local LrTasks = import 'LrTasks'
local LrApplication = import 'LrApplication'
local LrFunctionContext = import 'LrFunctionContext'
local LrDevelopController = import 'LrDevelopController'

local json2 = require 'Json2'
require 'Globals'

adjustmentObservingInterval = 0.2 -- 200ms
photoObservingInterval = 1 -- 1s

adjustmentsCache = {}
observableAdjustments = {}

adjustmentsValueObserverIsWorking = false

function enableValueSync(adjustmentsToObserve)
    adjustmentsCache = {}
    observableAdjustments = adjustmentsToObserve
    if not photoChangedObserverIsWorking then
        startObservingPhotoChange()
        photoChangedCallback()
    end
    if not adjustmentsValueObserverIsWorking then
        startObservingAdjustmentsValueChange()
    end
end

function disableValueSync()
    adjustmentsCache = {}
    if photoChangedObserverIsWorking then
        stopObservingPhotoChange()
    end
    if adjustmentsValueObserverIsWorking then
        stopObservingAdjustmentsValueChange()
    end
end

-- This method works only for non reference values. If you want compare tables or arrays, please update this method
function updateCache()
    local changedAdjustments = {}
    for _, adjustmentName in ipairs(observableAdjustments) do
        local newAdjustmentValue = LrDevelopController.getValue(adjustmentName)
        if adjustmentsCache[adjustmentName] ~= newAdjustmentValue then 
            adjustmentsCache[adjustmentName] = newAdjustmentValue
            changedAdjustments[adjustmentName] = newAdjustmentValue
        end
    end
    return changedAdjustments
end

function checkUpdatedAdjustmentValuesAndSendEvent()
    local changedAdjustments = updateCache()
    if not tableIsEmpty(changedAdjustments) then
        sendEvent('adjustmentvaluechanged', json2:encode(changedAdjustments))
    end
end

-- Function to start observing changes.
function startObservingAdjustmentsValueChange()
    adjustmentsValueObserverIsWorking = true

    LrTasks.startAsyncTask(function()
        while adjustmentsValueObserverIsWorking do 
            checkUpdatedAdjustmentValuesAndSendEvent()
            LrTasks.sleep(adjustmentObservingInterval) -- 200ms 
        end
    end)
end

-- Function to stop observing changes.
function stopObservingAdjustmentsValueChange()
    adjustmentsValueObserverIsWorking = false
end


photoChangedObserver = {}
photoChangedObserverIsWorking = false
catalog = LrApplication.activeCatalog()

function startObservingPhotoChange()
    photoChangedObserverIsWorking = true
    LrTasks.startAsyncTask(function()
        LrFunctionContext.callWithContext("Observer", function(context)
            LrApplication.addActivePhotoChangeObserver(context, photoChangedObserver, photoChangedCallback)
            while photoChangedObserverIsWorking do 
                LrTasks.sleep(photoObservingInterval) -- 1s
            end
        end)
    end)
end

function photoChangedCallback()
    catalog:withReadAccessDo(function()
        local targetPhoto = catalog:getTargetPhoto()
        if targetPhoto then
            -- a photo is selected
            sendEvent('newphotoselected', '')
        else
            -- no photo is selected
            sendEvent('photodeselected', '')
        end
    end)
end

function stopObservingPhotoChange()
    photoChangedObserverIsWorking = false
end