chore: vendor

vendor/github.com/rivo/uniseg/line.go

@@ -0,0 +1,134 @@
+package uniseg
+
+import "unicode/utf8"
+
+// FirstLineSegment returns the prefix of the given byte slice after which a
+// decision to break the string over to the next line can or must be made,
+// according to the rules of [Unicode Standard Annex #14]. This is used to
+// implement line breaking.
+//
+// Line breaking, also known as word wrapping, is the process of breaking a
+// section of text into lines such that it will fit in the available width of a
+// page, window or other display area.
+//
+// The returned "segment" may not be broken into smaller parts, unless no other
+// breaking opportunities present themselves, in which case you may break by
+// grapheme clusters (using the [FirstGraphemeCluster] function to determine the
+// grapheme clusters).
+//
+// The "mustBreak" flag indicates whether you MUST break the line after the
+// given segment (true), for example after newline characters, or you MAY break
+// the line after the given segment (false).
+//
+// This function can be called continuously to extract all non-breaking sub-sets
+// from a byte slice, as illustrated in the example below.
+//
+// If you don't know the current state, for example when calling the function
+// for the first time, you must pass -1. For consecutive calls, pass the state
+// and rest slice returned by the previous call.
+//
+// The "rest" slice is the sub-slice of the original byte slice "b" starting
+// after the last byte of the identified line segment. If the length of the
+// "rest" slice is 0, the entire byte slice "b" has been processed. The
+// "segment" byte slice is the sub-slice of the input slice containing the
+// identified line segment.
+//
+// Given an empty byte slice "b", the function returns nil values.
+//
+// Note that in accordance with [UAX #14 LB3], the final segment will end with
+// "mustBreak" set to true. You can choose to ignore this by checking if the
+// length of the "rest" slice is 0 and calling [HasTrailingLineBreak] or
+// [HasTrailingLineBreakInString] on the last rune.
+//
+// Note also that this algorithm may break within grapheme clusters. This is
+// addressed in Section 8.2 Example 6 of UAX #14. To avoid this, you can use
+// the [Step] function instead.
+//
+// [Unicode Standard Annex #14]: https://www.unicode.org/reports/tr14/
+// [UAX #14 LB3]: https://www.unicode.org/reports/tr14/#Algorithm
+func FirstLineSegment(b []byte, state int) (segment, rest []byte, mustBreak bool, newState int) {
+	// An empty byte slice returns nothing.
+	if len(b) == 0 {
+		return
+	}
+
+	// Extract the first rune.
+	r, length := utf8.DecodeRune(b)
+	if len(b) <= length { // If we're already past the end, there is nothing else to parse.
+		return b, nil, true, lbAny // LB3.
+	}
+
+	// If we don't know the state, determine it now.
+	if state < 0 {
+		state, _ = transitionLineBreakState(state, r, b[length:], "")
+	}
+
+	// Transition until we find a boundary.
+	var boundary int
+	for {
+		r, l := utf8.DecodeRune(b[length:])
+		state, boundary = transitionLineBreakState(state, r, b[length+l:], "")
+
+		if boundary != LineDontBreak {
+			return b[:length], b[length:], boundary == LineMustBreak, state
+		}
+
+		length += l
+		if len(b) <= length {
+			return b, nil, true, lbAny // LB3
+		}
+	}
+}
+
+// FirstLineSegmentInString is like [FirstLineSegment] but its input and outputs
+// are strings.
+func FirstLineSegmentInString(str string, state int) (segment, rest string, mustBreak bool, newState int) {
+	// An empty byte slice returns nothing.
+	if len(str) == 0 {
+		return
+	}
+
+	// Extract the first rune.
+	r, length := utf8.DecodeRuneInString(str)
+	if len(str) <= length { // If we're already past the end, there is nothing else to parse.
+		return str, "", true, lbAny // LB3.
+	}
+
+	// If we don't know the state, determine it now.
+	if state < 0 {
+		state, _ = transitionLineBreakState(state, r, nil, str[length:])
+	}
+
+	// Transition until we find a boundary.
+	var boundary int
+	for {
+		r, l := utf8.DecodeRuneInString(str[length:])
+		state, boundary = transitionLineBreakState(state, r, nil, str[length+l:])
+
+		if boundary != LineDontBreak {
+			return str[:length], str[length:], boundary == LineMustBreak, state
+		}
+
+		length += l
+		if len(str) <= length {
+			return str, "", true, lbAny // LB3.
+		}
+	}
+}
+
+// HasTrailingLineBreak returns true if the last rune in the given byte slice is
+// one of the hard line break code points defined in LB4 and LB5 of [UAX #14].
+//
+// [UAX #14]: https://www.unicode.org/reports/tr14/#Algorithm
+func HasTrailingLineBreak(b []byte) bool {
+	r, _ := utf8.DecodeLastRune(b)
+	property, _ := propertyLineBreak(r)
+	return property == prBK || property == prCR || property == prLF || property == prNL
+}
+
+// HasTrailingLineBreakInString is like [HasTrailingLineBreak] but for a string.
+func HasTrailingLineBreakInString(str string) bool {
+	r, _ := utf8.DecodeLastRuneInString(str)
+	property, _ := propertyLineBreak(r)
+	return property == prBK || property == prCR || property == prLF || property == prNL
+}