/*
 * Copyright 2017 IoT.bzh
 *
 * author: Loïc Collignon <loic.collignon@iot.bzh>
 * author: Jose Bollo <jose.bollo@iot.bzh>
 *
 * 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
 *
 *     http://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.
 */

#define _GNU_SOURCE
#include <unistd.h>
#include <sys/types.h>
#include <pwd.h>
#include <stdio.h>
#include <string.h>
#include <limits.h>

#include <json-c/json.h>

#define AFB_BINDING_VERSION 3
#include <afb/afb-binding.h>

#if !defined(TO_STRING_FLAGS)
# if !defined(JSON_C_TO_STRING_NOSLASHESCAPE)
#  define JSON_C_TO_STRING_NOSLASHESCAPE (1<<4)
# endif
# define TO_STRING_FLAGS (JSON_C_TO_STRING_PLAIN | JSON_C_TO_STRING_NOSLASHESCAPE)
#endif

#if defined(USE_BERKELEY_DB)
#  undef USE_BERKELEY_DB
#endif

#if defined(USE_GDBM)
#  undef USE_GDBM
#  define USE_GDBM        1
#  define USE_BERKELEY_DB 0
#else
#  define USE_GDBM        0
#  define USE_BERKELEY_DB 1
#endif

// ----- Berkeley database -----
#if USE_BERKELEY_DB

#include <db.h>

#define DBFILE	"ll-database-binding.db"
#define DATA	DBT
#define DATA_SET(k,d,s)  do{memset((k),0,sizeof*(k));(k)->data=(void*)d;(k)->size=(uint32_t)s;}while(0)
#define DATA_PTR(k)      ((void*)((k).data))
#define DATA_STR(k)      ((char*)((k).data))
#define DATA_SZ(k)       ((size_t)((k).size))

static DB *database;

static int xdb_open(const char *path)
{
	int ret;

	ret = db_create(&database, NULL, 0);
	if (ret != 0)
	{
		AFB_API_ERROR(afbBindingRoot, "Failed to create database: %s.", db_strerror(ret));
		return -1;
	}

	ret = database->open(database, NULL, path, NULL, DB_BTREE, DB_CREATE, 0600);
	if (ret != 0)
	{
		AFB_API_ERROR(afbBindingRoot, "Failed to open the '%s' database: %s.", path, db_strerror(ret));
		database->close(database, 0);
		return -1;
	}
	return 0;
}

static void xdb_put(afb_req_t req, DBT *key, DBT *data, int replace)
{
	int ret;

	ret = database->put(database, NULL, key, data, replace ? 0 : DB_NOOVERWRITE);
	if (ret == 0)
		afb_req_reply(req, NULL, NULL, NULL);
	else
	{
		AFB_API_ERROR(afbBindingRoot, "can't %s key %s with %s", replace ? "replace" : "insert", DATA_STR(*key), DATA_STR(*data));
		afb_req_reply_f(req, NULL, "failed", "%s", db_strerror(ret));
	}
}

static void xdb_delete(afb_req_t req, DBT *key)
{
	int ret;

	ret = database->del(database, NULL, key, 0);
	if (ret == 0)
		afb_req_reply_f(req, NULL, NULL, NULL);
	else
	{
		AFB_API_ERROR(afbBindingRoot, "can't delete key %s", DATA_STR(*key));
		afb_req_reply_f(req, NULL, "failed", "%s", db_strerror(ret));
	}

	free(DATA_PTR(key));
}

static void verb_read(afb_req_t req)
{
	DATA key;
	DATA data;
	int ret;

	char value[4096];

	struct json_object* result;
	struct json_object* val;


	if (get_key(req, &key))
		return;

	AFB_API_DEBUG(afbBindingRoot, "read: key=%s", DATA_STR(key));

	memset(&data, 0, sizeof data);
	data.data = value;
	data.ulen = 4096;
	data.flags = DB_DBT_USERMEM;

	ret = database->get(database, NULL, &key, &data, 0);
	if (ret == 0)
	{
		result = json_object_new_object();
		val = json_tokener_parse(DATA_STR(data));
		json_object_object_add(result, "value", val ? val : json_object_new_string(DATA_STR(data)));

		afb_req_reply_f(req, result, NULL, "db success: read %s=%s.", DATA_STR(key), DATA_STR(data));
	}
	else
		afb_req_reply_f(req, NULL, "Failed to read datas.", "db fail: read %s - %s", DATA_STR(key), db_strerror(ret));

	free(DATA_PTR(key));
}

#endif

// ----- gdbm database -----
#if USE_GDBM

#include <errno.h>
#include <gdbm.h>

#define DBFILE	"ll-database-binding.dbm"
#define DATA	datum
#define DATA_SET(k,d,s)  do{(k)->dptr=(char*)d;(k)->dsize=(int)s;}while(0)
#define DATA_PTR(k)      ((void*)((k).dptr))
#define DATA_STR(k)      ((char*)((k).dptr))
#define DATA_SZ(k)       ((size_t)((k).dsize))

#if GDBM_VERSION_MAJOR > 1 || (GDBM_VERSION_MAJOR == 1 && GDBM_VERSION_MINOR >= 13)
# define IFSYS(yes,no)   (gdbm_syserr[gdbm_errno] ? (yes) : (no))
#else
# define IFSYS(yes,no)   (no)
#endif

static GDBM_FILE database;

static void onfatal(const char *text)
{
	AFB_API_ERROR(afbBindingRoot, "fatal gdbm message: %s", text);
}

static int xdb_open(const char *path)
{
	database = gdbm_open(path, 512, GDBM_WRCREAT|GDBM_SYNC, 0600, onfatal);
	if (!database)
	{
		AFB_API_ERROR(afbBindingRoot, "Fail to open/create database: %s%s%s",
			gdbm_strerror(gdbm_errno),
			IFSYS(", ", ""),
			IFSYS(strerror(errno), ""));
		return -1;
		
	}
	return 0;
}

static void xdb_put(afb_req_t req, datum *key, datum *data, int replace)
{
	int ret;

	ret = gdbm_store(database, *key, *data, replace ? GDBM_REPLACE : GDBM_INSERT);
	if (ret == 0)
		afb_req_reply(req, NULL, NULL, NULL);
	else
	{
		AFB_API_ERROR(afbBindingRoot, "can't %s key %s with %s: %s%s%s",
			replace ? "replace" : "insert",
			DATA_STR(*key),
			DATA_STR(*data),
			gdbm_strerror(gdbm_errno),
			IFSYS(", ", ""),
			IFSYS(strerror(errno), ""));
		afb_req_reply_f(req, NULL, "failed", "%s", ret > 0 ? "key already exists" : gdbm_strerror(gdbm_errno));
	}
}

static void xdb_delete(afb_req_t req, datum *key)
{
	int ret;

	ret = gdbm_delete(database, *key);
	if (ret == 0)
		afb_req_reply_f(req, NULL, NULL, NULL);
	else
	{
		AFB_API_ERROR(afbBindingRoot, "can't delete key %s: %s%s%s",
			DATA_STR(*key),
			gdbm_strerror(gdbm_errno),
			IFSYS(", ", ""),
			IFSYS(strerror(errno), ""));
		afb_req_reply_f(req, NULL, "failed", "%s", gdbm_strerror(gdbm_errno));
	}
}

static void xdb_get(afb_req_t req, datum *key)
{
	struct json_object* obj;
	struct json_object* args;
	struct json_object* item = NULL;
	datum result;

	/* get the key */
        args = afb_req_json(req);

	obj = json_object_new_object();

	if (json_object_object_get_ex(args, "key", &item))
        {
		json_object_object_add(obj, "key", json_object_get(item));
        }

	result = gdbm_fetch(database, *key);
	if (result.dptr)
	{

		json_object_object_add(obj, "value", json_tokener_parse(result.dptr));

		afb_req_reply(req, obj, NULL, NULL);

		free(result.dptr);

	}
	else
	{
		json_object_object_add(obj, "value", NULL);
		AFB_API_ERROR(afbBindingRoot, "can't get key %s: %s%s%s",
			DATA_STR(*key),
			gdbm_strerror(gdbm_errno),
			IFSYS(", ", ""),
			IFSYS(strerror(errno), ""));
		afb_req_reply_f(req, obj, "failed", "%s", gdbm_strerror(gdbm_errno));
	}
}
#endif

// ----- Binding's implementations -----

/**
 * @brief Get the path to the database
 */
static int get_database_path(char *buffer, size_t size)
{
	static const char dbfile[] = DBFILE;

	char *home, *config;
	int rc;

	config = secure_getenv("XDG_CONFIG_HOME");
	if (config)
		rc = snprintf(buffer, size, "%s/%s", config, dbfile);
	else
	{
		home = secure_getenv("HOME");
		if (home)
			rc = snprintf(buffer, size, "%s/.config/%s", home, dbfile);
		else
		{
			uid_t uid = getuid();
			struct passwd *pwd = getpwuid(uid);
			if (pwd)
				rc = snprintf(buffer, size, "%s/.config/%s", pwd->pw_dir, dbfile);
			else
				rc = snprintf(buffer, size, "/home/%d/.config/%s", (int)uid, dbfile);
		}
	}
	return rc;
}

/**
 * @brief Initialize the binding.
 * @return Exit code, zero if success.
 */
static int ll_database_binding_init(afb_api_t api)
{
	char path[PATH_MAX];
	int ret;

	ret = get_database_path(path, sizeof path);
	if (ret < 0 || (int)ret >=  (int)(sizeof path))
	{
		AFB_API_ERROR(afbBindingRoot, "Can't compute the database filename");
		return -1;
	}

	AFB_API_INFO(afbBindingRoot, "opening database %s", path);
	return xdb_open(path);
}

/**
 * Returns the database key for the 'req'
 */
static int get_key(afb_req_t req, DATA *key)
{
	char *appid, *data;
	const char *jkey;

	size_t ljkey, lappid, size;

	struct json_object* args;
	struct json_object* item;

	/* get the key */
	args = afb_req_json(req);
	if (!json_object_object_get_ex(args, "key", &item))
	{
		afb_req_reply(req, NULL, "no-key", NULL);
		return -1;
	}
	if (!item
     || !(jkey = json_object_to_json_string_ext(item, JSON_C_TO_STRING_PLAIN))
	 || !(ljkey = strlen(jkey)))
	{
		afb_req_reply(req, NULL, "bad-key", NULL);
		return -1;
	}

	/* get the appid */
	appid = afb_req_get_application_id(req);
#if 1
	if (!appid)
		appid = strdup("#UNKNOWN-APP#");
#endif
	if (!appid)
	{
		afb_req_reply(req, NULL, "bad-context", NULL);
		return -1;
	}

	/* make the db-key */
	lappid = strlen(appid);
	size = lappid + ljkey + 2;
	data = realloc(appid, size);
	if (!data)
	{
		free(appid);
		afb_req_reply(req, NULL, "out-of-memory", NULL);
		return -1;
	}
	data[lappid] = ':';
	memcpy(&data[lappid + 1], jkey, ljkey + 1);

	/* return the key */
	DATA_SET(key, data, size);
	return 0;
}

static void put(afb_req_t req, int replace)
{
	DATA key;
	DATA data;

	const char* value;

	struct json_object* args;
	struct json_object* item;

	/* get the value */
	args = afb_req_json(req);
	if (!json_object_object_get_ex(args, "value", &item))
	{
		afb_req_reply(req, NULL, "no-value", NULL);
		return;
	}
	value = json_object_to_json_string_ext(item, TO_STRING_FLAGS);
	if (!value)
	{
		afb_req_reply(req, NULL, "out-of-memory", NULL);
		return;
	}
	DATA_SET(&data, value, strlen(value) + 1); /* includes the tailing null */

	/* get the key */
	if (get_key(req, &key))
		return;

	AFB_API_DEBUG(afbBindingRoot, "put: key=%s, value=%s", DATA_STR(key), DATA_STR(data));
	xdb_put(req, &key, &data, replace);
	free(DATA_PTR(key));
}

static void verb_insert(afb_req_t req)
{
	put(req, 0);
}

static void verb_update(afb_req_t req)
{
	put(req, 1);
}

static void verb_delete(afb_req_t req)
{
	DATA key;

	if (get_key(req, &key))
		return;

	AFB_API_DEBUG(afbBindingRoot, "delete: key=%s", DATA_STR(key));
	xdb_delete(req, &key);
	free(DATA_PTR(key));
}

static void verb_read(afb_req_t req)
{
	DATA key;

	if (get_key(req, &key))
		return;

	AFB_API_DEBUG(afbBindingRoot, "read: key=%s", DATA_STR(key));
	xdb_get(req, &key);
	free(DATA_PTR(key));
}

// ----- Binding's configuration -----
/*
static const struct afb_auth ll_database_binding_auths[] = {
};
*/

#define VERB(name_,auth_,info_,sess_) {\
	.verb = #name_, \
	.callback = verb_##name_, \
	.auth = auth_, \
	.info = info_, \
	.session = sess_ }

static const afb_verb_t ll_database_binding_verbs[]= {
	VERB(insert,	NULL, NULL, AFB_SESSION_NONE),
	VERB(update,	NULL, NULL, AFB_SESSION_NONE),
	VERB(delete,	NULL, NULL, AFB_SESSION_NONE),
	VERB(read,	NULL, NULL, AFB_SESSION_NONE),
        { .verb = NULL}
};

const afb_binding_t afbBindingExport = {
	.api = "persistence",
	.specification = NULL,
	.verbs = ll_database_binding_verbs,
	.preinit = NULL,
	.init = ll_database_binding_init,
	.onevent = NULL,
	.noconcurrency = 0
};