import fs = require('fs');

import * as initSqlJs from 'sql.js';
import initSqlJs2 from 'sql.js';
import initSqlJs3 = require('sql.js');

const DB_PATH = 'data.db';

initSqlJs().then(SQL => {
    function createFile(path: string): void {
        const fd = fs.openSync(path, 'a');
        fs.closeSync(fd);
    }

    // Open the database file. If it does not exist, create a blank database in memory.
    const databaseData = fs.existsSync(DB_PATH) ? fs.readFileSync(DB_PATH) : null;
    const db = new SQL.Database(databaseData);

    // Create a new table 'test_table' in the database in memory.
    const createTableStatement =
        'DROP TABLE IF EXISTS test_table;' + 'CREATE TABLE test_table (id INTEGER PRIMARY KEY, content TEXT);';
    db.run(createTableStatement);

    // Insert 2 records for testing.
    const insertRecordStatement = 'INSERT INTO test_table (id, content) VALUES (@id, @content);';
    db.run(insertRecordStatement, {
        '@id': 1,
        '@content': 'Content 1',
    });
    db.run(insertRecordStatement, {
        '@id': 2,
        '@content': 'Content 2',
    });

    db.getRowsModified();

    try {
        // This query will throw exception: primary key constraint failed.
        db.run(insertRecordStatement, {
            '@id': 1,
            '@content': 'Content 3',
        });
    } catch (ex) {
        console.warn(ex);
    }

    // A simple SELECT query.
    const selectRecordStatement = 'SELECT * FROM test_table WHERE id = @id;';
    const selectStatementObject = db.prepare(selectRecordStatement);
    const results = selectStatementObject.get({
        '@id': 1,
    });
    console.log(results);
    selectStatementObject.free();

    // Access the results one by one, asynchronously.
    const selectRecordsStatement = 'SELECT * FROM test_table;';
    db.each(
        selectRecordsStatement,
        (obj: { [columnName: string]: number | string | Uint8Array }): void => {
            console.log(obj);
        },
        (): void => {
            console.info('Iteration done.');
            dbAccessDone();
        },
    );

    function dbAccessDone(): void {
        // Save the database into SQLite version 3 format.
        if (!fs.existsSync(DB_PATH)) {
            createFile(DB_PATH);
        }
        const exportedData = db.export();
        fs.writeFileSync(DB_PATH, exportedData);

        // Finally, close the database connection and release the resources in memory.
        db.close();
    }

    // Create a database
    const db2 = new SQL.Database();

    // You can also use javascript functions inside your SQL code
    // Create the js function you need
    function add(a: number, b: number): number {
        return a + b;
    }
    // Specifies the SQL function's name, the number of it's arguments, and the js function to use
    db2.create_function('add_js', add);
    // Run a query in which the function is used
    db2.run("INSERT INTO hello VALUES (add_js(7, 3), add_js('Hello ', 'world'));"); // Inserts 10 and 'Hello world'

    new SQL.Database(null);
});