var (
	ClientErrorCount, _       = stats.Int64("grpc.io/client/error_count", "RPC Errors", stats.UnitNone)
	ClientRequestBytes, _     = stats.Int64("grpc.io/client/request_bytes", "Request bytes", stats.UnitBytes)
	ClientResponseBytes, _    = stats.Int64("grpc.io/client/response_bytes", "Response bytes", stats.UnitBytes)
	ClientStartedCount, _     = stats.Int64("grpc.io/client/started_count", "Number of client RPCs (streams) started", stats.UnitNone)
	ClientFinishedCount, _    = stats.Int64("grpc.io/client/finished_count", "Number of client RPCs (streams) finished", stats.UnitNone)
	ClientRequestCount, _     = stats.Int64("grpc.io/client/request_count", "Number of client RPC request messages", stats.UnitNone)
	ClientResponseCount, _    = stats.Int64("grpc.io/client/response_count", "Number of client RPC response messages", stats.UnitNone)
	ClientRoundTripLatency, _ = stats.Float64("grpc.io/client/roundtrip_latency", "RPC roundtrip latency in msecs", stats.UnitMilliseconds)
)

var (
	ClientErrorCountView = &view.View{
		Name:        "grpc.io/client/error_count",
		Description: "RPC Errors",
		TagKeys:     []tag.Key{KeyStatus, KeyMethod},
		Measure:     ClientErrorCount,
		Aggregation: view.MeanAggregation{},
	}

	ClientRoundTripLatencyView = &view.View{
		Name:        "grpc.io/client/roundtrip_latency",
		Description: "Latency in msecs",
		TagKeys:     []tag.Key{KeyMethod},
		Measure:     ClientRoundTripLatency,
		Aggregation: DefaultMillisecondsDistribution,
	}

	ClientRequestBytesView = &view.View{
		Name:        "grpc.io/client/request_bytes",
		Description: "Request bytes",
		TagKeys:     []tag.Key{KeyMethod},
		Measure:     ClientRequestBytes,
		Aggregation: DefaultBytesDistribution,
	}

	ClientResponseBytesView = &view.View{
		Name:        "grpc.io/client/response_bytes",
		Description: "Response bytes",
		TagKeys:     []tag.Key{KeyMethod},
		Measure:     ClientResponseBytes,
		Aggregation: DefaultBytesDistribution,
	}

	ClientRequestCountView = &view.View{
		Name:        "grpc.io/client/request_count",
		Description: "Count of request messages per client RPC",
		TagKeys:     []tag.Key{KeyMethod},
		Measure:     ClientRequestCount,
		Aggregation: DefaultMessageCountDistribution,
	}

	ClientResponseCountView = &view.View{
		Name:        "grpc.io/client/response_count",
		Description: "Count of response messages per client RPC",
		TagKeys:     []tag.Key{KeyMethod},
		Measure:     ClientResponseCount,
		Aggregation: DefaultMessageCountDistribution,
	}
)

var (
	ServerErrorCount, _        = stats.Int64("grpc.io/server/error_count", "RPC Errors", stats.UnitNone)
	ServerServerElapsedTime, _ = stats.Float64("grpc.io/server/server_elapsed_time", "Server elapsed time in msecs", stats.UnitMilliseconds)
	ServerRequestBytes, _      = stats.Int64("grpc.io/server/request_bytes", "Request bytes", stats.UnitBytes)
	ServerResponseBytes, _     = stats.Int64("grpc.io/server/response_bytes", "Response bytes", stats.UnitBytes)
	ServerStartedCount, _      = stats.Int64("grpc.io/server/started_count", "Number of server RPCs (streams) started", stats.UnitNone)
	ServerFinishedCount, _     = stats.Int64("grpc.io/server/finished_count", "Number of server RPCs (streams) finished", stats.UnitNone)
	ServerRequestCount, _      = stats.Int64("grpc.io/server/request_count", "Number of server RPC request messages", stats.UnitNone)
	ServerResponseCount, _     = stats.Int64("grpc.io/server/response_count", "Number of server RPC response messages", stats.UnitNone)
)

var (
	ServerErrorCountView = &view.View{
		Name:        "grpc.io/server/error_count",
		Description: "RPC Errors",
		TagKeys:     []tag.Key{KeyMethod, KeyStatus},
		Measure:     ServerErrorCount,
		Aggregation: view.CountAggregation{},
	}

	ServerServerElapsedTimeView = &view.View{
		Name:        "grpc.io/server/server_elapsed_time",
		Description: "Server elapsed time in msecs",
		TagKeys:     []tag.Key{KeyMethod},
		Measure:     ServerServerElapsedTime,
		Aggregation: DefaultMillisecondsDistribution,
	}

	ServerRequestBytesView = &view.View{
		Name:        "grpc.io/server/request_bytes",
		Description: "Request bytes",
		TagKeys:     []tag.Key{KeyMethod},
		Measure:     ServerRequestBytes,
		Aggregation: DefaultBytesDistribution,
	}

	ServerResponseBytesView = &view.View{
		Name:        "grpc.io/server/response_bytes",
		Description: "Response bytes",
		TagKeys:     []tag.Key{KeyMethod},
		Measure:     ServerResponseBytes,
		Aggregation: DefaultBytesDistribution,
	}

	ServerRequestCountView = &view.View{
		Name:        "grpc.io/server/request_count",
		Description: "Count of request messages per server RPC",
		TagKeys:     []tag.Key{KeyMethod},
		Measure:     ServerRequestCount,
		Aggregation: DefaultMessageCountDistribution,
	}

	ServerResponseCountView = &view.View{
		Name:        "grpc.io/server/response_count",
		Description: "Count of response messages per server RPC",
		TagKeys:     []tag.Key{KeyMethod},
		Measure:     ServerResponseCount,
		Aggregation: DefaultMessageCountDistribution,
	}
)

var (
	DefaultBytesDistribution        = view.DistributionAggregation{0, 1024, 2048, 4096, 16384, 65536, 262144, 1048576, 4194304, 16777216, 67108864, 268435456, 1073741824, 4294967296}
	DefaultMillisecondsDistribution = view.DistributionAggregation{0, 1, 2, 3, 4, 5, 6, 8, 10, 13, 16, 20, 25, 30, 40, 50, 65, 80, 100, 130, 160, 200, 250, 300, 400, 500, 650, 800, 1000, 2000, 5000, 10000, 20000, 50000, 100000}
	DefaultMessageCountDistribution = view.DistributionAggregation{0, 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536}
)

var (
	KeyMethod, _ = tag.NewKey("method")           // gRPC service and method name
	KeyStatus, _ = tag.NewKey("canonical_status") // Canonical status code
)

var DefaultClientViews = []*view.View{
	ClientErrorCountView,
	ClientRoundTripLatencyView,
	ClientRequestBytesView,
	ClientResponseBytesView,
	ClientRequestCountView,
	ClientResponseCountView,
}

var DefaultServerViews = []*view.View{
	ServerErrorCountView,
	ServerServerElapsedTimeView,
	ServerRequestBytesView,
	ServerResponseBytesView,
	ServerRequestCountView,
	ServerResponseCountView,
}

type ClientHandler struct {
	// NoStats may be set to disable recording OpenCensus Stats around each
	// gRPC method.
	NoStats bool

	// StartOptions allows configuring the StartOptions used to create new spans.
	StartOptions trace.StartOptions
}

type ServerHandler struct {
	// NoStats may be set to true to disable recording OpenCensus stats for RPCs.
	NoStats bool

	// IsPublicEndpoint may be set to true to always start a new trace around
	// each RPC. Any SpanContext in the RPC metadata will be added as a linked
	// span instead of making it the parent of the span created around the
	// server RPC.
	//
	// Be aware that if you leave this false (the default) on a public-facing
	// server, callers will be able to send tracing metadata in gRPC headers
	// and trigger traces in your backend.
	IsPublicEndpoint bool

	// StartOptions to use for to spans started around RPCs handled by this server.
	//
	// These will apply even if there is tracing metadata already
	// present on the inbound RPC but the SpanContext is not sampled. This
	// ensures that each service has some opportunity to be traced. If you would
	// like to not add any additional traces for this gRPC service, set:
	//   StartOptions.Sampler = trace.ProbabilitySampler(0.0)
	StartOptions trace.StartOptions
}