blah/price.go

package main

import (
	"os"
)

type PriceRecord struct {
	MTGO  map[string]PriceList `json:"mtgo,omitempty"`
	Paper map[string]PriceList `json:"paper,omitempty"`
}

type PricePoints struct {
	Normal map[string]float64 `json:"normal,omitempty"`
	Foil   map[string]float64 `json:"foil,omitempty"`
}

type PriceList struct {
	Retail   *PricePoints `json:"retail,omitempty"`
	Currency string       `json:"currency"`
	Buylist  *PricePoints `json:"buylist,omitempty"`
}

type PriceDB struct {
	Data map[string]PriceRecord `json:"data"`
}

type CardPriceEntry struct {
	UUID     string  `json:"uuid"`
	Price    float64 `json:"price"`
	Currency string  `json:"currency"`
	Seller   string  `json:"seller"`
}

func loadPrices(pricesFile string, priceFilter float64) func() ([]CardPriceEntry, error) {
	return func() ([]CardPriceEntry, error) {
		// Check if prices file exists
		_, err := os.Stat(pricesFile)
		if os.IsNotExist(err) {
			// Download prices file
			err = downloadFile(pricesURL, pricesFile)
		}
		if err != nil {
			return nil, err
		}

		// Read prices file
		var priceDB PriceDB
		err = readJSONFile(pricesFile, &priceDB)
		if err != nil {
			return nil, err
		}

		// Filter cards we care about
		entries := make([]CardPriceEntry, 0)
		for uuid, priceCatalog := range priceDB.Data {
			// Get all paper retail prices
			lowestPrice, currency, seller := getLowestPrice(priceCatalog.Paper)

			if priceFilter < lowestPrice {
				continue
			}

			entries = append(entries, CardPriceEntry{
				UUID:     uuid,
				Price:    lowestPrice,
				Currency: currency,
				Seller:   seller,
			})
		}

		return entries, nil
	}
}

func getLowestPrice(sellers map[string]PriceList) (lowestPrice float64, currency string, seller string) {
	lowestPrice = 9999
	for cardSeller, priceList := range sellers {
		if priceList.Retail == nil {
			continue
		}
		for _, price := range priceList.Retail.Normal {
			if price < lowestPrice {
				lowestPrice = price
				currency = priceList.Currency
				seller = cardSeller
			}
		}
		for _, price := range priceList.Retail.Foil {
			if price < lowestPrice {
				lowestPrice = price
				currency = priceList.Currency
				seller = cardSeller
			}
		}
	}
	return
}