Improve pagination (#105)

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

@@ -0,0 +1,152 @@
+// 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 (
+	"fmt"
+	"net/url"
+	"os"
+	"path"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"unicode"
+)
+
+const fileScheme = "file"
+
+// URI represents the full URI for a file.
+type URI string
+
+// Filename returns the file path for the given URI.
+// It is an error to call this on a URI that is not a valid filename.
+func (uri URI) Filename() string {
+	filename, err := filename(uri)
+	if err != nil {
+		panic(err)
+	}
+	return filepath.FromSlash(filename)
+}
+
+func filename(uri URI) (string, error) {
+	if uri == "" {
+		return "", nil
+	}
+	u, err := url.ParseRequestURI(string(uri))
+	if err != nil {
+		return "", err
+	}
+	if u.Scheme != fileScheme {
+		return "", fmt.Errorf("only file URIs are supported, got %q from %q", u.Scheme, uri)
+	}
+	if isWindowsDriveURI(u.Path) {
+		u.Path = u.Path[1:]
+	}
+	return u.Path, nil
+}
+
+// NewURI returns a span URI for the string.
+// It will attempt to detect if the string is a file path or uri.
+func NewURI(s string) URI {
+	if u, err := url.PathUnescape(s); err == nil {
+		s = u
+	}
+	if strings.HasPrefix(s, fileScheme+"://") {
+		return URI(s)
+	}
+	return FileURI(s)
+}
+
+func CompareURI(a, b URI) int {
+	if equalURI(a, b) {
+		return 0
+	}
+	if a < b {
+		return -1
+	}
+	return 1
+}
+
+func equalURI(a, b URI) bool {
+	if a == b {
+		return true
+	}
+	// If we have the same URI basename, we may still have the same file URIs.
+	if !strings.EqualFold(path.Base(string(a)), path.Base(string(b))) {
+		return false
+	}
+	fa, err := filename(a)
+	if err != nil {
+		return false
+	}
+	fb, err := filename(b)
+	if err != nil {
+		return false
+	}
+	// Stat the files to check if they are equal.
+	infoa, err := os.Stat(filepath.FromSlash(fa))
+	if err != nil {
+		return false
+	}
+	infob, err := os.Stat(filepath.FromSlash(fb))
+	if err != nil {
+		return false
+	}
+	return os.SameFile(infoa, infob)
+}
+
+// FileURI returns a span URI for the supplied file path.
+// It will always have the file scheme.
+func FileURI(path string) URI {
+	if path == "" {
+		return ""
+	}
+	// Handle standard library paths that contain the literal "$GOROOT".
+	// TODO(rstambler): The go/packages API should allow one to determine a user's $GOROOT.
+	const prefix = "$GOROOT"
+	if len(path) >= len(prefix) && strings.EqualFold(prefix, path[:len(prefix)]) {
+		suffix := path[len(prefix):]
+		path = runtime.GOROOT() + suffix
+	}
+	if !isWindowsDrivePath(path) {
+		if abs, err := filepath.Abs(path); err == nil {
+			path = abs
+		}
+	}
+	// Check the file path again, in case it became absolute.
+	if isWindowsDrivePath(path) {
+		path = "/" + path
+	}
+	path = filepath.ToSlash(path)
+	u := url.URL{
+		Scheme: fileScheme,
+		Path:   path,
+	}
+	uri := u.String()
+	if unescaped, err := url.PathUnescape(uri); err == nil {
+		uri = unescaped
+	}
+	return URI(uri)
+}
+
+// isWindowsDrivePath returns true if the file path is of the form used by
+// Windows. We check if the path begins with a drive letter, followed by a ":".
+func isWindowsDrivePath(path string) bool {
+	if len(path) < 4 {
+		return false
+	}
+	return unicode.IsLetter(rune(path[0])) && path[1] == ':'
+}
+
+// isWindowsDriveURI returns true if the file URI is of the format used by
+// Windows URIs. The url.Parse package does not specially handle Windows paths
+// (see https://golang.org/issue/6027). We check if the URI path has
+// a drive prefix (e.g. "/C:"). If so, we trim the leading "/".
+func isWindowsDriveURI(uri string) bool {
+	if len(uri) < 4 {
+		return false
+	}
+	return uri[0] == '/' && unicode.IsLetter(rune(uri[1])) && uri[2] == ':'
+}