Trading Windows - Technical Guide

def _normalize_hhmm(value: int) -> int:
    hours = value // 100
    minutes = value % 100

    if hours < 0:
        hours = 0
    if hours > 23:
        hours = 23
    if minutes < 0:
        minutes = 0
    if minutes > 59:
        minutes = 59

    return (hours * 100) + minutes


def _parse_hhmm_text(value: str, fallback: int) -> int:
    length = len(value)

    if length == 0:
        return _normalize_hhmm(fallback)

    if length <= 2:
        return _normalize_hhmm(int(value) * 100)

    if length == 3:
        hours = int(value[0:1])
        minutes = int(value[1:3])
        return _normalize_hhmm((hours * 100) + minutes)

    hhmm = value[0:4]
    hours = int(hhmm[0:2])
    minutes = int(hhmm[2:4])
    return _normalize_hhmm((hours * 100) + minutes)

def _intervals_overlap(start_a: int, end_a: int, start_b: int, end_b: int) -> bool:
    return start_a < end_b and start_b < end_a


def _bar_overlaps_session(current_hhmm: int, bar_minutes: int, start_hhmm: int, end_hhmm: int) -> bool:
    bar_start = _hhmm_to_minutes(current_hhmm)
    bar_end = bar_start + bar_minutes

    bar_a_start = bar_start % (24 * 60)
    bar_a_end = min(bar_end, 24 * 60)
    bar_b_start = 0
    bar_b_end = bar_end - (24 * 60)
    has_wrap = bar_end > (24 * 60)

    session_start = _hhmm_to_minutes(start_hhmm)
    session_end = _hhmm_to_minutes(end_hhmm)

    if session_start <= session_end:
        if _intervals_overlap(bar_a_start, bar_a_end, session_start, session_end):
            return True
        if has_wrap and _intervals_overlap(bar_b_start, bar_b_end, session_start, session_end):
            return True
        return False

    # Overnight session, split into [start, 24:00) and [00:00, end).
    if _intervals_overlap(bar_a_start, bar_a_end, session_start, 24 * 60):
        return True
    if _intervals_overlap(bar_a_start, bar_a_end, 0, session_end):
        return True
    if has_wrap and _intervals_overlap(bar_b_start, bar_b_end, session_start, 24 * 60):
        return True
    if has_wrap and _intervals_overlap(bar_b_start, bar_b_end, 0, session_end):
        return True
    return False

def _uk_dst_offset_hours(utc_dt: datetime) -> int:
    year = utc_dt.year
    march_last_sunday = _last_sunday(year, 3).day
    october_last_sunday = _last_sunday(year, 10).day
    dst_start_utc = datetime(year=year, month=3, day=march_last_sunday, hour=1, minute=0).timestamp()
    dst_end_utc = datetime(year=year, month=10, day=october_last_sunday, hour=1, minute=0).timestamp()

    utc_ts = utc_dt.timestamp()

    if utc_ts >= dst_start_utc and utc_ts < dst_end_utc:
        return 1
    return 0


def _us_dst_offset_hours(utc_dt: datetime, standard_utc_offset: int) -> int:
    year = utc_dt.year
    march_second_sunday = _second_sunday(year, 3).day
    november_first_sunday = _first_sunday(year, 11).day

    # DST starts at 02:00 local standard time.
    dst_start_utc = (datetime(year=year, month=3, day=march_second_sunday, hour=2, minute=0) - timedelta(hours=standard_utc_offset)).timestamp()
    # DST ends at 02:00 local daylight time.
    dst_end_utc = (datetime(year=year, month=11, day=november_first_sunday, hour=2, minute=0) - timedelta(hours=(standard_utc_offset + 1))).timestamp()

    utc_ts = utc_dt.timestamp()

    if utc_ts >= dst_start_utc and utc_ts < dst_end_utc:
        return standard_utc_offset + 1
    return standard_utc_offset


def _sydney_dst_offset_hours(utc_dt: datetime) -> int:
    # Sydney DST season spans calendar years (Oct -> Apr).
    season_start_year = utc_dt.year
    season_end_year = utc_dt.year

    if utc_dt.month >= 10:
        season_start_year = utc_dt.year
        season_end_year = utc_dt.year + 1
    else:
        season_start_year = utc_dt.year - 1
        season_end_year = utc_dt.year

    october_first_sunday = _first_sunday(season_start_year, 10).day
    april_first_sunday = _first_sunday(season_end_year, 4).day

    def calc(
        self,
        timezone_mode,
        use_default_settings,
        show_session_zones,
        show_session_boundaries,
        show_session_labels,
        weekdays_only,
        enable_asia,
        asia_name,
        asia_start,
        asia_end,
        asia_zone_color,
        enable_london,
        london_name,
        london_start,
        london_end,
        london_zone_color,
        enable_us,
        us_name,
        us_start,
        us_end,
        us_zone_color,
    ):
        if self.time_frame >= TimeFrame(1, time_frame_unit.DAY):
            return plot.Background(color=color.TRANSPARENT), plot.Background(color=color.TRANSPARENT), plot.Background(color=color.TRANSPARENT)

        if use_default_settings:
            # Keep timezone_mode user-configurable while preset lock is enabled.
            show_session_zones = True
            show_session_boundaries = True
            show_session_labels = True
            weekdays_only = True

            enable_asia = True
            asia_name = 'Asia'
            asia_start = '0000'
            asia_end = '0900'
            asia_zone_color = color.AQUA(0.08)

            enable_london = True
            london_name = 'London'
            london_start = '0800'
            london_end = '1700'
            london_zone_color = color.YELLOW(0.08)

        day_key = (current_dt.year * 10000) + (current_dt.month * 100) + current_dt.day

        asia_can_label = False
        london_can_label = False
        us_can_label = False

        if enable_asia and show_session_labels and is_asia and len(asia_name) > 0:
            asia_mid_reached = _session_elapsed_minutes(current_time, asia_start_hhmm) >= (_session_duration_minutes(asia_start_hhmm, asia_end_hhmm) // 2)
            asia_can_label = asia_mid_reached and self._last_asia_label_day != day_key

        if enable_london and show_session_labels and is_london and len(london_name) > 0:
            london_mid_reached = _session_elapsed_minutes(current_time, london_start_hhmm) >= (_session_duration_minutes(london_start_hhmm, london_end_hhmm) // 2)
            london_can_label = london_mid_reached and self._last_london_label_day != day_key

        if enable_us and show_session_labels and is_us and len(us_name) > 0:
            us_mid_reached = _session_elapsed_minutes(current_time, us_start_hhmm) >= (_session_duration_minutes(us_start_hhmm, us_end_hhmm) // 2)
            us_can_label = us_mid_reached and self._last_us_label_day != day_key

        should_draw_labels = asia_can_label or london_can_label or us_can_label

        if should_draw_labels:
            label_y = _label_price_y(self)

            if asia_can_label:
                asia_mid_ts = _session_midpoint_timestamp_for_active_session(self.time[0], timezone_mode, current_time, asia_start_hhmm, asia_end_hhmm)
                self.chart.draw(LabelAbs(asia_name, AbsolutePosition(asia_mid_ts, label_y), bg_color=color.TRANSPARENT, text_color=color.AQUA, font_size=12))
                self._last_asia_label_day = day_key

            if london_can_label:
                london_mid_ts = _session_midpoint_timestamp_for_active_session(self.time[0], timezone_mode, current_time, london_start_hhmm, london_end_hhmm)
                self.chart.draw(LabelAbs(london_name, AbsolutePosition(london_mid_ts, label_y), bg_color=color.TRANSPARENT, text_color=color.YELLOW, font_size=12))
                self._last_london_label_day = day_key

            if us_can_label:
                us_mid_ts = _session_midpoint_timestamp_for_active_session(self.time[0], timezone_mode, current_time, us_start_hhmm, us_end_hhmm)
                self.chart.draw(LabelAbs(us_name, AbsolutePosition(us_mid_ts, label_y), bg_color=color.TRANSPARENT, text_color=color.BLUE, font_size=12))
                self._last_us_label_day = day_key

# Copyright (c) 2025 @nightranger. All rights reserved.

# This work is licensed under the MIT License.
# For a copy, see <https://opensource.org/licenses/MIT>

# indie:lang_version = 5
from datetime import datetime, timedelta
from math import isnan

from indie import TimeFrame, MainContext, color, indicator, line_style, param, plot, time_frame_unit
from indie.drawings import AbsolutePosition, LabelAbs


def _normalize_hhmm(value: int) -> int:
    hours = value // 100
    minutes = value % 100

    if hours < 0:
        hours = 0
    if hours > 23:
        hours = 23
    if minutes < 0:
        minutes = 0
    if minutes > 59:
        minutes = 59

    return (hours * 100) + minutes


def _parse_hhmm_text(value: str, fallback: int) -> int:
    length = len(value)

    if length == 0:
        return _normalize_hhmm(fallback)

    if length <= 2:
        return _normalize_hhmm(int(value) * 100)

    if length == 3:
        hours = int(value[0:1])
        minutes = int(value[1:3])
        return _normalize_hhmm((hours * 100) + minutes)

    hhmm = value[0:4]
    hours = int(hhmm[0:2])
    minutes = int(hhmm[2:4])
    return _normalize_hhmm((hours * 100) + minutes)


def _hhmm_to_minutes(value: int) -> int:
    return ((value // 100) * 60) + (value % 100)


def _minutes_to_hhmm(value: int) -> int:
    hours = value // 60
    minutes = value % 60
    return (hours * 100) + minutes


def _session_midpoint_hhmm(start_hhmm: int, end_hhmm: int) -> int:
    start_minutes = _hhmm_to_minutes(start_hhmm)
    end_minutes = _hhmm_to_minutes(end_hhmm)
    duration = 0

    if end_minutes >= start_minutes:
        duration = end_minutes - start_minutes
    else:
        duration = (24 * 60) - start_minutes + end_minutes

    midpoint = (start_minutes + (duration // 2)) % (24 * 60)
    return _minutes_to_hhmm(midpoint)


def _session_midpoint_timestamp_from_current(current_utc_ts: float, current_hhmm: int, start_hhmm: int, end_hhmm: int) -> float:
    midpoint_hhmm = _session_midpoint_hhmm(start_hhmm, end_hhmm)
    current_minutes = _hhmm_to_minutes(current_hhmm)
    midpoint_minutes = _hhmm_to_minutes(midpoint_hhmm)

    delta_minutes = midpoint_minutes - current_minutes
    if delta_minutes < 0:
        delta_minutes += 24 * 60

    return current_utc_ts + (delta_minutes * 60.0)


def _session_midpoint_timestamp_for_active_session(current_utc_ts: float, timezone_mode: str, current_hhmm: int, start_hhmm: int, end_hhmm: int) -> float:
    local_dt = _session_datetime(current_utc_ts, timezone_mode)
    local_session_start = datetime(
        year=local_dt.year,
        month=local_dt.month,
        day=local_dt.day,
        hour=(start_hhmm // 100),
        minute=(start_hhmm % 100),
    )

    # For overnight sessions, bars after midnight belong to the prior session start day.
    if start_hhmm > end_hhmm and current_hhmm <= end_hhmm:
        local_session_start = local_session_start - timedelta(days=1)

    midpoint_local = local_session_start + timedelta(minutes=(_session_duration_minutes(start_hhmm, end_hhmm) // 2))

    current_utc_dt = datetime.utcfromtimestamp(current_utc_ts)
    offset_hours = _timezone_offset_hours(current_utc_dt, timezone_mode)
    midpoint_utc_dt = midpoint_local - timedelta(hours=offset_hours)

    # Re-evaluate offset at midpoint to handle rare DST-shift edge cases.
    midpoint_offset_hours = _timezone_offset_hours(midpoint_utc_dt, timezone_mode)
    if midpoint_offset_hours != offset_hours:
        midpoint_utc_dt = midpoint_local - timedelta(hours=midpoint_offset_hours)

    return midpoint_utc_dt.timestamp()


def _label_price_y(ctx: MainContext, lookback_bars: int = 300) -> float:
    highest = ctx.high[0]
    lowest = ctx.low[0]

    i = 1
    while i < lookback_bars:
        if isnan(ctx.time[i]):
            break

        if ctx.high[i] > highest:
            highest = ctx.high[i]
        if ctx.low[i] < lowest:
            lowest = ctx.low[i]

        i += 1

    price_range = highest - lowest
    if price_range <= 0:
        price_range = highest * 0.01 if highest > 0 else 1.0

    # Strong padding to keep tags near the pane top rather than near candles.
    return highest + (price_range * 0.25)


def _is_in_window(current_hhmm: int, start_hhmm: int, end_hhmm: int) -> bool:
    if start_hhmm <= end_hhmm:
        return current_hhmm >= start_hhmm and current_hhmm <= end_hhmm
    # Overnight window support, e.g. 2200 -> 0300.
    return current_hhmm >= start_hhmm or current_hhmm <= end_hhmm


def _session_duration_minutes(start_hhmm: int, end_hhmm: int) -> int:
    start_minutes = _hhmm_to_minutes(start_hhmm)
    end_minutes = _hhmm_to_minutes(end_hhmm)
    if end_minutes >= start_minutes:
        return end_minutes - start_minutes
    return (24 * 60) - start_minutes + end_minutes


def _session_elapsed_minutes(current_hhmm: int, start_hhmm: int) -> int:
    current_minutes = _hhmm_to_minutes(current_hhmm)
    start_minutes = _hhmm_to_minutes(start_hhmm)
    if current_minutes >= start_minutes:
        return current_minutes - start_minutes
    return (24 * 60) - start_minutes + current_minutes


def _intervals_overlap(start_a: int, end_a: int, start_b: int, end_b: int) -> bool:
    return start_a < end_b and start_b < end_a


def _bar_overlaps_session(current_hhmm: int, bar_minutes: int, start_hhmm: int, end_hhmm: int) -> bool:
    bar_start = _hhmm_to_minutes(current_hhmm)
    bar_end = bar_start + bar_minutes

    bar_a_start = bar_start % (24 * 60)
    bar_a_end = min(bar_end, 24 * 60)
    bar_b_start = 0
    bar_b_end = bar_end - (24 * 60)
    has_wrap = bar_end > (24 * 60)

    session_start = _hhmm_to_minutes(start_hhmm)
    session_end = _hhmm_to_minutes(end_hhmm)

    if session_start <= session_end:
        if _intervals_overlap(bar_a_start, bar_a_end, session_start, session_end):
            return True
        if has_wrap and _intervals_overlap(bar_b_start, bar_b_end, session_start, session_end):
            return True
        return False

    # Overnight session, split into [start, 24:00) and [00:00, end).
    if _intervals_overlap(bar_a_start, bar_a_end, session_start, 24 * 60):
        return True
    if _intervals_overlap(bar_a_start, bar_a_end, 0, session_end):
        return True
    if has_wrap and _intervals_overlap(bar_b_start, bar_b_end, session_start, 24 * 60):
        return True
    if has_wrap and _intervals_overlap(bar_b_start, bar_b_end, 0, session_end):
        return True
    return False


def _bar_minutes_from_context(ctx: MainContext) -> int:
    if isnan(ctx.time[1]):
        return 1

    seconds = int(ctx.time[0] - ctx.time[1])
    if seconds <= 0:
        return 1

    minutes = seconds // 60
    if minutes < 1:
        minutes = 1
    if minutes > 24 * 60:
        minutes = 24 * 60
    return minutes


def _is_session_bar_active(enable_session: bool, is_active_day: bool, current_hhmm: int, bar_minutes: int, start_hhmm: int, end_hhmm: int) -> bool:
    if not enable_session or not is_active_day:
        return False
    return _bar_overlaps_session(current_hhmm, bar_minutes, start_hhmm, end_hhmm)


def _session_day_for_weekday_filter(day_index: int, current_hhmm: int, start_hhmm: int, end_hhmm: int) -> int:
    # For overnight windows, bars after midnight belong to the previous session day.
    if start_hhmm > end_hhmm and current_hhmm <= end_hhmm:
        return (day_index + 6) % 7
    return day_index


def _is_active_day_for_session(day_index: int, current_hhmm: int, weekdays_only: bool, start_hhmm: int, end_hhmm: int) -> bool:
    if not weekdays_only:
        return True
    session_day = _session_day_for_weekday_filter(day_index, current_hhmm, start_hhmm, end_hhmm)
    return session_day >= 0 and session_day <= 4


def _is_session_active(enable_session: bool, is_active_day: bool, current_hhmm: int, start_hhmm: int, end_hhmm: int) -> bool:
    if not enable_session or not is_active_day:
        return False
    return _is_in_window(current_hhmm, start_hhmm, end_hhmm)


def _is_leap_year(year: int) -> bool:
    if year % 400 == 0:
        return True
    if year % 100 == 0:
        return False
    return year % 4 == 0


def _days_in_month(year: int, month: int) -> int:
    if month == 2:
        return 29 if _is_leap_year(year) else 28
    if month in [4, 6, 9, 11]:
        return 30
    return 31


def _last_sunday(year: int, month: int) -> datetime:
    day = _days_in_month(year, month)
    dt = datetime(year=year, month=month, day=day)
    days_back = (dt.weekday() + 1) % 7
    return datetime(year=year, month=month, day=(day - days_back))


def _first_sunday(year: int, month: int) -> datetime:
    dt = datetime(year=year, month=month, day=1)
    days_forward = (6 - dt.weekday()) % 7
    return datetime(year=year, month=month, day=(1 + days_forward))


def _second_sunday(year: int, month: int) -> datetime:
    return _first_sunday(year, month) + timedelta(days=7)


def _uk_dst_offset_hours(utc_dt: datetime) -> int:
    year = utc_dt.year
    march_last_sunday = _last_sunday(year, 3).day
    october_last_sunday = _last_sunday(year, 10).day
    dst_start_utc = datetime(year=year, month=3, day=march_last_sunday, hour=1, minute=0).timestamp()
    dst_end_utc = datetime(year=year, month=10, day=october_last_sunday, hour=1, minute=0).timestamp()

    utc_ts = utc_dt.timestamp()

    if utc_ts >= dst_start_utc and utc_ts < dst_end_utc:
        return 1
    return 0


def _us_dst_offset_hours(utc_dt: datetime, standard_utc_offset: int) -> int:
    year = utc_dt.year
    march_second_sunday = _second_sunday(year, 3).day
    november_first_sunday = _first_sunday(year, 11).day

    # DST starts at 02:00 local standard time.
    dst_start_utc = (datetime(year=year, month=3, day=march_second_sunday, hour=2, minute=0) - timedelta(hours=standard_utc_offset)).timestamp()
    # DST ends at 02:00 local daylight time.
    dst_end_utc = (datetime(year=year, month=11, day=november_first_sunday, hour=2, minute=0) - timedelta(hours=(standard_utc_offset + 1))).timestamp()

    utc_ts = utc_dt.timestamp()

    if utc_ts >= dst_start_utc and utc_ts < dst_end_utc:
        return standard_utc_offset + 1
    return standard_utc_offset


def _sydney_dst_offset_hours(utc_dt: datetime) -> int:
    # Sydney DST season spans calendar years (Oct -> Apr).
    season_start_year = utc_dt.year
    season_end_year = utc_dt.year

    if utc_dt.month >= 10:
        season_start_year = utc_dt.year
        season_end_year = utc_dt.year + 1
    else:
        season_start_year = utc_dt.year - 1
        season_end_year = utc_dt.year

    october_first_sunday = _first_sunday(season_start_year, 10).day
    april_first_sunday = _first_sunday(season_end_year, 4).day

    # Start: 02:00 local standard time (UTC+10).
    dst_start_utc = (datetime(year=season_start_year, month=10, day=october_first_sunday, hour=2, minute=0) - timedelta(hours=10)).timestamp()
    # End: 03:00 local daylight time (UTC+11).
    dst_end_utc = (datetime(year=season_end_year, month=4, day=april_first_sunday, hour=3, minute=0) - timedelta(hours=11)).timestamp()

    utc_ts = utc_dt.timestamp()

    if utc_ts >= dst_start_utc and utc_ts < dst_end_utc:
        return 11
    return 10


def _timezone_offset_hours(utc_dt: datetime, timezone_mode: str) -> int:
    if timezone_mode == 'UTC':
        return 0

    if timezone_mode == 'Europe/London (DST Auto)':
        return _uk_dst_offset_hours(utc_dt)

    if timezone_mode == 'America/New_York (DST Auto)':
        return _us_dst_offset_hours(utc_dt, -5)

    if timezone_mode == 'America/Chicago (DST Auto)':
        return _us_dst_offset_hours(utc_dt, -6)

    if timezone_mode == 'America/Los_Angeles (DST Auto)':
        return _us_dst_offset_hours(utc_dt, -8)

    if timezone_mode == 'Asia/Tokyo':
        return 9

    if timezone_mode == 'Asia/Singapore':
        return 8

    if timezone_mode == 'Australia/Sydney (DST Auto)':
        return _sydney_dst_offset_hours(utc_dt)

    return 0


def _session_datetime(timestamp: float, timezone_mode: str) -> datetime:
    utc_dt = datetime.utcfromtimestamp(timestamp)
    return utc_dt + timedelta(hours=_timezone_offset_hours(utc_dt, timezone_mode))


@indicator('Trading Windows', overlay_main_pane=True)
@param.str(
    'timezone_mode',
    default='Europe/London (DST Auto)',
    title='Timezone Mode',
    options=[
        'Europe/London (DST Auto)',
        'America/New_York (DST Auto)',
        'America/Chicago (DST Auto)',
        'America/Los_Angeles (DST Auto)',
        'Asia/Tokyo',
        'Asia/Singapore',
        'Australia/Sydney (DST Auto)',
        'UTC',
    ],
)
@param.bool('use_default_settings', default=True, title='Use Default Settings (Preset Lock)')
@param.bool('show_session_zones', default=True, title='Show Session Zones')
@param.bool('show_session_boundaries', default=True, title='Show Session Boundary Bars')
@param.bool('show_session_labels', default=True, title='Show Session Labels')
@param.bool('weekdays_only', default=True, title='Weekdays Only (Mon-Fri)')
@param.bool('enable_asia', default=True, title='Enable Asia Session')
@param.str('asia_name', default='Asia', title='Session 1 Name')
@param.str('asia_start', default='0000', title='Asia Start (HHMM)')
@param.str('asia_end', default='0900', title='Asia End (HHMM)')
@param.color('asia_zone_color', default=color.AQUA(0.08), title='Asia Zone Color')
@param.bool('enable_london', default=True, title='Enable London Session')
@param.str('london_name', default='London', title='Session 2 Name')
@param.str('london_start', default='0800', title='London Start (HHMM)')
@param.str('london_end', default='1700', title='London End (HHMM)')
@param.color('london_zone_color', default=color.YELLOW(0.08), title='London Zone Color')
@param.bool('enable_us', default=True, title='Enable US Session')
@param.str('us_name', default='US', title='Session 3 Name')
@param.str('us_start', default='1430', title='US Start (HHMM)')
@param.str('us_end', default='2100', title='US End (HHMM)')
@param.color('us_zone_color', default=color.BLUE(0.08), title='US Zone Color')
@plot.background(title='Asia Session Zone', outline_color=color.AQUA, outline_style=line_style.DASHED, outline_width=1)
@plot.background(title='London Session Zone', outline_color=color.YELLOW, outline_style=line_style.DASHED, outline_width=1)
@plot.background(title='US Session Zone', outline_color=color.BLUE, outline_style=line_style.DASHED, outline_width=1)
class Main(MainContext):
    def __init__(self):
        self._asia_start_text = ''
        self._asia_end_text = ''
        self._london_start_text = ''
        self._london_end_text = ''
        self._us_start_text = ''
        self._us_end_text = ''

        self._asia_start_hhmm = 0
        self._asia_end_hhmm = 900
        self._london_start_hhmm = 800
        self._london_end_hhmm = 1700
        self._us_start_hhmm = 1430
        self._us_end_hhmm = 2100

        self._last_asia_label_day = -1
        self._last_london_label_day = -1
        self._last_us_label_day = -1

    def _refresh_hhmm_cache(self, asia_start: str, asia_end: str, london_start: str, london_end: str, us_start: str, us_end: str) -> None:
        if asia_start != self._asia_start_text:
            self._asia_start_text = asia_start
            self._asia_start_hhmm = _parse_hhmm_text(asia_start, 0)

        if asia_end != self._asia_end_text:
            self._asia_end_text = asia_end
            self._asia_end_hhmm = _parse_hhmm_text(asia_end, 900)

        if london_start != self._london_start_text:
            self._london_start_text = london_start
            self._london_start_hhmm = _parse_hhmm_text(london_start, 800)

        if london_end != self._london_end_text:
            self._london_end_text = london_end
            self._london_end_hhmm = _parse_hhmm_text(london_end, 1700)

        if us_start != self._us_start_text:
            self._us_start_text = us_start
            self._us_start_hhmm = _parse_hhmm_text(us_start, 1430)

        if us_end != self._us_end_text:
            self._us_end_text = us_end
            self._us_end_hhmm = _parse_hhmm_text(us_end, 2100)

    def calc(
        self,
        timezone_mode,
        use_default_settings,
        show_session_zones,
        show_session_boundaries,
        show_session_labels,
        weekdays_only,
        enable_asia,
        asia_name,
        asia_start,
        asia_end,
        asia_zone_color,
        enable_london,
        london_name,
        london_start,
        london_end,
        london_zone_color,
        enable_us,
        us_name,
        us_start,
        us_end,
        us_zone_color,
    ):
        if self.time_frame >= TimeFrame(1, time_frame_unit.DAY):
            return plot.Background(color=color.TRANSPARENT), plot.Background(color=color.TRANSPARENT), plot.Background(color=color.TRANSPARENT)

        if use_default_settings:
            # Keep timezone_mode user-configurable while preset lock is enabled.
            show_session_zones = True
            show_session_boundaries = True
            show_session_labels = True
            weekdays_only = True

            enable_asia = True
            asia_name = 'Asia'
            asia_start = '0000'
            asia_end = '0900'
            asia_zone_color = color.AQUA(0.08)

            enable_london = True
            london_name = 'London'
            london_start = '0800'
            london_end = '1700'
            london_zone_color = color.YELLOW(0.08)

            enable_us = True
            us_name = 'US'
            us_start = '1430'
            us_end = '2100'
            us_zone_color = color.BLUE(0.08)

        self._refresh_hhmm_cache(asia_start, asia_end, london_start, london_end, us_start, us_end)
        asia_start_hhmm = self._asia_start_hhmm
        asia_end_hhmm = self._asia_end_hhmm
        london_start_hhmm = self._london_start_hhmm
        london_end_hhmm = self._london_end_hhmm
        us_start_hhmm = self._us_start_hhmm
        us_end_hhmm = self._us_end_hhmm

        current_dt = _session_datetime(self.time[0], timezone_mode)
        current_day = current_dt.weekday()  # Monday = 0, Sunday = 6
        current_time = (current_dt.hour * 100) + current_dt.minute
        bar_minutes = _bar_minutes_from_context(self)

        is_asia_day = _is_active_day_for_session(current_day, current_time, weekdays_only, asia_start_hhmm, asia_end_hhmm)
        is_london_day = _is_active_day_for_session(current_day, current_time, weekdays_only, london_start_hhmm, london_end_hhmm)
        is_us_day = _is_active_day_for_session(current_day, current_time, weekdays_only, us_start_hhmm, us_end_hhmm)

        is_asia = _is_session_active(enable_asia, is_asia_day, current_time, asia_start_hhmm, asia_end_hhmm)
        is_london = _is_session_active(enable_london, is_london_day, current_time, london_start_hhmm, london_end_hhmm)
        is_us = _is_session_active(enable_us, is_us_day, current_time, us_start_hhmm, us_end_hhmm)

        is_asia_zone = _is_session_bar_active(enable_asia, is_asia_day, current_time, bar_minutes, asia_start_hhmm, asia_end_hhmm)
        is_london_zone = _is_session_bar_active(enable_london, is_london_day, current_time, bar_minutes, london_start_hhmm, london_end_hhmm)
        is_us_zone = _is_session_bar_active(enable_us, is_us_day, current_time, bar_minutes, us_start_hhmm, us_end_hhmm)

        prev_is_asia = False
        prev_is_london = False
        prev_is_us = False
        prev_is_asia_zone = False
        prev_is_london_zone = False
        prev_is_us_zone = False

        if isnan(self.time[1]):
            prev_is_asia = False
            prev_is_london = False
            prev_is_us = False
        else:
            prev_dt = _session_datetime(self.time[1], timezone_mode)
            prev_day = prev_dt.weekday()
            prev_time = (prev_dt.hour * 100) + prev_dt.minute

            prev_is_asia_day = _is_active_day_for_session(prev_day, prev_time, weekdays_only, asia_start_hhmm, asia_end_hhmm)
            prev_is_london_day = _is_active_day_for_session(prev_day, prev_time, weekdays_only, london_start_hhmm, london_end_hhmm)
            prev_is_us_day = _is_active_day_for_session(prev_day, prev_time, weekdays_only, us_start_hhmm, us_end_hhmm)

            prev_is_asia = _is_session_active(enable_asia, prev_is_asia_day, prev_time, asia_start_hhmm, asia_end_hhmm)
            prev_is_london = _is_session_active(enable_london, prev_is_london_day, prev_time, london_start_hhmm, london_end_hhmm)
            prev_is_us = _is_session_active(enable_us, prev_is_us_day, prev_time, us_start_hhmm, us_end_hhmm)

            prev_is_asia_zone = _is_session_bar_active(enable_asia, prev_is_asia_day, prev_time, bar_minutes, asia_start_hhmm, asia_end_hhmm)
            prev_is_london_zone = _is_session_bar_active(enable_london, prev_is_london_day, prev_time, bar_minutes, london_start_hhmm, london_end_hhmm)
            prev_is_us_zone = _is_session_bar_active(enable_us, prev_is_us_day, prev_time, bar_minutes, us_start_hhmm, us_end_hhmm)

        asia_ends = show_session_boundaries and prev_is_asia_zone and not is_asia_zone
        london_ends = show_session_boundaries and prev_is_london_zone and not is_london_zone
        us_ends = show_session_boundaries and prev_is_us_zone and not is_us_zone

        # Render compensation: keep color on the transition-out bar so visual fill meets boundary lines.
        asia_zone_paint = is_asia_zone or (prev_is_asia_zone and not is_asia_zone)
        london_zone_paint = is_london_zone or (prev_is_london_zone and not is_london_zone)
        us_zone_paint = is_us_zone or (prev_is_us_zone and not is_us_zone)

        asia_background = plot.Background(color=color.TRANSPARENT)
        if show_session_zones and asia_zone_paint:
            asia_background.color = asia_zone_color
        asia_background.outline_left = show_session_boundaries and is_asia_zone and not prev_is_asia_zone
        asia_background.outline_right = show_session_boundaries and asia_ends

        london_background = plot.Background(color=color.TRANSPARENT)
        if show_session_zones and london_zone_paint:
            london_background.color = london_zone_color
        london_background.outline_left = show_session_boundaries and is_london_zone and not prev_is_london_zone
        london_background.outline_right = show_session_boundaries and london_ends

        us_background = plot.Background(color=color.TRANSPARENT)
        if show_session_zones and us_zone_paint:
            us_background.color = us_zone_color
        us_background.outline_left = show_session_boundaries and is_us_zone and not prev_is_us_zone
        us_background.outline_right = show_session_boundaries and us_ends

        day_key = (current_dt.year * 10000) + (current_dt.month * 100) + current_dt.day

        asia_can_label = False
        london_can_label = False
        us_can_label = False

        if enable_asia and show_session_labels and is_asia and len(asia_name) > 0:
            asia_mid_reached = _session_elapsed_minutes(current_time, asia_start_hhmm) >= (_session_duration_minutes(asia_start_hhmm, asia_end_hhmm) // 2)
            asia_can_label = asia_mid_reached and self._last_asia_label_day != day_key

        if enable_london and show_session_labels and is_london and len(london_name) > 0:
            london_mid_reached = _session_elapsed_minutes(current_time, london_start_hhmm) >= (_session_duration_minutes(london_start_hhmm, london_end_hhmm) // 2)
            london_can_label = london_mid_reached and self._last_london_label_day != day_key

        if enable_us and show_session_labels and is_us and len(us_name) > 0:
            us_mid_reached = _session_elapsed_minutes(current_time, us_start_hhmm) >= (_session_duration_minutes(us_start_hhmm, us_end_hhmm) // 2)
            us_can_label = us_mid_reached and self._last_us_label_day != day_key

        should_draw_labels = asia_can_label or london_can_label or us_can_label

        if should_draw_labels:
            label_y = _label_price_y(self)

            if asia_can_label:
                asia_mid_ts = _session_midpoint_timestamp_for_active_session(self.time[0], timezone_mode, current_time, asia_start_hhmm, asia_end_hhmm)
                self.chart.draw(LabelAbs(asia_name, AbsolutePosition(asia_mid_ts, label_y), bg_color=color.TRANSPARENT, text_color=color.AQUA, font_size=12))
                self._last_asia_label_day = day_key

            if london_can_label:
                london_mid_ts = _session_midpoint_timestamp_for_active_session(self.time[0], timezone_mode, current_time, london_start_hhmm, london_end_hhmm)
                self.chart.draw(LabelAbs(london_name, AbsolutePosition(london_mid_ts, label_y), bg_color=color.TRANSPARENT, text_color=color.YELLOW, font_size=12))
                self._last_london_label_day = day_key

            if us_can_label:
                us_mid_ts = _session_midpoint_timestamp_for_active_session(self.time[0], timezone_mode, current_time, us_start_hhmm, us_end_hhmm)
                self.chart.draw(LabelAbs(us_name, AbsolutePosition(us_mid_ts, label_y), bg_color=color.TRANSPARENT, text_color=color.BLUE, font_size=12))
                self._last_us_label_day = day_key

        return asia_background, london_background, us_background