package main

import (
	"fmt"
	"math"

	h "git.bullercodeworks.com/brian/adventofcode/helpers"
)

func main() {
	inp := h.StdinToStringSlice()
	part1(inp)
	fmt.Println()
	part2(inp)
}

func part1(inp []string) {
	fmt.Println("# Part 1")
	games := parseInput(inp)
	var total int
	for i := range games {
		tokens := games[i].Solve()
		if tokens > 0 {
			total = total + tokens
		}
	}
	fmt.Println("Total Tokens:", total)
}

func part2(inp []string) {
	fmt.Println("# Part 2")
	games := parseInput(inp)
	var total int
	for i := range games {
		games[i].Prize.X += 10000000000000
		games[i].Prize.Y += 10000000000000
		tokens := games[i].Solve()
		if tokens > 0 {
			total = total + tokens
		}
	}
	fmt.Println("Total Tokens:", total)
}

type Game struct {
	Line1 h.Coordinate
	Line2 h.Coordinate
	Prize h.Coordinate
}

/*
Our answer is, in algebraic terms:
(g.Line1.X * n) + (g.Line2.X * m) = g.Prize.X
(g.Line1.Y * n) + (g.Line2.Y * m) = g.Prize.Y
where n is the number of 'A' button presses
and m is the number of 'B' button presses

Solving for n & m gives us these formulas:
n = (g.Prize.X * g.Line2.Y - g.Prize.Y * g.Line2.X) / (g.Line1.X * g.Line2.Y - g.Line2.x * g.Line1.Y)
m = (g.Prize.X - g.Line1.X * n) / g.Line2.X
Then just make sure that n and m are integers
*/
func (g *Game) Solve() int {
	n := float64(g.Prize.X*g.Line2.Y-g.Prize.Y*g.Line2.X) / float64(g.Line1.X*g.Line2.Y-g.Line2.X*g.Line1.Y)
	m := (float64(g.Prize.X) - float64(g.Line1.X)*n) / float64(g.Line2.X)
	if math.Mod(n, 1) != 0 || math.Mod(m, 1) != 0 {
		return -1
	}
	return int(n)*3 + int(m)
}

func parseInput(inp []string) []Game {
	var res []Game
	for i := 0; i < len(inp); {
		var line1, line2, prize h.Coordinate
		fmt.Sscanf(inp[i], "Button A: X+%d, Y+%d", &line1.X, &line1.Y)
		fmt.Sscanf(inp[i+1], "Button B: X+%d, Y+%d", &line2.X, &line2.Y)
		fmt.Sscanf(inp[i+2], "Prize: X=%d, Y=%d", &prize.X, &prize.Y)
		g := Game{
			Line1: line1, Line2: line2, Prize: prize,
		}
		res = append(res, g)
		i = i + 4
	}
	return res
}

func (g Game) String() string {
	res := fmt.Sprintf("Button A: X+%d, Y+%d\n", g.Line1.X, g.Line1.Y)
	res = fmt.Sprintf("%sButton B: X+%d, Y+%d\n", res, g.Line2.X, g.Line2.Y)
	res = fmt.Sprintf("%sPrize: X=%d, Y=%d", res, g.Prize.X, g.Prize.Y)
	return res
}