record.gno

 1package gnotif
 2
 3import (
 4	"strconv"
 5	"strings"
 6)
 7
 8const recordFields = 8
 9
10// record is a trigger, its target and its name as the registry stores them:
11// one string per trigger, because a tree holds a string inline and a struct
12// is one more stored object.
13type record struct {
14	Target string
15	Name   string
16	T      Trigger
17}
18
19func (r record) encode() string {
20	return packFields(r.Target, r.Name, r.T.Event, r.T.Filter, r.T.Param, r.T.Title, r.T.Body, r.T.Link)
21}
22
23// decodeRecord reads a string made by encode and panics on any other.
24func decodeRecord(v any) record {
25	f := unpackFields(v.(string), recordFields)
26	return record{
27		Target: f[0],
28		Name:   f[1],
29		T:      Trigger{Event: f[2], Filter: f[3], Param: f[4], Title: f[5], Body: f[6], Link: f[7]},
30	}
31}
32
33// packFields writes each field as its byte length, a colon and the field, so
34// a field may hold colons and digits.
35func packFields(fields ...string) string {
36	var b strings.Builder
37	for _, f := range fields {
38		b.WriteString(strconv.Itoa(len(f)) + ":" + f)
39	}
40	return b.String()
41}
42
43// unpackFields reads exactly n fields made by packFields and panics on any
44// other string.
45func unpackFields(s string, n int) []string {
46	fields := make([]string, n)
47	for i := range fields {
48		field, rest, ok := cutField(s)
49		if !ok {
50			panic("corrupt record")
51		}
52		fields[i], s = field, rest
53	}
54	if s != "" {
55		panic("corrupt record")
56	}
57	return fields
58}
59
60func cutField(s string) (field, rest string, ok bool) {
61	length, body, found := strings.Cut(s, ":")
62	if !found {
63		return "", "", false
64	}
65	n, err := strconv.Atoi(length)
66	if err != nil || n < 0 || n > len(body) {
67		return "", "", false
68	}
69	return body[:n], body[n:], true
70}