Hammerspoon configuration to switch keyboard languages with shortcuts(left CMD, right CMD, right Option)

langswitcher.lua

-- Hammerspoon configuration to switch keyboard languages with shortcuts
-- Table to keep track of the last modifiers and if another key was pressed
local lastModifiers = {}
local otherKeyPressed = false

-- Function to handle single taps on modifier keys
local function singleTapHandler(event)
    local newModifiers = event:getFlags()
    local keyCode = event:getKeyCode()

    -- If other keys are pressed along with modifiers, we set a flag
    if event:getType() == hs.eventtap.event.types.keyDown then
        otherKeyPressed = true
    end

    -- When all keys are released, check if it was a single modifier tap
    if event:getType() == hs.eventtap.event.types.flagsChanged and not next(newModifiers) then
        if not otherKeyPressed then -- no other keys were pressed
            if lastModifiers["cmd"] and not newModifiers["cmd"] then -- CMD was released
                if keyCode == 55 then -- left CMD
                    hs.keycodes.setLayout('ABC')
                elseif keyCode == 54 then -- right CMD
                    hs.keycodes.setLayout('Ukrainian – Legacy')
                end
            elseif lastModifiers["alt"] and not newModifiers["alt"] then -- Option was released
                if keyCode == 61 then -- right Option
                    hs.keycodes.setLayout('Russian')
                end
            end
        end
        -- Reset the flag when all keys are released
        otherKeyPressed = false
    end

    -- Update the lastModifiers table
    lastModifiers = newModifiers
end

-- Event tap to catch keyDown and flagsChanged events
eventTap = hs.eventtap.new({hs.eventtap.event.types.flagsChanged, hs.eventtap.event.types.keyDown}, singleTapHandler)

-- Start the event tap
eventTap:start()

-- Display a message to indicate the config has been loaded
hs.alert.show("Language switcher loaded")