package main

import (
	"database/sql"
	"flag"
	"fmt"
	"math/rand"
	"os"
	"os/exec"
	"time"

	_ "modernc.org/sqlite"
)

var (
	verbose = flag.Bool("v", false, "debug output")
	file    = flag.String("f", "cards", "cards file")
)

func main() {
	if !*verbose {
		// Seed the RNG
		rand.Seed(time.Now().UnixNano())
	}

	flag.Parse()

	db, err := sql.Open("sqlite", *file)
	if err != nil {
		panic(err)
	}

	// Get number of cards
	var N int
	_ = db.QueryRow("SELECT COUNT(*) FROM cards").Scan(&N)
	s := segmentTree{N, make([]int, 4*N)}

	// Build segment tree
	rows, err := db.Query("SELECT weight FROM cards")
	if err != nil {
		panic(err)
	}
	s.Build(rows, 0, N-1, 1)
	rows.Close()

	if *verbose {
		fmt.Println(s)
	}

	// https://stackoverflow.com/questions/14094190/function-similar-to-getchar
	// disable input buffering
	exec.Command("stty", "-F", "/dev/tty", "cbreak", "min", "1").Run()
	// do not display entered characters on the screen
	exec.Command("stty", "-F", "/dev/tty", "-echo").Run()
	// restore the echoing state when exiting
	defer exec.Command("stty", "-F", "/dev/tty", "echo").Run()

	for {
		// Choose a random card
		x := rand.Intn(s.seg[1])
		w, i := s.Query(x, 0, N-1, 1)

		if *verbose {
			fmt.Println(s.seg[1])
			fmt.Println(x)
			fmt.Println(w)
			fmt.Println(i)
		}

		// Get card contents from database
		var key, val string
		db.QueryRow("SELECT key, val FROM cards WHERE idx=?", i).Scan(&key, &val)
		fmt.Println("> " + key)

		// Wait for confirmation
		var b []byte = make([]byte, 1)
		os.Stdin.Read(b)
		fmt.Println(val)

		// Read user input
		os.Stdin.Read(b)
		if b[0] == byte('y') {
			w >>= 1
		} else if b[0] == byte('n') {
			w <<= 3
		} else {
			return
		}

		// Update segment tree and database
		s.Update(i, w, 0, N-1, 1)
		_, err = db.Exec("UPDATE cards SET weight=? WHERE idx=?", w, i)
		if err != nil {
			panic(err)
		}
	}
}