package cache

import (
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"time"
)

type Cache[T any] struct {
	Path string
}

func New[T any](path string) *Cache[T] {
	if path == "" {
		path = os.TempDir()
	}
	return &Cache[T]{path}
}

// Add data as JSON-file into cache-dir, returns nil if success
func (c *Cache[T]) Add(name string, data any) error {
	j, err := json.MarshalIndent(data, "", " ")
	if err != nil {
		return fmt.Errorf("Failed to convert data as JSON.")
	}
	err = os.MkdirAll(c.Path, 0646)
	if err != nil {
		return fmt.Errorf("Failed to ensure cache-dir is present.")
	}

	filePath := filepath.Join(c.Path, fmt.Sprintf("%s.json", name))
	d := []byte(j)
	err = os.WriteFile(filePath, d, 0646)
	if err != nil {
		return fmt.Errorf("Failed write data to cache-file.")
	}

	return nil
}

// Get data from JSON-file from cache-dir, returns nil if no result
func (c *Cache[T]) Get(name string) (*T, error) {
	filePath := filepath.Join(c.Path, fmt.Sprintf("%s.json", name))
	if _, err := os.Stat(filePath); errors.Is(err, os.ErrNotExist) {
		return nil, nil
	}

	rawFile, err := os.Open(filePath)
	if err != nil {
		return nil, fmt.Errorf("Failed to read cache-file.")
	}

	var result T

	bytes, err := io.ReadAll(rawFile)
	if err != nil {
		return nil, fmt.Errorf("Failed to read data from cache-file.")
	}

	err = json.Unmarshal(bytes, &result)
	if err != nil {
		return nil, fmt.Errorf("Failed to parse JSON from cache-file.")
	}

	return &result, nil
}

// Returns if t is expired
func IsExpired(expire time.Time, now *time.Time) bool {
	if now == nil {
		tmp := time.Now()
		now = &tmp
	}

	return now.Unix() >= expire.Unix()
}