feat(probe): add model discovery and canonical family normalization

internal/probe/models.go

@@ -0,0 +1,97 @@
+package probe
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/http"
+	"net/url"
+	"strings"
+	"time"
+)
+
+var ErrAuthFailed = errors.New("upstream auth failed")
+
+type ModelsResult struct {
+	RawModels  []string
+	HTTPStatus int
+	LatencyMs  int64
+	Error      string
+}
+
+func ProviderModels(ctx context.Context, baseURL, apiKey string) (*ModelsResult, error) {
+	client := &http.Client{Timeout: 15 * time.Second}
+
+	requestURL, err := joinGatewayPath(baseURL, "/v1/models")
+	if err != nil {
+		return nil, fmt.Errorf("resolve models endpoint: %w", err)
+	}
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, requestURL, nil)
+	if err != nil {
+		return nil, fmt.Errorf("build models request: %w", err)
+	}
+	if token := strings.TrimSpace(apiKey); token != "" {
+		req.Header.Set("Authorization", "Bearer "+token)
+	}
+
+	startedAt := time.Now()
+	resp, err := client.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("request models: %w", err)
+	}
+	defer resp.Body.Close()
+
+	result := &ModelsResult{
+		RawModels:  []string{},
+		HTTPStatus: resp.StatusCode,
+		LatencyMs:  time.Since(startedAt).Milliseconds(),
+	}
+
+	var payload struct {
+		Data []struct {
+			ID string `json:"id"`
+		} `json:"data"`
+		Error any `json:"error"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&payload); err != nil {
+		return nil, fmt.Errorf("decode models response: %w", err)
+	}
+
+	switch resp.StatusCode {
+	case http.StatusUnauthorized, http.StatusForbidden:
+		result.Error = "auth_failed"
+		return result, ErrAuthFailed
+	}
+
+	if resp.StatusCode < http.StatusOK || resp.StatusCode >= http.StatusMultipleChoices {
+		result.Error = fmt.Sprintf("unexpected_status_%d", resp.StatusCode)
+		return result, fmt.Errorf("models endpoint returned status %d", resp.StatusCode)
+	}
+
+	for _, item := range payload.Data {
+		if modelID := strings.TrimSpace(item.ID); modelID != "" {
+			result.RawModels = append(result.RawModels, modelID)
+		}
+	}
+
+	return result, nil
+}
+
+func joinGatewayPath(baseURL, path string) (string, error) {
+	parsedURL, err := url.Parse(strings.TrimSpace(baseURL))
+	if err != nil {
+		return "", err
+	}
+	if parsedURL.Scheme == "" || parsedURL.Host == "" {
+		return "", fmt.Errorf("base url must include scheme and host")
+	}
+
+	resolvedPath := strings.TrimSpace(path)
+	if !strings.HasPrefix(resolvedPath, "/") {
+		resolvedPath = "/" + resolvedPath
+	}
+
+	return parsedURL.ResolveReference(&url.URL{Path: resolvedPath}).String(), nil
+}