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// GoToSocial
// Copyright (C) GoToSocial Authors admin@gotosocial.org
// SPDX-License-Identifier: AGPL-3.0-or-later
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
package util
import (
"slices"
)
// Deduplicate deduplicates entries in the given slice.
func Deduplicate[T comparable](in []T) []T {
var (
inL = len(in)
unique = make(map[T]struct{}, inL)
deduped = make([]T, 0, inL)
)
for _, v := range in {
if _, ok := unique[v]; ok {
// Already have this.
continue
}
unique[v] = struct{}{}
deduped = append(deduped, v)
}
return deduped
}
// DeduplicateFunc deduplicates entries in the given
// slice, using the result of key() to gauge uniqueness.
func DeduplicateFunc[T any, C comparable](in []T, key func(v T) C) []T {
var (
inL = len(in)
unique = make(map[C]struct{}, inL)
deduped = make([]T, 0, inL)
)
if key == nil {
panic("nil func")
}
for _, v := range in {
k := key(v)
if _, ok := unique[k]; ok {
// Already have this.
continue
}
unique[k] = struct{}{}
deduped = append(deduped, v)
}
return deduped
}
// Gather will collect the values of type V from input type []T,
// passing each item to 'get' and appending V to the return slice.
func Gather[T, V any](out []V, in []T, get func(T) V) []V {
if get == nil {
panic("nil func")
}
// Starting write index
// in the resliced / re
// alloc'd output slice.
start := len(out)
// Total required slice len.
total := start + len(in)
if total > cap(out) {
// Reallocate output with
// capacity for total len.
out2 := make([]V, len(out), total)
copy(out2, out)
out = out2
}
// Reslice with capacity
// up to total required.
out = out[:total]
// Gather vs from 'in'.
for i, v := range in {
j := start + i
out[j] = get(v)
}
return out
}
// GatherIf is functionally similar to Gather(), but only when return bool is true.
// If you don't need to check the boolean, Gather() will be very slightly faster.
func GatherIf[T, V any](out []V, in []T, get func(T) (V, bool)) []V {
if get == nil {
panic("nil func")
}
if cap(out)-len(out) < len(in) {
// Reallocate output with capacity for 'in'.
out2 := make([]V, len(out), cap(out)+len(in))
copy(out2, out)
out = out2
}
// Gather vs from 'in'.
for _, v := range in {
if v, ok := get(v); ok {
out = append(out, v)
}
}
return out
}
// Collate will collect the values of type K from input type []T,
// passing each item to 'get' and deduplicating the end result.
// This is equivalent to calling Gather() followed by Deduplicate().
func Collate[T any, K comparable](in []T, get func(T) K) []K {
if get == nil {
panic("nil func")
}
ks := make([]K, 0, len(in))
km := make(map[K]struct{}, len(in))
for i := 0; i < len(in); i++ {
// Get next k.
k := get(in[i])
if _, ok := km[k]; !ok {
// New value, add
// to map + slice.
ks = append(ks, k)
km[k] = struct{}{}
}
}
return ks
}
// OrderBy orders a slice of given type by the provided alternative slice of comparable type.
func OrderBy[T any, K comparable](in []T, keys []K, key func(T) K) {
if key == nil {
panic("nil func")
}
// Create lookup of keys->idx.
m := make(map[K]int, len(in))
for i, k := range keys {
m[k] = i
}
// Sort according to the reverse lookup.
slices.SortFunc(in, func(a, b T) int {
ai := m[key(a)]
bi := m[key(b)]
if ai < bi {
return -1
} else if bi < ai {
return +1
}
return 0
})
}
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