local M = {}

local DEFAULT_INTERVAL_S = 5.0
local MANUAL_PAUSE_S     = 30.0
local MAX_DOTS           = 7
local ARROW_W            = 32
local DOT_R              = 4
local DOT_GAP            = 6
local COLOR_ARROW_BG     = 0x00000080
local COLOR_ARROW_FG     = 0xE0E0E0FF
local COLOR_DOT          = 0xC0C0C060
local COLOR_DOT_ACTIVE   = 0xFFFFFFFF
local COLOR_OVERLAY      = 0xE0E0E0FF
local COLOR_FALLBACK_BG  = 0x303030FF

function M.new_state(module_id, teaser_paths, interval)
    return {
        module_id    = module_id,
        teaser_paths = teaser_paths or {},
        textures     = {},     -- index -> texture or nil if load-failed
        loaded       = {},     -- index -> true once loaded
        index        = 1,
        timer        = 0,
        interval     = interval or DEFAULT_INTERVAL_S,
        manual_pause = 0,
        left_rect    = nil,
        right_rect   = nil,
    }
end

local function ensure_texture(s, i, default_texture)
    if s.loaded[i] then return s.textures[i] end
    s.loaded[i] = true
    local path = s.teaser_paths[i]
    if not path then s.textures[i] = default_texture; return default_texture end
    local tex, err = engine.module.load_texture(s.module_id, path)
    s.textures[i] = tex or default_texture
    return s.textures[i]
end

function M.update(s, dt)
    if #s.teaser_paths < 2 then return end
    if s.manual_pause > 0 then
        s.manual_pause = s.manual_pause - dt
        return
    end
    s.timer = s.timer + dt
    if s.timer >= s.interval then
        s.timer = 0
        s.index = s.index + 1
        if s.index > #s.teaser_paths then s.index = 1 end
    end
end

function M.render(s, x, y, w, h, default_texture)
    -- Background (clipping is up to the parent panel — we just clip-render).
    engine.render.draw_rect(x, y, w, h, COLOR_FALLBACK_BG)

    local total = math.max(1, #s.teaser_paths)
    local tex = ensure_texture(s, s.index, default_texture) or default_texture
    if tex then engine.render.draw_texture(tex, x, y) end

    if total > 1 then
        -- Arrows.
        s.left_rect  = { x = x,           y = y + h / 2 - 16, w = ARROW_W, h = 32 }
        s.right_rect = { x = x + w - ARROW_W, y = y + h / 2 - 16, w = ARROW_W, h = 32 }
        engine.render.draw_rect(s.left_rect.x,  s.left_rect.y,  ARROW_W, 32, COLOR_ARROW_BG)
        engine.render.draw_rect(s.right_rect.x, s.right_rect.y, ARROW_W, 32, COLOR_ARROW_BG)
        engine.render.draw_text("<", s.left_rect.x + 10,  s.left_rect.y + 6, 20, COLOR_ARROW_FG)
        engine.render.draw_text(">", s.right_rect.x + 10, s.right_rect.y + 6, 20, COLOR_ARROW_FG)

        -- Dots.
        local dot_count = math.min(total, MAX_DOTS)
        local dots_w = dot_count * (DOT_R * 2) + (dot_count - 1) * DOT_GAP
        local dot_x  = x + (w - dots_w) / 2
        local dot_y  = y + h - 16
        for i = 1, dot_count do
            local col = (i == s.index) and COLOR_DOT_ACTIVE or COLOR_DOT
            engine.render.draw_rect(dot_x, dot_y, DOT_R * 2, DOT_R * 2, col)
            dot_x = dot_x + DOT_R * 2 + DOT_GAP
        end
        if total > MAX_DOTS then
            local label = string.format("%d / %d", s.index, total)
            engine.render.draw_text(label, x + w - 80, dot_y - 4, 14, COLOR_OVERLAY)
        end
    end
end

function M.handle_click(s, mx, my)
    if not s or not s.left_rect then return false end
    if engine.spatial.aabb_contains_point(s.left_rect, mx, my) then
        s.index = s.index - 1
        if s.index < 1 then s.index = #s.teaser_paths end
        s.timer = 0
        s.manual_pause = MANUAL_PAUSE_S
        return true
    end
    if engine.spatial.aabb_contains_point(s.right_rect, mx, my) then
        s.index = s.index + 1
        if s.index > #s.teaser_paths then s.index = 1 end
        s.timer = 0
        s.manual_pause = MANUAL_PAUSE_S
        return true
    end
    return false
end

return M