138 lines
2.7 KiB
Go
138 lines
2.7 KiB
Go
package main
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import (
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"bytes"
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"context"
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"database/sql"
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"encoding/json"
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"flag"
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"io"
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"log"
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"net/http"
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"net/url"
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"os"
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"strconv"
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"strings"
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"text/template"
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"time"
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_ "github.com/glebarez/sqlite"
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)
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var httpc = &http.Client{
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Timeout: time.Minute,
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Transport: &http.Transport{
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DisableKeepAlives: true,
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},
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}
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type Handler struct {
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tmpl *template.Template
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target *url.URL
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idempotency *sql.DB
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}
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func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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if err := h.serveHTTP(w, r); err != nil {
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log.Println("!", err)
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http.Error(w, err.Error(), http.StatusBadRequest)
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}
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}
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func (h Handler) serveHTTP(w http.ResponseWriter, r *http.Request) error {
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b, err := adapt(r.Body, h.tmpl)
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if err != nil {
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return err
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}
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resp, err := proxy(h.target, r, io.NopCloser(bytes.NewReader(b)))
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if err != nil {
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return err
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}
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defer resp.Body.Close()
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return forward(w, resp)
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}
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func main() {
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fs := flag.NewFlagSet(os.Args[0], flag.ContinueOnError)
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p := fs.Int("p", 28080, "port")
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t := fs.String("t", "{{ . }}", "template")
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y := fs.String("y", "http://localhost:41912", "target")
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db := fs.String("db", "/tmp/json-adapter.db", "sqlite db for idempotency")
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if err := fs.Parse(os.Args[1:]); err != nil {
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panic(err)
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}
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db, err := sql.Open("sqlite", *db)
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if err != nil {
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panic(err)
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}
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defer db.Close()
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if err := db.PingContext(context.Background()); err != nil {
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panic(err)
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}
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tmpl, err := template.New("").Parse(*t)
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if err != nil {
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panic(err)
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}
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u, err := url.Parse(*y)
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if err != nil {
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panic(err)
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}
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h := Handler{tmpl: tmpl, target: u, idempotency: db}
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log.Println("listening on", *p)
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if err := http.ListenAndServe(":"+strconv.Itoa(*p), h); err != nil {
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panic(err)
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}
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}
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func adapt(r io.Reader, tmpl *template.Template) ([]byte, error) {
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b, _ := io.ReadAll(io.LimitReader(r, 1024*1024))
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var v interface{}
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buff := bytes.NewBuffer(nil)
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if err := json.Unmarshal(b, &v); err != nil {
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return nil, err
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} else if err := tmpl.Execute(buff, v); err != nil {
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return nil, err
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}
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log.Printf("%s => %s", b, buff.Bytes())
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return buff.Bytes(), nil
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}
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func proxy(u *url.URL, r *http.Request, rc io.ReadCloser) (*http.Response, error) {
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req, err := http.NewRequest(r.Method, u.String(), rc)
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if err != nil {
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return nil, err
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}
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req = req.WithContext(r.Context())
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for k, v := range r.Header {
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switch strings.ToLower(k) {
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case "content-length":
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default:
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req.Header.Set(k, v[0])
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for _, v := range v[1:] {
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req.Header.Add(k, v)
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}
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}
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}
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return httpc.Do(req)
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}
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func forward(w http.ResponseWriter, resp *http.Response) error {
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for k, v := range resp.Header {
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w.Header().Set(k, v[0])
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for _, v := range v[1:] {
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w.Header().Add(k, v)
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}
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}
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w.WriteHeader(resp.StatusCode)
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io.Copy(w, resp.Body)
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return nil
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}
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