-- Demonstrates how to use vector fonts, Rich Text effects and color emoji.

-- Emojis displayed in sequence, changing every second.
local EMOJI = { "🚀", "😀", "😉", "👍" }

-- Path to the COLRv1 font containing full-color emoji glyphs.
local EMOJI_FONT_PATH = "/fonts/Twemoji-COLRv1.ttf"

-- Rich Text tags control color, size and animated effects.
-- The emoji is appended dynamically to the first line.
local function text_for(emoji)
    return "Hello <color=#61DAFB><wave>World</wave></color>! " .. emoji
    .. "\n\n <size=0.5em><shake>RichText</shake>, <gradient left=#FFD313 right=#FD6623>Vector Fonts</gradient> and <gradient left=#1E64EA right=#00E6E1>Emoji</gradient> 😉</size>"
end

-- Called when the font glyphs have finished prewarming.
local function on_prewarmed(self, request_id, ok, err)
    if not ok then
        print("Emoji/font prewarm failed: " .. tostring(err))
        return
    end

    -- Get the GUI text node and assign the vector font.
    self.text = gui.get_node("text")
    gui.set_font(self.text, "hello")
    gui.set_pivot(self.text, gui.PIVOT_CENTER)
    gui.set_line_break(self.text, false)
    gui.set_color(self.text, vmath.vector4(1, 1, 1, 1))

    -- Update the text with Rich Text formatting and the current emoji.
    gui.set_text(self.text, text_for(EMOJI[self.emoji_index]))

    -- Animate the change of the scale of the text smoothly.
    gui.set_scale(self.text, vmath.vector3(3.8, 3.8, 1))
    gui.animate(self.text, gui.PROP_SCALE,
        vmath.vector3(4.5, 4.5, 1), gui.EASING_INOUTSINE,
        1.5, 0, nil, gui.PLAYBACK_LOOP_PINGPONG)
end

function init(self)
    -- Track the current emoji and elapsed time.
    self.emoji_index = 1
    self.emoji_timer = 0

    -- Add the COLRv1 font as a fallback for color emojis.
    local font_resource = gui.get_font_resource("hello")

    -- Register the emoji font as a fallback for the main vector font.
    font.add_font(font_resource, EMOJI_FONT_PATH)

    -- Preload the required glyphs and call on_prewarmed when ready.
    -- We prewarm glyphs before displaying the text to avoid missing characters.
    font.prewarm_text(font_resource, "Hello World! 🚀 😀 😉 👍", on_prewarmed)
end

function update(self, dt)
    -- Wait until the font is ready and the text node is set up.
    if not self.text then return end

    -- Accumulate frame time (dt) to change the emoji every second.
    self.emoji_timer = self.emoji_timer + dt
    while self.emoji_timer >= 1.0 do
        self.emoji_timer = self.emoji_timer - 1.0

        -- Advance to the next emoji, wrapping back to the first.
        self.emoji_index = self.emoji_index % #EMOJI + 1

        -- Update the text while keeping the zoom animation running.
        gui.set_text(self.text, text_for(EMOJI[self.emoji_index]))
    end
end