Bollinger Band Strategy

//Run the following Script on PINE EDITOR or any platform supporting Pine Script

// This source code is subject to the terms of the Mozilla Public License 2.0 at https://mozilla.org/MPL/2.0/
// © might-tree

//@version=5
strategy("Bollinger Band Strategy", overlay=true, margin_long=100, margin_short=100)

start_time = input.time(timestamp("20 Jul 2020 00:00 +0300"), "Strategy Start Date")
exit_time = input.time(timestamp("20 Jul 2023 00:00 +0300"), "Strategy Exit Date")

in_period = time>=timestamp("20 Jul 2022 00:00 +0300") and time<=timestamp("20 Jul 2023 00:00 +0300")


bb_length = input.int(20)
bb_mult = input.int(2)

[middle, upper, lower] = ta.bb(close,bb_length, bb_mult)
plot(middle, color=color.rgb(228, 231, 75))
plot(upper, color=color.rgb(0, 255, 34))
plot(lower, color=color.rgb(255, 0, 85))
long_cond = ta.crossover(close,lower)
short_cond = ta.crossunder(close,upper)

var saved_ph = 0.0
if strategy.opentrades>0 and strategy.opentrades[1]==0 and strategy.position_size > 0
    saved_ph := upper[1]
var saved_pl = 0.0
if strategy.opentrades>0 and strategy.opentrades[1]==0 and strategy.position_size < 0
    saved_pl := lower[1]

avg = strategy.position_avg_price

long_diff = saved_ph-avg
short_diff = saved_pl-avg

long_stoploss = avg - 1*long_diff
short_stoploss = avg - 1*short_diff

long_avgdown = avg - 0.5*long_diff
short_avgup = avg - 0.5*short_diff

long_profit_price = avg + 0.5*long_diff
short_profit_price = avg + 0.5*short_diff

var label _label = na
if in_period
    if long_cond and strategy.opentrades==0
        strategy.entry("Long",strategy.long)
    if long_cond and strategy.opentrades >0 and (close[1]<long_avgdown or close[2]<long_avgdown)
        strategy.entry("Long",strategy.long)

    if short_cond and strategy.opentrades==0
        strategy.entry("Short", strategy.short)
    if short_cond and strategy.opentrades>0 and (close[1]>short_avgup or close[2]>short_avgup)
        strategy.entry("Short",strategy.short)

plot(avg, style=plot.style_linebr)


plot(strategy.position_size > 0? long_profit_price: na,color=color.green, style=plot.style_linebr)
plot(strategy.position_size > 0? long_avgdown: na,color=color.rgb(177, 255, 59), style=plot.style_linebr)
plot(strategy.position_size > 0? long_stoploss: na,color=color.rgb(82, 255, 192), style=plot.style_linebr)

plot(strategy.position_size < 0? short_profit_price: na,color=color.rgb(243, 255, 74), style=plot.style_linebr)
plot(strategy.position_size < 0? short_avgup: na,color=color.rgb(248, 190, 97), style=plot.style_linebr)
plot(strategy.position_size < 0? short_stoploss: na,color=color.rgb(255, 0, 0), style=plot.style_linebr)

var co = false
if strategy.position_size > 0 and ta.crossover(close, middle)
    co := true
var cu = false
if strategy.position_size < 0 and ta.crossunder(close, middle)
    cu := true
if strategy.opentrades == 0
    co := false
    cu := false

if strategy.position_size > 0
    if co
        strategy.exit("Long Exit", "Long", limit=long_profit_price, stop=middle)
    else
        strategy.exit("Long Exit", "Long", limit=long_profit_price, stop=long_stoploss)
if strategy.position_size < 0
    if cu
        strategy.exit("Short Exit", "Short", limit=short_profit_price, stop=middle)
    else
        strategy.exit("Short Exit", "Short", limit=short_profit_price, stop=short_stoploss)