cache.go

package main

import (
	"encoding/json"
	"fmt"
	"os"
	"time"
)

type cacheData struct {
	DrawnNums  drawnNums `json:"drawnNums"`
	LastVisit  time.Time `json:"lastVisit"`
	NumOfDraws int       `json:"numOfDraws"`
}

func read() (cacheData, error) {
	data := cacheData{
		DrawnNums: make(drawnNums),
	}

	f, err := os.OpenFile("./tmp/cache.json", os.O_RDONLY, 0644)
	if err != nil {
		if os.IsNotExist(err) {
			return data, nil
		}
		return data, fmt.Errorf("failed to open cache file: %w", err)
	}
	defer closeFile(f)

	dec := json.NewDecoder(f)
	if err := dec.Decode(&data); err != nil {
		return data, fmt.Errorf("failed to decode cache file: %w", err)
	}

	return data, nil
}

func write(numOfDraws int, drawnNums drawnNums) error {
	if err := os.MkdirAll("./tmp", 0744); err != nil {
		return fmt.Errorf("failed to create tmp directory: %w", err)
	}

	f, err := os.OpenFile("./tmp/cache.json", os.O_WRONLY|os.O_CREATE, 0644)
	if err != nil {
		return fmt.Errorf("failed to open cache file: %w", err)
	}
	defer closeFile(f)

	data := cacheData{
		DrawnNums:  drawnNums,
		LastVisit:  time.Now().UTC().Truncate(24 * time.Hour),
		NumOfDraws: numOfDraws,
	}

	enc := json.NewEncoder(f)
	enc.SetIndent("", " ")
	if err := enc.Encode(data); err != nil {
		return fmt.Errorf("failed to write cache: %w", err)
	}

	return nil
}

func closeFile(f *os.File) {
	if err := f.Close(); err != nil {
		fmt.Println("failed to close cache file:", err)
	}
}