package main

import (
	"database/sql"
	"fmt"
	"math/rand"
	"net/http"
	"net/url"
	"time"

	_ "modernc.org/sqlite"
)

func main() {
	db, err := sql.Open("sqlite", "base.db")
	if err != nil {
		panic(err)
	}
	defer db.Close()

	_, err = db.Exec("CREATE TABLE IF NOT EXISTS urls (short TEXT, long TEXT)")
	if err != nil {
		panic(err)
	}

	s := "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
	rng := rand.New(rand.NewSource(time.Now().UnixNano()))
	c := rng.Int63()

	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		if r.URL.Path == "/" && r.Method == "GET" {
			fmt.Fprintln(w, "<h1>shortener</h1>")
			fmt.Fprintln(w, "<form method='POST'>")
			fmt.Fprintln(w, "<input name='url' placeholder='https://example.com'>")
			fmt.Fprintln(w, "<button>ok</button>")
			fmt.Fprintln(w, "</form>")
			return
		}

		if r.URL.Path == "/" && r.Method == "POST" {
			a := r.FormValue("url")

			if a == "" {
				fmt.Fprintln(w, "empty")
				return
			}

			u, err := url.Parse(a)
			if err != nil || u.Scheme == "" || u.Host == "" {
				fmt.Fprintln(w, "bad url")
				return
			}

			b := ""
			t := c
			c = c + 1
			for t > 0 {
				b = string(s[t%62]) + b
				t = t / 62
			}
			for len(b) < 6 {
				b = string(s[0]) + b
			}

			// сохранение в базу
			_, err = db.Exec("INSERT INTO urls (short, long) VALUES (?, ?)", b, a)
			if err != nil {
				fmt.Fprintln(w, "db error")
				return
			}

			fmt.Fprintln(w, "short url: http://localhost:8080/"+b)
			return
		}

		x := r.URL.Path[1:]
		y := ""

		err = db.QueryRow("SELECT long FROM urls WHERE short = ?", x).Scan(&y)

		if err != nil || y == "" {
			fmt.Fprintln(w, "not found")
			return
		}

		http.Redirect(w, r, y, 302)
	})

	fmt.Println("start http://localhost:8080")
	http.ListenAndServe(":8080", nil)
}