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// Copyright 2018 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.
// Module file printer.
package modfile
import (
"bytes"
"fmt"
"strings"
)
func Format(f *FileSyntax) []byte {
pr := &printer{}
pr.file(f)
return pr.Bytes()
}
// A printer collects the state during printing of a file or expression.
type printer struct {
bytes.Buffer // output buffer
comment []Comment // pending end-of-line comments
margin int // left margin (indent), a number of tabs
}
// printf prints to the buffer.
func (p *printer) printf(format string, args ...interface{}) {
fmt.Fprintf(p, format, args...)
}
// indent returns the position on the current line, in bytes, 0-indexed.
func (p *printer) indent() int {
b := p.Bytes()
n := 0
for n < len(b) && b[len(b)-1-n] != '\n' {
n++
}
return n
}
// newline ends the current line, flushing end-of-line comments.
func (p *printer) newline() {
if len(p.comment) > 0 {
p.printf(" ")
for i, com := range p.comment {
if i > 0 {
p.trim()
p.printf("\n")
for i := 0; i < p.margin; i++ {
p.printf("\t")
}
}
p.printf("%s", strings.TrimSpace(com.Token))
}
p.comment = p.comment[:0]
}
p.trim()
p.printf("\n")
for i := 0; i < p.margin; i++ {
p.printf("\t")
}
}
// trim removes trailing spaces and tabs from the current line.
func (p *printer) trim() {
// Remove trailing spaces and tabs from line we're about to end.
b := p.Bytes()
n := len(b)
for n > 0 && (b[n-1] == '\t' || b[n-1] == ' ') {
n--
}
p.Truncate(n)
}
// file formats the given file into the print buffer.
func (p *printer) file(f *FileSyntax) {
for _, com := range f.Before {
p.printf("%s", strings.TrimSpace(com.Token))
p.newline()
}
for i, stmt := range f.Stmt {
switch x := stmt.(type) {
case *CommentBlock:
// comments already handled
p.expr(x)
default:
p.expr(x)
p.newline()
}
for _, com := range stmt.Comment().After {
p.printf("%s", strings.TrimSpace(com.Token))
p.newline()
}
if i+1 < len(f.Stmt) {
p.newline()
}
}
}
func (p *printer) expr(x Expr) {
// Emit line-comments preceding this expression.
if before := x.Comment().Before; len(before) > 0 {
// Want to print a line comment.
// Line comments must be at the current margin.
p.trim()
if p.indent() > 0 {
// There's other text on the line. Start a new line.
p.printf("\n")
}
// Re-indent to margin.
for i := 0; i < p.margin; i++ {
p.printf("\t")
}
for _, com := range before {
p.printf("%s", strings.TrimSpace(com.Token))
p.newline()
}
}
switch x := x.(type) {
default:
panic(fmt.Errorf("printer: unexpected type %T", x))
case *CommentBlock:
// done
case *LParen:
p.printf("(")
case *RParen:
p.printf(")")
case *Line:
sep := ""
for _, tok := range x.Token {
p.printf("%s%s", sep, tok)
sep = " "
}
case *LineBlock:
for _, tok := range x.Token {
p.printf("%s ", tok)
}
p.expr(&x.LParen)
p.margin++
for _, l := range x.Line {
p.newline()
p.expr(l)
}
p.margin--
p.newline()
p.expr(&x.RParen)
}
// Queue end-of-line comments for printing when we
// reach the end of the line.
p.comment = append(p.comment, x.Comment().Suffix...)
}
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