// Copyright 2017 Istio Authors
//
// 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.

// THIS FILE IS AUTOMATICALLY GENERATED.

package metric

import (
	"context"

	"istio.io/istio/mixer/pkg/adapter"
)

// Fully qualified name of the template
const TemplateName = "metric"

// Instance is constructed by Mixer for the 'metric' template.
//
// Metric represents a single piece of data to report.
//
// When writing the configuration, the value for the fields associated with this template can either be a
// literal or an [expression](https://istio.io/docs/reference/config/mixer/expression-language.html). Please note that if the datatype of a field is not istio.mixer.v1.config.descriptor.ValueType,
// then the expression's [inferred type](https://istio.io/docs/reference/config/mixer/expression-language.html#type-checking) must match the datatype of the field.
//
// Example config:
// ```
// apiVersion: "config.istio.io/v1alpha2"
// kind: metric
// metadata:
//   name: requestsize
//   namespace: istio-system
// spec:
//   value: request.size | 0
//   dimensions:
//     source_service: source.service | "unknown"
//     source_version: source.labels["version"] | "unknown"
//     destination_service: destination.service | "unknown"
//     destination_version: destination.labels["version"] | "unknown"
//     response_code: response.code | 200
//   monitored_resource_type: '"UNSPECIFIED"'
// ```
type Instance struct {
	// Name of the instance as specified in configuration.
	Name string

	// The value being reported.
	Value interface{}

	// The unique identity of the particular metric to report.
	Dimensions map[string]interface{}

	// Optional. An expression to compute the type of the monitored resource this metric is being reported on.
	// If the metric backend supports monitored resources, these fields are used to populate that resource. Otherwise
	// these fields will be ignored by the adapter.
	MonitoredResourceType string

	// Optional. A set of expressions that will form the dimensions of the monitored resource this metric is being reported on.
	// If the metric backend supports monitored resources, these fields are used to populate that resource. Otherwise
	// these fields will be ignored by the adapter.
	MonitoredResourceDimensions map[string]interface{}
}

// HandlerBuilder must be implemented by adapters if they want to
// process data associated with the 'metric' template.
//
// Mixer uses this interface to call into the adapter at configuration time to configure
// it with adapter-specific configuration as well as all template-specific type information.
type HandlerBuilder interface {
	adapter.HandlerBuilder

	// SetMetricTypes is invoked by Mixer to pass the template-specific Type information for instances that an adapter
	// may receive at runtime. The type information describes the shape of the instance.
	SetMetricTypes(map[string]*Type /*Instance name -> Type*/)
}

// Handler must be implemented by adapter code if it wants to
// process data associated with the 'metric' template.
//
// Mixer uses this interface to call into the adapter at request time in order to dispatch
// created instances to the adapter. Adapters take the incoming instances and do what they
// need to achieve their primary function.
//
// The name of each instance can be used as a key into the Type map supplied to the adapter
// at configuration time via the method 'SetMetricTypes'.
// These Type associated with an instance describes the shape of the instance
type Handler interface {
	adapter.Handler

	// HandleMetric is called by Mixer at request time to deliver instances to
	// to an adapter.
	HandleMetric(context.Context, []*Instance) error
}
