well-goknown/vendor/github.com/fiatjaf/eventstore/internal/helpers.go

183 lines
4.8 KiB
Go

package internal
import (
"cmp"
"math"
"slices"
"strings"
mergesortedslices "fiatjaf.com/lib/merge-sorted-slices"
"github.com/nbd-wtf/go-nostr"
)
func IsOlder(previous, next *nostr.Event) bool {
return previous.CreatedAt < next.CreatedAt ||
(previous.CreatedAt == next.CreatedAt && previous.ID > next.ID)
}
func ChooseNarrowestTag(filter nostr.Filter) (key string, values []string, goodness int) {
var tagKey string
var tagValues []string
for key, values := range filter.Tags {
switch key {
case "e", "E", "q":
// 'e' and 'q' are the narrowest possible, so if we have that we will use it and that's it
tagKey = key
tagValues = values
goodness = 9
break
case "a", "A", "i", "I", "g", "r":
// these are second-best as they refer to relatively static things
goodness = 8
tagKey = key
tagValues = values
case "d":
// this is as good as long as we have an "authors"
if len(filter.Authors) != 0 && goodness < 7 {
goodness = 7
tagKey = key
tagValues = values
} else if goodness < 4 {
goodness = 4
tagKey = key
tagValues = values
}
case "h", "t", "l", "k", "K":
// these things denote "categories", so they are a little more broad
if goodness < 6 {
goodness = 6
tagKey = key
tagValues = values
}
case "p":
// this is broad and useless for a pure tag search, but we will still prefer it over others
// for secondary filtering
if goodness < 2 {
goodness = 2
tagKey = key
tagValues = values
}
default:
// all the other tags are probably too broad and useless
if goodness == 0 {
tagKey = key
tagValues = values
}
}
}
return tagKey, tagValues, goodness
}
func CopyMapWithoutKey[K comparable, V any](originalMap map[K]V, key K) map[K]V {
newMap := make(map[K]V, len(originalMap)-1)
for k, v := range originalMap {
if k != key {
newMap[k] = v
}
}
return newMap
}
type IterEvent struct {
*nostr.Event
Q int
}
// MergeSortMultipleBatches takes the results of multiple iterators, which are already sorted,
// and merges them into a single big sorted slice
func MergeSortMultiple(batches [][]IterEvent, limit int, dst []IterEvent) []IterEvent {
// clear up empty lists here while simultaneously computing the total count.
// this helps because if there are a bunch of empty lists then this pre-clean
// step will get us in the faster 'merge' branch otherwise we would go to the other.
// we would have to do the cleaning anyway inside it.
// and even if we still go on the other we save one iteration by already computing the
// total count.
total := 0
for i := len(batches) - 1; i >= 0; i-- {
if len(batches[i]) == 0 {
batches = SwapDelete(batches, i)
} else {
total += len(batches[i])
}
}
if limit == -1 {
limit = total
}
// this amazing equation will ensure that if one of the two sides goes very small (like 1 or 2)
// the other can go very high (like 500) and we're still in the 'merge' branch.
// if values go somewhere in the middle then they may match the 'merge' branch (batches=20,limit=70)
// or not (batches=25, limit=60)
if math.Log(float64(len(batches)*2))+math.Log(float64(limit)) < 8 {
if dst == nil {
dst = make([]IterEvent, limit)
} else if cap(dst) < limit {
dst = slices.Grow(dst, limit-len(dst))
}
dst = dst[0:limit]
return mergesortedslices.MergeFuncNoEmptyListsIntoSlice(dst, batches, compareIterEvent)
} else {
if dst == nil {
dst = make([]IterEvent, total)
} else if cap(dst) < total {
dst = slices.Grow(dst, total-len(dst))
}
dst = dst[0:total]
// use quicksort in a dumb way that will still be fast because it's cheated
lastIndex := 0
for _, batch := range batches {
copy(dst[lastIndex:], batch)
lastIndex += len(batch)
}
slices.SortFunc(dst, compareIterEvent)
for i, j := 0, total-1; i < j; i, j = i+1, j-1 {
dst[i], dst[j] = dst[j], dst[i]
}
if limit < len(dst) {
return dst[0:limit]
}
return dst
}
}
// BatchSizePerNumberOfQueries tries to make an educated guess for the batch size given the total filter limit and
// the number of abstract queries we'll be conducting at the same time
func BatchSizePerNumberOfQueries(totalFilterLimit int, numberOfQueries int) int {
if numberOfQueries == 1 || totalFilterLimit*numberOfQueries < 50 {
return totalFilterLimit
}
return int(
math.Ceil(
math.Pow(float64(totalFilterLimit), 0.80) / math.Pow(float64(numberOfQueries), 0.71),
),
)
}
func SwapDelete[A any](arr []A, i int) []A {
arr[i] = arr[len(arr)-1]
return arr[:len(arr)-1]
}
func compareIterEvent(a, b IterEvent) int {
if a.Event == nil {
if b.Event == nil {
return 0
} else {
return -1
}
} else if b.Event == nil {
return 1
}
if a.CreatedAt == b.CreatedAt {
return strings.Compare(a.ID, b.ID)
}
return cmp.Compare(a.CreatedAt, b.CreatedAt)
}