api: return structured error on unauthorized push

This commit implements a structured error response system for the Ollama API, replacing
ad-hoc error handling and string parsing with proper error types and codes through a new
ErrorResponse struct. Instead of relying on regex to parse error messages for SSH keys,
the API now passes this data in a structured format with standardized fields for error
messages, codes, and additional data. This structured approach makes the API more
maintainable and reliable while improving the developer experience by enabling
programmatic error handling, consistent error formats, and better error
documentation.

api/client_test.go

@@ -1,6 +1,12 @@
 package api
 
 import (
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"net/url"
 	"testing"
 )
 
@@ -43,3 +49,117 @@ func TestClientFromEnvironment(t *testing.T) {
 		})
 	}
 }
+
+func TestStream(t *testing.T) {
+	tests := []struct {
+		name           string
+		serverResponse []string
+		statusCode     int
+		expectedError  error
+	}{
+		{
+			name: "unknown key error",
+			serverResponse: []string{
+				`{"error":"unauthorized access","code":"unknown_key","data":{"key":"test-key"}}`,
+			},
+			statusCode: http.StatusUnauthorized,
+			expectedError: &ErrUnknownOllamaKey{
+				Message: "unauthorized access",
+				Key:     "test-key",
+			},
+		},
+		{
+			name: "general error message",
+			serverResponse: []string{
+				`{"error":"something went wrong"}`,
+			},
+			statusCode:    http.StatusInternalServerError,
+			expectedError: fmt.Errorf("something went wrong"),
+		},
+		{
+			name: "malformed json response",
+			serverResponse: []string{
+				`{invalid-json`,
+			},
+			statusCode:    http.StatusOK,
+			expectedError: fmt.Errorf("unmarshal: invalid character 'i' looking for beginning of object key string"),
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				w.Header().Set("Content-Type", "application/x-ndjson")
+				w.WriteHeader(tt.statusCode)
+				for _, resp := range tt.serverResponse {
+					fmt.Fprintln(w, resp)
+				}
+			}))
+			defer server.Close()
+
+			baseURL, err := url.Parse(server.URL)
+			if err != nil {
+				t.Fatalf("failed to parse server URL: %v", err)
+			}
+
+			client := &Client{
+				http: server.Client(),
+				base: baseURL,
+			}
+
+			var responses [][]byte
+			err = client.stream(context.Background(), "POST", "/test", "test", func(bts []byte) error {
+				responses = append(responses, bts)
+				return nil
+			})
+
+			// Error checking
+			if tt.expectedError == nil {
+				if err != nil {
+					t.Fatalf("unexpected error: %v", err)
+				}
+				return
+			}
+
+			if err == nil {
+				t.Fatalf("expected error %v, got nil", tt.expectedError)
+			}
+
+			// Check for specific error types
+			var unknownKeyErr ErrUnknownOllamaKey
+			if errors.As(tt.expectedError, &unknownKeyErr) {
+				var gotErr ErrUnknownOllamaKey
+				if !errors.As(err, &gotErr) {
+					t.Fatalf("expected ErrUnknownOllamaKey, got %T", err)
+				}
+				if unknownKeyErr.Key != gotErr.Key {
+					t.Errorf("expected key %q, got %q", unknownKeyErr.Key, gotErr.Key)
+				}
+				if unknownKeyErr.Message != gotErr.Message {
+					t.Errorf("expected message %q, got %q", unknownKeyErr.Message, gotErr.Message)
+				}
+				return
+			}
+
+			var statusErr StatusError
+			if errors.As(tt.expectedError, &statusErr) {
+				var gotErr StatusError
+				if !errors.As(err, &gotErr) {
+					t.Fatalf("expected StatusError, got %T", err)
+				}
+				if statusErr.StatusCode != gotErr.StatusCode {
+					t.Errorf("expected status code %d, got %d", statusErr.StatusCode, gotErr.StatusCode)
+				}
+				if statusErr.ErrorMessage != gotErr.ErrorMessage {
+					t.Errorf("expected error message %q, got %q", statusErr.ErrorMessage, gotErr.ErrorMessage)
+				}
+				return
+			}
+
+			// For other errors, compare error strings
+			if err.Error() != tt.expectedError.Error() {
+				t.Errorf("expected error %q, got %q", tt.expectedError, err)
+			}
+		})
+	}
+}