impl with.CachedHTTP

http.go

@@ -0,0 +1,140 @@
+package with
+
+import (
+	"bytes"
+	"context"
+	"database/sql"
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"time"
+)
+
+type RoundTripper struct {
+	http.RoundTripper
+	kv SQLKV
+}
+
+func CachedHTTP(ctx context.Context, foo func(*http.Client) error) error {
+	return Sqlite(ctx, ":memory:", func(db *sql.DB) error {
+		return KV(ctx, db, func(kv SQLKV) error {
+			return foo(&http.Client{
+				Timeout: time.Minute,
+				Transport: RoundTripper{
+					RoundTripper: &http.Transport{
+						DisableKeepAlives: true,
+					},
+					kv: kv,
+				},
+			})
+		})
+	})
+}
+
+func (c RoundTripper) RoundTrip(r *http.Request) (*http.Response, error) {
+	req := newCacheableRequest(r)
+	if v, err := c.kv.Get(r.Context(), req.cacheK()); err != nil {
+	} else if resp := parseCacheableResponse(v); resp != nil {
+		return resp.response(), nil
+	}
+
+	resp, err := c.RoundTripper.RoundTrip(r)
+	if err != nil {
+		return nil, err
+	}
+	c.kv.Set(r.Context(), req.cacheK(), newCacheableResponse(resp).cacheV())
+
+	return resp, nil
+}
+
+type cacheableRequest struct {
+	URLHost  string
+	URLPath  string
+	URLQuery cacheableHTTPHeader
+	Header   cacheableHTTPHeader
+	Body     string
+}
+
+func newCacheableRequest(r *http.Request) cacheableRequest {
+	defer r.Body.Close()
+	b, _ := io.ReadAll(r.Body)
+	r.Body = io.NopCloser(bytes.NewReader(b))
+	return cacheableRequest{
+		URLHost:  r.URL.Host,
+		URLPath:  r.URL.Path,
+		URLQuery: newCacheableHTTPHeader(r.URL.Query()),
+		Header:   newCacheableHTTPHeader(r.Header),
+		Body:     string(b),
+	}
+}
+
+func (c cacheableRequest) cacheK() string {
+	return fmt.Sprint(c)
+}
+
+type cacheableResponse struct {
+	Code   int
+	Header cacheableHTTPHeader
+	Body   string
+}
+
+func newCacheableResponse(resp *http.Response) cacheableResponse {
+	defer resp.Body.Close()
+	b, _ := io.ReadAll(resp.Body)
+	resp.Body = io.NopCloser(bytes.NewReader(b))
+	return cacheableResponse{
+		Code:   resp.StatusCode,
+		Header: newCacheableHTTPHeader(resp.Header),
+		Body:   string(b),
+	}
+}
+
+func parseCacheableResponse(b []byte) *cacheableResponse {
+	var c cacheableResponse
+	if err := json.Unmarshal(b, &c); err != nil {
+		return nil
+	}
+	return &c
+}
+
+func (c cacheableResponse) cacheV() []byte {
+	b, _ := json.Marshal(c)
+	return b
+}
+
+func (c cacheableResponse) response() *http.Response {
+	return &http.Response{
+		StatusCode: c.Code,
+		Header:     c.Header.header(),
+		Body:       io.NopCloser(bytes.NewReader([]byte(c.Body))),
+	}
+}
+
+type cacheableHTTPHeader [][]string
+
+func newCacheableHTTPHeader(m map[string][]string) cacheableHTTPHeader {
+	result := [][]string{}
+	for k, v := range m {
+		result = append(result, append([]string{k}, v...))
+	}
+	return result
+}
+
+func (c cacheableHTTPHeader) header() http.Header {
+	return http.Header(c.m())
+}
+
+func (c cacheableHTTPHeader) query() url.Values {
+	return url.Values(c.m())
+}
+
+func (c cacheableHTTPHeader) m() map[string][]string {
+	m := map[string][]string{}
+	for _, v := range c {
+		v := v
+		m[v[0]] = v[1:]
+	}
+	return m
+}