import.go

package main

import (
	"flag"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"github.com/dsoprea/go-exif/v3"
	exifcommon "github.com/dsoprea/go-exif/v3/common"
)

// Copy a file from src to dst
func copyFile(src, dst string) (err error) {
	sfi, err := os.Stat(src)
	if err != nil {
		return
	}
	if !sfi.Mode().IsRegular() {
		// Cannot copy non-regular files (directories, symlinks, devices, etc.)
		return fmt.Errorf("Non-regular source file %s (%q)", sfi.Name(), sfi.Mode().String())
	}
	dfi, err := os.Stat(dst)
	if err != nil {
		if !os.IsNotExist(err) {
			return
		}
	} else {
		if !(dfi.Mode().IsRegular()) {
			return fmt.Errorf("Non-regular destination file %s (%q)", dfi.Name(), dfi.Mode().String())
		}
		if os.SameFile(sfi, dfi) {
			return
		}
	}
	err = copyFileContents(src, dst, sfi.ModTime())
	return
}

// Copy the contents of the file named src to the file named by dst setting the given mtime. If the
// destination file exists, all of its contents will be replaced by the contents of the source file.
func copyFileContents(src, dst string, mtime time.Time) (err error) {
	in, err := os.Open(src)
	if err != nil {
		return
	}
	defer in.Close()
	out, err := os.Create(dst)
	if err != nil {
		return
	}
	defer func() {
		cerr := out.Close()
		if err == nil {
			err = cerr
		}
	}()
	if _, err = io.Copy(out, in); err != nil {
		return
	}

	// Update the timestamps
	if err := os.Chtimes(dst, time.Now(), mtime); err != nil {
		log.Fatal(err)
	}
	err = out.Sync()
	return
}

// Return whether the given file or directory exists
func pathExists(path string) (bool, error) {
	_, err := os.Stat(path)
	if err == nil {
		return true, nil
	}
	if os.IsNotExist(err) {
		return false, nil
	}
	return true, err
}

// Convert an offset string to seconds
func offsetToSeconds(offset string) (int, error) {
	if len(offset) != 6 {
		return 0, fmt.Errorf("Invalid offset format")
	}

	sign := 1
	if offset[0] == '-' {
		sign = -1
	} else if offset[0] != '+' {
		return 0, fmt.Errorf("Invalid offset format")
	}

	hours, err := strconv.Atoi(offset[1:3])
	if err != nil {
		return 0, err
	}

	minutes, err := strconv.Atoi(offset[4:6])
	if err != nil {
		return 0, err
	}

	return sign * (hours*3600 + minutes*60), nil
}

// Find a tag in all IFDs and return the value as a string
func findTagInAllIfds(index *exif.IfdIndex, tagName string) (string, error) {
	ifds := index.Ifds
	for _, ifd := range ifds {
		results, err := ifd.FindTagWithName(tagName)
		if err == nil && len(results) > 0 {
			valueRaw, err := results[0].Value()
			if err != nil {
				return "", err
			}
			return valueRaw.(string), nil
		}
	}
	return "", fmt.Errorf("tag not found")
}

func main() {
	var from, to, filter string
	flag.StringVar(&from, "from", "", "Source path")
	flag.StringVar(&to, "to", "", "Destination path")
	flag.StringVar(&filter, "filter", "", "Optional file type filter")

	var start, end uint
	flag.UintVar(&start, "start", uint(0), "Start date")
	flag.UintVar(&end, "end", ^uint(0), "End date")
	flag.Parse()

	if from == "" || to == "" {
		fmt.Fprintf(os.Stderr, "Error: Need source and target directory (use '--from' and '--to')\n\n")
		flag.Usage()
		os.Exit(-1)
	}

	// Read the source directory
	fmt.Printf("Importing files from %s -> %s\n", from, to)
	files, err := ioutil.ReadDir(from)
	if err != nil {
		log.Fatal(err)
	}

	for _, f := range files {
		// Skip directories
		if f.IsDir() {
			continue
		}

		// Filter for file extension
		ext := strings.Trim(filepath.Ext(f.Name()), ".")
		if filter != "" && ext != filter {
			continue
		}

		// Filter for EXIF DateTime if it exists, otherwise ModTime
		file, err := os.Open(filepath.Join(from, f.Name()))
		if err != nil {
			log.Fatal(err)
		}
		defer file.Close()

		var timestampValue time.Time
		rawExif, err := exif.SearchAndExtractExifWithReader(file)
		if err != nil {
			fmt.Printf("%s: No EXIF data found (%s), using ModTime\n", f.Name(), err)
			timestampValue = f.ModTime().In(time.UTC)
		} else {
			im, err := exifcommon.NewIfdMappingWithStandard()
			if err != nil {
				log.Fatal(err)
			}
			ti := exif.NewTagIndex()
			_, index, err := exif.Collect(im, ti, rawExif)
			if err != nil {
				log.Fatal(err)
			}

			// Search for DateTimeOriginal tag
			dateTimeString, err := findTagInAllIfds(&index, "DateTimeOriginal")
			if err != nil {
				fmt.Printf("%s: DateTimeOriginal not found (%s), using ModTime\n", f.Name(), err)
				timestampValue = f.ModTime().In(time.UTC)
			} else {
				fmt.Printf("%s: DateTimeOriginal = %s\n", f.Name(), dateTimeString)

				layout := "2006:01:02 15:04:05"
				timestampValue, err = time.Parse(layout, dateTimeString)
				if err != nil {
					log.Fatal(err)
				}

				// Determine corresponding timezone from EXIF or use local timezone
				// offsetString, err := findTagInAllIfds(&index, "OffsetTime")
				// if err != nil {
				// 	fmt.Printf("OffsetTime - tag not found (%s), using Local\n", err)
				// 	timestampValue = timestampValue.In(time.Local)
				// } else {
				// 	fmt.Printf("OffsetTime = %s\n", offsetString)

				// 	offsetSeconds, err := offsetToSeconds(offsetString)
				// 	if err != nil {
				// 		log.Fatal(err)
				// 	}
				// 	location := time.FixedZone("FixedZone", offsetSeconds)
				// 	timestampValue = timestampValue.In(location)
				// }
			}
		}

		i, _ := strconv.Atoi(timestampValue.Format("20060102"))
		if uint(i) < start || uint(i) > end {
			continue
		}

		// Create folder if needed
		timestamp := timestampValue.Format("2006-01-02")
		folder := filepath.Join(to, timestamp+"-"+strings.ToLower(ext))
		if value, err := pathExists(folder); value == false && err == nil {
			fmt.Printf("Creating folder: %s\n", folder)
			os.Mkdir(folder, 0755)
		}

		// Copy the file
		fromFile := filepath.Join(from, f.Name())
		toFile := filepath.Join(folder, f.Name())
		fmt.Printf("Copying %s -> %s (%s)\n", fromFile, toFile, timestampValue)
		err = copyFile(fromFile, toFile)
		if err != nil {
			fmt.Printf("Copy file failed: %q\n", err)
		}
	}
}