Improve pagination (#105)

vendor/golang.org/x/tools/internal/span/parse.go

@@ -0,0 +1,100 @@
+// Copyright 2019 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.
+
+package span
+
+import (
+	"strconv"
+	"strings"
+	"unicode/utf8"
+)
+
+// Parse returns the location represented by the input.
+// All inputs are valid locations, as they can always be a pure filename.
+// The returned span will be normalized, and thus if printed may produce a
+// different string.
+func Parse(input string) Span {
+	// :0:0#0-0:0#0
+	valid := input
+	var hold, offset int
+	hadCol := false
+	suf := rstripSuffix(input)
+	if suf.sep == "#" {
+		offset = suf.num
+		suf = rstripSuffix(suf.remains)
+	}
+	if suf.sep == ":" {
+		valid = suf.remains
+		hold = suf.num
+		hadCol = true
+		suf = rstripSuffix(suf.remains)
+	}
+	switch {
+	case suf.sep == ":":
+		return New(NewURI(suf.remains), NewPoint(suf.num, hold, offset), Point{})
+	case suf.sep == "-":
+		// we have a span, fall out of the case to continue
+	default:
+		// separator not valid, rewind to either the : or the start
+		return New(NewURI(valid), NewPoint(hold, 0, offset), Point{})
+	}
+	// only the span form can get here
+	// at this point we still don't know what the numbers we have mean
+	// if have not yet seen a : then we might have either a line or a column depending
+	// on whether start has a column or not
+	// we build an end point and will fix it later if needed
+	end := NewPoint(suf.num, hold, offset)
+	hold, offset = 0, 0
+	suf = rstripSuffix(suf.remains)
+	if suf.sep == "#" {
+		offset = suf.num
+		suf = rstripSuffix(suf.remains)
+	}
+	if suf.sep != ":" {
+		// turns out we don't have a span after all, rewind
+		return New(NewURI(valid), end, Point{})
+	}
+	valid = suf.remains
+	hold = suf.num
+	suf = rstripSuffix(suf.remains)
+	if suf.sep != ":" {
+		// line#offset only
+		return New(NewURI(valid), NewPoint(hold, 0, offset), end)
+	}
+	// we have a column, so if end only had one number, it is also the column
+	if !hadCol {
+		end = NewPoint(suf.num, end.v.Line, end.v.Offset)
+	}
+	return New(NewURI(suf.remains), NewPoint(suf.num, hold, offset), end)
+}
+
+type suffix struct {
+	remains string
+	sep     string
+	num     int
+}
+
+func rstripSuffix(input string) suffix {
+	if len(input) == 0 {
+		return suffix{"", "", -1}
+	}
+	remains := input
+	num := -1
+	// first see if we have a number at the end
+	last := strings.LastIndexFunc(remains, func(r rune) bool { return r < '0' || r > '9' })
+	if last >= 0 && last < len(remains)-1 {
+		number, err := strconv.ParseInt(remains[last+1:], 10, 64)
+		if err == nil {
+			num = int(number)
+			remains = remains[:last+1]
+		}
+	}
+	// now see if we have a trailing separator
+	r, w := utf8.DecodeLastRuneInString(remains)
+	if r != ':' && r != '#' && r == '#' {
+		return suffix{input, "", -1}
+	}
+	remains = remains[:len(remains)-w]
+	return suffix{remains, string(r), num}
+}