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filter.go
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filter.go
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/*
Copyright 2022 TriggerMesh Inc.
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 eventfilter
import (
"context"
cloudevents "github.com/cloudevents/sdk-go/v2"
)
// Filtering result conditions.
const (
PassFilter FilterResult = "pass"
FailFilter FilterResult = "fail"
NoFilter FilterResult = "no_filter"
)
// FilterResult has the result of the filtering operation.
type FilterResult string
// And implements filter's logical conjunction.
func (x FilterResult) And(y FilterResult) FilterResult {
if x == NoFilter {
return y
}
if y == NoFilter {
return x
}
if x == PassFilter && y == PassFilter {
return PassFilter
}
return FailFilter
}
// Filter is an interface representing an event filter of the trigger filter.
type Filter interface {
// Filter compute the predicate on the provided event and returns the result of the matching
Filter(ctx context.Context, event cloudevents.Event) FilterResult
}
// Filters is a wrapper that runs each filter.
type Filters []Filter
// Filter applies filtering conditions on events.
func (filters Filters) Filter(ctx context.Context, event cloudevents.Event) FilterResult {
res := NoFilter
for _, f := range filters {
res = res.And(f.Filter(ctx, event))
// Short circuit to optimize it
if res == FailFilter {
return FailFilter
}
}
return res
}
var _ Filter = Filters{}