121 lines
2.7 KiB
Go
121 lines
2.7 KiB
Go
// GoToSocial
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// Copyright (C) GoToSocial Authors admin@gotosocial.org
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// SPDX-License-Identifier: AGPL-3.0-or-later
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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package util
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import "slices"
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// Deduplicate deduplicates entries in the given slice.
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func Deduplicate[T comparable](in []T) []T {
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var (
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inL = len(in)
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unique = make(map[T]struct{}, inL)
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deduped = make([]T, 0, inL)
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)
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for _, v := range in {
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if _, ok := unique[v]; ok {
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// Already have this.
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continue
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}
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unique[v] = struct{}{}
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deduped = append(deduped, v)
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}
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return deduped
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}
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// DeduplicateFunc deduplicates entries in the given
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// slice, using the result of key() to gauge uniqueness.
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func DeduplicateFunc[T any, C comparable](in []T, key func(v T) C) []T {
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var (
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inL = len(in)
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unique = make(map[C]struct{}, inL)
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deduped = make([]T, 0, inL)
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)
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if key == nil {
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panic("nil func")
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}
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for _, v := range in {
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k := key(v)
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if _, ok := unique[k]; ok {
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// Already have this.
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continue
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}
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unique[k] = struct{}{}
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deduped = append(deduped, v)
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}
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return deduped
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}
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// Collate will collect the values of type K from input type []T,
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// passing each item to 'get' and deduplicating the end result.
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// Compared to Deduplicate() this returns []K, NOT input type []T.
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func Collate[T any, K comparable](in []T, get func(T) K) []K {
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if get == nil {
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panic("nil func")
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}
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ks := make([]K, 0, len(in))
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km := make(map[K]struct{}, len(in))
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for i := 0; i < len(in); i++ {
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// Get next k.
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k := get(in[i])
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if _, ok := km[k]; !ok {
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// New value, add
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// to map + slice.
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ks = append(ks, k)
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km[k] = struct{}{}
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}
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}
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return ks
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}
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// OrderBy orders a slice of given type by the provided alternative slice of comparable type.
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func OrderBy[T any, K comparable](in []T, keys []K, key func(T) K) {
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if key == nil {
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panic("nil func")
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}
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// Create lookup of keys->idx.
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m := make(map[K]int, len(in))
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for i, k := range keys {
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m[k] = i
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}
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// Sort according to the reverse lookup.
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slices.SortFunc(in, func(a, b T) int {
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ai := m[key(a)]
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bi := m[key(b)]
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if ai < bi {
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return -1
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} else if bi < ai {
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return +1
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}
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return 0
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})
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}
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