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Module WhittakerTech::Midas::Coin::Bidi

Bidi provides Unicode bidirectional-text isolation helpers so that currency strings render correctly when embedded in mixed LTR/RTL sentences.

Background

In HTML, the Unicode Bidirectional Algorithm can reorder numeric and symbol characters in ways that produce confusing output when currency strings appear inside an RTL sentence (e.g. Arabic or Hebrew UI). Wrapping currency text in Unicode isolation marks prevents the algorithm from treating it as part of the surrounding paragraph direction.

Isolation marks used

Constants:

  • LRI (U+2066): Left-to-Right Isolate
  • RLI (U+2067): Right-to-Left Isolate
  • PDI (U+2069): Pop Directional Isolate (close)

Direction configuration

Currency direction defaults to :ltr for all currencies. Override per currency in an initializer:

WhittakerTech::Midas.currency_directions['ILS'] = :rtl
WhittakerTech::Midas.currency_directions['AED'] = :rtl

See also: WhittakerTech::Midas.currency_direction_for

  • @since 0.1.0

Constants

LRI

Unicode Left-to-Right Isolate mark (U+2066)

  • @since 0.1.0

PDI

Unicode Pop Directional Isolate mark — closes an isolation span (U+2069)

  • @since 0.1.0

RLI

Unicode Right-to-Left Isolate mark (U+2067)

  • @since 0.1.0

Public Instance Methods

bidi_currency_dir(currency_code)

Resolves the configured display direction for a currency code.

Reads from WhittakerTech::Midas.currency_directions. Defaults to :ltr for any currency not explicitly configured.

  • @param currency_code [String] ISO 4217 currency code
  • @return [Symbol] :ltr or :rtl
  • @since 0.1.0

bidi_isolate(text, dir:)

Wraps text in a Unicode directional-isolate span.

  • @param text [String, nil] the text to isolate; nil returns ""
  • @param dir [Symbol, nil] :ltr, :rtl, or nil (no wrapping)
  • @raise [ArgumentError] if dir is not :ltr, :rtl, or nil
  • @return [String]
  • @since 0.1.0

@example 

bidi_isolate('$29.99', dir: :ltr)  # => "\u2066$29.99\u2069"
bidi_isolate('29.99',  dir: nil)   # => "29.99"

bidi_isolate_number(text)

Wraps a number string with LTR isolation.

Numbers are always rendered LTR. This prevents the bidi algorithm from reordering digit sequences when they appear in an RTL context.

  • @param text [String, Integer, BigDecimal] the numeric value to isolate
  • @return [String]
  • @since 0.1.0