feat: simplify HTTP client proxy pools and authenticated JSON calls

httpc/request.go

@@ -0,0 +1,99 @@
+package httpc
+
+import (
+	"errors"
+	"net/http"
+	"strings"
+)
+
+type requestOptions struct {
+	headers          http.Header
+	maxResponseBytes int64
+}
+
+// RequestOption applies only to one JSON call. Returned options can be reused
+// concurrently; request headers are independent, with no client-wide credentials.
+type RequestOption func(*requestOptions) error
+
+// WithHeader sets a header for this call; later options replace earlier values.
+// Framing and Host must be controlled through a standard Request passed to Do.
+func WithHeader(name, value string) RequestOption {
+	name = http.CanonicalHeaderKey(name)
+	err := checkHeader(name, []string{value})
+	return func(o *requestOptions) error {
+		if err != nil {
+			return err
+		}
+		if o.headers == nil {
+			o.headers = make(http.Header)
+		}
+		o.headers[name] = []string{value}
+		return nil
+	}
+}
+
+// WithHeaders snapshots headers immediately. Editing the original map after
+// construction does not change the option; each invocation gets separate slices.
+func WithHeaders(headers http.Header) RequestOption {
+	snapshot := make(http.Header, len(headers))
+	var err error
+	for key, values := range headers {
+		name := http.CanonicalHeaderKey(key)
+		if err = checkHeader(name, values); err != nil {
+			break
+		}
+		if _, exists := snapshot[name]; exists {
+			err = errors.New("httpc: duplicate canonical header name")
+			break
+		}
+		snapshot[name] = append([]string(nil), values...)
+	}
+	return func(o *requestOptions) error {
+		if err != nil {
+			return err
+		}
+		if o.headers == nil {
+			o.headers = make(http.Header, len(snapshot))
+		}
+		for name, values := range snapshot {
+			o.headers[name] = append([]string(nil), values...)
+		}
+		return nil
+	}
+}
+
+// WithMaxResponseBytes overrides JSON's bounded response read for one call.
+// The size is positive and at most 1 GiB. Do remains a caller-owned stream.
+func WithMaxResponseBytes(limit int64) RequestOption {
+	return func(o *requestOptions) error {
+		if limit <= 0 || limit > maxResponseBytes {
+			return errors.New("httpc: response limit must be positive and at most 1 GiB")
+		}
+		o.maxResponseBytes = limit
+		return nil
+	}
+}
+func checkHeader(name string, values []string) error {
+	if name == "" {
+		return errors.New("httpc: header name must not be empty")
+	}
+	for _, c := range []byte(name) {
+		if c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z' || c >= '0' && c <= '9' || strings.ContainsRune("!#$%&'*+-.^_`|~", rune(c)) {
+			continue
+		}
+		return errors.New("httpc: invalid header name")
+	}
+	switch name {
+	case "Host", "Content-Length", "Transfer-Encoding", "Trailer":
+		return errors.New("httpc: use Do for Host or request framing controls")
+	}
+	for _, value := range values {
+		for i := 0; i < len(value); i++ {
+			c := value[i]
+			if c == '\x7f' || c < ' ' && c != '\t' {
+				return errors.New("httpc: invalid header value")
+			}
+		}
+	}
+	return nil
+}