set dest to "/Volumes/home/backup/photo/export"

tell application "Photos"
	activate
	set folderList to name of every folder
	set selectedFolders to choose from list folderList with prompt "Select folders:" with multiple selections allowed
	
	repeat with f in folders
		if selectedFolders contains name of f then
			my exportFolder(f, dest)
		end if
	end repeat
end tell

-- export a folder to a given destination
on exportFolder(tFolder, tPath)
	set folderName to tPath & "/" & my getFolderName(tFolder)
	log folderName
	
	using terms from application "Photos"
		tell tFolder
			repeat with childAlbum in albums
				my exportAlbum(childAlbum, folderName)
			end repeat
			
			repeat with childFolder in folders
				my exportFolder(childFolder, folderName)
			end repeat
		end tell
	end using terms from
end exportFolder

-- work out the folder name
on getFolderName(tFolder)
	set dateNames to {"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"}
	set folderName to name of tFolder
	
	if dateNames contains folderName then
		repeat with idx from 1 to the count of dateNames
			if item idx of dateNames is folderName then return text -2 thru -1 of ("0" & idx)
		end repeat
	end if
	
	return folderName
end getFolderName

-- export an album to a given destination
on exportAlbum(tAlbum, tPath)
	set albumName to tPath & "/" & my getAlbumName(tAlbum, tPath)
	my makeFolder(albumName)
	
	tell application "Photos"
		with timeout of 30 * 60 seconds
			export (get media items of tAlbum) to (albumName as POSIX file) with using originals
		end timeout
	end tell
end exportAlbum

-- get an album name
-- some albums have no date prefix (if they are in Misc folder or are empty)
-- if all the dates are the same, use "YYYY-MM-DD Album"
-- if date is within a month, use "YYYY-MM-DD–EE Album"
-- otherwise use "YYYY-MM-DD–ZZZZ-NN-EE Album"
on getAlbumName(tAlbum, tPath)
	using terms from application "Photos"
    -- to avoid Photos naming clash there are some with "(2)" or "(1 Apr)", remove this
		set albumName to do shell script "sed 's/ ([0-9].*)$//g' <<< " & quoted form of ((name of tAlbum) as text)
		if tPath contains "/Misc/" then return albumName
		
		set uniqueDates to {}
		set photoDates to date of every media item of tAlbum
		if (count of photoDates) = 0 then return albumName -- empty album
    repeat with photoDate in photoDates
      set [d, m, y] to [day, month, year] of photoDate
      set m to m * 1
      set m to text -1 thru -2 of ("0" & m)
      set d to text -1 thru -2 of ("0" & d)
      set the text item delimiters to "-"
      set newDate to {y, m, d} as string
      if uniqueDates does not contain newDate then set end of uniqueDates to newDate
    end repeat
    
    -- single date
    if length of uniqueDates = 1 then return first item of uniqueDates & " " & albumName
    
    set sortedDates to my sortList(uniqueDates)
    set minDate to first item of sortedDates
    set maxDate to last item of sortedDates

    -- same month
    if text 1 thru 7 of minDate = text 1 thru 7 of maxDate then
      return minDate & "–" & text 9 thru end of maxDate & " " & albumName
    end if

    -- different month/year
    return minDate & "–" & maxDate & " " & albumName
	end using terms from
end getAlbumName

on makeFolder(tPath)
	do shell script "mkdir -p " & quoted form of tPath
end makeFolder

-- from: https://developer.apple.com/library/content/documentation/LanguagesUtilities/Conceptual/MacAutomationScriptingGuide/ManipulateListsofItems.html
on sortList(theList)
	set theIndexList to {}
	set theSortedList to {}
	try
		repeat (length of theList) times
			set theLowItem to ""
			repeat with a from 1 to (length of theList)
				if a is not in theIndexList then
					set theCurrentItem to item a of theList as text
					if theLowItem is "" then
						set theLowItem to theCurrentItem
						set theLowItemIndex to a
					else if theCurrentItem comes before theLowItem then
						set theLowItem to theCurrentItem
						set theLowItemIndex to a
					end if
				end if
			end repeat
			set end of theSortedList to theLowItem
			set end of theIndexList to theLowItemIndex
		end repeat
	on error errMsg number errorNumber
		return {"An unknown error occurred:"} & theSortedList
	end try
	return theSortedList
end sortList