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replacer.go
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replacer.go
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package reinc
import (
"fmt"
"io"
"io/ioutil"
"os"
"path/filepath"
"regexp"
)
const (
Version = "0.1.0-beta"
)
type Rule struct {
Regexp *regexp.Regexp
PathFormat []byte
Once bool
OnceFormat []byte
IgnoreError bool
IgnoreErrorFormat []byte
Mode string
}
const (
RuleModeDefault string = ""
RuleModeFileDir = "filedir"
RuleModeWorkDir = "workdir"
)
type RuleConfig struct {
Pattern string `json:"pattern"`
PathFormat string `json:"path_format"`
Once bool `json:"once"`
OnceFormat string `json:"once_format"`
IgnoreError bool `json:"ignore_error"`
IgnoreErrorFormat string `json:"ignore_error_format"`
Mode string `json:"mode"`
}
type ReplacerConfig struct {
Rules []*RuleConfig `json:"rules"`
}
type Rules []*Rule
func NewRule(config *RuleConfig) (*Rule, error) {
re, err := regexp.Compile(config.Pattern)
if err != nil {
return nil, err
}
return &Rule{
Regexp: re,
PathFormat: []byte(config.PathFormat),
Once: config.Once,
OnceFormat: []byte(config.OnceFormat),
IgnoreError: config.IgnoreError,
IgnoreErrorFormat: []byte(config.IgnoreErrorFormat),
Mode: config.Mode,
}, nil
}
type Replacer struct {
Writer io.Writer
Reader io.Reader
Path string
Rules Rules
MaxDepth int
RootDir string
IncludedPathSet map[string]struct{}
depth int
}
func NewReplacer(w io.Writer, r io.Reader) *Replacer {
repl, err := NewReplacerWithConfig(w, r, nil)
if err != nil {
panic(err)
}
return repl
}
func NewReplacerWithConfig(w io.Writer, r io.Reader, config *ReplacerConfig) (*Replacer, error) {
rules := make(Rules, 0)
if config != nil {
for _, ruleConfig := range config.Rules {
rule, err := NewRule(ruleConfig)
if err != nil {
return nil, err
}
rules = append(rules, rule)
}
}
return &Replacer{
Writer: w,
Reader: r,
Rules: rules,
MaxDepth: 32,
IncludedPathSet: make(map[string]struct{}),
}, nil
}
func (r *Replacer) includeFile(fpath string) error {
file, err := os.Open(fpath)
if err != nil {
return err
}
defer file.Close()
subr := &Replacer{
Writer: r.Writer,
Reader: file,
Rules: r.Rules,
Path: fpath,
MaxDepth: r.MaxDepth,
RootDir: r.RootDir,
IncludedPathSet: r.IncludedPathSet,
depth: r.depth + 1,
}
_, err = subr.Replace()
return err
}
func (r *Replacer) resolvePathImpl(fpath string, mode string) (string, error) {
var err error
if filepath.IsAbs(fpath) {
return fpath, nil
}
if r.Path != "" {
var baseDir string
switch mode {
case RuleModeDefault, RuleModeFileDir:
baseDir = filepath.Dir(r.Path)
case RuleModeWorkDir:
baseDir, err = os.Getwd()
if err != nil {
return fpath, err
}
default:
return fpath, fmt.Errorf("invalid mode: %s", mode)
}
joined := filepath.Join(baseDir, fpath)
return filepath.Abs(joined)
}
return filepath.Abs(fpath)
}
func (r *Replacer) resolvePath(fpath string, mode string) (string, error) {
fpath, err := r.resolvePathImpl(fpath, mode)
if err != nil {
return "", err
}
if r.RootDir != "" && !filepath.HasPrefix(fpath, r.RootDir) {
return "", fmt.Errorf("banned: %s", fpath)
}
return fpath, nil
}
func (r *Replacer) replaceFirst(bs []byte, offset int) (bool, int, error) {
var err error
found := false
minOffset := len(bs)
minEnd := len(bs)
var minRule *Rule
for _, rule := range r.Rules {
loc := rule.Regexp.FindIndex(bs[offset:])
if loc == nil || offset+loc[0] >= minOffset {
continue
}
minOffset = offset + loc[0]
minEnd = offset + loc[1]
minRule = rule
found = true
}
if !found {
n, err := r.Writer.Write(bs[offset:])
return false, offset + n, err
}
_, err = r.Writer.Write(bs[offset:minOffset])
if err != nil {
return true, offset, err
}
target := bs[minOffset:minEnd]
fpath := minRule.Regexp.ReplaceAll(target, minRule.PathFormat)
resolvedFpath, err := r.resolvePath(string(fpath), minRule.Mode)
if err == nil {
if _, ok := r.IncludedPathSet[resolvedFpath]; ok {
if minRule.Once || len(minRule.Regexp.ReplaceAll(target, minRule.OnceFormat)) != 0 {
_, err = r.Writer.Write(target)
if err != nil {
return true, minOffset, err
}
}
}
err = r.includeFile(resolvedFpath)
if err != nil {
if minRule.IgnoreError || len(minRule.Regexp.ReplaceAll(target, minRule.IgnoreErrorFormat)) != 0 {
_, err = r.Writer.Write(target)
if err != nil {
return true, minOffset, err
}
} else {
return true, minOffset, err
}
}
r.IncludedPathSet[resolvedFpath] = struct{}{}
} else {
if minRule.IgnoreError || len(minRule.Regexp.ReplaceAll(target, minRule.IgnoreErrorFormat)) != 0 {
_, err = r.Writer.Write(target)
if err != nil {
return true, minOffset, err
}
} else {
return true, minOffset, err
}
}
return true, minEnd, nil
}
func (r *Replacer) Replace() (int, error) {
if r.depth > r.MaxDepth {
return 0, fmt.Errorf("too many levels of recursion: %d", r.depth)
}
var err error
bs, err := ioutil.ReadAll(r.Reader)
if err != nil {
return 0, err
}
found := false
offset := 0
for {
found, offset, err = r.replaceFirst(bs, offset)
if err != nil {
return offset, err
}
if !found {
break
}
}
return offset, nil
}