301 lines
9.6 KiB
Elixir
301 lines
9.6 KiB
Elixir
defmodule ToweropsWeb.TimeHelpers do
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@moduledoc """
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Helper functions for formatting time and date values with timezone support.
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All functions use a centralized `to_user_timezone/2` function to convert UTC
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datetimes to the user's preferred timezone.
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"""
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use Gettext, backend: ToweropsWeb.Gettext
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# Common timezone offsets in seconds
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# Note: These are standard time offsets. DST handling would require a full timezone database.
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@timezone_offsets %{
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"UTC" => 0,
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"America/New_York" => -18_000,
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# EST (UTC-5)
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"America/Chicago" => -21_600,
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# CST (UTC-6)
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"America/Denver" => -25_200,
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# MST (UTC-7)
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"America/Los_Angeles" => -28_800,
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# PST (UTC-8)
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"America/Phoenix" => -25_200,
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# MST (no DST)
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"Europe/London" => 0,
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# GMT (UTC+0)
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"Europe/Paris" => 3600,
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# CET (UTC+1)
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"Europe/Berlin" => 3600,
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# CET (UTC+1)
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"Asia/Tokyo" => 32_400,
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# JST (UTC+9)
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"Asia/Shanghai" => 28_800,
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# CST (UTC+8)
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"Asia/Dubai" => 14_400,
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# GST (UTC+4)
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"Australia/Sydney" => 36_000
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# AEST (UTC+10)
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}
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@timezone_abbrs %{
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"UTC" => "UTC",
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"America/New_York" => "EST",
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"America/Chicago" => "CST",
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"America/Denver" => "MST",
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"America/Los_Angeles" => "PST",
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"America/Phoenix" => "MST",
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"Europe/London" => "GMT",
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"Europe/Paris" => "CET",
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"Europe/Berlin" => "CET",
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"Asia/Tokyo" => "JST",
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"Asia/Shanghai" => "CST",
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"Asia/Dubai" => "GST",
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"Australia/Sydney" => "AEST"
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}
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@doc """
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Central function to convert a UTC DateTime to the user's timezone.
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All other formatting functions should use this function to ensure consistent
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timezone handling across the application.
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Returns `{:ok, shifted_datetime, timezone_abbr}` or `{:error, reason}`.
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## Examples
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iex> datetime = ~U[2026-01-15 14:34:00Z]
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iex> to_user_timezone(datetime, "America/New_York")
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{:ok, ~U[2026-01-15 09:34:00Z], "EST"}
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"""
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@spec to_user_timezone(DateTime.t(), String.t()) ::
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{:ok, DateTime.t(), String.t()} | {:error, atom()}
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def to_user_timezone(datetime, timezone) when is_binary(timezone) do
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case Map.get(@timezone_offsets, timezone) do
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nil ->
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{:error, :unknown_timezone}
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offset_seconds ->
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shifted_dt = DateTime.add(datetime, offset_seconds, :second)
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tz_abbr = Map.get(@timezone_abbrs, timezone, timezone)
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{:ok, shifted_dt, tz_abbr}
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end
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end
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@doc """
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Formats a DateTime into a human-readable "time ago" string.
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Supports short time periods (seconds, minutes, hours, days) and
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long time periods (months, years) for things like build timestamps.
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## Examples
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iex> datetime = DateTime.add(DateTime.utc_now(), -65, :second)
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iex> ToweropsWeb.TimeHelpers.format_time_ago(datetime)
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"1m ago"
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iex> datetime = DateTime.add(DateTime.utc_now(), -7200, :second)
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iex> ToweropsWeb.TimeHelpers.format_time_ago(datetime)
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"2h ago"
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"""
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@spec format_time_ago(DateTime.t() | nil) :: String.t()
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def format_time_ago(nil), do: gettext("Never")
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def format_time_ago(datetime) do
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now = DateTime.utc_now()
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diff = DateTime.diff(now, datetime, :second)
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cond do
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diff < 60 ->
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ngettext("%{count}s ago", "%{count}s ago", diff, count: diff)
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diff < 3600 ->
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minutes = div(diff, 60)
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ngettext("%{count}m ago", "%{count}m ago", minutes, count: minutes)
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diff < 86_400 ->
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hours = div(diff, 3600)
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ngettext("%{count}h ago", "%{count}h ago", hours, count: hours)
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diff < 2_592_000 ->
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days = div(diff, 86_400)
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ngettext("%{count}d ago", "%{count}d ago", days, count: days)
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diff < 31_536_000 ->
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months = div(diff, 2_592_000)
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ngettext("%{count}mo ago", "%{count}mo ago", months, count: months)
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true ->
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years = div(diff, 31_536_000)
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ngettext("%{count}y ago", "%{count}y ago", years, count: years)
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end
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end
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@doc """
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Formats a DateTime into a full date and time string in UTC with default 12h format.
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"""
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@spec format_datetime(DateTime.t() | nil) :: String.t()
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def format_datetime(datetime), do: format_datetime(datetime, "UTC", "12h")
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@doc """
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Formats a DateTime into a full date and time string, converted to the given timezone.
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## Examples
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iex> datetime = ~U[2026-01-15 14:34:00Z]
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iex> ToweropsWeb.TimeHelpers.format_datetime(datetime, "America/New_York", "12h")
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"Jan 15, 2026 at 09:34 AM EST"
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iex> datetime = ~U[2026-01-15 14:34:00Z]
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iex> ToweropsWeb.TimeHelpers.format_datetime(datetime, "UTC", "24h")
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"Jan 15, 2026 at 14:34 UTC"
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"""
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@spec format_datetime(DateTime.t() | nil, String.t() | nil, String.t()) :: String.t()
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def format_datetime(nil, _timezone, _time_format), do: gettext("Never")
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def format_datetime(datetime, nil, time_format), do: format_datetime(datetime, "UTC", time_format)
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def format_datetime(datetime, timezone, time_format) when is_binary(timezone) do
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case to_user_timezone(datetime, timezone) do
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{:ok, shifted_dt, tz_abbr} ->
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time_str = format_time_part(shifted_dt, time_format)
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Calendar.strftime(shifted_dt, "%b %d, %Y at #{time_str} #{tz_abbr}")
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{:error, _reason} ->
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# Fallback to UTC if timezone is invalid
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time_str = format_time_part(datetime, time_format)
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Calendar.strftime(datetime, "%b %d, %Y at #{time_str} UTC")
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end
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end
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# Backwards compatibility - accepts 2 args, defaults to 12h format
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def format_datetime(datetime, timezone) do
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format_datetime(datetime, timezone, "12h")
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end
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@doc """
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Formats a DateTime into a short date string in UTC.
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"""
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@spec format_date(DateTime.t() | nil) :: String.t()
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def format_date(datetime), do: format_date(datetime, "UTC")
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@doc """
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Formats a DateTime into a short date string, converted to the given timezone.
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## Examples
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iex> datetime = ~U[2026-01-15 14:34:00Z]
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iex> ToweropsWeb.TimeHelpers.format_date(datetime, "UTC")
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"Jan 15, 2026"
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iex> datetime = ~U[2026-01-15 02:00:00Z]
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iex> ToweropsWeb.TimeHelpers.format_date(datetime, "America/Los_Angeles")
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"Jan 14, 2026"
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"""
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@spec format_date(DateTime.t() | nil, String.t() | nil) :: String.t()
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def format_date(nil, _timezone), do: gettext("Never")
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def format_date(datetime, nil), do: format_date(datetime, "UTC")
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def format_date(datetime, timezone) when is_binary(timezone) do
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case to_user_timezone(datetime, timezone) do
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{:ok, shifted_dt, _tz_abbr} ->
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Calendar.strftime(shifted_dt, "%b %d, %Y")
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{:error, _reason} ->
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# Fallback to UTC if timezone is invalid
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Calendar.strftime(datetime, "%b %d, %Y")
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end
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end
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@doc """
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Formats a DateTime into ISO 8601 format in UTC with default 24h format.
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"""
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@spec format_iso8601(DateTime.t() | nil) :: String.t()
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def format_iso8601(datetime), do: format_iso8601(datetime, "UTC", "24h")
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@doc """
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Formats a DateTime into ISO 8601 format, converted to the given timezone.
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## Examples
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iex> datetime = ~U[2026-01-15 14:34:00Z]
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iex> ToweropsWeb.TimeHelpers.format_iso8601(datetime, "UTC", "24h")
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"2026-01-15 14:34:00 UTC"
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iex> datetime = ~U[2026-01-15 14:34:00Z]
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iex> ToweropsWeb.TimeHelpers.format_iso8601(datetime, "America/New_York", "12h")
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"2026-01-15 09:34:00 AM EST"
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"""
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@spec format_iso8601(DateTime.t() | nil, String.t() | nil, String.t()) :: String.t()
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def format_iso8601(nil, _timezone, _time_format), do: gettext("Never")
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def format_iso8601(datetime, nil, time_format), do: format_iso8601(datetime, "UTC", time_format)
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def format_iso8601(datetime, timezone, time_format) when is_binary(timezone) do
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case to_user_timezone(datetime, timezone) do
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{:ok, shifted_dt, tz_abbr} ->
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time_str = format_time_part(shifted_dt, time_format)
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Calendar.strftime(shifted_dt, "%Y-%m-%d #{time_str} #{tz_abbr}")
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{:error, _reason} ->
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# Fallback to UTC if timezone is invalid
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time_str = format_time_part(datetime, time_format)
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Calendar.strftime(datetime, "%Y-%m-%d #{time_str} UTC")
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end
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end
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# Backwards compatibility - accepts 2 args, defaults to 24h format for ISO8601
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def format_iso8601(datetime, timezone) do
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format_iso8601(datetime, timezone, "24h")
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end
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@doc """
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Formats a UTC hour (0-23) into the user's timezone with abbreviation.
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Uses 12-hour format with AM/PM.
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## Examples
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iex> format_utc_hour(7, "America/New_York")
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"2:00 AM EST"
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iex> format_utc_hour(7, "UTC")
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"7:00 AM UTC"
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"""
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def format_utc_hour(utc_hour, timezone \\ "UTC") when utc_hour >= 0 and utc_hour <= 23 do
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# Create a DateTime for today at the specified UTC hour
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today = Date.utc_today()
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{:ok, datetime} = DateTime.new(today, ~T[00:00:00], "Etc/UTC")
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datetime = DateTime.add(datetime, utc_hour * 3600, :second)
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case to_user_timezone(datetime, timezone) do
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{:ok, shifted_dt, tz_abbr} ->
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{hour_12, am_pm} = to_12hour_format(shifted_dt.hour)
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"#{hour_12}:00 #{am_pm} #{tz_abbr}"
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{:error, _reason} ->
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{hour_12, am_pm} = to_12hour_format(utc_hour)
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"#{hour_12}:00 #{am_pm} UTC"
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end
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end
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# Private helper to format the time portion based on user preference
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defp format_time_part(datetime, "24h") do
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Calendar.strftime(datetime, "%H:%M:%S")
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end
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defp format_time_part(datetime, _default_12h) do
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Calendar.strftime(datetime, "%I:%M %p")
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end
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# Private helper to convert 24-hour format to 12-hour format with AM/PM
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defp to_12hour_format(hour) when hour == 0, do: {12, "AM"}
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defp to_12hour_format(hour) when hour < 12, do: {hour, "AM"}
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defp to_12hour_format(hour) when hour == 12, do: {12, "PM"}
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defp to_12hour_format(hour), do: {hour - 12, "PM"}
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end
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