#include <zephyr/bluetooth/bluetooth.h>
#include <zephyr/bluetooth/conn.h>
#include <zephyr/settings/settings.h>
#include <errno.h>

#include <app_event_manager.h>

#define MODULE ble_bond
#include <caf/events/module_state_event.h>
#include <caf/events/ble_common_event.h>
#include <caf/events/power_event.h>

#include "config_event.h"

#include <zephyr/logging/log.h>
LOG_MODULE_REGISTER(MODULE, LOG_LEVEL_INF);

/* Application-visible options carried by config_event. */
enum ble_bond_cfg_opt {
	BLE_BOND_CFG_PEER_SELECT = 0,
	BLE_BOND_CFG_PEER_ERASE,
	BLE_BOND_CFG_PEER_ERASE_ALL,
	BLE_BOND_CFG_OPT_COUNT
};

/* Module ID in config_event event_id[7:4]. Keep stable for host side tooling. */
#define BLE_BOND_CFG_MODULE_ID  0x01

#define PEER_ID_KEY "peer_id"
#define BT_LUT_KEY  "bt_lut"

enum ble_bond_state {
	BLE_BOND_STATE_DISABLED,
	BLE_BOND_STATE_IDLE,
	BLE_BOND_STATE_STANDBY,
};

BUILD_ASSERT(CONFIG_BT_ID_MAX >= 2, "Need at least one resettable identity");

#define APP_PEER_COUNT (CONFIG_BT_ID_MAX - 1)
#define BLE_BOND_SLOT_COUNT 3

BUILD_ASSERT(BLE_BOND_SLOT_COUNT <= APP_PEER_COUNT,
	     "BLE slot count exceeds available Bluetooth identities");

struct ble_bond_storage {
	uint8_t bt_stack_id_lut[APP_PEER_COUNT];
	bool bt_stack_id_lut_valid;
	uint8_t cur_peer_id;
	bool cur_peer_id_valid;
};

struct ble_bond_ctx {
	enum ble_bond_state state;
	struct ble_bond_storage storage;
	bool auto_switch_in_progress;
};

static struct ble_bond_ctx bond = {
	.state = BLE_BOND_STATE_DISABLED,
};

static const char *state_name(enum ble_bond_state s)
{
	switch (s) {
	case BLE_BOND_STATE_DISABLED:
		return "DISABLED";
	case BLE_BOND_STATE_IDLE:
		return "IDLE";
	case BLE_BOND_STATE_STANDBY:
		return "STANDBY";
	default:
		return "UNKNOWN";
	}
}

static uint8_t get_bt_stack_peer_id(uint8_t app_id)
{
	__ASSERT_NO_MSG(app_id < BLE_BOND_SLOT_COUNT);
	return bond.storage.bt_stack_id_lut[app_id];
}

static int store_peer_id(uint8_t peer_id)
{
	char key[] = MODULE_NAME "/" PEER_ID_KEY;

	return settings_save_one(key, &peer_id, sizeof(peer_id));
}

static int store_bt_stack_id_lut(void)
{
	char key[] = MODULE_NAME "/" BT_LUT_KEY;

	return settings_save_one(key,
				bond.storage.bt_stack_id_lut,
				sizeof(bond.storage.bt_stack_id_lut));
}

static void submit_peer_op_event(enum peer_operation op, uint8_t app_id)
{
	struct ble_peer_operation_event *event = new_ble_peer_operation_event();

	event->op = op;
	event->bt_app_id = app_id;
	event->bt_stack_id = get_bt_stack_peer_id(app_id);
	APP_EVENT_SUBMIT(event);
}

static void init_bt_stack_id_lut(void)
{
	for (size_t i = 0; i < ARRAY_SIZE(bond.storage.bt_stack_id_lut); i++) {
		/* Keep id 0 (BT_ID_DEFAULT) untouched for safe reset/unpair flow. */
		bond.storage.bt_stack_id_lut[i] = i + 1;
	}
}

static bool storage_data_is_valid(void)
{
	if (!bond.storage.cur_peer_id_valid || !bond.storage.bt_stack_id_lut_valid) {
		LOG_WRN("Stored data invalid: peer_valid=%d lut_valid=%d",
			bond.storage.cur_peer_id_valid, bond.storage.bt_stack_id_lut_valid);
		return false;
	}

	if (bond.storage.cur_peer_id >= BLE_BOND_SLOT_COUNT) {
		LOG_WRN("Stored peer id out of range: peer_id=%u max=%u",
			bond.storage.cur_peer_id, BLE_BOND_SLOT_COUNT - 1);
		return false;
	}

	for (size_t i = 0; i < ARRAY_SIZE(bond.storage.bt_stack_id_lut); i++) {
		if ((bond.storage.bt_stack_id_lut[i] == BT_ID_DEFAULT) ||
		    (bond.storage.bt_stack_id_lut[i] >= CONFIG_BT_ID_MAX)) {
			LOG_WRN("Stored LUT invalid at idx=%u value=%u",
				(uint32_t)i, bond.storage.bt_stack_id_lut[i]);
			return false;
		}
	}

	return true;
}

static int settings_set(const char *key, size_t len_rd,
			settings_read_cb read_cb, void *cb_arg)
{
	ssize_t rc;

	if (!strcmp(key, PEER_ID_KEY)) {
		if (len_rd != sizeof(bond.storage.cur_peer_id)) {
			LOG_WRN("Settings '%s' size mismatch: got=%u expect=%u",
				PEER_ID_KEY, (uint32_t)len_rd, sizeof(bond.storage.cur_peer_id));
			bond.storage.cur_peer_id_valid = false;
			return 0;
		}

		rc = read_cb(cb_arg, &bond.storage.cur_peer_id, sizeof(bond.storage.cur_peer_id));
		bond.storage.cur_peer_id_valid = (rc == sizeof(bond.storage.cur_peer_id));
		if (!bond.storage.cur_peer_id_valid) {
			LOG_WRN("Settings '%s' read failed: rc=%d", PEER_ID_KEY, (int)rc);
		}
	} else if (!strcmp(key, BT_LUT_KEY)) {
		if (len_rd != sizeof(bond.storage.bt_stack_id_lut)) {
			LOG_WRN("Settings '%s' size mismatch: got=%u expect=%u",
				BT_LUT_KEY, (uint32_t)len_rd, sizeof(bond.storage.bt_stack_id_lut));
			bond.storage.bt_stack_id_lut_valid = false;
			return 0;
		}

		rc = read_cb(cb_arg,
			    bond.storage.bt_stack_id_lut,
			    sizeof(bond.storage.bt_stack_id_lut));
		bond.storage.bt_stack_id_lut_valid = (rc == sizeof(bond.storage.bt_stack_id_lut));
		if (!bond.storage.bt_stack_id_lut_valid) {
			LOG_WRN("Settings '%s' read failed: rc=%d", BT_LUT_KEY, (int)rc);
		}
	}

	return 0;
}

SETTINGS_STATIC_HANDLER_DEFINE(ble_bond, MODULE_NAME, NULL, settings_set, NULL, NULL);

static int load_identities(void)
{
	bt_addr_le_t addrs[CONFIG_BT_ID_MAX];
	size_t count = ARRAY_SIZE(addrs);

	bt_id_get(addrs, &count);
	LOG_INF("Identity count before ensure: %u / %u", (uint32_t)count, CONFIG_BT_ID_MAX);

	for (; count < CONFIG_BT_ID_MAX; count++) {
		int err = bt_id_create(NULL, NULL);
		if (err < 0) {
			LOG_ERR("Cannot create identity (err:%d)", err);
			return err;
		}
		LOG_INF("Created identity idx=%u", (uint32_t)count);
	}

	return 0;
}

static void disconnect_le_conn_cb(struct bt_conn *conn, void *user_data)
{
	(void)user_data;

	int err = bt_conn_disconnect(conn, BT_HCI_ERR_REMOTE_USER_TERM_CONN);

	if (!err) {
		LOG_INF("Disconnect LE peer for slot switch");
	} else if (err == -ENOTCONN) {
		LOG_INF("LE peer already disconnected during slot switch");
	} else {
		LOG_WRN("Failed to disconnect LE peer for slot switch err=%d", err);
	}
}

struct peer_bond_lookup {
	const bt_addr_le_t *peer_addr;
	bool found;
};

static void peer_bond_lookup_cb(const struct bt_bond_info *info, void *user_data)
{
	struct peer_bond_lookup *lookup = user_data;

	if (!bt_addr_le_cmp(&info->addr, lookup->peer_addr)) {
		lookup->found = true;
	}
}

static bool slot_has_peer_bond(uint8_t app_id, const bt_addr_le_t *peer_addr)
{
	struct peer_bond_lookup lookup = {
		.peer_addr = peer_addr,
	};

	bt_foreach_bond(get_bt_stack_peer_id(app_id), peer_bond_lookup_cb, &lookup);

	return lookup.found;
}

static bool find_peer_owner_slot(const bt_addr_le_t *peer_addr, uint8_t *owner_slot)
{
	for (uint8_t slot = 0; slot < BLE_BOND_SLOT_COUNT; slot++) {
		if (slot_has_peer_bond(slot, peer_addr)) {
			*owner_slot = slot;
			return true;
		}
	}

	return false;
}

static int select_peer(uint8_t peer_id)
{
	if (peer_id >= BLE_BOND_SLOT_COUNT) {
		return -EINVAL;
	}

	uint8_t previous_peer_id = bond.storage.cur_peer_id;

	if (bond.storage.cur_peer_id_valid && (previous_peer_id == peer_id)) {
		LOG_INF("Peer slot already selected: slot=%u stack_id=%u",
			peer_id, get_bt_stack_peer_id(peer_id));
		return 0;
	}

	bond.storage.cur_peer_id = peer_id;
	bond.storage.cur_peer_id_valid = true;

	int err = store_peer_id(bond.storage.cur_peer_id);

	if (err) {
		LOG_ERR("Failed to store peer_id=%u (err:%d)", bond.storage.cur_peer_id, err);
		return err;
	}

	submit_peer_op_event(PEER_OPERATION_SELECTED, bond.storage.cur_peer_id);
	bt_conn_foreach(BT_CONN_TYPE_LE, disconnect_le_conn_cb, NULL);
	return 0;
}

static bool handle_ble_peer_event(const struct ble_peer_event *event)
{
	if (event->state == PEER_STATE_CONNECTED) {
		const bt_addr_le_t *peer_addr = bt_conn_get_dst(event->id);
		uint8_t owner_slot;

		if (!peer_addr) {
			return false;
		}

		if (find_peer_owner_slot(peer_addr, &owner_slot) &&
		    (owner_slot != bond.storage.cur_peer_id)) {
			char addr_str[BT_ADDR_LE_STR_LEN];
			int err;

			bt_addr_le_to_str(peer_addr, addr_str, sizeof(addr_str));
			LOG_INF("Peer %s belongs to slot=%u, auto-switch from slot=%u",
				addr_str, owner_slot, bond.storage.cur_peer_id);

			bond.auto_switch_in_progress = true;
			err = select_peer(owner_slot);
			if (err) {
				bond.auto_switch_in_progress = false;
				LOG_ERR("Auto-switch to slot=%u failed err=%d",
					owner_slot, err);
				module_set_state(MODULE_STATE_ERROR);
			}
		}

		return false;
	}

	if (event->state == PEER_STATE_DISCONNECTED) {
		if (bond.auto_switch_in_progress) {
			bond.auto_switch_in_progress = false;
			LOG_INF("Auto-switch disconnect complete, waiting for reconnect on slot=%u",
				bond.storage.cur_peer_id);
		}
		return false;
	}

	if (event->state != PEER_STATE_SECURED) {
		return false;
	}

	struct bt_conn_info info;
	int err = bt_conn_get_info(event->id, &info);

	if (err) {
		LOG_ERR("Cannot get conn info for secured peer err=%d", err);
		module_set_state(MODULE_STATE_ERROR);
		return false;
	}

	uint8_t expected_stack_id = get_bt_stack_peer_id(bond.storage.cur_peer_id);

	if (info.id == expected_stack_id) {
		LOG_INF("Secured peer matches selected slot=%u stack_id=%u",
			bond.storage.cur_peer_id,
			expected_stack_id);
		return false;
	}

	LOG_INF("Disconnect peer on old id=%u expected=%u selected_slot=%u",
		info.id,
		expected_stack_id,
		bond.storage.cur_peer_id);

	err = bt_conn_disconnect(event->id, BT_HCI_ERR_REMOTE_USER_TERM_CONN);
	if (err && (err != -ENOTCONN)) {
		LOG_ERR("Cannot disconnect peer on old id err=%d", err);
		module_set_state(MODULE_STATE_ERROR);
	}

	return false;
}

static int erase_peer(uint8_t app_id)
{
	uint8_t stack_id = get_bt_stack_peer_id(app_id);
	int err;

	/* Tell ble_adv to restart advertising session for this identity. */
	submit_peer_op_event(PEER_OPERATION_ERASE_ADV, app_id);

	err = bt_unpair(stack_id, NULL);
	if (err) {
		LOG_ERR("Cannot unpair id %u (err:%d)", stack_id, err);
		return err;
	}

	err = bt_id_reset(stack_id, NULL, NULL);
	if (err < 0) {
		LOG_ERR("Cannot reset id %u (err:%d)", stack_id, err);
		return err;
	}

	submit_peer_op_event(PEER_OPERATION_ERASED, app_id);
	return 0;
}

static int erase_all_peers(void)
{
	for (uint8_t i = 0; i < BLE_BOND_SLOT_COUNT; i++) {
		int err = erase_peer(i);
		if (err) {
			return err;
		}
	}

	return 0;
}

static bool handle_config_event(const struct config_event *event)
{
	if (!event->is_request || (event->recipient != CFG_CHAN_RECIPIENT_LOCAL)) {
		return false;
	}

	if (MOD_FIELD_GET(event->event_id) != BLE_BOND_CFG_MODULE_ID) {
		return false;
	}

	struct config_event *rsp = new_config_event(0);
	rsp->transport_id = event->transport_id;
	rsp->is_request = false;
	rsp->event_id = event->event_id;
	rsp->recipient = event->recipient;
	rsp->status = CONFIG_STATUS_REJECT;

	if (event->status == CONFIG_STATUS_SET) {
		uint8_t opt_field = OPT_FIELD_GET(event->event_id);
		uint8_t opt_id = (opt_field == 0) ? UINT8_MAX : OPT_ID_GET(opt_field);

		switch (opt_id) {
		case BLE_BOND_CFG_PEER_SELECT:
			if (event->dyndata.size >= 1) {
				uint8_t peer_id = event->dyndata.data[0];
				if (!select_peer(peer_id)) {
					rsp->status = CONFIG_STATUS_SUCCESS;
				}
			}
			break;

		case BLE_BOND_CFG_PEER_ERASE:
			if (!erase_peer(bond.storage.cur_peer_id)) {
				rsp->status = CONFIG_STATUS_SUCCESS;
			}
			break;

		case BLE_BOND_CFG_PEER_ERASE_ALL:
			if (!erase_all_peers()) {
				rsp->status = CONFIG_STATUS_SUCCESS;
			}
			break;

		default:
			break;
		}
	} else if (event->status == CONFIG_STATUS_FETCH) {
		uint8_t opt_field = OPT_FIELD_GET(event->event_id);
		uint8_t opt_id = (opt_field == 0) ? UINT8_MAX : OPT_ID_GET(opt_field);

		if (opt_id == BLE_BOND_CFG_PEER_SELECT) {
			struct config_event *rsp_data = new_config_event(1);
			rsp_data->transport_id = event->transport_id;
			rsp_data->is_request = false;
			rsp_data->event_id = event->event_id;
			rsp_data->recipient = event->recipient;
			rsp_data->status = CONFIG_STATUS_SUCCESS;
			rsp_data->dyndata.data[0] = bond.storage.cur_peer_id;
			APP_EVENT_SUBMIT(rsp_data);
			return true;
		}
	}

	APP_EVENT_SUBMIT(rsp);
	return true;
}

static int init_after_settings_loaded(void)
{
	int err = load_identities();
	if (err) {
		LOG_ERR("Identity initialization failed: %d", err);
		return err;
	}

	if (!storage_data_is_valid()) {
		LOG_WRN("Stored BLE bond data invalid, reinitializing defaults");
		bond.storage.cur_peer_id = 0;
		bond.storage.cur_peer_id_valid = true;
		init_bt_stack_id_lut();
		bond.storage.bt_stack_id_lut_valid = true;

		err = store_peer_id(bond.storage.cur_peer_id);
		if (err) {
			LOG_ERR("Failed to store peer_id=%u (err:%d)",
				bond.storage.cur_peer_id, err);
			return -EIO;
		}

		err = store_bt_stack_id_lut();
		if (err) {
			LOG_ERR("Failed to store bt_stack_id_lut (err:%d)", err);
			return -EIO;
		}
	}

	bond.state = BLE_BOND_STATE_IDLE;
	LOG_INF("ble_bond init done: state=%s peer_id=%u stack_id=%u",
		state_name(bond.state),
		bond.storage.cur_peer_id,
		get_bt_stack_peer_id(bond.storage.cur_peer_id));
	submit_peer_op_event(PEER_OPERATION_SELECTED, bond.storage.cur_peer_id);
	module_set_state(MODULE_STATE_READY);

	return 0;
}

static bool app_event_handler(const struct app_event_header *aeh)
{
	if (is_module_state_event(aeh)) {
		const struct module_state_event *event = cast_module_state_event(aeh);

		if (check_state(event, MODULE_ID(settings_loader), MODULE_STATE_READY) &&
		    (bond.state == BLE_BOND_STATE_DISABLED)) {
			LOG_INF("settings_loader ready, starting ble_bond init");
			int err = init_after_settings_loaded();
			if (err) {
				LOG_ERR("ble_bond init failed (err:%d), state=%s",
					err, state_name(bond.state));
				module_set_state(MODULE_STATE_ERROR);
			}
		}

		return false;
	}

	if (is_power_down_event(aeh)) {
		if (bond.state == BLE_BOND_STATE_IDLE) {
			bond.state = BLE_BOND_STATE_STANDBY;
			module_set_state(MODULE_STATE_OFF);
		}
		return false;
	}

	if (is_wake_up_event(aeh)) {
		if (bond.state == BLE_BOND_STATE_STANDBY) {
			bond.state = BLE_BOND_STATE_IDLE;
			module_set_state(MODULE_STATE_READY);
			submit_peer_op_event(PEER_OPERATION_SELECTED, bond.storage.cur_peer_id);
		}
		return false;
	}

	if (is_ble_peer_event(aeh)) {
		return handle_ble_peer_event(cast_ble_peer_event(aeh));
	}

	if (is_config_event(aeh)) {
		return handle_config_event(cast_config_event(aeh));
	}

	__ASSERT_NO_MSG(false);
	return false;
}

APP_EVENT_LISTENER(MODULE, app_event_handler);
APP_EVENT_SUBSCRIBE(MODULE, module_state_event);
APP_EVENT_SUBSCRIBE(MODULE, power_down_event);
APP_EVENT_SUBSCRIBE(MODULE, wake_up_event);
APP_EVENT_SUBSCRIBE(MODULE, ble_peer_event);
APP_EVENT_SUBSCRIBE_EARLY(MODULE, config_event);