/*
 * Copyright (c) 2020 Peter Johanson <peter@peterjohanson.com>
 *
 * SPDX-License-Identifier: MIT
 */

#define DT_DRV_COMPAT zmk_behavior_mod_tap

#include <device.h>
#include <drivers/behavior.h>
#include <logging/log.h>

#include <zmk/matrix.h>
#include <zmk/endpoints.h>
#include <zmk/event-manager.h>
#include <zmk/events/keycode-state-changed.h>
#include <zmk/events/modifiers-state-changed.h>
#include <zmk/hid.h>

LOG_MODULE_DECLARE(zmk, CONFIG_ZMK_LOG_LEVEL);

#define ZMK_BHV_MOD_TAP_MAX_HELD 4
#define ZMK_BHV_MOD_TAP_MAX_PENDING_KC 4

struct active_mod_tap_item {
  u32_t keycode;
  u8_t mods;
  bool pending;
  zmk_mod_flags active_mods;
};

struct captured_keycode_state_change_item {
  struct keycode_state_changed* event;
  zmk_mod_flags active_mods;
};

struct behavior_mod_tap_config { };
struct behavior_mod_tap_data {
  struct active_mod_tap_item active_mod_taps[ZMK_BHV_MOD_TAP_MAX_HELD];
  struct captured_keycode_state_change_item captured_keycode_events[ZMK_BHV_MOD_TAP_MAX_PENDING_KC];
};

bool have_pending_mods(char *label) {
  struct device *dev = device_get_binding(label);
  struct behavior_mod_tap_data *data = dev->driver_data;

  for (int i = 0; i < ZMK_BHV_MOD_TAP_MAX_HELD; i++) {
    if (data->active_mod_taps[i].mods) {
      LOG_DBG("Found pending mods for %d and keycode 0x%02X", data->active_mod_taps[i].mods, data->active_mod_taps[i].keycode);
      return true;
    }
  }

  return false;
}

struct captured_keycode_state_change_item* find_pending_keycode(struct behavior_mod_tap_data *data, u32_t keycode)
{
  for (int i = 0; i < ZMK_BHV_MOD_TAP_MAX_PENDING_KC; i++) {
    if (data->captured_keycode_events[i].event == NULL) {
      continue;
    }

    if (data->captured_keycode_events[i].event->keycode == keycode) {
      return &data->captured_keycode_events[i];
    }
  }

  return NULL;
}

zmk_mod_flags behavior_mod_tap_active_mods(struct behavior_mod_tap_data *data)
{
  zmk_mod_flags mods = 0;

  for (int i = 0; i < ZMK_BHV_MOD_TAP_MAX_HELD; i++) {
    mods |= data->active_mod_taps[i].mods;
  }

  return mods;
}

int behavior_mod_tap_capture_keycode_event(struct behavior_mod_tap_data *data, struct keycode_state_changed *ev)
{
  for (int i = 0; i < ZMK_BHV_MOD_TAP_MAX_PENDING_KC; i++) {
    if (data->captured_keycode_events[i].event != NULL) {
      continue;
    }

    data->captured_keycode_events[i].event = ev;
    data->captured_keycode_events[i].active_mods = behavior_mod_tap_active_mods(data);
    return 0;
  }

  return -ENOMEM;
}

void behavior_mod_tap_update_active_mods_state(struct behavior_mod_tap_data *data, zmk_mod_flags used_flags)
{
  for (int i = 0; i < ZMK_BHV_MOD_TAP_MAX_HELD; i++) {
    if ((data->active_mod_taps[i].mods & used_flags) == data->active_mod_taps[i].mods) {
      data->active_mod_taps[i].pending = false;
    }
  }
}

// How to pass context to subscription?!
int behavior_mod_tap_listener(const struct zmk_event_header *eh)
{
  if (is_keycode_state_changed(eh) && have_pending_mods(DT_INST_LABEL(0))) {
    struct device *dev = device_get_binding(DT_INST_LABEL(0));
    struct keycode_state_changed *ev = cast_keycode_state_changed(eh);
    struct behavior_mod_tap_data *data = dev->driver_data;
    struct captured_keycode_state_change_item* pending_keycode;
    if (ev->state) {
      LOG_DBG("Have pending mods, capturing keycode 0x%02X event to ressend later", ev->keycode);
      behavior_mod_tap_capture_keycode_event(data, ev);
      return ZMK_EV_EVENT_CAPTURED;
    } else if ((pending_keycode = find_pending_keycode(data, ev->keycode)) != NULL) {
      LOG_DBG("Key released, going to activate mods 0x%02X then send pending key press for keycode 0x%02X",
              pending_keycode->active_mods, pending_keycode->event->keycode);

      zmk_hid_register_mods(pending_keycode->active_mods);
      behavior_mod_tap_update_active_mods_state(data, pending_keycode->active_mods);

      ZMK_EVENT_RELEASE(pending_keycode->event);
      k_msleep(10);

      pending_keycode->event = NULL;
      pending_keycode->active_mods = 0;
    }
  }
  return 0;
}

ZMK_LISTENER(behavior_mod_tap, behavior_mod_tap_listener);
ZMK_SUBSCRIPTION(behavior_mod_tap, keycode_state_changed);

static int behavior_mod_tap_init(struct device *dev)
{
	return 0;
};


static int on_keymap_binding_pressed(struct device *dev, u32_t position, u32_t mods, u32_t keycode)
{
  struct behavior_mod_tap_data *data = dev->driver_data;
  LOG_DBG("mods: %d, keycode: 0x%02X", mods, keycode);
  for (int i = 0; i < ZMK_BHV_MOD_TAP_MAX_HELD; i++) {
    if (data->active_mod_taps[i].mods != 0) {
      continue;
    }

    zmk_mod_flags active_mods = behavior_mod_tap_active_mods(data);

    data->active_mod_taps[i].active_mods = active_mods;
    data->active_mod_taps[i].mods = mods;
    data->active_mod_taps[i].keycode = keycode;
    data->active_mod_taps[i].pending = true;

    return 0;
  }

  LOG_WRN("Failed to record mod-tap activation, at maximum concurrent mod-tap activations");

  return -ENOMEM;
}

static int on_keymap_binding_released(struct device *dev, u32_t position, u32_t mods, u32_t keycode)
{
  struct behavior_mod_tap_data *data = dev->driver_data;
  LOG_DBG("mods: %d, keycode: %d", mods, keycode);
  
  for (int i = 0; i < ZMK_BHV_MOD_TAP_MAX_HELD; i++) {
    struct active_mod_tap_item *item = &data->active_mod_taps[i];
    if (item->mods == mods && item->keycode == keycode) {
      if (item->pending) {
        LOG_DBG("Sending un-triggered mod-tap for keycode: 0x%02X", keycode);

        if (item->active_mods) {
          LOG_DBG("Registering recorded active mods captured when mod-tap initially activated: 0x%02X", item->active_mods);
          behavior_mod_tap_update_active_mods_state(data, item->active_mods);
          zmk_hid_register_mods(item->active_mods);
        }

        struct keycode_state_changed *key_press = create_keycode_state_changed(USAGE_KEYPAD, item->keycode, true);
        ZMK_EVENT_RAISE_AFTER(key_press, behavior_mod_tap);
        k_msleep(10);

        for (int j = 0; j < ZMK_BHV_MOD_TAP_MAX_PENDING_KC; j++) {
          if (data->captured_keycode_events[j].event == NULL) {
            continue;
          }

          struct keycode_state_changed *ev = data->captured_keycode_events[j].event;
          data->captured_keycode_events[j].event = NULL;
          data->captured_keycode_events[j].active_mods = 0;
          LOG_DBG("Re-sending latched key press for usage page 0x%02X keycode 0x%02X state %s", ev->usage_page, ev->keycode, (ev->state ? "pressed" : "released"));
          ZMK_EVENT_RELEASE(ev);
          k_msleep(10);
        }

        struct keycode_state_changed *key_release = create_keycode_state_changed(USAGE_KEYPAD, keycode, false);
        LOG_DBG("Sending un-triggered mod-tap release for keycode: 0x%02X", keycode);
        ZMK_EVENT_RAISE_AFTER(key_release, behavior_mod_tap);
        k_msleep(10);

        if (item->active_mods) {
          LOG_DBG("Unregistering recorded active mods captured when mod-tap initially activated: 0x%02X", item->active_mods);
          zmk_hid_unregister_mods(item->active_mods);
          zmk_endpoints_send_report(USAGE_KEYPAD);
        }

        
      } else {
        LOG_DBG("Releasing triggered mods: %d", mods);
        zmk_hid_unregister_mods(mods);
        zmk_endpoints_send_report(USAGE_KEYPAD);
      }

      item->mods = 0;
      item->keycode = 0;
      item->active_mods = 0;

      LOG_DBG("Removing mods %d from active_mods for other held mod-taps", mods);
      for (int j = 0; j < ZMK_BHV_MOD_TAP_MAX_HELD; j++) {
        if (data->active_mod_taps[j].active_mods & mods) {
          LOG_DBG("Removing 0x%02X from active mod tap mods 0x%02X keycode 0x%02X", mods, data->active_mod_taps[j].mods, data->active_mod_taps[j].keycode);
          data->active_mod_taps[j].active_mods &= ~mods;
        }
      }
      break;
    }
  }

  return 0;
}

static const struct behavior_driver_api behavior_mod_tap_driver_api = {
  .binding_pressed = on_keymap_binding_pressed,
  .binding_released = on_keymap_binding_released,
};

static const struct behavior_mod_tap_config behavior_mod_tap_config = {};

static struct behavior_mod_tap_data behavior_mod_tap_data;

DEVICE_AND_API_INIT(behavior_mod_tap, DT_INST_LABEL(0), behavior_mod_tap_init,
                    &behavior_mod_tap_data,
                    &behavior_mod_tap_config,
                    APPLICATION, CONFIG_KERNEL_INIT_PRIORITY_DEFAULT,
                    &behavior_mod_tap_driver_api);