// Copyright 2020 New Relic Corporation. All rights reserved.
// SPDX-License-Identifier: Apache-2.0

package nrlambda

import (
	"os"
	"time"

	newrelic "github.com/newrelic/go-agent/v3/newrelic"
)

// ConfigOption populates a newrelic.Config with correct default settings for a
// Lambda serverless environment.  ConfigOption will populate fields based on
// environment variables common to all New Relic agents that support Lambda.
// Environment variables NEW_RELIC_ACCOUNT_ID, NEW_RELIC_TRUSTED_ACCOUNT_KEY,
// and NEW_RELIC_PRIMARY_APPLICATION_ID configure fields required for
// distributed tracing.  Environment variable NEW_RELIC_APDEX_T may be used to
// set a custom apdex threshold.
func ConfigOption() newrelic.ConfigOption { return newConfigInternal(os.Getenv) }

func newConfigInternal(getenv func(string) string) newrelic.ConfigOption {
	return func(cfg *newrelic.Config) {
		cfg.ServerlessMode.Enabled = true

		cfg.ServerlessMode.AccountID = getenv("NEW_RELIC_ACCOUNT_ID")
		cfg.ServerlessMode.TrustedAccountKey = getenv("NEW_RELIC_TRUSTED_ACCOUNT_KEY")
		cfg.ServerlessMode.PrimaryAppID = getenv("NEW_RELIC_PRIMARY_APPLICATION_ID")

		cfg.DistributedTracer.Enabled = true

		if s := getenv("NEW_RELIC_APDEX_T"); "" != s {
			if apdex, err := time.ParseDuration(s + "s"); nil == err {
				cfg.ServerlessMode.ApdexThreshold = apdex
			}
		}
	}
}
