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|
package main
import (
"bufio"
"bytes"
"encoding/json"
"fmt"
"io"
"os"
"strings"
"sync"
)
type Manager struct {
Input Input
Filter Filter
Output Output
}
type Input interface {
Start() chan *Work
}
type StdinInput struct {
retchan chan *Work
}
type Filter interface {
Filter(*Work) *Work
}
type StringFilter struct {
retchan chan *Work
FilterFuncMap map[string]func(string) string
}
type Output interface {
Output(*Work)
}
type StdoutOutput struct {
}
type Work struct {
data []byte
err error
}
func (w *Work) Error() error {
return w.err
}
func (i *StdinInput) Start() chan *Work {
i.retchan = make(chan *Work, 100)
r := bufio.NewReader(os.Stdin)
go func() {
for {
bs, err := r.ReadBytes(byte('\n'))
if err == io.EOF {
break
}
if err != nil {
fmt.Printf("Error when reading input from Stdin: %q", err)
os.Exit(1)
}
i.retchan <- &Work{data: bs}
}
close(i.retchan)
}()
return i.retchan
}
func NewStringFilter(ffmap map[string]func(string) string) *StringFilter {
return &StringFilter{FilterFuncMap: ffmap}
}
func (f *StringFilter) Filter(w *Work) *Work {
dec := json.NewDecoder(bytes.NewReader(w.data))
jm := make(map[string]string, 10)
err := dec.Decode(&jm)
if err == io.EOF {
fmt.Printf("EOF jm: %v\n", jm)
return w
}
if err != nil {
fmt.Printf("Error when decoding JSON: %q\n", err)
w.err = err
return w
}
changed := false
for field, ff := range f.FilterFuncMap {
str, ok := jm[field]
if !ok {
continue
}
jm[field] = ff(str)
changed = true
}
if changed {
bs, err := json.Marshal(jm)
if err != nil {
fmt.Printf("Error when marshalling JSON: %q\n", err)
w.err = err
} else {
w.data = bs
}
}
return w
}
func (o *StdoutOutput) Output(w *Work) {
fmt.Printf("%s\n", w.data)
}
func (m *Manager) Run() {
var wg sync.WaitGroup
ic := m.Input.Start()
for w := range ic {
wg.Add(1)
go func(w *Work) {
nw := m.Filter.Filter(w)
err := nw.Error()
if err != nil {
fmt.Printf("Got an error when processing Work: %q\n", err)
}
m.Output.Output(nw)
wg.Done()
}(w)
}
wg.Wait()
}
func main() {
ffmap := make(map[string]func(string) string, 10)
ffmap["F"] = func(s string) string { return strings.ToUpper(s) }
m := Manager{
Input: &StdinInput{},
Filter: NewStringFilter(ffmap),
Output: &StdoutOutput{},
}
m.Run()
}
|
