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diff --git a/intl/components/src/Bidi.h b/intl/components/src/Bidi.h
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+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#ifndef intl_components_Bidi_h_
+#define intl_components_Bidi_h_
+
+#include "mozilla/intl/BidiEmbeddingLevel.h"
+#include "mozilla/intl/ICU4CGlue.h"
+
+// Restrict use of the Rust unicode-bidi implementation to Nightly builds,
+// pending investigation of perf regressions; Beta/Release builds will
+// continue to use the ICU4C implementation for now.
+#ifdef NIGHTLY_BUILD
+#  define USE_RUST_UNICODE_BIDI 1
+#else
+#  define USE_RUST_UNICODE_BIDI 0
+#endif
+
+#if USE_RUST_UNICODE_BIDI
+#  include "mozilla/intl/unicode_bidi_ffi_generated.h"
+#else
+struct UBiDi;
+#endif
+
+namespace mozilla::intl {
+
+/**
+ * This component is a Mozilla-focused API for working with bidirectional (bidi)
+ * text. Text is commonly displayed left to right (LTR), especially for
+ * Latin-based alphabets. However, languages like Arabic and Hebrew displays
+ * text right to left (RTL). When displaying text, LTR and RTL text can be
+ * combined together in the same paragraph. This class gives tools for working
+ * with unidirectional, and mixed direction paragraphs.
+ *
+ * See the Unicode Bidirectional Algorithm document for implementation details:
+ * https://unicode.org/reports/tr9/
+ */
+class Bidi final {
+ public:
+  Bidi();
+  ~Bidi();
+
+  // Not copyable or movable
+  Bidi(const Bidi&) = delete;
+  Bidi& operator=(const Bidi&) = delete;
+
+  /**
+   * This enum indicates the text direction for the set paragraph. Some
+   * paragraphs are unidirectional, where they only have one direction, or a
+   * paragraph could use both LTR and RTL. In this case the paragraph's
+   * direction would be mixed.
+   */
+  enum class ParagraphDirection { LTR, RTL, Mixed };
+
+  /**
+   * Set the current paragraph of text to analyze for its bidi properties. This
+   * performs the Unicode bidi algorithm as specified by:
+   * https://unicode.org/reports/tr9/
+   *
+   * After setting the text, the other getter methods can be used to find out
+   * the directionality of the paragraph text.
+   */
+  ICUResult SetParagraph(Span<const char16_t> aParagraph,
+                         BidiEmbeddingLevel aLevel);
+
+  /**
+   * Get the embedding level for the paragraph that was set by SetParagraph.
+   */
+  BidiEmbeddingLevel GetParagraphEmbeddingLevel() const;
+
+  /**
+   * Get the directionality of the paragraph text that was set by SetParagraph.
+   */
+  ParagraphDirection GetParagraphDirection() const;
+
+  /**
+   * Get the number of runs. This function may invoke the actual reordering on
+   * the Bidi object, after SetParagraph may have resolved only the levels of
+   * the text. Therefore, `CountRuns` may have to allocate memory, and may fail
+   * doing so.
+   */
+  Result<int32_t, ICUError> CountRuns();
+
+  /**
+   * Get the next logical run. The logical runs are a run of text that has the
+   * same directionality and embedding level. These runs are in memory order,
+   * and not in display order.
+   *
+   * Important! `Bidi::CountRuns` must be called before calling this method.
+   *
+   * @param aLogicalStart is the offset into the paragraph text that marks the
+   *      logical start of the text.
+   * @param aLogicalLimitOut is an out param that is the length of the string
+   *      that makes up the logical run.
+   * @param aLevelOut is an out parameter that returns the embedding level for
+   *      the run
+   */
+  void GetLogicalRun(int32_t aLogicalStart, int32_t* aLogicalLimitOut,
+                     BidiEmbeddingLevel* aLevelOut);
+
+  /**
+   * This is a convenience function that does not use the ICU Bidi object.
+   * It is intended to be used for when an application has determined the
+   * embedding levels of objects (character sequences) and just needs to have
+   * them reordered (L2).
+   *
+   * @param aLevels is an array with `aLength` levels that have been
+   *      determined by the application.
+   *
+   * @param aLength is the number of levels in the array, or, semantically,
+   *      the number of objects to be reordered. It must be greater than 0.
+   *
+   * @param aIndexMap is a pointer to an array of `aLength`
+   *      indexes which will reflect the reordering of the characters.
+   *      The array does not need to be initialized.
+   *      The index map will result in
+   *        `aIndexMap[aVisualIndex]==aLogicalIndex`.
+   */
+  static void ReorderVisual(const BidiEmbeddingLevel* aLevels, int32_t aLength,
+                            int32_t* aIndexMap);
+
+  /**
+   * This enum indicates the bidi character type of the first strong character
+   * for the set paragraph.
+   * LTR: bidi character type 'L'.
+   * RTL: bidi character type 'R' or 'AL'.
+   * Neutral: The rest of bidi character types.
+   */
+  enum class BaseDirection { LTR, RTL, Neutral };
+
+  /**
+   * Get the base direction of the text.
+   */
+  static BaseDirection GetBaseDirection(Span<const char16_t> aText);
+
+  /**
+   * Get one run's logical start, length, and directionality. In an RTL run, the
+   * character at the logical start is visually on the right of the displayed
+   * run. The length is the number of characters in the run.
+   * `Bidi::CountRuns` should be called before the runs are retrieved.
+   *
+   * @param aRunIndex is the number of the run in visual order, in the
+   *      range `[0..CountRuns-1]`.
+   *
+   * @param aLogicalStart is the first logical character index in the text.
+   *      The pointer may be `nullptr` if this index is not needed.
+   *
+   * @param aLength is the number of characters (at least one) in the run.
+   *      The pointer may be `nullptr` if this is not needed.
+   *
+   * Note that in right-to-left runs, the code places modifier letters before
+   * base characters and second surrogates before first ones.
+   */
+  BidiDirection GetVisualRun(int32_t aRunIndex, int32_t* aLogicalStart,
+                             int32_t* aLength);
+
+ private:
+#if USE_RUST_UNICODE_BIDI
+  using UnicodeBidi = mozilla::intl::ffi::UnicodeBidi;
+  struct BidiFreePolicy {
+    void operator()(void* aPtr) {
+      bidi_destroy(static_cast<UnicodeBidi*>(aPtr));
+    }
+  };
+  mozilla::UniquePtr<UnicodeBidi, BidiFreePolicy> mBidi;
+#else
+  ICUPointer<UBiDi> mBidi = ICUPointer<UBiDi>(nullptr);
+
+  /**
+   * An array of levels that is the same length as the paragraph from
+   * `Bidi::SetParagraph`.
+   */
+  const BidiEmbeddingLevel* mLevels = nullptr;
+
+  /**
+   * The length of the paragraph from `Bidi::SetParagraph`.
+   */
+  int32_t mLength = 0;
+#endif
+};
+
+}  // namespace mozilla::intl
+#endif