1// Copyright 2019 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// Package core provides support for event based telemetry.
6package core
7
8import (
9	"fmt"
10	"time"
11
12	"golang.org/x/tools/internal/event/label"
13)
14
15// Event holds the information about an event of note that occurred.
16type Event struct {
17	at time.Time
18
19	// As events are often on the stack, storing the first few labels directly
20	// in the event can avoid an allocation at all for the very common cases of
21	// simple events.
22	// The length needs to be large enough to cope with the majority of events
23	// but no so large as to cause undue stack pressure.
24	// A log message with two values will use 3 labels (one for each value and
25	// one for the message itself).
26
27	static  [3]label.Label // inline storage for the first few labels
28	dynamic []label.Label  // dynamically sized storage for remaining labels
29}
30
31// eventLabelMap implements label.Map for a the labels of an Event.
32type eventLabelMap struct {
33	event Event
34}
35
36func (ev Event) At() time.Time { return ev.at }
37
38func (ev Event) Format(f fmt.State, r rune) {
39	if !ev.at.IsZero() {
40		fmt.Fprint(f, ev.at.Format("2006/01/02 15:04:05 "))
41	}
42	for index := 0; ev.Valid(index); index++ {
43		if l := ev.Label(index); l.Valid() {
44			fmt.Fprintf(f, "\n\t%v", l)
45		}
46	}
47}
48
49func (ev Event) Valid(index int) bool {
50	return index >= 0 && index < len(ev.static)+len(ev.dynamic)
51}
52
53func (ev Event) Label(index int) label.Label {
54	if index < len(ev.static) {
55		return ev.static[index]
56	}
57	return ev.dynamic[index-len(ev.static)]
58}
59
60func (ev Event) Find(key label.Key) label.Label {
61	for _, l := range ev.static {
62		if l.Key() == key {
63			return l
64		}
65	}
66	for _, l := range ev.dynamic {
67		if l.Key() == key {
68			return l
69		}
70	}
71	return label.Label{}
72}
73
74func MakeEvent(static [3]label.Label, labels []label.Label) Event {
75	return Event{
76		static:  static,
77		dynamic: labels,
78	}
79}
80
81// CloneEvent event returns a copy of the event with the time adjusted to at.
82func CloneEvent(ev Event, at time.Time) Event {
83	ev.at = at
84	return ev
85}
86