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ergo/irc/history/targets.go

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2021-04-07 11:40:39 +02:00
// Copyright (c) 2021 Shivaram Lingamneni <slingamn@cs.stanford.edu>
// released under the MIT license
package history
import (
"sort"
"time"
)
type TargetListing struct {
CfName string
Time time.Time
}
// Merge `base`, a paging window of targets, with `extras` (the target entries
// for all joined channels).
func MergeTargets(base []TargetListing, extra []TargetListing, start, end time.Time, limit int) (results []TargetListing) {
if len(extra) == 0 {
return base
}
SortCorrespondents(extra)
start, end, ascending := MinMaxAsc(start, end, time.Time{})
predicate := func(t time.Time) bool {
return (start.IsZero() || start.Before(t)) && (end.IsZero() || end.After(t))
}
prealloc := len(base) + len(extra)
if limit < prealloc {
prealloc = limit
}
results = make([]TargetListing, 0, prealloc)
if !ascending {
ReverseCorrespondents(base)
ReverseCorrespondents(extra)
}
for len(results) < limit {
if len(extra) != 0 {
if !predicate(extra[0].Time) {
extra = extra[1:]
continue
}
if len(base) != 0 {
if base[0].Time.Before(extra[0].Time) == ascending {
results = append(results, base[0])
base = base[1:]
} else {
results = append(results, extra[0])
extra = extra[1:]
}
} else {
results = append(results, extra[0])
extra = extra[1:]
}
} else if len(base) != 0 {
results = append(results, base[0])
base = base[1:]
} else {
break
}
}
if !ascending {
ReverseCorrespondents(results)
}
return
}
func ReverseCorrespondents(results []TargetListing) {
// lol, generics when?
for i, j := 0, len(results)-1; i < j; i, j = i+1, j-1 {
results[i], results[j] = results[j], results[i]
}
}
func SortCorrespondents(list []TargetListing) {
sort.Slice(list, func(i, j int) bool {
return list[i].Time.Before(list[j].Time)
})
}