.prom-gowrap.tmpl

import (
  "time"

  migrate "github.com/golang-migrate/migrate/v4"
  "github.com/prometheus/client_golang/prometheus"
  "github.com/prometheus/client_golang/prometheus/promauto"
)

{{ $decorator := (or .Vars.DecoratorName (printf "%sWithPrometheus" .Interface.Name)) }}

// {{$decorator}} implements {{.Interface.Type}} interface with all methods wrapped
// with Prometheus metrics
type {{$decorator}} struct {
  base {{.Interface.Type}}
  instanceName string
}

var {{down .Interface.Name}}DurationSummaryVec = promauto.NewSummaryVec(
  prometheus.SummaryOpts{
    Name: "{{down .Interface.Name}}_duration_seconds",
    Help: "{{down .Interface.Name}} runtime duration and result",
    MaxAge: time.Minute,
    Objectives: map[float64]float64{0.5: 0.05, 0.9: 0.01, 0.99: 0.001},
  },
  []string{"instance_name", "method", "result"})

// New{{.Interface.Name}}WithPrometheus returns an instance of the {{.Interface.Type}} decorated with prometheus summary metric
func New{{$decorator}}(base {{.Interface.Type}}, instanceName string) {{$decorator}} {
  return {{$decorator}} {
    base: base,
    instanceName: instanceName,
  }
}

{{range $method := .Interface.Methods}}
  // {{$method.Name}} implements {{$.Interface.Type}}
  func (_d {{$decorator}}) {{$method.Declaration}} {
      _since := time.Now()
      defer func() {
        result := "ok"
        {{- if $method.ReturnsError}}
          if err != nil {
            result = "error"
          }
        {{end}}
        {{down $.Interface.Name}}DurationSummaryVec.WithLabelValues(_d.instanceName, "{{$method.Name}}", result).Observe(time.Since(_since).Seconds())
      }()
    {{$method.Pass "_d.base."}}
  }
{{end}}