//@version=5
indicator("Trend Strength Index", shorttitle="TSI", format=format.price, precision=2, timeframe="", timeframe_gaps=true)

period = input.int(14, "Length", minval = 2)
tsi    = ta.correlation(close, bar_index, period)

bullishColorInput = input.color(color.new(#089981, 90), "Bullish Color")
bearishColorInput = input.color(color.new(#F23645, 90), "Bearish Color")

tsiPlot = plot(tsi, "Trend Strength Index",  color = #7E57C2)
hline( 0,           "TSI Middle Band",       color = color.new(#787B86, 50))
hline( 1,           "TSI Bullish Band",      color = color.new(bullishColorInput, 0))
hline(-1,           "TSI Bearish Band",      color = color.new(bearishColorInput, 0))

midLinePlot = plot(0, color = na, editable = false, display = display.none)
fill(tsiPlot, midLinePlot, 1,  0, top_color = bullishColorInput,  bottom_color = color.new(bullishColorInput, 100), title = "Bullish Gradient Fill")
fill(tsiPlot, midLinePlot, 0, -1, top_color = color.new(bearishColorInput, 100), bottom_color = bearishColorInput,  title = "Bearish Gradient Fill")