/*
 * Copyright 2011 - 2017 Maas-Maarten Zeeman
 *
 * 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.
*/

/* adapted for sqlcipher by: Felix Kiunke <dev@fkiunke.de> */

/*
 * sqlcipher_nif -- an erlang sqlite nif.
*/

#include <erl_nif.h>
#include <string.h>
#include <stdio.h>
#include <limits.h>

#include <sqlite3.h>
#include "queue.h"

#define MAX_ATOM_LENGTH 255 /* from atom.h, not exposed in erlang include */
#define MAX_PATHNAME 512 /* unfortunately not in sqlite.h. */
#define MAX_KEY_LENGTH 8192

static ErlNifResourceType *esqlcipher_connection_type = NULL;
static ErlNifResourceType *esqlcipher_statement_type = NULL;

/* database connection context */
typedef struct {
    ErlNifTid tid;
    ErlNifThreadOpts* opts;
    ErlNifPid notification_pid;

    sqlite3 *db;
    queue *commands;

} esqlcipher_connection;

/* prepared statement */
typedef struct {
    sqlite3_stmt *statement;
} esqlcipher_statement;


typedef enum {
    cmd_unknown,
    cmd_open,
    cmd_key,
    cmd_rekey,
    cmd_update_hook_set,
    cmd_notification,
    cmd_exec,
    cmd_changes,
    cmd_prepare,
    cmd_bind,
    cmd_multi_step,
    cmd_reset,
    cmd_column_names,
    cmd_column_types,
    cmd_close,
    cmd_stop,
    cmd_insert,
    cmd_get_autocommit,
} command_type;

typedef struct {
    command_type type;

    ErlNifEnv *env;
    ERL_NIF_TERM ref;
    ErlNifPid pid;
    ERL_NIF_TERM arg;
    ERL_NIF_TERM stmt;
} esqlcipher_command;

static ERL_NIF_TERM atom_ok;
static ERL_NIF_TERM atom_true;
static ERL_NIF_TERM atom_false;
static ERL_NIF_TERM atom_nil;
static ERL_NIF_TERM atom_blob;
static ERL_NIF_TERM atom_error;
static ERL_NIF_TERM atom_interror;
static ERL_NIF_TERM atom_badarg;
static ERL_NIF_TERM atom_oom;
static ERL_NIF_TERM atom_rows;
static ERL_NIF_TERM atom_busy;
static ERL_NIF_TERM atom_done;
static ERL_NIF_TERM atom_esqlcipher;
static ERL_NIF_TERM atom_esqlcipher_raise;

static ERL_NIF_TERM push_command(ErlNifEnv *env, esqlcipher_connection *conn, esqlcipher_command *cmd);

static ERL_NIF_TERM
make_atom(ErlNifEnv *env, const char *atom_name)
{
    ERL_NIF_TERM atom;

    if (enif_make_existing_atom(env, atom_name, &atom, ERL_NIF_LATIN1))
	   return atom;

    return enif_make_atom(env, atom_name);
}

static ERL_NIF_TERM
make_ok_tuple(ErlNifEnv *env, ERL_NIF_TERM value)
{
    return enif_make_tuple2(env, atom_ok, value);
}

static ERL_NIF_TERM
make_error_tuple(ErlNifEnv *env, const char *type, const char *reason)
{
    return enif_make_tuple2(env, atom_error,
        enif_make_tuple2(env, make_atom(env, type),
            enif_make_string(env, reason, ERL_NIF_LATIN1)));
}

/*static ERL_NIF_TERM
make_row_tuple(ErlNifEnv *env, ERL_NIF_TERM value)
{
    return enif_make_tuple2(env, make_atom(env, "row"), value);
}*/

static const char *
get_sqlite3_return_code_msg(int r)
{
    switch(r) {
    case SQLITE_OK: return "ok";
    case SQLITE_ERROR : return "sqlite_error";
    case SQLITE_INTERNAL: return "internal";
    case SQLITE_PERM: return "perm";
    case SQLITE_ABORT: return "abort";
    case SQLITE_BUSY: return "busy";
    case SQLITE_LOCKED: return  "locked";
    case SQLITE_NOMEM: return  "nomem";
    case SQLITE_READONLY: return  "readonly";
    case SQLITE_INTERRUPT: return  "interrupt";
    case SQLITE_IOERR: return  "ioerror";
    case SQLITE_CORRUPT: return  "corrupt";
    case SQLITE_NOTFOUND: return  "notfound";
    case SQLITE_FULL: return  "full";
    case SQLITE_CANTOPEN: return  "cantopen";
    case SQLITE_PROTOCOL: return  "protocol";
    case SQLITE_EMPTY: return  "empty";
    case SQLITE_SCHEMA: return  "schema";
    case SQLITE_TOOBIG: return  "toobig";
    case SQLITE_CONSTRAINT: return  "constraint";
    case SQLITE_MISMATCH: return  "mismatch";
    case SQLITE_MISUSE: return  "misuse";
    case SQLITE_NOLFS: return  "nolfs";
    case SQLITE_AUTH: return  "auth";
    case SQLITE_FORMAT: return  "format";
    case SQLITE_RANGE: return  "range";
    case SQLITE_NOTADB: return  "notadb";
    case SQLITE_ROW: return  "row";
    case SQLITE_DONE: return  "done";
    }
    return  "unknown";
}

static const char *
get_sqlite3_error_msg(int error_code, sqlite3 *db)
{
    static const char *msg;

    if (error_code == SQLITE_MISUSE)
        return "Sqlite3 was invoked incorrectly.";

    msg = sqlite3_errmsg(db);
    if (!msg)
        return "No sqlite3 error message found.";

    return msg;
}

static ERL_NIF_TERM
make_sqlite3_error_tuple(ErlNifEnv *env, int error_code, sqlite3 *db)
{
    const char *error_code_msg = get_sqlite3_return_code_msg(error_code);
    const char *msg = get_sqlite3_error_msg(error_code, db);

    return enif_make_tuple2(env, atom_error,
        enif_make_tuple2(env, make_atom(env, error_code_msg),
            enif_make_string(env, msg, ERL_NIF_LATIN1)));
}

static void
command_destroy(void *obj)
{
    esqlcipher_command *cmd = (esqlcipher_command *) obj;

    if (cmd->env != NULL)
	   enif_free_env(cmd->env);

    enif_free(cmd);
}

static esqlcipher_command *
command_create()
{
    esqlcipher_command *cmd = (esqlcipher_command *) enif_alloc(sizeof(esqlcipher_command));
    if (cmd == NULL)
	   return NULL;

    cmd->env = enif_alloc_env();
    if (cmd->env == NULL) {
	    command_destroy(cmd);
        return NULL;
    }

    cmd->type = cmd_unknown;
    cmd->ref = 0;
    cmd->arg = 0;
    cmd->stmt = 0;

    return cmd;
}

/*
 *
 */
static void
destroy_esqlcipher_connection(ErlNifEnv *env, void *arg)
{
    esqlcipher_connection *db = (esqlcipher_connection *) arg;
    esqlcipher_command *cmd = command_create();

    /* Send the stop command
     */
    cmd->type = cmd_stop;
    queue_push(db->commands, cmd);

    /* Wait for the thread to finish
     */
    enif_thread_join(db->tid, NULL);

    enif_thread_opts_destroy(db->opts);

    /* The thread has finished... now remove the command queue, and close
     * the database (if it was still open).
     */
    while(queue_has_item(db->commands)) {
        command_destroy(queue_pop(db->commands));
    }
    queue_destroy(db->commands);

    sqlite3_close_v2(db->db);
    db->db = NULL;
}

static void
destroy_esqlcipher_statement(ErlNifEnv *env, void *arg)
{
    esqlcipher_statement *stmt = (esqlcipher_statement *) arg;
    sqlite3_finalize(stmt->statement);
    stmt->statement = NULL;
}

static ERL_NIF_TERM
do_open(ErlNifEnv *env, esqlcipher_connection *db, const ERL_NIF_TERM arg)
{
    ErlNifBinary bin;
    ERL_NIF_TERM eos = enif_make_int(env, 0);
    int rc;
    ERL_NIF_TERM error;

    if (!enif_inspect_iolist_as_binary(env, enif_make_list2(env, arg, eos), &bin)) {
        return atom_badarg;
    }

    if (bin.size <= 0 || bin.size > MAX_PATHNAME) {
        return atom_badarg;
    }

    /* Open the database.
     */
    rc = sqlite3_open((char *)bin.data, &db->db);
    if (rc != SQLITE_OK) {
        error = make_sqlite3_error_tuple(env, rc, db->db);
        sqlite3_close_v2(db->db);
        db->db = NULL;
     
        return error;
    }

    sqlite3_busy_timeout(db->db, 2000);

    return atom_ok;
}

static ERL_NIF_TERM
do_key(ErlNifEnv *env, esqlcipher_connection *conn, const ERL_NIF_TERM arg) 
{
    ErlNifBinary bin;

    if (!enif_inspect_iolist_as_binary(env, arg, &bin)) {
        return atom_badarg;
    }

    if (bin.size > INT_MAX || bin.size < 1)
        return atom_badarg;

    int rc;

    rc = sqlite3_key(conn->db, bin.data, bin.size);
    if (rc != SQLITE_OK) {
        return make_sqlite3_error_tuple(env, rc, conn->db);
    }

    return atom_ok;
}

static ERL_NIF_TERM
do_rekey(ErlNifEnv *env, esqlcipher_connection *conn, const ERL_NIF_TERM arg) 
{
    ErlNifBinary bin;

    if (!enif_inspect_iolist_as_binary(env, arg, &bin)) {
        return atom_badarg;
    }

    if (bin.size > INT_MAX || bin.size < 1)
        return atom_badarg;

    int rc;

    rc = sqlite3_rekey(conn->db, bin.data, bin.size);
    if (rc != SQLITE_OK)
        return make_sqlite3_error_tuple(env, rc, conn->db);

    return atom_ok;
}

void
update_callback(void *arg, int sqlite_operation_type, char const *sqlite_database, char const *sqlite_table, sqlite3_int64 sqlite_rowid)
{
    esqlcipher_connection *db = (esqlcipher_connection *)arg;
    esqlcipher_command *cmd = NULL;
    ERL_NIF_TERM type, table, rowid;
    cmd = command_create();

    if (db == NULL)
        return;

    if (!cmd)
	    return;

    rowid = enif_make_int64(cmd->env, sqlite_rowid);
    table = enif_make_string(cmd->env, sqlite_table, ERL_NIF_LATIN1);

    switch(sqlite_operation_type) {
        case SQLITE_INSERT:
            type = make_atom(cmd->env, "insert");
            break;
        case SQLITE_DELETE:
            type = make_atom(cmd->env, "delete");
            break;
        case SQLITE_UPDATE:
            type = make_atom(cmd->env, "update");
            break;
        default:
            return;
    }
    cmd->type = cmd_notification;
    cmd->arg = enif_make_tuple3(cmd->env, type, table, rowid);
    push_command(cmd->env, db, cmd);
}

static ERL_NIF_TERM
do_set_update_hook(ErlNifEnv *env, esqlcipher_connection *db, const ERL_NIF_TERM arg)
{
    if (!enif_get_local_pid(env, arg, &db->notification_pid))
	    return atom_badarg;

    sqlite3_update_hook(db->db, NULL, NULL);
    if (sqlite3_update_hook(db->db, update_callback, db) != SQLITE_OK)
        return atom_error;

    return atom_ok;
}

/*
 * Execute sql statement
 */
static ERL_NIF_TERM
do_exec(ErlNifEnv *env, esqlcipher_connection *conn, const ERL_NIF_TERM arg)
{
    ErlNifBinary bin;
    int rc;
    ERL_NIF_TERM eos = enif_make_int(env, 0);

    if (!enif_inspect_iolist_as_binary(env, enif_make_list2(env, arg, eos), &bin)) {
        return atom_badarg;
    }

    rc = sqlite3_exec(conn->db, (char *) bin.data, NULL, NULL, NULL);
    if (rc != SQLITE_OK)
	    return make_sqlite3_error_tuple(env, rc, conn->db);

    return atom_ok;
}

/*
 * Nr of changes
 */
static ERL_NIF_TERM
do_changes(ErlNifEnv *env, esqlcipher_connection *conn, const ERL_NIF_TERM arg)
{
    sqlite3_int64 changes = sqlite3_changes(conn->db);

    ERL_NIF_TERM changes_term = enif_make_int64(env, changes);
    return changes_term;
}

/*
* insert action
*/
static ERL_NIF_TERM
do_insert(ErlNifEnv *env, esqlcipher_connection *conn, const ERL_NIF_TERM arg)
{
    ErlNifBinary bin;
    int rc;
    ERL_NIF_TERM eos = enif_make_int(env, 0);

    if (!enif_inspect_iolist_as_binary(env, enif_make_list2(env, arg, eos), &bin)) {
        return atom_badarg;
    }

    rc = sqlite3_exec(conn->db, (char *) bin.data, NULL, NULL, NULL);
    if (rc != SQLITE_OK)
        return make_sqlite3_error_tuple(env, rc, conn->db);
    sqlite3_int64 last_rowid = sqlite3_last_insert_rowid(conn->db);
    ERL_NIF_TERM last_rowid_term = enif_make_int64(env, last_rowid);
    return make_ok_tuple(env, last_rowid_term);
}

/*
 */
static ERL_NIF_TERM
do_prepare(ErlNifEnv *env, esqlcipher_connection *conn, const ERL_NIF_TERM arg)
{
    ErlNifBinary bin;
    esqlcipher_statement *stmt;
    ERL_NIF_TERM esqlcipher_stmt;
    const char *tail;
    int rc;
    ERL_NIF_TERM eos = enif_make_int(env, 0);

    if (!enif_inspect_iolist_as_binary(env, enif_make_list2(env, arg, eos), &bin))
	    return atom_badarg;

    stmt = enif_alloc_resource(esqlcipher_statement_type, sizeof(esqlcipher_statement));
    if (!stmt)
	    return atom_oom;

    rc = sqlite3_prepare_v2(conn->db, (char *) bin.data, bin.size, &(stmt->statement), &tail);
    if (rc != SQLITE_OK) {
        enif_release_resource(stmt);
        return make_sqlite3_error_tuple(env, rc, conn->db);
    }

    esqlcipher_stmt = enif_make_resource(env, stmt);
    enif_release_resource(stmt);

    return make_ok_tuple(env, esqlcipher_stmt);
}

static int
bind_cell(ErlNifEnv *env, const ERL_NIF_TERM cell, sqlite3_stmt *stmt)
{
    int i;
    int cell_arity;
    const ERL_NIF_TERM* cell_tuple;
    char param_name[MAX_ATOM_LENGTH+2];
    ERL_NIF_TERM value;

    int the_int;
    ErlNifSInt64 the_long_int;
    double the_double;
    char the_atom[MAX_ATOM_LENGTH+1];
    ErlNifBinary the_blob;
    int arity;
    const ERL_NIF_TERM* tuple;

    if (!enif_get_tuple(env, cell, &cell_arity, &cell_tuple) || cell_arity != 2) {
        return -1;
    }

    // If the first element of the tuple is an integer, take it as the param id
    if (!enif_get_int(env, cell_tuple[0], &i)) {
        // Otherwise, it must be an atom:
        if (enif_get_atom(env, cell_tuple[0], param_name + 1, MAX_ATOM_LENGTH + 1, ERL_NIF_LATIN1)) {
            // The first character (:, @, or $) is part of the parameter name;
            // if the passed atom contains none of these characters, we prefix :
            if (param_name[1] == ':' || param_name[1] == '@' || param_name[1] == '$') {
                // Get the id for the named parameter
                i = sqlite3_bind_parameter_index(stmt, param_name + 1);
            } else {
                param_name[0] = ':';
                i = sqlite3_bind_parameter_index(stmt, param_name);
            }
            if (i <= 0) { // Non-existent parameter
                return -2;
            }
        } else {
            return -1;
        }
    }

    value = cell_tuple[1];

    if (enif_get_int(env, value, &the_int))
	    return sqlite3_bind_int(stmt, i, the_int);

    if (enif_get_int64(env, value, &the_long_int))
        return sqlite3_bind_int64(stmt, i, the_long_int);

    if (enif_get_double(env, value, &the_double))
	    return sqlite3_bind_double(stmt, i, the_double);

    if (enif_get_atom(env, value, the_atom, sizeof(the_atom), ERL_NIF_LATIN1)) {
	    if (strcmp("nil", the_atom) == 0) {
	       return sqlite3_bind_null(stmt, i);
	    }

	    return -1;
    }

    /* Bind as text assume it is utf-8 encoded text */
    if (enif_inspect_iolist_as_binary(env, value, &the_blob)) {
        return sqlite3_bind_text(stmt, i, (char *) the_blob.data, the_blob.size, SQLITE_TRANSIENT);
    }

    /* Check for blob tuple */
    if (enif_get_tuple(env, value, &arity, &tuple)) {
        if (arity != 2)
            return -1;

        /* length 2! */
        if (enif_get_atom(env, tuple[0], the_atom, sizeof(the_atom), ERL_NIF_LATIN1)) {
            /* its a blob... */
            if (0 == strcmp("$blob", the_atom)) {
                /* with a iolist as argument */
                if (enif_inspect_iolist_as_binary(env, tuple[1], &the_blob)) {
                    /* kaboom... get the blob */
	                return sqlite3_bind_blob(stmt, i, the_blob.data, the_blob.size, SQLITE_TRANSIENT);
                }
            }
        }
    }

    return -1;
}

static ERL_NIF_TERM
do_bind(ErlNifEnv *env, sqlite3 *db, sqlite3_stmt *stmt, const ERL_NIF_TERM arg)
{
    int rc;
    ERL_NIF_TERM list, head, tail;

    if (!enif_is_list(env, arg)) {
	    return atom_badarg;
    }

    list = arg;

    while (enif_get_list_cell(env, list, &head, &tail)) {
        rc = bind_cell(env, head, stmt);
        if (rc == -2) {
            return make_error_tuple(env, "badarg", "invalid parameter name");
        }
        if (rc < 0) {
            return make_error_tuple(env, "badarg", "invalid parameter type");
        }
        if (rc != SQLITE_OK) {
            return make_sqlite3_error_tuple(env, rc, db);
        }
        list = tail;
    }

    return atom_ok;
}

static ERL_NIF_TERM
do_get_autocommit(ErlNifEnv *env, esqlcipher_connection *conn)
{
    if (sqlite3_get_autocommit(conn->db) != 0) {
        return atom_true;
    } else {
        return atom_false;
    }
}

static ERL_NIF_TERM
make_cell(ErlNifEnv *env, sqlite3_stmt *statement, unsigned int i)
{
    int type = sqlite3_column_type(statement, i);
    ERL_NIF_TERM bin;
    const void *blob;
    unsigned char *bindata;
    size_t bytes;

    switch(type) {
    case SQLITE_INTEGER:
        return enif_make_int64(env, sqlite3_column_int64(statement, i));
    case SQLITE_FLOAT:
        return enif_make_double(env, sqlite3_column_double(statement, i));
    case SQLITE_NULL:
        return atom_nil;
    case SQLITE_BLOB:
    case SQLITE_TEXT:
        blob = sqlite3_column_blob(statement, i);
        if (blob == NULL) {
            return atom_oom;
        }
        bytes = sqlite3_column_bytes(statement, i);
        bindata = enif_make_new_binary(env, bytes, &bin);
        memcpy(bindata, blob, bytes);

        if (type == SQLITE_BLOB) {
            return enif_make_tuple2(env, atom_blob, bin);
        } else {
            return bin;
        }
    default:
        return atom_interror;
    }
}

static ERL_NIF_TERM
make_row(ErlNifEnv *env, sqlite3_stmt *statement, ERL_NIF_TERM *array, int size)
{
    if (!array) {
        return atom_oom;
    }

    for (int i = 0; i < size; i++) {
        array[i] = make_cell(env, statement, i);
        if (array[i] == atom_oom || array[i] == atom_interror) {
            return array[i];
        }
    }

    return enif_make_list_from_array(env, array, size);
}

static ERL_NIF_TERM
do_multi_step(ErlNifEnv *env, sqlite3 *db, sqlite3_stmt *stmt, const ERL_NIF_TERM arg)
{
    ERL_NIF_TERM status;
    ERL_NIF_TERM rows = enif_make_list_from_array(env, NULL, 0);
    ERL_NIF_TERM *rowBuffer = NULL;
    int rowBufferSize = 0;

    int chunk_size = 0;
    enif_get_int(env, arg, &chunk_size);

    int rc = sqlite3_step(stmt);
    while (rc == SQLITE_ROW && chunk_size-- > 0)
    {
        if (!rowBufferSize)
            rowBufferSize = sqlite3_column_count(stmt);
        if (rowBuffer == NULL)
            rowBuffer = (ERL_NIF_TERM *) enif_alloc(sizeof(ERL_NIF_TERM)*rowBufferSize);

        rows = enif_make_list_cell(env, make_row(env, stmt, rowBuffer, rowBufferSize), rows);

        if (rows == atom_oom || rows == atom_interror) {
            return rows;
        }

        if (chunk_size > 0)
            rc = sqlite3_step(stmt);
    }

    switch(rc) {
    case SQLITE_ROW:
        status = atom_rows;
        break;
    case SQLITE_BUSY:
        status = atom_busy;
        break;
    case SQLITE_DONE:
        /*
        * Automatically reset the statement after a done so
        * column_names will work after the statement is done.
        *
        * Not resetting the statement can lead to vm crashes.
        */
        sqlite3_reset(stmt);
        status = atom_done;
        break;
    default:
        /* We use prepare_v2, so any error code can be returned. */
        return make_sqlite3_error_tuple(env, rc, db);
    }

    enif_free(rowBuffer);
    return enif_make_tuple2(env, status, rows);
}

static ERL_NIF_TERM
do_reset(ErlNifEnv *env, sqlite3 *db, sqlite3_stmt *stmt, const ERL_NIF_TERM arg)
{
    char the_atom[MAX_ATOM_LENGTH+1];
    int clear_values;

    if (enif_get_atom(env, arg, the_atom, sizeof(the_atom), ERL_NIF_LATIN1)) {
        if (0 == strcmp("false", the_atom)) {
            clear_values = 0;
        } else if (0 == strcmp("true", the_atom)) {
            clear_values = 1;
        } else {
            return atom_badarg;
        }
    } else {
        return atom_badarg;
    }

    int rc = sqlite3_reset(stmt);

    if (rc == SQLITE_OK && clear_values == 1) {
        rc = sqlite3_clear_bindings(stmt);
    }

    if (rc == SQLITE_OK) {
        return atom_ok;
    }

    return make_sqlite3_error_tuple(env, rc, db);
}

static ERL_NIF_TERM
do_column_names(ErlNifEnv *env, sqlite3_stmt *stmt)
{
    int i, size, len;
    const char *name;
    unsigned char *binname;
    ERL_NIF_TERM *array;
    ERL_NIF_TERM column_names;

    size = sqlite3_column_count(stmt);
    if (size == 0) {
        return make_ok_tuple(env, enif_make_list(env, 0));
    } else if (size < 0) {
        return atom_oom;
    }

    array = (ERL_NIF_TERM *) enif_alloc(sizeof(ERL_NIF_TERM) * size);
    if (!array) {
        return atom_oom;
    }

    for (i = 0; i < size; i++) {
        name = sqlite3_column_name(stmt, i);
        if (name == NULL) {
            enif_free(array);
            return atom_oom;
        }

        len = strlen(name);
        binname = enif_make_new_binary(env, len, &array[i]);
        memcpy(binname, name, len);
    }

    column_names = enif_make_list_from_array(env, array, size);
    enif_free(array);
    return make_ok_tuple(env, column_names);
}

static ERL_NIF_TERM
do_column_types(ErlNifEnv *env, sqlite3_stmt *stmt)
{
    int i, size, len;
    const char *type;
    unsigned char *bintype;
    ERL_NIF_TERM *array;
    ERL_NIF_TERM column_types;

    size = sqlite3_column_count(stmt);
    if (size == 0) {
        return make_ok_tuple(env, enif_make_list(env, 0));
    } else if (size < 0) {
        return atom_oom;
    }

    array = (ERL_NIF_TERM *) enif_alloc(sizeof(ERL_NIF_TERM) * size);
    if (!array)
        return atom_oom;

    for (i = 0; i < size; i++) {
        type = sqlite3_column_decltype(stmt, i);
        if (type == NULL) {
	       array[i] = atom_nil;
        } else {
            len = strlen(type);
            bintype = enif_make_new_binary(env, len, &array[i]);
            memcpy(bintype, type, len);
        }
    }

    column_types = enif_make_list_from_array(env, array, size);
    enif_free(array);
    return make_ok_tuple(env, column_types);
}

static ERL_NIF_TERM
do_close(ErlNifEnv *env, esqlcipher_connection *conn, const ERL_NIF_TERM arg)
{
    int rc;

    rc = sqlite3_close_v2(conn->db);
    if (rc != SQLITE_OK)
	    return make_sqlite3_error_tuple(env, rc, conn->db);

    conn->db = NULL;
    return atom_ok;
}

static ERL_NIF_TERM
evaluate_command(esqlcipher_command *cmd, esqlcipher_connection *conn)
{
    esqlcipher_statement *stmt = NULL;

    if (cmd->stmt) {
        if (!enif_get_resource(cmd->env, cmd->stmt, esqlcipher_statement_type, (void **) &stmt)) {
	       return atom_interror;
        }
    }

    switch(cmd->type) {
    case cmd_open:
        return do_open(cmd->env, conn, cmd->arg);
    case cmd_key:
        return do_key(cmd->env, conn, cmd->arg);
    case cmd_rekey:
        return do_rekey(cmd->env, conn, cmd->arg);
    case cmd_update_hook_set:
        return do_set_update_hook(cmd->env, conn, cmd->arg);
    case cmd_exec:
	    return do_exec(cmd->env, conn, cmd->arg);
    case cmd_changes:
	    return do_changes(cmd->env, conn, cmd->arg);
    case cmd_prepare:
	    return do_prepare(cmd->env, conn, cmd->arg);
    case cmd_multi_step:
        return do_multi_step(cmd->env, conn->db, stmt->statement, cmd->arg);
    case cmd_reset:
	    return do_reset(cmd->env, conn->db, stmt->statement, cmd->arg);
    case cmd_bind:
	    return do_bind(cmd->env, conn->db, stmt->statement, cmd->arg);
    case cmd_column_names:
	    return do_column_names(cmd->env, stmt->statement);
    case cmd_column_types:
	    return do_column_types(cmd->env, stmt->statement);
    case cmd_close:
	    return do_close(cmd->env, conn, cmd->arg);
	case cmd_insert:
	    return do_insert(cmd->env, conn, cmd->arg);
    case cmd_get_autocommit:
        return do_get_autocommit(cmd->env, conn);
    default:
	    return atom_interror;
    }
}

static ERL_NIF_TERM
push_command(ErlNifEnv *env, esqlcipher_connection *conn, esqlcipher_command *cmd) {
    if (!queue_push(conn->commands, cmd))
        return enif_raise_exception(env, atom_interror);

    return atom_ok;
}

static ERL_NIF_TERM
make_answer(esqlcipher_command *cmd, ERL_NIF_TERM answer)
{
    if (answer == atom_badarg || answer == atom_oom || answer == atom_error || answer == atom_interror) {
        return enif_make_tuple3(cmd->env, atom_esqlcipher_raise, cmd->ref, answer);
    } else {
        return enif_make_tuple3(cmd->env, atom_esqlcipher, cmd->ref, answer);
    }
}

static void *
esqlcipher_connection_run(void *arg)
{
    esqlcipher_connection *db = (esqlcipher_connection *) arg;
    esqlcipher_command *cmd;
    int continue_running = 1;

    while(continue_running) {
	    cmd = queue_pop(db->commands);

	    if (cmd->type == cmd_stop) {
	        continue_running = 0;
        } else if (cmd->type == cmd_notification) {
            enif_send(NULL, &db->notification_pid, cmd->env, cmd->arg);
        } else {
	        enif_send(NULL, &cmd->pid, cmd->env, make_answer(cmd, evaluate_command(cmd, db)));
        }

	    command_destroy(cmd);
    }

    return NULL;
}

/*
 * Start the processing thread
 */
static ERL_NIF_TERM
esqlcipher_start(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
{
    esqlcipher_connection *conn;
    ERL_NIF_TERM db_conn;

    /* Initialize the resource */
    conn = enif_alloc_resource(esqlcipher_connection_type, sizeof(esqlcipher_connection));
    if (!conn)
	    return enif_raise_exception(env, atom_oom);

    conn->db = NULL;

    /* Create command queue */
    conn->commands = queue_create();
    if (!conn->commands) {
	    enif_release_resource(conn);
	    return enif_raise_exception(env, atom_interror);
    }

    /* Start command processing thread */
    conn->opts = enif_thread_opts_create("esqldb_thread_opts");
    if (enif_thread_create("esqlcipher_connection", &conn->tid, esqlcipher_connection_run, conn, conn->opts) != 0) {
	    enif_release_resource(conn);
	    return enif_raise_exception(env, atom_interror);
    }

    db_conn = enif_make_resource(env, conn);
    enif_release_resource(conn);

    return make_ok_tuple(env, db_conn);
}

/*
 * Open the database
 */
static ERL_NIF_TERM
esqlcipher_open(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
{
    esqlcipher_connection *db;
    esqlcipher_command *cmd = NULL;
    ErlNifPid pid;

    if (argc != 4) {
	    return enif_make_badarg(env);
    }
    if (!enif_get_resource(env, argv[0], esqlcipher_connection_type, (void **) &db)) {
	    return enif_make_badarg(env);
    }
    if (!enif_is_ref(env, argv[1])) {
	    return enif_make_badarg(env);
    }
    if (!enif_get_local_pid(env, argv[2], &pid)) {
	    return enif_make_badarg(env);
    }

    if (!sqlite3_threadsafe()) {
        // sqlite3 was not build thread safe (built with -DSQLITE_THREADSAFE=0)
	    return enif_raise_exception(env, atom_interror);
    }

    /* Note, no check is made for the type of the argument */
    cmd = command_create();
    if (!cmd) {
	    return enif_raise_exception(env, atom_interror);
    }

    cmd->type = cmd_open;
    cmd->ref = enif_make_copy(cmd->env, argv[1]);
    cmd->pid = pid;
    cmd->arg = enif_make_copy(cmd->env, argv[3]);

    return push_command(env, db, cmd);
}

static ERL_NIF_TERM
set_update_hook(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
{
    esqlcipher_connection *db;
    esqlcipher_command *cmd = NULL;
    ErlNifPid pid;

    if (argc != 4)
	    return enif_make_badarg(env);
    if (!enif_get_resource(env, argv[0], esqlcipher_connection_type, (void **) &db))
	    return enif_make_badarg(env);
    if (!enif_is_ref(env, argv[1]))
	    return enif_make_badarg(env);
    if (!enif_get_local_pid(env, argv[2], &pid))
	    return enif_make_badarg(env);

    cmd = command_create();
    if (!cmd)
	    return enif_raise_exception(env, atom_interror);

    /* command */
    cmd->type = cmd_update_hook_set;
    cmd->ref = enif_make_copy(cmd->env, argv[1]);
    cmd->pid = pid;
    cmd->arg = enif_make_copy(cmd->env, argv[3]);

    return push_command(env, db, cmd);
}

/*
 * Give a database key
 */
static ERL_NIF_TERM
esqlcipher_key(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
{
    esqlcipher_connection *db;
    esqlcipher_command *cmd = NULL;
    ErlNifPid pid;
     
    if (argc != 4)
        return enif_make_badarg(env);
    if (!enif_get_resource(env, argv[0], esqlcipher_connection_type, (void **) &db))
        return enif_make_badarg(env);
    if (!enif_is_ref(env, argv[1]))
        return enif_make_badarg(env);
    if (!enif_get_local_pid(env, argv[2], &pid))
        return enif_make_badarg(env);

    /* Note, no check is made for the type of the argument */
    cmd = command_create();
    if (!cmd)
        return enif_raise_exception(env, atom_interror);

    cmd->type = cmd_key;
    cmd->ref = enif_make_copy(cmd->env, argv[1]);
    cmd->pid = pid;
    cmd->arg = enif_make_copy(cmd->env, argv[3]);

    return push_command(env, db, cmd);
}

/*
 * Change the database key
 */
static ERL_NIF_TERM
esqlcipher_rekey(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
{
    esqlcipher_connection *db;
    esqlcipher_command *cmd = NULL;
    ErlNifPid pid;
     
    if (argc != 4)
        return enif_make_badarg(env);
    if (!enif_get_resource(env, argv[0], esqlcipher_connection_type, (void **) &db))
        return enif_make_badarg(env);
    if (!enif_is_ref(env, argv[1]))
        return enif_make_badarg(env);
    if (!enif_get_local_pid(env, argv[2], &pid))
        return enif_make_badarg(env);

    /* Note, no check is made for the type of the argument */
    cmd = command_create();
    if (!cmd)
        return enif_raise_exception(env, atom_interror);

    cmd->type = cmd_rekey;
    cmd->ref = enif_make_copy(cmd->env, argv[1]);
    cmd->pid = pid;
    cmd->arg = enif_make_copy(cmd->env, argv[3]);

    return push_command(env, db, cmd);
}

/*
 * Execute the sql statement
 */
static ERL_NIF_TERM
esqlcipher_exec(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
{
    esqlcipher_connection *db;
    esqlcipher_command *cmd = NULL;
    ErlNifPid pid;

    if (argc != 4)
	    return enif_make_badarg(env);
    if (!enif_get_resource(env, argv[0], esqlcipher_connection_type, (void **) &db))
	    return enif_make_badarg(env);
    if (!enif_is_ref(env, argv[1]))
	    return enif_make_badarg(env);
    if (!enif_get_local_pid(env, argv[2], &pid))
	    return enif_make_badarg(env);

    cmd = command_create();
    if (!cmd)
	    return enif_raise_exception(env, atom_interror);

    /* command */
    cmd->type = cmd_exec;
    cmd->ref = enif_make_copy(cmd->env, argv[1]);
    cmd->pid = pid;
    cmd->arg = enif_make_copy(cmd->env, argv[3]);

    return push_command(env, db, cmd);
}

/*
 * Count the nr of changes of last statement
 */
static ERL_NIF_TERM
esqlcipher_changes(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
{
    esqlcipher_connection *db;
    esqlcipher_command *cmd = NULL;
    ErlNifPid pid;

    if (argc != 3)
	    return enif_make_badarg(env);
    if (!enif_get_resource(env, argv[0], esqlcipher_connection_type, (void **) &db))
	    return enif_make_badarg(env);
    if (!enif_is_ref(env, argv[1]))
	    return enif_make_badarg(env);
    if (!enif_get_local_pid(env, argv[2], &pid))
	    return enif_make_badarg(env);

    cmd = command_create();
    if (!cmd)
	    return enif_raise_exception(env, atom_interror);

    /* command */
    cmd->type = cmd_changes;
    cmd->ref = enif_make_copy(cmd->env, argv[1]);
    cmd->pid = pid;

    return push_command(env, db, cmd);
}

static ERL_NIF_TERM
esqlcipher_insert(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
{
    esqlcipher_connection *db;
    esqlcipher_command *cmd = NULL;
    ErlNifPid pid;

    if (argc != 4)
        return enif_make_badarg(env);
    if (!enif_get_resource(env, argv[0], esqlcipher_connection_type, (void **) &db))
        return enif_make_badarg(env);
    if (!enif_is_ref(env, argv[1]))
        return enif_make_badarg(env);
    if (!enif_get_local_pid(env, argv[2], &pid))
        return enif_make_badarg(env);

    cmd = command_create();
    if (!cmd)
        return enif_raise_exception(env, atom_interror);

    /* command */
    cmd->type = cmd_insert;
    cmd->ref = enif_make_copy(cmd->env, argv[1]);
    cmd->pid = pid;
    cmd->arg = enif_make_copy(cmd->env, argv[3]);

    return push_command(env, db, cmd);
}

static ERL_NIF_TERM
esqlcipher_get_autocommit(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
{
    esqlcipher_connection *db;
    esqlcipher_command *cmd = NULL;
    ErlNifPid pid;

    if (argc != 3)
        return enif_make_badarg(env);
    if (!enif_get_resource(env, argv[0], esqlcipher_connection_type, (void **) &db))
        return enif_make_badarg(env);
    if (!enif_is_ref(env, argv[1]))
        return enif_make_badarg(env);
    if (!enif_get_local_pid(env, argv[2], &pid))
        return enif_make_badarg(env);

    cmd = command_create();
    if (!cmd)
        return enif_raise_exception(env, atom_interror);

    /* command */
    cmd->type = cmd_get_autocommit;
    cmd->ref = enif_make_copy(cmd->env, argv[1]);
    cmd->pid = pid;

    return push_command(env, db, cmd);
}

/*
 * Prepare the sql statement
 */
static ERL_NIF_TERM
esqlcipher_prepare(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
{
    esqlcipher_connection *conn;
    esqlcipher_command *cmd = NULL;
    ErlNifPid pid;

    if (argc != 4)
	    return enif_make_badarg(env);
    if (!enif_get_resource(env, argv[0], esqlcipher_connection_type, (void **) &conn))
	    return enif_make_badarg(env);
    if (!enif_is_ref(env, argv[1]))
	    return enif_make_badarg(env);
    if (!enif_get_local_pid(env, argv[2], &pid))
	    return enif_make_badarg(env);

    cmd = command_create();
    if (!cmd)
	    return enif_raise_exception(env, atom_interror);

    cmd->type = cmd_prepare;
    cmd->ref = enif_make_copy(cmd->env, argv[1]);
    cmd->pid = pid;
    cmd->arg = enif_make_copy(cmd->env, argv[3]);

    return push_command(env, conn, cmd);
}

/*
 * Bind a variable to a prepared statement
 */
static ERL_NIF_TERM
esqlcipher_bind(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
{
    esqlcipher_connection *conn;
    esqlcipher_statement *stmt;
    esqlcipher_command *cmd = NULL;
    ErlNifPid pid;

    if (argc != 5)
	    return enif_make_badarg(env);

    if (!enif_get_resource(env, argv[0], esqlcipher_connection_type, (void **) &conn))
	    return enif_make_badarg(env);
    if (!enif_get_resource(env, argv[1], esqlcipher_statement_type, (void **) &stmt))
	    return enif_make_badarg(env);
    if (!enif_is_ref(env, argv[2]))
	    return enif_make_badarg(env);
    if (!enif_get_local_pid(env, argv[3], &pid))
	    return enif_make_badarg(env);

    cmd = command_create();
    if (!cmd)
	    return enif_raise_exception(env, atom_interror);

    cmd->type = cmd_bind;
    cmd->ref = enif_make_copy(cmd->env, argv[2]);
    cmd->pid = pid;
    cmd->stmt = enif_make_copy(cmd->env, argv[1]);
    cmd->arg = enif_make_copy(cmd->env, argv[4]);

    return push_command(env, conn, cmd);
}

/*
 * Multi step to a prepared statement
 */
static ERL_NIF_TERM
esqlcipher_multi_step(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
{
    esqlcipher_connection *conn;
    esqlcipher_statement *stmt;
    esqlcipher_command *cmd = NULL;
    ErlNifPid pid;
    int chunk_size = 0;

    if (argc != 5)
        return enif_make_badarg(env);

    if (!enif_get_resource(env, argv[0], esqlcipher_connection_type, (void **) &conn))
        return enif_make_badarg(env);

    if (!enif_get_resource(env, argv[1], esqlcipher_statement_type, (void **) &stmt))
        return enif_make_badarg(env);

    if (!enif_get_int(env, argv[2], &chunk_size))
        return enif_make_badarg(env);

    if (!enif_is_ref(env, argv[3]))
        return enif_make_badarg(env);

    if (!enif_get_local_pid(env, argv[4], &pid))
        return enif_make_badarg(env);

    if (!stmt->statement)
        return enif_make_badarg(env);

    cmd = command_create();
    if (!cmd)
        return enif_raise_exception(env, atom_interror);

    cmd->type = cmd_multi_step;
    cmd->ref = enif_make_copy(cmd->env, argv[3]);
    cmd->pid = pid;
    cmd->stmt = enif_make_copy(cmd->env, argv[1]);
    cmd->arg = enif_make_copy(cmd->env, argv[2]);

    return push_command(env, conn, cmd);
}

/*
 * Reset a prepared statement to its initial state
 */
static ERL_NIF_TERM
esqlcipher_reset(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
{
    esqlcipher_connection *conn;
    esqlcipher_statement *stmt;
    esqlcipher_command *cmd = NULL;
    ErlNifPid pid;

    if (argc != 5)
	    return enif_make_badarg(env);
    if (!enif_get_resource(env, argv[0], esqlcipher_connection_type, (void **) &conn))
	    return enif_make_badarg(env);
    if (!enif_get_resource(env, argv[1], esqlcipher_statement_type, (void **) &stmt))
	    return enif_make_badarg(env);
    if (!enif_is_ref(env, argv[2]))
	    return enif_make_badarg(env);
    if (!enif_get_local_pid(env, argv[3], &pid))
	    return enif_make_badarg(env);
    if (!stmt->statement)
	    return enif_make_badarg(env);

    cmd = command_create();
    if (!cmd)
	   return enif_raise_exception(env, atom_interror);

    cmd->type = cmd_reset;
    cmd->ref = enif_make_copy(cmd->env, argv[2]);
    cmd->pid = pid;
    cmd->stmt = enif_make_copy(cmd->env, argv[1]);
    cmd->arg = enif_make_copy(cmd->env, argv[4]);

    return push_command(env, conn, cmd);
}

/*
 * Get the column names of the prepared statement.
 */
static ERL_NIF_TERM
esqlcipher_column_names(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
{
    esqlcipher_connection *conn;
    esqlcipher_statement *stmt;
    esqlcipher_command *cmd = NULL;
    ErlNifPid pid;

    if (argc != 4)
	    return enif_make_badarg(env);
    if (!enif_get_resource(env, argv[0], esqlcipher_connection_type, (void **) &conn))
	    return enif_make_badarg(env);
    if (!enif_get_resource(env, argv[1], esqlcipher_statement_type, (void **) &stmt))
	    return enif_make_badarg(env);
    if (!enif_is_ref(env, argv[2]))
	    return enif_make_badarg(env);
    if (!enif_get_local_pid(env, argv[3], &pid))
	    return enif_make_badarg(env);
    if (!stmt->statement)
	    return enif_make_badarg(env);

    cmd = command_create();
    if (!cmd)
	    return enif_raise_exception(env, atom_interror);

    cmd->type = cmd_column_names;
    cmd->ref = enif_make_copy(cmd->env, argv[2]);
    cmd->pid = pid;
    cmd->stmt = enif_make_copy(cmd->env, argv[1]);

    return push_command(env, conn, cmd);
}

/*
 * Get the column types of the prepared statement.
 */
static ERL_NIF_TERM
esqlcipher_column_types(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
{
    esqlcipher_connection *conn;
    esqlcipher_statement *stmt;
    esqlcipher_command *cmd = NULL;
    ErlNifPid pid;

    if (argc != 4)
	    return enif_make_badarg(env);

    if (!enif_get_resource(env, argv[0], esqlcipher_connection_type, (void **) &conn))
	    return enif_make_badarg(env);
    if (!enif_get_resource(env, argv[1], esqlcipher_statement_type, (void **) &stmt))
	    return enif_make_badarg(env);
    if (!enif_is_ref(env, argv[2]))
	    return enif_make_badarg(env);
    if (!enif_get_local_pid(env, argv[3], &pid))
	    return enif_make_badarg(env);

    if (!stmt->statement)
	    return enif_make_badarg(env);

    cmd = command_create();
    if (!cmd)
	    return enif_raise_exception(env, atom_interror);

    cmd->type = cmd_column_types;
    cmd->ref = enif_make_copy(cmd->env, argv[2]);
    cmd->pid = pid;
    cmd->stmt = enif_make_copy(cmd->env, argv[1]);

    return push_command(env, conn, cmd);
}

/*
 * Close the database
 */
static ERL_NIF_TERM
esqlcipher_close(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[])
{
    esqlcipher_connection *conn;
    esqlcipher_command *cmd = NULL;
    ErlNifPid pid;

    if (!enif_get_resource(env, argv[0], esqlcipher_connection_type, (void **) &conn))
	    return enif_make_badarg(env);
    if (!enif_is_ref(env, argv[1]))
	    return enif_make_badarg(env);
    if (!enif_get_local_pid(env, argv[2], &pid))
	    return enif_make_badarg(env);

    cmd = command_create();
    if (!cmd)
	    return enif_raise_exception(env, atom_interror);

    cmd->type = cmd_close;
    cmd->ref = enif_make_copy(cmd->env, argv[1]);
    cmd->pid = pid;

    return push_command(env, conn, cmd);
}

/*
 * Load the nif. Initialize some stuff and such
 */
static int
on_load(ErlNifEnv* env, void** priv, ERL_NIF_TERM info)
{
    ErlNifResourceType *rt;
     
    rt = enif_open_resource_type(env, "esqlcipher_nif", "esqlcipher_connection_type",
				destroy_esqlcipher_connection, ERL_NIF_RT_CREATE, NULL);
    if (!rt)
	    return -1;
    esqlcipher_connection_type = rt;

    rt =  enif_open_resource_type(env, "esqlcipher_nif", "esqlcipher_statement_type",
				   destroy_esqlcipher_statement, ERL_NIF_RT_CREATE, NULL);
    if (!rt)
	    return -1;
    esqlcipher_statement_type = rt;

    atom_ok         = make_atom(env, "ok");
    atom_true       = make_atom(env, "true");
    atom_false      = make_atom(env, "false");
    atom_nil        = make_atom(env, "nil");
    atom_blob       = make_atom(env, "$blob");
    atom_rows       = make_atom(env, "rows");
    atom_busy       = make_atom(env, "$busy");
    atom_done       = make_atom(env, "$done");
    atom_error      = make_atom(env, "error");
    atom_interror   = make_atom(env, "esqlcipher_internal_error");
    atom_badarg     = make_atom(env, "badarg");
    atom_oom        = make_atom(env, "oom");
    atom_esqlcipher = make_atom(env, "esqlcipher");
    atom_esqlcipher_raise = make_atom(env, "esqlcipher_raise");

    return 0;
}

static int on_reload(ErlNifEnv* env, void** priv_data, ERL_NIF_TERM load_info)
{
    return 0;
}

static int on_upgrade(ErlNifEnv* env, void** priv, void** old_priv_data, ERL_NIF_TERM load_info)
{
    return 0;
}

static ErlNifFunc nif_funcs[] = {
    {"start", 0, esqlcipher_start},
    {"open", 4, esqlcipher_open},
    {"close", 3, esqlcipher_close},
    {"key", 4, esqlcipher_key},
    {"rekey", 4, esqlcipher_rekey},
    {"exec", 4, esqlcipher_exec},
    {"insert", 4, esqlcipher_insert},
    {"prepare", 4, esqlcipher_prepare},
    {"bind", 5, esqlcipher_bind},
    {"multi_step", 5, esqlcipher_multi_step},
    {"reset", 5, esqlcipher_reset},
    {"changes", 3, esqlcipher_changes},
    {"column_names", 4, esqlcipher_column_names},
    {"column_types", 4, esqlcipher_column_types},
    {"get_autocommit", 3, esqlcipher_get_autocommit},
    {"set_update_hook", 4, set_update_hook}
};

ERL_NIF_INIT(esqlcipher_nif, nif_funcs, on_load, on_reload, on_upgrade, NULL)