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metaschemalocator.go
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metaschemalocator.go
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// Copyright Axis Communications AB.
//
// For a full list of individual contributors, please see the commit history.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package validator
import (
"context"
"fmt"
"io"
"net/http"
"net/url"
)
// HTTPGetter is capable of downloading an HTTP resource via a GET request.
type HTTPGetter interface {
Do(req *http.Request) (*http.Response, error)
}
// MetaSchemaLocator is a SchemaLocator implementation that downloads
// an event's schema from its non-empty meta.schemaURI member via HTTP(S).
type MetaSchemaLocator struct {
getter HTTPGetter
}
func NewMetaSchemaLocator(getter HTTPGetter) *MetaSchemaLocator {
return &MetaSchemaLocator{
getter: getter,
}
}
// GetSchema downloads the event's schema via HTTP(S) if schemaURI is non-empty.
// Returns (nil, nil) if schemaURI is empty or if the URI scheme isn't "http"
// or "https".
func (msl *MetaSchemaLocator) GetSchema(ctx context.Context, eventType string, version string, schemaURI string) (io.ReadCloser, error) {
if schemaURI == "" {
return nil, nil
}
// We only support HTTP(S) URI schemes.
u, err := url.Parse(schemaURI)
if err != nil {
return nil, fmt.Errorf("error parsing schema URI: %w", err)
}
if u.Scheme != "http" && u.Scheme != "https" {
return nil, nil
}
req, err := http.NewRequestWithContext(ctx, http.MethodGet, schemaURI, nil)
if err != nil {
return nil, fmt.Errorf("error creating HTTP request: %w", err)
}
resp, err := msl.getter.Do(req)
if err != nil {
return nil, fmt.Errorf("error fetching schema: %w", err)
}
if resp.StatusCode != http.StatusOK {
return nil, fmt.Errorf("request to fetch schema returned status %d", resp.StatusCode)
}
return resp.Body, nil
}