-- Navigation System for Virtual Smartphone
-- Handles screen transitions and state management

-- Screen registry - maps screen names to RML file paths
local screens = {
    home = "screens/home.rml",
    lock = "screens/lock.rml",
    dialer = "screens/dialer.rml",
    contacts = "screens/contacts.rml",
    messages = "screens/messages.rml",
    settings = "screens/settings.rml",
    browser = "screens/browser.rml"
}

-- Use global state to persist across document loads
-- Initialize only if not already set
if not _G.nav_state then
    _G.nav_state = {
        history = {},
        current_screen = "home"
    }
end

-- Local references for convenience
local history = _G.nav_state.history
local function get_current() return _G.nav_state.current_screen end
local function set_current(s) _G.nav_state.current_screen = s end

-- Navigate to a screen by name
function navigateTo(screen_name)
    print("navigateTo called with: " .. tostring(screen_name))
    local path = screens[screen_name]
    if path then
        -- Push current screen to history before navigating
        table.insert(history, get_current())
        set_current(screen_name)

        -- Load the new screen using C++ function
        local success = loadScreen(path)
        if success then
            print("Navigated to: " .. screen_name .. " (history depth: " .. #history .. ")")
        else
            -- Restore previous state on failure
            set_current(table.remove(history))
            print("Failed to navigate to: " .. screen_name)
        end
        return success
    else
        print("Unknown screen: " .. screen_name)
        return false
    end
end

-- Go back to previous screen
function goBack()
    print("goBack called (history depth: " .. #history .. ")")
    if #history > 0 then
        local previous = table.remove(history)
        local path = screens[previous]
        if path then
            set_current(previous)
            loadScreen(path)
            print("Back to: " .. previous)
            return true
        end
    else
        print("No history to go back to")
    end
    return false
end

-- Go to home screen (clear history)
function goHome()
    -- Clear the history table
    for i = #history, 1, -1 do
        history[i] = nil
    end
    set_current("home")
    loadScreen(screens.home)
    print("Navigated to home")
end

-- Get current screen name
function getCurrentScreen()
    return get_current()
end

-- Check if we can go back
function canGoBack()
    return #history > 0
end

-- Clear navigation history
function clearHistory()
    for i = #history, 1, -1 do
        history[i] = nil
    end
end

-- Get history depth
function getHistoryDepth()
    return #history
end

print("Navigation system initialized (current: " .. get_current() .. ", history: " .. #history .. ")")