text: // Copyright 2015 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  //go:generate go run gen.go gen_trieval.go gen_ranges.go
  
  // Package bidi contains functionality for bidirectional text support.
  //
  // See https://www.unicode.org/reports/tr9.
  //
  // NOTE: UNDER CONSTRUCTION. This API may change in backwards incompatible ways
  // and without notice.
  package bidi // import "golang.org/x/text/unicode/bidi"
  
  // TODO:
  // The following functionality would not be hard to implement, but hinges on
  // the definition of a Segmenter interface. For now this is up to the user.
  // - Iterate over paragraphs
  // - Segmenter to iterate over runs directly from a given text.
  // Also:
  // - Transformer for reordering?
  // - Transformer (validator, really) for Bidi Rule.
  
  // This API tries to avoid dealing with embedding levels for now. Under the hood
  // these will be computed, but the question is to which extent the user should
  // know they exist. We should at some point allow the user to specify an
  // embedding hierarchy, though.
  
  // A Direction indicates the overall flow of text.
  type Direction int
  
  const (
  	// LeftToRight indicates the text contains no right-to-left characters and
  	// that either there are some left-to-right characters or the option
  	// DefaultDirection(LeftToRight) was passed.
  	LeftToRight Direction = iota
  
  	// RightToLeft indicates the text contains no left-to-right characters and
  	// that either there are some right-to-left characters or the option
  	// DefaultDirection(RightToLeft) was passed.
  	RightToLeft
  
  	// Mixed indicates text contains both left-to-right and right-to-left
  	// characters.
  	Mixed
  
  	// Neutral means that text contains no left-to-right and right-to-left
  	// characters and that no default direction has been set.
  	Neutral
  )
  
  type options struct{}
  
  // An Option is an option for Bidi processing.
  type Option func(*options)
  
  // ICU allows the user to define embedding levels. This may be used, for example,
  // to use hierarchical structure of markup languages to define embeddings.
  // The following option may be a way to expose this functionality in this API.
  // // LevelFunc sets a function that associates nesting levels with the given text.
  // // The levels function will be called with monotonically increasing values for p.
  // func LevelFunc(levels func(p int) int) Option {
  // 	panic("unimplemented")
  // }
  
  // DefaultDirection sets the default direction for a Paragraph. The direction is
  // overridden if the text contains directional characters.
  func DefaultDirection(d Direction) Option {
  	panic("unimplemented")
  }
  
  // A Paragraph holds a single Paragraph for Bidi processing.
  type Paragraph struct {
  	// buffers
  }
  
  // SetBytes configures p for the given paragraph text. It replaces text
  // previously set by SetBytes or SetString. If b contains a paragraph separator
  // it will only process the first paragraph and report the number of bytes
  // consumed from b including this separator. Error may be non-nil if options are
  // given.
  func (p *Paragraph) SetBytes(b []byte, opts ...Option) (n int, err error) {
  	panic("unimplemented")
  }
  
  // SetString configures p for the given paragraph text. It replaces text
  // previously set by SetBytes or SetString. If b contains a paragraph separator
  // it will only process the first paragraph and report the number of bytes
  // consumed from b including this separator. Error may be non-nil if options are
  // given.
  func (p *Paragraph) SetString(s string, opts ...Option) (n int, err error) {
  	panic("unimplemented")
  }
  
  // IsLeftToRight reports whether the principle direction of rendering for this
  // paragraphs is left-to-right. If this returns false, the principle direction
  // of rendering is right-to-left.
  func (p *Paragraph) IsLeftToRight() bool {
  	panic("unimplemented")
  }
  
  // Direction returns the direction of the text of this paragraph.
  //
  // The direction may be LeftToRight, RightToLeft, Mixed, or Neutral.
  func (p *Paragraph) Direction() Direction {
  	panic("unimplemented")
  }
  
  // RunAt reports the Run at the given position of the input text.
  //
  // This method can be used for computing line breaks on paragraphs.
  func (p *Paragraph) RunAt(pos int) Run {
  	panic("unimplemented")
  }
  
  // Order computes the visual ordering of all the runs in a Paragraph.
  func (p *Paragraph) Order() (Ordering, error) {
  	panic("unimplemented")
  }
  
  // Line computes the visual ordering of runs for a single line starting and
  // ending at the given positions in the original text.
  func (p *Paragraph) Line(start, end int) (Ordering, error) {
  	panic("unimplemented")
  }
  
  // An Ordering holds the computed visual order of runs of a Paragraph. Calling
  // SetBytes or SetString on the originating Paragraph invalidates an Ordering.
  // The methods of an Ordering should only be called by one goroutine at a time.
  type Ordering struct{}
  
  // Direction reports the directionality of the runs.
  //
  // The direction may be LeftToRight, RightToLeft, Mixed, or Neutral.
  func (o *Ordering) Direction() Direction {
  	panic("unimplemented")
  }
  
  // NumRuns returns the number of runs.
  func (o *Ordering) NumRuns() int {
  	panic("unimplemented")
  }
  
  // Run returns the ith run within the ordering.
  func (o *Ordering) Run(i int) Run {
  	panic("unimplemented")
  }
  
  // TODO: perhaps with options.
  // // Reorder creates a reader that reads the runes in visual order per character.
  // // Modifiers remain after the runes they modify.
  // func (l *Runs) Reorder() io.Reader {
  // 	panic("unimplemented")
  // }
  
  // A Run is a continuous sequence of characters of a single direction.
  type Run struct {
  }
  
  // String returns the text of the run in its original order.
  func (r *Run) String() string {
  	panic("unimplemented")
  }
  
  // Bytes returns the text of the run in its original order.
  func (r *Run) Bytes() []byte {
  	panic("unimplemented")
  }
  
  // TODO: methods for
  // - Display order
  // - headers and footers
  // - bracket replacement.
  
  // Direction reports the direction of the run.
  func (r *Run) Direction() Direction {
  	panic("unimplemented")
  }
  
  // Position of the Run within the text passed to SetBytes or SetString of the
  // originating Paragraph value.
  func (r *Run) Pos() (start, end int) {
  	panic("unimplemented")
  }
  
  // AppendReverse reverses the order of characters of in, appends them to out,
  // and returns the result. Modifiers will still follow the runes they modify.
  // Brackets are replaced with their counterparts.
  func AppendReverse(out, in []byte) []byte {
  	panic("unimplemented")
  }
  
  // ReverseString reverses the order of characters in s and returns a new string.
  // Modifiers will still follow the runes they modify. Brackets are replaced with
  // their counterparts.
  func ReverseString(s string) string {
  	panic("unimplemented")
  }
  