package database;

import java.io.File;

import java.io.FileNotFoundException;

import java.io.RandomAccessFile;

import java.util.Scanner;

public class QueryHandler{

public static void parse(String query)

{

String[] substrings = query.split(" ");

switch (substrings[0])

{

case "create":

createQuery(query);

break;

case "insert":

insertQuery(query);

break;

case "select":

selectQuery(query);

break;

case "drop":

dropQuery(query);

break;

case "update":

updateQuery(query);

break;

case "show":

String tables = substrings[1];

System.out.println();

if(tables.equals("tables")){

Commands.show();

}

else{

System.out.println("\nIncorrect input. Please check the readme.txt file to know the supported commands\n");

}

break;

case "exit":

System.out.println();

break;

case "version":

System.out.println("\nDavisBase: Version 1.0\n");

break;

default:

System.out.println("\nIncorrect input. Please check the readme.txt file to know the supported commands\n");

break;

}

}

public static void createQuery(String query){

String[] subs = query.split(" ");

if(subs[1].equals("table")){

String tablename = subs[2];

String[] temp = query.split(tablename);

String temp2 = temp[1].trim();

int length=temp2.length();

if(temp2.charAt(0)=='(' && temp2.charAt(length-1)==')'){

String[] colnames = temp2.substring(1, temp2.length() - 1).split(",");

for (int i = 0; i < colnames.length; i++){

colnames[i] = colnames[i].trim();

}

if (!DavisBase.tableExist(tablename))

{

Commands.createTable(tablename, colnames);

System.out.println("Table "+tablename+" created successfully.\n");

}

else{

System.out.println("Table " + tablename + " already exists.\n");

}

}

else{

System.out.println("Incorrect input. Please check the readme.txt file to know about the supported commands\n");

}

}

else{

System.out.println("Incorrect input. Please check the readme.txt file to know about the supported commands\n");

}

}

public static void insertQuery(String query){

String[] subs = query.split(" ");

String insert_table = subs[2];

String insert_vals1 = query.split("values")[1].trim();

insert_vals1 = insert_vals1.substring(1, insert_vals1.length() - 1);

String[] insert_vals2 = insert_vals1.split(",");

for (int i = 0; i < insert_vals2.length; i++)

insert_vals2[i] = insert_vals2[i].trim();

if (!DavisBase.tableExist(insert_table)) {

System.out.println("Table " + insert_table + " doesn't exist.\n");

return;

}

RandomAccessFile insertfile;

try {

insertfile = new RandomAccessFile("data//user_data//"+insert_table+"//"+insert_table+".tbl", "rw");

Commands.insertInto(insertfile,insert_table, insert_vals2);

System.out.println("Inserted Successfully\n");

insertfile.close();

} catch (Exception e)

{

e.printStackTrace();

}

}

public static void selectQuery(String query){

String[] subs = query.split(" ");

String[] condition;

String[] select_column;

String[] temp = query.split("where");

String[] temp1 = temp[0].split("from");

String table = temp1[1].trim();

String columns = temp1[0].replace("select", "").trim();

if(table.equals("davisbase_tables") || table.equals("davisbase_columns"))

{

if (columns.contains("*"))

{

select_column = new String[1];

select_column[0] = "*";

}

else {

select_column = columns.split(",");

for (int i = 0; i < select_column.length; i++)

select_column[i] = select_column[i].trim();

}

if (temp.length > 1) {

String filter = temp[1].trim();

condition = DavisBase.parserEquation(filter);

} else {

condition = new String[0];

}

if(table.equals("davisbase_tables")){

Commands.select("data//catalog//davisbase_tables.tbl", table, select_column, condition);

System.out.println();

return;

}

else{

Commands.select("data//catalog//davisbase_columns.tbl", table, select_column, condition);

System.out.println();

return;

}

}

else{

if(!DavisBase.tableExist(table)) {

System.out.println("Table " + table + " doesn't exist.");

System.out.println("Please enter the correct table name.\n");

return;

}

}

if (temp.length > 1)

{

String filter = temp[1].trim();

condition = DavisBase.parserEquation(filter);

}

else {

condition = new String[0];

}

if (columns.contains("*")) {

select_column = new String[1];

select_column[0] = "*";

} else {

select_column = columns.split(",");

for (int i = 0; i < select_column.length; i++)

select_column[i] = select_column[i].trim();

}

Commands.select("data//user_data//"+table+"//"+table+".tbl", table, select_column, condition);

System.out.println();

}

public static void updateQuery(String query){

String[] subs = query.split(" ");

String updateTable = subs[1];

String[] update_temp1 = query.split("set");

String[] update_temp2 = update_temp1[1].split("where");

String where = update_temp2[1];

String set = update_temp2[0];

String[] filteredset = DavisBase.parserEquation(set);

String[] filteredwhere = DavisBase.parserEquation(where);

if (!DavisBase.tableExist(updateTable))

{

System.out.println("Table " + updateTable + " does not exist.\n");

return;

}

Commands.update(updateTable, filteredset, filteredwhere);

System.out.println("Table "+updateTable+" updated successfully.\n");

}

public static void dropQuery(String query){

String[] subs = query.split(" ");

if(subs[1].equals("table")){

String dropTable = subs[2];

if (DavisBase.tableExist(dropTable))

{

Commands.drop(dropTable,"user_data");

System.out.println("Table "+dropTable+" dropped successfully.\n");

}

else{

System.out.println("Table " + dropTable + " does not exist.\n");

}

}

else{

System.out.println("Incorrect input. Please check the readme.txt file to know the supported commands\n");

}

}

}