local state = {
    ratio = 0.58,
    offset = 0,
}

local sides = { "left", "top", "right", "bottom" }
local opposite = {
    left = "right",
    right = "left",
    top = "bottom",
    bottom = "top",
}

local function clamp(x, min, max)
    return math.max(min, math.min(max, x))
end

hl.layout.register("spiral", {
    recalculate = function(ctx)
        local n = #ctx.targets
        if n == 0 then
            return
        end

        local area = ctx.area

        for i, target in ipairs(ctx.targets) do
            if i == n then
                target:place(area)
            else
                local side = sides[((i - 1 + state.offset) % #sides) + 1]
                target:place(ctx:split(area, side, state.ratio))
                area = ctx:split(area, opposite[side], 1.0 - state.ratio)
            end
        end
    end,

    layout_msg = function(ctx, msg)
        local command, arg = msg:match("^(%S+)%s*(.*)$")

        if command == "ratio" then
            state.ratio = clamp(tonumber(arg) or state.ratio, 0.1, 0.9)
        elseif command == "grow" then
            state.ratio = clamp(state.ratio + 0.05, 0.1, 0.9)
        elseif command == "shrink" then
            state.ratio = clamp(state.ratio - 0.05, 0.1, 0.9)
        elseif command == "rotate" then
            state.offset = (state.offset + 1) % #sides
        else
            return "spiral: expected ratio <0.1..0.9>, grow, shrink, or rotate"
        end

        return true
    end,
})