Add upstream model list fetching and a Codex-specific model section

internal/gateway/handlers.go

@@ -1,10 +1,15 @@
 package gateway
 
 import (
+	"context"
+	"errors"
 	"fmt"
 	"net/http"
+	"net/url"
+	"strings"
 	"time"
 
+	"gitea.rutua.cn/kate522/CrossRelay/internal/chatcmpl"
 	"gitea.rutua.cn/kate522/CrossRelay/internal/claudecfg"
 	"gitea.rutua.cn/kate522/CrossRelay/internal/codexcfg"
 	"gitea.rutua.cn/kate522/CrossRelay/internal/config"
@@ -71,6 +76,48 @@ func (s *Server) handleListProviders(w http.ResponseWriter, r *http.Request) {
 	writeJSON(w, http.StatusOK, map[string]any{"items": items})
 }
 
+type fetchModelsInput struct {
+	BaseURL string `json:"base_url"`
+	APIKey  string `json:"api_key"`
+}
+
+// handleFetchModels proxies the upstream model catalog so the UI can
+// offer a picker without talking to the provider directly.
+func (s *Server) handleFetchModels(w http.ResponseWriter, r *http.Request) {
+	var in fetchModelsInput
+	if err := decodeJSON(r, &in, 1<<20); err != nil {
+		writeAPIError(w, http.StatusBadRequest, "invalid request body: "+err.Error())
+		return
+	}
+	in.BaseURL = strings.TrimSpace(in.BaseURL)
+	in.APIKey = strings.TrimSpace(in.APIKey)
+	if in.BaseURL == "" || in.APIKey == "" {
+		writeAPIError(w, http.StatusBadRequest, "base URL and API key are required")
+		return
+	}
+	if u, err := url.Parse(in.BaseURL); err != nil || (u.Scheme != "http" && u.Scheme != "https") || u.Host == "" {
+		writeAPIError(w, http.StatusBadRequest, "base URL must be an http(s) URL")
+		return
+	}
+	ctx, cancel := context.WithTimeout(r.Context(), 20*time.Second)
+	defer cancel()
+	list, err := chatcmpl.NewClient(in.BaseURL, in.APIKey).ListModels(ctx)
+	if err != nil {
+		var ue *chatcmpl.UpstreamError
+		if errors.As(err, &ue) {
+			writeAPIError(w, http.StatusBadGateway, fmt.Sprintf("upstream %d: %s", ue.StatusCode, ue.Message))
+			return
+		}
+		writeAPIError(w, http.StatusBadGateway, fmt.Sprintf("upstream request failed: %v", err))
+		return
+	}
+	items := []chatcmpl.ModelInfo{}
+	if list != nil {
+		items = list.Data
+	}
+	writeJSON(w, http.StatusOK, map[string]any{"items": items})
+}
+
 func (s *Server) handleCreateProvider(w http.ResponseWriter, r *http.Request) {
 	var in providerInput
 	if err := decodeJSON(r, &in, 1<<20); err != nil {