main.go

package main

import (
	"os"
	"net/http"
	"io"
	"path/filepath"
	"encoding/json"
	"github.com/go-redis/redis"
	"fmt"
	"encoding/base64"
	"crypto/rand"
)

func writeBody(reader io.ReadCloser, path string) error {
	out, err := os.Create(path)
	if err != nil {
		return err
	}
	defer out.Close()

	_, err = io.Copy(out, reader)
	if err != nil {
		return err
	}
	return out.Close()
}

func detectMimeType(path string) (string, error) {
	file, err := os.Open(path)
	if err != nil {
		return "", err
	}

	buffer := make([]byte, 512)
	_, err = file.Read(buffer)
	if err != nil {
		return "", err
	}

	return http.DetectContentType(buffer), nil
}

func generateId() string {
	buffer := make([]byte, 4)
	rand.Read(buffer)

	return base64.URLEncoding.WithPadding(base64.NoPadding).EncodeToString(buffer)
}

func createImage(config *Config, body io.ReadCloser) (Image, error) {
	id := generateId()
	path := filepath.Join(config.SourceFolder, id)

	err := writeBody(body, path)
	if err != nil {
		return Image{}, err
	}

	mimeType, err := detectMimeType(path)
	if err != nil {
		return Image{}, err
	}

	image := Image{
		Id:       id,
		MimeType: mimeType,
	}
	return image, nil
}