// Package market prices ore and settles deliveries. Prices are integers
// (credits per kg) that fall as supply accumulates and recover over time.
package market

import "wh/world"

var basePrice = [world.NumOre]int64{world.Iron: 2, world.Nickel: 6, world.Ice: 3, world.Platinum: 300}

// saturation is the supply (kg) at which an ore's price has halved.
var saturation = [world.NumOre]int64{world.Iron: 400_000, world.Nickel: 200_000, world.Ice: 300_000, world.Platinum: 5_000}

type Market struct {
	Supply [world.NumOre]int64 // decayed running total of kg sold
	Prices [world.NumOre]int64 // credits per kg, fixed for the day
}

func New() Market {
	m := Market{}
	m.reprice()
	return m
}

func (m *Market) reprice() {
	for o := range m.Prices {
		p := basePrice[o] * saturation[o] / (saturation[o] + m.Supply[o])
		if p < 1 {
			p = 1
		}
		m.Prices[o] = p
	}
}

// Value returns the payout for a cargo at today's prices.
func (m *Market) Value(cargo [world.NumOre]int64) int64 {
	var v int64
	for o, kg := range cargo {
		v += kg * m.Prices[o]
	}
	return v
}

// EndOfDay folds the day's sales into supply (with 10% decay) and reprices.
func (m *Market) EndOfDay(sold [world.NumOre]int64) {
	for o := range m.Supply {
		m.Supply[o] = m.Supply[o]*9/10 + sold[o]
	}
	m.reprice()
}