-- initializes the indicator
function Init()
    indicator:name("DeMarker");
    indicator:description("")
    indicator:requiredSource(core.Bar);
    indicator:type(core.Oscillator);

    indicator.parameters:addInteger("N", "Number of periods for smoothing", "", 14);
    indicator.parameters:addColor("C", "Color of the oscillator", "", core.rgb(0, 127, 127));
end

local source;
local first;
local out;
local max;
local min;
local smax;
local smin;
local n;

-- process parameters and prepare for calculations
function Prepare()
    n = instance.parameters.N;
    source = instance.source;

    max = instance:addInternalStream(source:first() + 1);
    min = instance:addInternalStream(source:first() + 1);
    smax = core.indicators:create("MVA", max, n, core.rgb(0, 0, 0));
    smin = core.indicators:create("MVA", min, n, core.rgb(0, 0, 0));
    first = smax.DATA:first();
    name = profile:id() .. "(" .. n .. ")";
    instance:name(name);
    out = instance:addStream("DeM", core.Line, name .. ".DeM", "DeM", instance.parameters.C, first);
    out:addLevel(0);
    out:addLevel(0.3);
    out:addLevel(0.5);
    out:addLevel(0.7);
    out:addLevel(1);
end

-- Indicator calculation routine
function Update(period, mode)
    if (period > source:first() + 1) then
        if (source.high[period] > source.high[period - 1]) then
            max[period] = source.high[period] - source.high[period - 1]
        else
            max[period] = 0;
        end
        if (source.low[period] < source.low[period - 1]) then
            min[period] = source.low[period - 1] - source.low[period];
        else
            min[period] = 0;
        end
    end
    smax:update(mode);
    smin:update(mode);
    if (period >= first) then
        local vmax;
        local vmin;
        vmax = smax.DATA[period];
        vmin = smin.DATA[period];
        if (vmax == 0 and vmin == 0) then
            out[period] = nil;
        else
            out[period] = vmax / (vmax + vmin);
        end
    end
end