LrTagImporter.lua

--[[ Debug ]]
local Require = require 'Require'.path ("../debugscript.lrdevplugin")
local Debug = require 'Debug'.init ()
require 'strict'

local json = require("json")
local FileUtil = import("LrFileUtils") --for readFile
local Dialogs = import("LrDialogs") --for runOpenPanel to select tags file
local Application = import("LrApplication") --for activeCatalog
local Tasks = import("LrTasks")
local Catalog = Application.activeCatalog()

function tableLength(tab)
    local i = 0
    for _ in pairs(tab) do
        i = i + 1
    end
    return i
end

function writeTagsToCatalog(data)
	local progress = LrDialogs.showModelProgressDialog({
			title = ""
	})
	
	local photos = Catalog:getMultipleSelectedOrAllPhotos()
	local nPhotos = #photos
	local importKeyword = nil --A container for our imported keywords so as not to make mess.
	local photoMatches = {} --array - {LrPhoto, {LrKeywords}}
	Catalog:withWriteAccessDo("createImport", function()
		importKeyword = Catalog:createKeyword("Imported", {}, true, nil, true)
	end)
	--create keywords
	Catalog:withWriteAccessDo("createKeywords", function()
		for i, photo in pairs(photos) do
			local name = photo:getFormattedMetadata("fileName")
			if data[name] then
				-- create keywords
				local photoKeyPair = {photo = photo, keywords = {}}
				for _, tag in pairs(data[name].tags) do
					table.insert(photoKeyPair.keywords, tag)
				end
				table.insert(photoMatches, photoKeyPair)
				--write some other information to the photo
					--data[name].artist
					--data[name].category (parent to a category keyword)
					--data[name].submission (rename to source, should be custom field)
					--data[name].title (also custom field)
					--if custom fields don't work keyword groups should work well enough.
			end
			Tasks.yield();
		end)
		Catalog:withWriteAccessDo("writeKeywords", function()
			for i,v in pairs(photoMatches) do
				for _, tag in pairs(v.keywords) do
					v.photo:addKeyword(tag)
				end
			end
		end)
	end
end

function activate()
	local tagData = {}
	local tagFilePath = Dialogs.runOpenPanel({ 	--file prompt
		title = "Select a tag file",
		canChooseFiles = true,
		canChooseDirectories = true,
		allowMultipleSelection = false,
		fileTypes = "json",
	})
	if tagFilePath then --A file was selected now decode it
		Debug.logn("decoding json file")
		local tagFile = FileUtil.readFile(tagFilePath[1])
		tagData = json.decode(tagFile)
		Tasks.startAsyncTask(function()
					writeTagsToCatalog(tagData, progress)
		end)
	end
end

activate()