sub init()
    m.top.setFocus(true)
    m.backend = m.top.findNode("backend")
    m.status = m.top.findNode("status")
    m.refreshTimer = m.top.findNode("refreshTimer")
    m.cameraPosters = [
        m.top.findNode("poster1"),
        m.top.findNode("poster2"),
        m.top.findNode("poster3"),
        m.top.findNode("poster4")
    ]
    m.cameraNodes = [
        m.top.findNode("cam1"),
        m.top.findNode("cam2"),
        m.top.findNode("cam3"),
        m.top.findNode("cam4")
    ]
    m.refreshToken = 0

    loadConfig()
end sub

sub loadConfig()
    raw = ReadAsciiFile("pkg:/config/cameras.json")
    config = ParseJson(raw)

    if type(config) <> "roAssociativeArray" then
        m.status.text = "Unable to parse cameras.json"
        return
    end if

    m.config = config

    if config.doesExist("backend") and config.backend.doesExist("baseUrl") then
        m.backend.text = "Frigate snapshot source"
    end if

    if not config.doesExist("cameras") then
        m.status.text = "No cameras found in config"
        return
    end if

    if config.doesExist("backend") and config.backend.doesExist("refreshSeconds") then
        m.refreshTimer.duration = config.backend.refreshSeconds
    end if

    m.refreshTimer.observeField("fire", "onRefreshTimerFire")
    m.refreshTimer.control = "start"

    renderCameras()
end sub

sub renderCameras()
    if m.config = invalid or not m.config.doesExist("cameras") then
        return
    end if

    cameras = m.config.cameras
    m.status.text = cameras.count().toStr() + " cameras loaded, refreshing every " + m.refreshTimer.duration.toStr() + "s"

    for i = 0 to m.cameraNodes.count() - 1
        poster = m.cameraPosters[i]
        node = m.cameraNodes[i]

        if i < cameras.count() then
            camera = cameras[i]
            poster.uri = addCacheBust(buildSnapshotUrl(m.config, camera))
            node.text = camera.name
        else
            poster.uri = ""
            node.text = "Empty slot"
        end if
    end for
end sub

sub onRefreshTimerFire()
    m.refreshToken = m.refreshToken + 1
    renderCameras()
end sub

function buildSnapshotUrl(config as Object, camera as Object) as String
    if not config.doesExist("backend") or not config.backend.doesExist("baseUrl") then
        return ""
    end if

    baseUrl = config.backend.baseUrl
    path = ""

    if camera.doesExist("snapshotPath") then
        path = camera.snapshotPath
    else if camera.doesExist("frigateCamera") then
        path = "/api/" + camera.frigateCamera + "/latest.jpg"
    else
        return ""
    end if

    if right(baseUrl, 1) = "/" and left(path, 1) = "/" then
        return left(baseUrl, len(baseUrl) - 1) + path
    else if right(baseUrl, 1) <> "/" and left(path, 1) <> "/" then
        return baseUrl + "/" + path
    end if

    return baseUrl + path
end function

function addCacheBust(url as String) as String
    token = m.refreshToken.toStr()

    if instr(1, url, "?") > 0 then
        return url + "&cb=" + token
    end if

    return url + "?cb=" + token
end function