server-btcpay.lua

-- server.lua
dofile("credentials.lua")

print("server code begin ---")

local srv = net.createServer(net.TCP, 30)

local function discardOldIPN(invoiceID, payload)
    local currentTime = rtctime.get()
    print("Current time", currentTime)
    local _, indexEndApiCallTime = string.find(payload, "\"currentTime\": ")
    local apiCallTime = string.sub(payload, indexEndApiCallTime, indexEndApiCallTime + 10)
    print("API call time", apiCallTime)
    if  (currentTime - apiCallTime) > 10 then
        print(invoiceID, "IPN expired")
        print(currentTime - apiCallTime, "seconds old")
        return false
    end
    return true
end

local function getInvoiceID(payload)
    local _, indexEndInvoiceID = string.find(payload, "id")
    if indexEndInvoiceID ~= nil then
        return string.match(payload, [["id":%s+"([^"]+)]])
    end
end

local function onReceive(sck, payload)
    local invoiceID = getInvoiceID(payload)

    -- Get IPN code
    local _, indexEndCode = string.find(payload, "code")
    if indexEndCode ~= nil then
        local code = string.sub(payload, indexEndCode + 4, indexEndCode + 7)

        -- If invoice_completed IPN
        if code == '1006' then
            print(invoiceID, code, "IPN final")

            -- Discard old 1006 IPNs with timestamp comparison (10 sec difference max)
            -- currentTime and apiCallTime are supposed to be equal
            if discardOldIPN(invoiceID, payload) == false then return end

            -- Get invoice data
            local url = "https://btcpay.bitcoin-studio.com/invoices/" .. invoiceID
            local headers = "Accept: */*\r\nContent-Type: application/json\r\nAuthorization: Basic" .. BTCPAY_BASIC .. "\r\n"
            http.get(url, headers, function(code, res)
                if (code < 0) then
                    print("HTTPS request failed with code", code)
                else
                    print("HTTPS request success")
                    local t = sjson.decode(res)
                    print("Coffee selected", t.data.itemDesc)

                    if(t.data.itemDesc == "Master Origin Ethiopia")then
                        activateServo(2)
                    elseif(t.data.itemDesc == "Fortissio Lungo")then
                        activateServo(3)
                    elseif(t.data.itemDesc == "Capriccio Espresso")then
                        activateServo(4)
                    elseif(t.data.itemDesc == "Arpeggio Intenso")then
                        activateServo(5)
                    elseif(t.data.itemDesc == "Caramelito Variation")then
                        activateServo(6)
                    end
                end
            end)
        else
            print(invoiceID, code, "IPN non-final")
        end
    end
    sck:send("HTTP/1.1 200 OK\r\n\r\n", function(sck) sck:close() end)
end


if srv then
    print("start listening on port 80...")
    srv:listen(80, function(conn)
        conn:on("receive", onReceive)
    end)
end

print("server code end ---")