Add projects

backend/internal/util/header_helpers.go

@@ -0,0 +1,95 @@
+package util
+
+import (
+	"net/http"
+	"strings"
+
+	"github.com/gin-gonic/gin"
+)
+
+// ApplyCustomHeadersFromAttrs applies user-defined headers stored in the provided attributes map.
+// Custom headers override built-in defaults when conflicts occur.
+// If clientHeaders is provided (or if the request context carries a Gin context), any custom header
+// whose value starts with "$" (e.g. "$ABC" or "$X-Claude-Code-Session-Id") is dynamically
+// resolved from the client's request headers. If the client did not provide that header,
+// the custom header is omitted from the outgoing request.
+func ApplyCustomHeadersFromAttrs(r *http.Request, attrs map[string]string, clientHeaders ...http.Header) {
+	if r == nil {
+		return
+	}
+	var ch http.Header
+	if len(clientHeaders) > 0 && clientHeaders[0] != nil {
+		ch = clientHeaders[0]
+	} else if r.Context() != nil {
+		if ginCtx, ok := r.Context().Value("gin").(*gin.Context); ok && ginCtx != nil && ginCtx.Request != nil {
+			ch = ginCtx.Request.Header
+		} else if ginCtx, ok := r.Context().(*gin.Context); ok && ginCtx != nil && ginCtx.Request != nil {
+			ch = ginCtx.Request.Header
+		}
+	}
+	applyCustomHeaders(r, extractCustomHeaders(attrs, ch))
+}
+
+func extractCustomHeaders(attrs map[string]string, clientHeaders http.Header) map[string]string {
+	if len(attrs) == 0 {
+		return nil
+	}
+	headers := make(map[string]string)
+	for k, v := range attrs {
+		if !strings.HasPrefix(k, "header:") {
+			continue
+		}
+		name := strings.TrimSpace(strings.TrimPrefix(k, "header:"))
+		if name == "" {
+			continue
+		}
+		val := strings.TrimSpace(v)
+		if val == "" {
+			continue
+		}
+		if strings.HasPrefix(val, "$") {
+			varName := strings.TrimSpace(strings.TrimPrefix(val, "$"))
+			if varName == "" || clientHeaders == nil {
+				continue
+			}
+			clientVal := clientHeaders.Get(varName)
+			if clientVal == "" {
+				for ck, cv := range clientHeaders {
+					if strings.EqualFold(ck, varName) && len(cv) > 0 && cv[0] != "" {
+						clientVal = cv[0]
+						break
+					}
+				}
+			}
+			if clientVal == "" {
+				continue
+			}
+			val = clientVal
+		}
+		headers[name] = val
+	}
+	if len(headers) == 0 {
+		return nil
+	}
+	return headers
+}
+
+func applyCustomHeaders(r *http.Request, headers map[string]string) {
+	if r == nil || len(headers) == 0 {
+		return
+	}
+	for k, v := range headers {
+		if k == "" || v == "" {
+			continue
+		}
+		// net/http reads Host from req.Host (not req.Header) when writing
+		// a real request, so we must mirror it there. Some callers pass
+		// synthetic requests (e.g. &http.Request{Header: ...}) and only
+		// consume r.Header afterwards, so keep the value in the header
+		// map too.
+		if http.CanonicalHeaderKey(k) == "Host" {
+			r.Host = v
+		}
+		r.Header.Set(k, v)
+	}
+}