package main

import (
	"errors"
	"flag"
	"fmt"
	"io/ioutil"
	"os"
	"strings"

	"github.com/rwcarlsen/goexif/exif"
)

var inJson bool
var filename string

func init() {
	const (
		filenameUsage = "The File/Directory to scan"
		inJsonDefault = false
		inJsonUsage   = "Output the result in JSON"
	)
	flag.StringVar(&filename, "filename", "", filenameUsage)
	flag.BoolVar(&inJson, "json", inJsonDefault, inJsonUsage)
}

func main() {
	flag.Parse()

	fInfo, err := os.Lstat(filename)
	if err != nil {
		fmt.Println("Error reading passed file/directory")
		os.Exit(1)
	}
	if fInfo.IsDir() {
		ProcessDirectory(filename, inJson)
	} else {
		PrintJpegData(filename, inJson)
	}
}

func ProcessDirectory(dirname string, inJson bool) {
	if !inJson {
		fmt.Println("Reading Directory:", dirname)
	}
	files, err := ioutil.ReadDir(dirname)
	if err != nil {
		panic(err)
	}

	if !strings.HasSuffix(dirname, "/") {
		dirname += "/"
	}

	if inJson {
		fmt.Print("[")
	}
	foundFirst := false
	for _, file := range files {
		if isJpeg(dirname+file.Name()) && inJson && foundFirst {
			fmt.Print(",")
		}
		if PrintJpegData(dirname+file.Name(), inJson) == nil {
			foundFirst = true
			if !inJson {
				fmt.Println("")
			}
		}
	}
	if inJson {
		fmt.Print("]")
	}
}

func isJpeg(filename string) bool {
	nm := strings.ToUpper(filename)
	return strings.HasSuffix(nm, ".JPG") || strings.HasSuffix(nm, ".JPEG")
}

func PrintJpegData(filename string, inJson bool) error {
	if !isJpeg(filename) {
		return errors.New("Not a JPEG")
	}
	exif, err := ReadExifData(filename)
	if err != nil {
		if !inJson {
			fmt.Println("Error: " + err.Error())
			return err
		}
	}
	if inJson {
		fmt.Print("{\"Filename\":\"" + filename + "\",\"Exif\":")
		if exif == nil {
			fmt.Print("{}")
		} else {
			json, err := exif.MarshalJSON()
			if err != nil {
				fmt.Print("{}")
			}
			fmt.Print(string(json))
		}
		fmt.Print("}")
	} else {
		fmt.Println("= " + filename + " =")
		fmt.Println(exif)
	}
	return nil
}

func ReadExifData(filename string) (*exif.Exif, error) {
	f, err := os.Open(filename)
	if err != nil {
		fmt.Println("Error:", err.Error())
		return &exif.Exif{}, err
	}
	defer f.Close()
	return exif.Decode(f)
}