFT
  add_mods(held_mods);
#endif  // CAPS_WORD_INVERT_ON_SHIFT
  return true;
}

void caps_word_on(void) {
  if (caps_word_active) {
    return;
  }

  clear_mods();
#ifndef NO_ACTION_ONESHOT
  clear_oneshot_mods();
#endif  // NO_ACTION_ONESHOT
#if CAPS_WORD_IDLE_TIMEOUT > 0
  idle_timer = timer_read() + CAPS_WORD_IDLE_TIMEOUT;
#endif  // CAPS_WORD_IDLE_TIMEOUT > 0

  caps_word_active = true;
  caps_word_set_user(true);
}

void caps_word_off(void) {
  if (!caps_word_active) {
    return;
  }

  unregister_weak_mods(MOD_BIT(KC_LSFT));  // Make sure weak shift is off.
  caps_word_active = false;
  caps_word_set_user(false);
}

void caps_word_toggle(void) {
  if (caps_word_active) {
    caps_word_off();
  } else {
    caps_word_on();
  }
}

bool is_caps_word_on(void) { return caps_word_active; }

__attribute__((weak)) void caps_word_set_user(bool active) {}

__attribute__((weak)) bool caps_word_press_user(uint16_t keycode) {
  switch (keycode) {
    // Keycodes that continue Caps Word, with shift applied.
    case KC_A ... KC_Z:
    case KC_MINS:
      add_weak_mods(MOD_BIT(KC_LSFT));  // Apply shift to the next key.
      return true;

    // Keycodes that continue Caps Word, without shifting.
    case KC_1 ... KC_0:
    case KC_BSPC:
    case KC_DEL:
    case KC_UNDS:
      return true;

    default:
      return false;  // Deactivate Caps Word.
  }
}
#endif  // version check