-- master.lua
-- Automatically broadcasts TTS announcements for train arrival/departure (negative redstone logic)

local modemSide = "back"  -- Change to your wireless modem side
rednet.open(modemSide)

-- Map each redstone side to a platform name
local platforms = {
    front  = "A",
    left = "B",
    back = "C",
    right  = "D"
}

-- Generate announcement text
local function generateAnnouncement(platform, isArriving)
    if isArriving then
        return "Attention please. The train is arriving at platform "
            .. tostring(platform)
            .. ". Please stand behind the yellow line and allow passengers to alight before boarding. Thank you."
    else
        return "Attention please. The train at platform "
            .. tostring(platform)
            .. " is now departing. Please stand clear of the doors. Thank you."
    end
end

-- Store previous redstone states
local previous = {}
for side, _ in pairs(platforms) do
    previous[side] = redstone.getInput(side)
end

print("Starting platform redstone monitoring (negative logic)...")

while true do
    for side, platformName in pairs(platforms) do
        local current = redstone.getInput(side)

        -- Detect state change
        if current ~= previous[side] then
            if current == true then
                -- No signal → Has signal = Train arriving
                local message = generateAnnouncement(platformName, true)
                rednet.broadcast({type = "tts", text = message})
                print("Train arriving at platform " .. platformName)
            else
                -- Has signal → No signal = Train departing
                local message = generateAnnouncement(platformName, false)
                rednet.broadcast({type = "tts", text = message})
                print("Train departing from platform " .. platformName)
            end
            previous[side] = current
        end
    end

    sleep(1) -- Check every second
end