/*
   Copyright The containerd 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.
*/

/*
   Copyright The OpenTelemetry 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.
*/

package otelttrpc

import (
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/metric"
	"go.opentelemetry.io/otel/propagation"
	semconv "go.opentelemetry.io/otel/semconv/v1.17.0"
	"go.opentelemetry.io/otel/trace"
)

const (
	// instrumentationName is the name of this instrumentation package.
	instrumentationName = "github.com/containerd/otelttrpc"

	// TTRPCStatusCodeKey is convention for numeric status code of a ttRPC request.
	TTRPCStatusCodeKey = attribute.Key("rpc.ttrpc.status_code")
)

// config is a group of options for this instrumentation.
type config struct {
	Propagators    propagation.TextMapPropagator
	TracerProvider trace.TracerProvider
	MeterProvider  metric.MeterProvider

	ReceivedEvent bool
	SentEvent     bool

	meter             metric.Meter
	rpcServerDuration metric.Int64Histogram
}

// Option applies an option value for a config.
type Option interface {
	apply(*config)
}

// newConfig returns a config configured with all the passed Options.
func newConfig(opts []Option) *config {
	c := &config{
		Propagators:    otel.GetTextMapPropagator(),
		TracerProvider: otel.GetTracerProvider(),
		MeterProvider:  otel.GetMeterProvider(),
	}
	for _, o := range opts {
		o.apply(c)
	}

	var err error
	c.meter = c.MeterProvider.Meter(
		instrumentationName,
		metric.WithInstrumentationVersion(Version()),
		metric.WithSchemaURL(semconv.SchemaURL),
	)
	if c.rpcServerDuration, err = c.meter.Int64Histogram(
		"rpc.server.duration",
		metric.WithUnit("ms"),
	); err != nil {
		otel.Handle(err)
	}

	return c
}

type propagatorsOption struct{ p propagation.TextMapPropagator }

func (o propagatorsOption) apply(c *config) {
	if o.p != nil {
		c.Propagators = o.p
	}
}

// WithPropagators returns an Option for setting the Propagators used
// to inject and extract trace context from requests. If this option
// is not provided the global TextMapPropagator will be used.
func WithPropagators(p propagation.TextMapPropagator) Option {
	return propagatorsOption{p: p}
}

type tracerProviderOption struct{ tp trace.TracerProvider }

func (o tracerProviderOption) apply(c *config) {
	if o.tp != nil {
		c.TracerProvider = o.tp
	}
}

// WithTracerProvider returns an Option for setting the TracerProvider
// for creating a Tracer. If this option is not provided the global
// TracerProvider will be used.
func WithTracerProvider(tp trace.TracerProvider) Option {
	return tracerProviderOption{tp: tp}
}

type meterProviderOption struct{ mp metric.MeterProvider }

func (o meterProviderOption) apply(c *config) {
	if o.mp != nil {
		c.MeterProvider = o.mp
	}
}

// WithMeterProvider returns an Option for setting the MeterProvider
// when creating a Meter. If this option is not provided the global
// MeterProvider will be used.
func WithMeterProvider(mp metric.MeterProvider) Option {
	return meterProviderOption{mp: mp}
}

// Event type that can be recorded, see WithMessageEvents.
type Event int

// Different types of events that can be recorded, see WithMessageEvents.
const (
	ReceivedEvents Event = iota
	SentEvents
)

type messageEventsProviderOption struct {
	events []Event
}

func (m messageEventsProviderOption) apply(c *config) {
	for _, e := range m.events {
		switch e {
		case ReceivedEvents:
			c.ReceivedEvent = true
		case SentEvents:
			c.SentEvent = true
		}
	}
}

// WithMessageEvents configures the interceptors to record the specified
// events (span.AddEvent) on spans. By default only summary attributes
// are added at the end of the request.
//
// Valid events are:
//   - ReceivedEvents: Record an event for every message received.
//   - SentEvents: Record an event for every message sent.
func WithMessageEvents(events ...Event) Option {
	return messageEventsProviderOption{events: events}
}