package de.srsoftware.widerhall.data;

import de.srsoftware.widerhall.Configuration;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.*;

import static de.srsoftware.widerhall.Util.t;

public class Database {
    public static final String EMAIL = "email";
    public static final String NAME = "name";
    public static final String HASHED_PASS = "hashedPassword";
    public static final String SALT = "salt";

    private static final Logger LOG = LoggerFactory.getLogger(Database.class);
    private static final String VARCHAR = "VARCHAR(255)";
    private static Database singleton = null;
    private static Connection conn;

    public Request insertInto(String tbName) {
        return query("INSERT INTO "+tbName);
    }

    public class Request{

        private final String sql;
        private HashMap<String,List<Object>> where = new HashMap<>();
        private HashMap<String,Object> values = new HashMap<>();

        public Request(String sql) {
            this.sql = sql;
        }

        public Request where(String key, Object ... values) {
            for (var val : values) where(key,val);
            return this;
        }

        public Request where(String key, Object value) {
            var list = where.get(key);
            if (list == null) where.put(key,list = new ArrayList<Object>());
            list.add(value);
            return this;
        }

        public Request values(Map<String,Object> newValues) {
            values.putAll(newValues);
            return this;
        }

        public Request values(String key, Object value) {
            values.put(key,value);
            return this;
        }

        public void run() throws SQLException {
            var sb = new StringBuilder(sql);
            var args = new ArrayList<Object>();
            if (!values.isEmpty()){
                var keys = new ArrayList<String>();
                for (var entry : values.entrySet()) {
                    keys.add(entry.getKey());
                    args.add(entry.getValue());
                }
                sb.append("("+String.join(", ",keys)+")");
                sb.append(" VALUES ");
                var arr = new String[args.size()];
                Arrays.fill(arr,"?");
                var marks = String.join(", ",arr);
                sb.append("(").append(marks).append(")");
            }
            var sql = sb.toString();
            LOG.debug(sql);
            try {
                var stmt = conn.prepareStatement(sql);
                if (!args.isEmpty()) {
                    for (int i = 0; i < args.size(); i++) stmt.setObject(i+1, args.get(i));
                }
                stmt.execute();
            } catch (SQLException sqle) {
                throw new SQLException(t("Query '{}' failed:",sql),sqle);
            }
        }

        public ResultSet exec() throws SQLException {
            var sb = new StringBuilder(sql);
            var args = new ArrayList<Object>();
            if (!where.isEmpty()){
                var clauses = new ArrayList<String>();
                sb.append(" WHERE ");

                for (var entry : where.entrySet()){
                    var arr = new String[entry.getValue().size()];
                    Arrays.fill(arr,"?");
                    var marks = String.join(", ",arr);
                    clauses.add("("+entry.getKey()+" IN ("+marks+"))");
                    args.addAll(entry.getValue());
                }
                sb.append(String.join(" AND ",clauses));

            }
            var sql = sb.toString();
            LOG.debug(sql);
            try {
                var stmt = conn.prepareStatement(sql);
                if (!args.isEmpty()) {
                    for (int i = 0; i < args.size(); i++) stmt.setObject(i+1, args.get(i));
                }
                return stmt.executeQuery();
            } catch (SQLException sqle) {
                throw new SQLException(t("Query '{}' failed:",sql),sqle);
            }
        }
    }

    public Database(Connection connection) {
        this.conn = connection;
    }

    public static Database open() {
        if (singleton == null){
            Configuration config = Configuration.instance();
            var dbFile = config.dbFile();
            String url = "jdbc:sqlite:"+dbFile;
            LOG.debug("Opening {}",url);
            dbFile.getParentFile().mkdirs();
            try {
                singleton = new Database(DriverManager.getConnection(url)).assertTables();
            } catch (SQLException sqle) {
                sqle.printStackTrace();
            }
        }
        return singleton;
    }

    private Database assertTables() throws SQLException {
        if (!tableExists("Users")) createUsersTable();
        return this;
    }

    private void createUsersTable() throws SQLException {
        query("CREATE TABLE Users ("+EMAIL+" "+ VARCHAR +", "+SALT+" "+VARCHAR+", "+HASHED_PASS+" "+VARCHAR+", "+NAME+" "+VARCHAR+");").run();
    }

    private boolean tableExists(String tbName) throws SQLException {
        try {
            ResultSet rs = query("SELECT EXISTS (SELECT name FROM sqlite_schema WHERE type='table' AND name='" + tbName + "')").exec();
            int val = 0;
            if (rs.next()) val = rs.getInt(1);
            rs.close();
            return val > 0;
        } catch (SQLException e) {
            throw new SQLException(t("Was not able to check existence of table {}!",tbName),e);
        }
    }

    public Request query(String sql) {
        return new Request(sql);
    }
}