package main

import (
	"database/sql"
	"fmt"
	"log"
	"crypto/md5"
	"strings"
	"net"
	"encoding/json"
	_ "github.com/mattn/go-sqlite3"
)

type Data struct {
	Type int `json:"type"`
	URL string `json:"url"`
}

var DB *sql.DB
func init_DB() {
	var err error;
	DB, err = sql.Open("sqlite3", "./app.db");
	if err != nil {
		log.Fatal(err);
	}

	sql_q := `
		CREATE TABLE IF NOT EXISTS urls (
			id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
			url TEXT NOT NULL,
			short TEXT NOT NULL UNIQUE
		)`;

	_, err = DB.Exec(sql_q);
	if err != nil {
		log.Fatal(err);
	}
}

var units = [16]string{"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f"};
func gen_hash(url string) string{
	data := []byte(url);
	hash := md5.Sum(data);
	var ret string;
	for i := 0; i < 3; i++ {
		ret = ret + units[hash[i] / 16];
		ret = ret + units[hash[i] % 16];
	}
	return ret;
}

func correct_url(url string) string {
	if(url[:7] == "https:/") {
		return "https://" + url[7:];
	}
	if(url[:6] == "http:/") {
		return "http://" + url[:6];
	}
	return "https://" + url;
}

func add_url(url string) string{
	hurl := correct_url(url);
	hsh  := gen_hash(hurl);
	fmt.Printf("adding: %s -> %s \n", hurl, hsh);
	_, err := DB.Exec("INSERT INTO urls (url, short) VALUES (?, ?)", hurl, hsh);
	if err != nil {
		var ok bool;
		ok = false;
		tmp := strings.Split(err.Error(), " ");
		for i := 0; i < len(tmp); i++ {
			if tmp[i] == "UNIQUE" {
				ok = true;
				break;
			}
		}
		if ok{
			fmt.Println("hash ja existe na tabela: Deletando valor antigo...");
			_, err := DB.Exec("DELETE FROM urls WHERE short = ?", hsh);
			if err != nil {
				log.Fatal(err);
			}

			fmt.Println("Adicionando...");
			_, err = DB.Exec("INSERT INTO urls (url, short) VALUES (?, ?)", hurl, hsh);
			if err != nil {
				log.Fatal(err);
			}
		}else{
			log.Fatal(err);
		}
	}
	return hsh;	
}

func get_hash_from_db(hash string) string{
	rows, err := DB.Query("SELECT url FROM urls WHERE short = ?", hash);
	if err != nil {
		log.Fatal(err);
	}
	defer rows.Close();

	var url string;
	for rows.Next() {
		err = rows.Scan(&url);
		if err != nil {
			log.Fatal(err);
		}
		fmt.Println(url);
	}
	return url;
}

func read_json(cont []byte) (Data, error) {
	var data Data;
	err := json.Unmarshal(cont, &data);
	if err != nil {
		return data, err;
	}

	return data, nil;
}

func handle_request(conn net.Conn, data Data) {
	if data.Type == 1 {
		ret := add_url(data.URL);
		conn.Write([]byte(fmt.Sprintf("%s\n", ret)));
	}else if data.Type == 2 {
		ret := get_hash_from_db(data.URL);
		conn.Write([]byte(fmt.Sprintf("%s\n", ret)));
	}else {
	}
}
func handle_client(conn net.Conn){
	defer conn.Close();

	buffer := make([]byte, 1024);
	for {
		n, err := conn.Read(buffer);
		if err != nil {
			log.Println(err);
			return;
		}
		fmt.Printf("Recebido: %s\n", buffer[:n]);
		data, err := read_json(buffer[:n]);
		if err != nil {
			log.Println(err);
		}else {
			handle_request(conn, data);
		}
	}
}

func main() {
	init_DB();
	/*add_url("google.com");
	get_hash_from_db("99999e");*/
	ln, err := net.Listen("tcp", "localhost:5555");
	defer ln.Close();
	fmt.Println("Listen on port 5555");
	if err != nil {
		log.Fatal(err);
	}
	
	for {
		conn, err := ln.Accept();
		if err != nil {
			log.Println(err);
			continue;
		}
		fmt.Println("New connection accepted");
		go handle_client(conn);

	}
}