[chore] much improved paging package (#2182)

internal/api/client/blocks/blocksget.go

@@ -103,8 +103,12 @@ func (m *Module) BlocksGETHandler(c *gin.Context) {
 		return
 	}
 
-	limit, errWithCode := apiutil.ParseLimit(c.Query(LimitKey), 20, 100, 2)
+	page, errWithCode := paging.ParseIDPage(c,
-	if err != nil {
+		1,   // min limit
+		100, // max limit
+		20,  // default limit
+	)
+	if errWithCode != nil {
 		apiutil.ErrorHandler(c, errWithCode, m.processor.InstanceGetV1)
 		return
 	}
@@ -112,11 +116,7 @@ func (m *Module) BlocksGETHandler(c *gin.Context) {
 	resp, errWithCode := m.processor.BlocksGet(
 		c.Request.Context(),
 		authed.Account,
-		paging.Pager{
+		page,
-			SinceID: c.Query(SinceIDKey),
-			MaxID:   c.Query(MaxIDKey),
-			Limit:   limit,
-		},
 	)
 	if errWithCode != nil {
 		apiutil.ErrorHandler(c, errWithCode, m.processor.InstanceGetV1)

internal/cache/slice.go

@@ -49,28 +49,3 @@ func (c *SliceCache[T]) Load(key string, load func() ([]T, error)) ([]T, error)
 	// Return data clone for safety.
 	return slices.Clone(data), nil
 }
-
-// LoadRange is functionally the same as .Load(), but will pass the result through provided reslice function before returning a cloned result.
-func (c *SliceCache[T]) LoadRange(key string, load func() ([]T, error), reslice func([]T) []T) ([]T, error) {
-	// Look for follow IDs list in cache under this key.
-	data, ok := c.Get(key)
-
-	if !ok {
-		var err error
-
-		// Not cached, load!
-		data, err = load()
-		if err != nil {
-			return nil, err
-		}
-
-		// Store the data.
-		c.Set(key, data)
-	}
-
-	// Reslice to range.
-	slice := reslice(data)
-
-	// Return range clone for safety.
-	return slices.Clone(slice), nil
-}

internal/db/bundb/relationship.go

@@ -150,9 +150,9 @@ func (r *relationshipDB) GetAccountFollowRequesting(ctx context.Context, account
 	return r.GetFollowRequestsByIDs(ctx, followReqIDs)
 }
 
-func (r *relationshipDB) GetAccountBlocks(ctx context.Context, accountID string, page *paging.Pager) ([]*gtsmodel.Block, error) {
+func (r *relationshipDB) GetAccountBlocks(ctx context.Context, accountID string, page *paging.Page) ([]*gtsmodel.Block, error) {
 	// Load block IDs from cache with database loader callback.
-	blockIDs, err := r.state.Caches.GTS.BlockIDs().LoadRange(accountID, func() ([]string, error) {
+	blockIDs, err := r.state.Caches.GTS.BlockIDs().Load(accountID, func() ([]string, error) {
 		var blockIDs []string
 
 		// Block IDs not in cache, perform DB query!
@@ -162,11 +162,22 @@ func (r *relationshipDB) GetAccountBlocks(ctx context.Context, accountID string,
 		}
 
 		return blockIDs, nil
-	}, page.PageDesc)
+	})
 	if err != nil {
 		return nil, err
 	}
 
+	// Our cached / selected block IDs are
+	// ALWAYS stored in descending order.
+	// Depending on the paging requested
+	// this may be an unexpected order.
+	if !page.GetOrder().Ascending() {
+		blockIDs = paging.Reverse(blockIDs)
+	}
+
+	// Page the resulting block IDs.
+	blockIDs = page.Page(blockIDs)
+
 	// Convert these IDs to full block objects.
 	return r.GetBlocksByIDs(ctx, blockIDs)
 }

internal/db/relationship.go

@@ -174,7 +174,7 @@ type Relationship interface {
 	CountAccountFollowRequesting(ctx context.Context, accountID string) (int, error)
 
 	// GetAccountBlocks returns all blocks originating from the given account, with given optional paging parameters.
-	GetAccountBlocks(ctx context.Context, accountID string, paging *paging.Pager) ([]*gtsmodel.Block, error)
+	GetAccountBlocks(ctx context.Context, accountID string, paging *paging.Page) ([]*gtsmodel.Block, error)
 
 	// GetNote gets a private note from a source account on a target account, if it exists.
 	GetNote(ctx context.Context, sourceAccountID string, targetAccountID string) (*gtsmodel.AccountNote, error)

internal/paging/boundary.go

@@ -0,0 +1,135 @@
+// 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 paging
+
+// MinID returns an ID boundary with given min ID value,
+// using either the `since_id`,"DESC" name,ordering or
+// `min_id`,"ASC" name,ordering depending on which is set.
+func MinID(minID, sinceID string) Boundary {
+	/*
+
+	           Paging with `since_id` vs `min_id`:
+
+	                limit = 4       limit = 4
+	               +----------+    +----------+
+	     max_id--> |xxxxxxxxxx|    |          | <-- max_id
+	               +----------+    +----------+
+	               |xxxxxxxxxx|    |          |
+	               +----------+    +----------+
+	               |xxxxxxxxxx|    |          |
+	               +----------+    +----------+
+	               |xxxxxxxxxx|    |xxxxxxxxxx|
+	               +----------+    +----------+
+	               |          |    |xxxxxxxxxx|
+	               +----------+    +----------+
+	               |          |    |xxxxxxxxxx|
+	               +----------+    +----------+
+	   since_id--> |          |    |xxxxxxxxxx| <-- min_id
+	               +----------+    +----------+
+	               |          |    |          |
+	               +----------+    +----------+
+
+	*/
+	switch {
+	case minID != "":
+		return Boundary{
+			Name:  "min_id",
+			Value: minID,
+			Order: OrderAscending,
+		}
+	default:
+		// default min is `since_id`
+		return Boundary{
+			Name:  "since_id",
+			Value: sinceID,
+			Order: OrderDescending,
+		}
+	}
+}
+
+// MaxID returns an ID boundary with given max
+// ID value, and the "max_id" query key set.
+func MaxID(maxID string) Boundary {
+	return Boundary{
+		Name:  "max_id",
+		Value: maxID,
+		Order: OrderDescending,
+	}
+}
+
+// MinShortcodeDomain returns a boundary with the given minimum emoji
+// shortcode@domain, and the "min_shortcode_domain" query key set.
+func MinShortcodeDomain(min string) Boundary {
+	return Boundary{
+		Name:  "min_shortcode_domain",
+		Value: min,
+		Order: OrderAscending,
+	}
+}
+
+// MaxShortcodeDomain returns a boundary with the given maximum emoji
+// shortcode@domain, and the "max_shortcode_domain" query key set.
+func MaxShortcodeDomain(max string) Boundary {
+	return Boundary{
+		Name:  "max_shortcode_domain",
+		Value: max,
+		Order: OrderDescending,
+	}
+}
+
+// Boundary represents the upper or lower limit in a page slice.
+type Boundary struct {
+	Name  string // i.e. query key
+	Value string
+	Order Order // NOTE: see Order type for explanation
+}
+
+// new creates a new Boundary with the same ordering and name
+// as the original (receiving), but with the new provided value.
+func (b Boundary) new(value string) Boundary {
+	return Boundary{
+		Name:  b.Name,
+		Value: value,
+		Order: b.Order,
+	}
+}
+
+// Find finds the boundary's set value in input slice, or returns -1.
+func (b Boundary) Find(in []string) int {
+	if zero(b.Value) {
+		return -1
+	}
+	for i := range in {
+		if in[i] == b.Value {
+			return i
+		}
+	}
+	return -1
+}
+
+// Query returns this boundary as assembled query key=value pair.
+func (b Boundary) Query() string {
+	switch {
+	case zero(b.Value):
+		return ""
+	case b.Name == "":
+		panic("value without boundary name")
+	default:
+		return b.Name + "=" + b.Value
+	}
+}

internal/paging/order.go

@@ -0,0 +1,55 @@
+// 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 paging
+
+// Order represents the order an input
+// page should be sorted and paged in.
+//
+// NOTE: this does not effect the order of returned
+// API results, which must always be in descending
+// order. This behaviour is confusing, but we adopt
+// it to stay inline with Mastodon API expectations.
+type Order int
+
+const (
+	_default Order = iota
+	OrderDescending
+	OrderAscending
+)
+
+// Ascending returns whether this Order is ascending.
+func (i Order) Ascending() bool {
+	return i == OrderAscending
+}
+
+// Descending returns whether this Order is descending.
+func (i Order) Descending() bool {
+	return i == OrderDescending
+}
+
+// String returns a string representation of Order.
+func (i Order) String() string {
+	switch i {
+	case OrderDescending:
+		return "Descending"
+	case OrderAscending:
+		return "Ascending"
+	default:
+		return "not-specified"
+	}
+}

internal/paging/page.go

@@ -0,0 +1,251 @@
+// 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 paging
+
+import (
+	"net/url"
+	"strconv"
+	"strings"
+
+	"golang.org/x/exp/slices"
+)
+
+type Page struct {
+	// Min is the Page's lower limit value.
+	Min Boundary
+
+	// Max is this Page's upper limit value.
+	Max Boundary
+
+	// Limit will limit the returned
+	// page of items to at most 'limit'.
+	Limit int
+}
+
+// GetMin is a small helper function to return minimum boundary value (checking for nil page).
+func (p *Page) GetMin() string {
+	if p == nil {
+		return ""
+	}
+	return p.Min.Value
+}
+
+// GetMax is a small helper function to return maximum boundary value (checking for nil page).
+func (p *Page) GetMax() string {
+	if p == nil {
+		return ""
+	}
+	return p.Max.Value
+}
+
+// GetLimit is a small helper function to return limit (checking for nil page and unusable limit).
+func (p *Page) GetLimit() int {
+	if p == nil || p.Limit < 0 {
+		return 0
+	}
+	return p.Limit
+}
+
+// GetOrder is a small helper function to return page sort ordering (checking for nil page).
+func (p *Page) GetOrder() Order {
+	if p == nil {
+		return 0
+	}
+	return p.order()
+}
+
+func (p *Page) order() Order {
+	var (
+		// Check if min/max values set.
+		minValue = zero(p.Min.Value)
+		maxValue = zero(p.Max.Value)
+
+		// Check if min/max orders set.
+		minOrder = (p.Min.Order != 0)
+		maxOrder = (p.Max.Order != 0)
+	)
+
+	switch {
+	// Boundaries with a value AND order set
+	// take priority. Min always comes first.
+	case minValue && minOrder:
+		return p.Min.Order
+	case maxValue && maxOrder:
+		return p.Max.Order
+	case minOrder:
+		return p.Min.Order
+	case maxOrder:
+		return p.Max.Order
+	default:
+		return 0
+	}
+}
+
+// Page will page the given slice of input according
+// to the receiving Page's minimum, maximum and limit.
+// NOTE: input slice MUST be sorted according to the order is
+// expected to be paged in, i.e. it is currently sorted
+// according to Page.Order(). Sorted data isn't always according
+// to string inequalities so this CANNOT be checked here.
+func (p *Page) Page(in []string) []string {
+	if p == nil {
+		// no paging.
+		return in
+	}
+
+	if o := p.order(); !o.Ascending() {
+		// Default sort is descending,
+		// catching all cases when NOT
+		// ascending (even zero value).
+		//
+		// NOTE: sorted data does not always
+		// occur according to string ineqs
+		// so we unfortunately cannot check.
+
+		if maxIdx := p.Max.Find(in); maxIdx != -1 {
+			// Reslice skipping up to max.
+			in = in[maxIdx+1:]
+		}
+
+		if minIdx := p.Min.Find(in); minIdx != -1 {
+			// Reslice stripping past min.
+			in = in[:minIdx]
+		}
+	} else {
+		// Sort type is ascending, input
+		// data is assumed to be ascending.
+		//
+		// NOTE: sorted data does not always
+		// occur according to string ineqs
+		// so we unfortunately cannot check.
+
+		if minIdx := p.Min.Find(in); minIdx != -1 {
+			// Reslice skipping up to min.
+			in = in[minIdx+1:]
+		}
+
+		if maxIdx := p.Max.Find(in); maxIdx != -1 {
+			// Reslice stripping past max.
+			in = in[:maxIdx]
+		}
+
+		if len(in) > 1 {
+			// Clone input before
+			// any modifications.
+			in = slices.Clone(in)
+
+			// Output slice must
+			// ALWAYS be descending.
+			in = Reverse(in)
+		}
+	}
+
+	if p.Limit > 0 && p.Limit < len(in) {
+		// Reslice input to limit.
+		in = in[:p.Limit]
+	}
+
+	return in
+}
+
+// Next creates a new instance for the next returnable page, using
+// given max value. This preserves original limit and max key name.
+func (p *Page) Next(max string) *Page {
+	if p == nil || max == "" {
+		// no paging.
+		return nil
+	}
+
+	// Create new page.
+	p2 := new(Page)
+
+	// Set original limit.
+	p2.Limit = p.Limit
+
+	// Create new from old.
+	p2.Max = p.Max.new(max)
+
+	return p2
+}
+
+// Prev creates a new instance for the prev returnable page, using
+// given min value. This preserves original limit and min key name.
+func (p *Page) Prev(min string) *Page {
+	if p == nil || min == "" {
+		// no paging.
+		return nil
+	}
+
+	// Create new page.
+	p2 := new(Page)
+
+	// Set original limit.
+	p2.Limit = p.Limit
+
+	// Create new from old.
+	p2.Min = p.Min.new(min)
+
+	return p2
+}
+
+// ToLink builds a URL link for given endpoint information and extra query parameters,
+// appending this Page's minimum / maximum boundaries and available limit (if any).
+func (p *Page) ToLink(proto, host, path string, queryParams []string) string {
+	if p == nil {
+		// no paging.
+		return ""
+	}
+
+	// Check length before
+	// adding boundary params.
+	old := len(queryParams)
+
+	if minParam := p.Min.Query(); minParam != "" {
+		// A page-minimum query parameter is available.
+		queryParams = append(queryParams, minParam)
+	}
+
+	if maxParam := p.Max.Query(); maxParam != "" {
+		// A page-maximum query parameter is available.
+		queryParams = append(queryParams, maxParam)
+	}
+
+	if len(queryParams) == old {
+		// No page boundaries.
+		return ""
+	}
+
+	if p.Limit > 0 {
+		// Build limit key-value query parameter.
+		param := "limit=" + strconv.Itoa(p.Limit)
+
+		// Append `limit=$value` query parameter.
+		queryParams = append(queryParams, param)
+	}
+
+	// Join collected params into query str.
+	query := strings.Join(queryParams, "&")
+
+	// Build URL string.
+	return (&url.URL{
+		Scheme:   proto,
+		Host:     host,
+		Path:     path,
+		RawQuery: query,
+	}).String()
+}

internal/paging/page_test.go

@@ -0,0 +1,298 @@
+// 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 paging_test
+
+import (
+	"math/rand"
+	"testing"
+	"time"
+
+	"github.com/oklog/ulid"
+	"github.com/superseriousbusiness/gotosocial/internal/paging"
+	"golang.org/x/exp/slices"
+)
+
+// random reader according to current-time source seed.
+var randRd = rand.New(rand.NewSource(time.Now().Unix()))
+
+type Case struct {
+	// Name is the test case name.
+	Name string
+
+	// Page to use for test.
+	Page *paging.Page
+
+	// Input contains test case input ID slice.
+	Input []string
+
+	// Expect contains expected test case output.
+	Expect []string
+}
+
+// CreateCase creates a new test case with random input for function defining test page parameters and expected output.
+func CreateCase(name string, getParams func([]string) (input []string, page *paging.Page, expect []string)) Case {
+	i := randRd.Intn(100)
+	in := generateSlice(i)
+	input, page, expect := getParams(in)
+	return Case{
+		Name:   name,
+		Page:   page,
+		Input:  input,
+		Expect: expect,
+	}
+}
+
+func TestPage(t *testing.T) {
+	for _, c := range cases {
+		t.Run(c.Name, func(t *testing.T) {
+			// Page the input slice.
+			out := c.Page.Page(c.Input)
+
+			// Log the results for case of error returns.
+			t.Logf("\ninput=%v\noutput=%v\nexpected=%v", c.Input, out, c.Expect)
+
+			// Check paged output is as expected.
+			if !slices.Equal(out, c.Expect) {
+				t.Error("unexpected paged output")
+			}
+		})
+	}
+}
+
+var cases = []Case{
+	CreateCase("minID and maxID set", func(ids []string) ([]string, *paging.Page, []string) {
+		// Ensure input slice sorted ascending for min_id
+		slices.SortFunc(ids, func(a, b string) bool {
+			return a > b // i.e. largest at lowest idx
+		})
+
+		// Select random indices in slice.
+		minIdx := randRd.Intn(len(ids))
+		maxIdx := randRd.Intn(len(ids))
+
+		// Select the boundaries.
+		minID := ids[minIdx]
+		maxID := ids[maxIdx]
+
+		// Create expected output.
+		expect := slices.Clone(ids)
+		expect = cutLower(expect, minID)
+		expect = cutUpper(expect, maxID)
+		expect = paging.Reverse(expect)
+
+		// Return page and expected IDs.
+		return ids, &paging.Page{
+			Min: paging.MinID(minID, ""),
+			Max: paging.MaxID(maxID),
+		}, expect
+	}),
+	CreateCase("minID, maxID and limit set", func(ids []string) ([]string, *paging.Page, []string) {
+		// Ensure input slice sorted ascending for min_id
+		slices.SortFunc(ids, func(a, b string) bool {
+			return a > b // i.e. largest at lowest idx
+		})
+
+		// Select random parameters in slice.
+		minIdx := randRd.Intn(len(ids))
+		maxIdx := randRd.Intn(len(ids))
+		limit := randRd.Intn(len(ids))
+
+		// Select the boundaries.
+		minID := ids[minIdx]
+		maxID := ids[maxIdx]
+
+		// Create expected output.
+		expect := slices.Clone(ids)
+		expect = cutLower(expect, minID)
+		expect = cutUpper(expect, maxID)
+		expect = paging.Reverse(expect)
+
+		// Now limit the slice.
+		if limit < len(expect) {
+			expect = expect[:limit]
+		}
+
+		// Return page and expected IDs.
+		return ids, &paging.Page{
+			Min:   paging.MinID(minID, ""),
+			Max:   paging.MaxID(maxID),
+			Limit: limit,
+		}, expect
+	}),
+	CreateCase("minID, maxID and too-large limit set", func(ids []string) ([]string, *paging.Page, []string) {
+		// Ensure input slice sorted ascending for min_id
+		slices.SortFunc(ids, func(a, b string) bool {
+			return a > b // i.e. largest at lowest idx
+		})
+
+		// Select random parameters in slice.
+		minIdx := randRd.Intn(len(ids))
+		maxIdx := randRd.Intn(len(ids))
+
+		// Select the boundaries.
+		minID := ids[minIdx]
+		maxID := ids[maxIdx]
+
+		// Create expected output.
+		expect := slices.Clone(ids)
+		expect = cutLower(expect, minID)
+		expect = cutUpper(expect, maxID)
+		expect = paging.Reverse(expect)
+
+		// Return page and expected IDs.
+		return ids, &paging.Page{
+			Min:   paging.MinID(minID, ""),
+			Max:   paging.MaxID(maxID),
+			Limit: len(ids) * 2,
+		}, expect
+	}),
+	CreateCase("sinceID and maxID set", func(ids []string) ([]string, *paging.Page, []string) {
+		// Ensure input slice sorted descending for since_id
+		slices.SortFunc(ids, func(a, b string) bool {
+			return a < b // i.e. smallest at lowest idx
+		})
+
+		// Select random indices in slice.
+		sinceIdx := randRd.Intn(len(ids))
+		maxIdx := randRd.Intn(len(ids))
+
+		// Select the boundaries.
+		sinceID := ids[sinceIdx]
+		maxID := ids[maxIdx]
+
+		// Create expected output.
+		expect := slices.Clone(ids)
+		expect = cutLower(expect, maxID)
+		expect = cutUpper(expect, sinceID)
+
+		// Return page and expected IDs.
+		return ids, &paging.Page{
+			Min: paging.MinID("", sinceID),
+			Max: paging.MaxID(maxID),
+		}, expect
+	}),
+	CreateCase("maxID set", func(ids []string) ([]string, *paging.Page, []string) {
+		// Ensure input slice sorted descending for max_id
+		slices.SortFunc(ids, func(a, b string) bool {
+			return a < b // i.e. smallest at lowest idx
+		})
+
+		// Select random indices in slice.
+		maxIdx := randRd.Intn(len(ids))
+
+		// Select the boundaries.
+		maxID := ids[maxIdx]
+
+		// Create expected output.
+		expect := slices.Clone(ids)
+		expect = cutLower(expect, maxID)
+
+		// Return page and expected IDs.
+		return ids, &paging.Page{
+			Max: paging.MaxID(maxID),
+		}, expect
+	}),
+	CreateCase("sinceID set", func(ids []string) ([]string, *paging.Page, []string) {
+		// Ensure input slice sorted descending for since_id
+		slices.SortFunc(ids, func(a, b string) bool {
+			return a < b
+		})
+
+		// Select random indices in slice.
+		sinceIdx := randRd.Intn(len(ids))
+
+		// Select the boundaries.
+		sinceID := ids[sinceIdx]
+
+		// Create expected output.
+		expect := slices.Clone(ids)
+		expect = cutUpper(expect, sinceID)
+
+		// Return page and expected IDs.
+		return ids, &paging.Page{
+			Min: paging.MinID("", sinceID),
+		}, expect
+	}),
+	CreateCase("minID set", func(ids []string) ([]string, *paging.Page, []string) {
+		// Ensure input slice sorted ascending for min_id
+		slices.SortFunc(ids, func(a, b string) bool {
+			return a > b // i.e. largest at lowest idx
+		})
+
+		// Select random indices in slice.
+		minIdx := randRd.Intn(len(ids))
+
+		// Select the boundaries.
+		minID := ids[minIdx]
+
+		// Create expected output.
+		expect := slices.Clone(ids)
+		expect = cutLower(expect, minID)
+		expect = paging.Reverse(expect)
+
+		// Return page and expected IDs.
+		return ids, &paging.Page{
+			Min: paging.MinID(minID, ""),
+		}, expect
+	}),
+}
+
+// cutLower cuts off the lower part of the slice from `bound` downwards.
+func cutLower(in []string, bound string) []string {
+	for i := 0; i < len(in); i++ {
+		if in[i] == bound {
+			return in[i+1:]
+		}
+	}
+	return in
+}
+
+// cutUpper cuts off the upper part of the slice from `bound` onwards.
+func cutUpper(in []string, bound string) []string {
+	for i := 0; i < len(in); i++ {
+		if in[i] == bound {
+			return in[:i]
+		}
+	}
+	return in
+}
+
+// generateSlice generates a new slice of len containing ascending sorted slice.
+func generateSlice(len int) []string {
+	if len <= 0 {
+		// minimum testable
+		// pageable amount
+		len = 2
+	}
+	now := time.Now()
+	in := make([]string, len)
+	for i := 0; i < len; i++ {
+		// Convert now to timestamp.
+		t := ulid.Timestamp(now)
+
+		// Create anew ulid for now.
+		u := ulid.MustNew(t, randRd)
+
+		// Add to slice.
+		in[i] = u.String()
+
+		// Bump now by 1 second.
+		now = now.Add(time.Second)
+	}
+	return in
+}

internal/paging/paging.go

@@ -1,227 +0,0 @@
-// 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 paging
-
-import "golang.org/x/exp/slices"
-
-// Pager provides a means of paging serialized IDs,
-// using the terminology of our API endpoint queries.
-type Pager struct {
-	// SinceID will limit the returned
-	// page of IDs to contain newer than
-	// since ID (excluding it). Result
-	// will be returned DESCENDING.
-	SinceID string
-
-	// MinID will limit the returned
-	// page of IDs to contain newer than
-	// min ID (excluding it). Result
-	// will be returned ASCENDING.
-	MinID string
-
-	// MaxID will limit the returned
-	// page of IDs to contain older
-	// than (excluding) this max ID.
-	MaxID string
-
-	// Limit will limit the returned
-	// page of IDs to at most 'limit'.
-	Limit int
-}
-
-// Page will page the given slice of GoToSocial IDs according
-// to the receiving Pager's SinceID, MinID, MaxID and Limits.
-// NOTE THE INPUT SLICE MUST BE SORTED IN ASCENDING ORDER
-// (I.E. OLDEST ITEMS AT LOWEST INDICES, NEWER AT HIGHER).
-func (p *Pager) PageAsc(ids []string) []string {
-	if p == nil {
-		// no paging.
-		return ids
-	}
-
-	var asc bool
-
-	if p.SinceID != "" {
-		// If a sinceID is given, we
-		// page down i.e. descending.
-		asc = false
-
-		for i := 0; i < len(ids); i++ {
-			if ids[i] == p.SinceID {
-				// Hit the boundary.
-				// Reslice to be:
-				// "from here"
-				ids = ids[i+1:]
-				break
-			}
-		}
-	} else if p.MinID != "" {
-		// We only support minID if
-		// no sinceID is provided.
-		//
-		// If a minID is given, we
-		// page up, i.e. ascending.
-		asc = true
-
-		for i := 0; i < len(ids); i++ {
-			if ids[i] == p.MinID {
-				// Hit the boundary.
-				// Reslice to be:
-				// "from here"
-				ids = ids[i+1:]
-				break
-			}
-		}
-	}
-
-	if p.MaxID != "" {
-		for i := 0; i < len(ids); i++ {
-			if ids[i] == p.MaxID {
-				// Hit the boundary.
-				// Reslice to be:
-				// "up to here"
-				ids = ids[:i]
-				break
-			}
-		}
-	}
-
-	if !asc && len(ids) > 1 {
-		var (
-			// Start at front.
-			i = 0
-
-			// Start at back.
-			j = len(ids) - 1
-		)
-
-		// Clone input IDs before
-		// we perform modifications.
-		ids = slices.Clone(ids)
-
-		for i < j {
-			// Swap i,j index values in slice.
-			ids[i], ids[j] = ids[j], ids[i]
-
-			// incr + decr,
-			// looping until
-			// they meet in
-			// the middle.
-			i++
-			j--
-		}
-	}
-
-	if p.Limit > 0 && p.Limit < len(ids) {
-		// Reslice IDs to given limit.
-		ids = ids[:p.Limit]
-	}
-
-	return ids
-}
-
-// Page will page the given slice of GoToSocial IDs according
-// to the receiving Pager's SinceID, MinID, MaxID and Limits.
-// NOTE THE INPUT SLICE MUST BE SORTED IN ASCENDING ORDER.
-// (I.E. NEWEST ITEMS AT LOWEST INDICES, OLDER AT HIGHER).
-func (p *Pager) PageDesc(ids []string) []string {
-	if p == nil {
-		// no paging.
-		return ids
-	}
-
-	var asc bool
-
-	if p.MaxID != "" {
-		for i := 0; i < len(ids); i++ {
-			if ids[i] == p.MaxID {
-				// Hit the boundary.
-				// Reslice to be:
-				// "from here"
-				ids = ids[i+1:]
-				break
-			}
-		}
-	}
-
-	if p.SinceID != "" {
-		// If a sinceID is given, we
-		// page down i.e. descending.
-		asc = false
-
-		for i := 0; i < len(ids); i++ {
-			if ids[i] == p.SinceID {
-				// Hit the boundary.
-				// Reslice to be:
-				// "up to here"
-				ids = ids[:i]
-				break
-			}
-		}
-	} else if p.MinID != "" {
-		// We only support minID if
-		// no sinceID is provided.
-		//
-		// If a minID is given, we
-		// page up, i.e. ascending.
-		asc = true
-
-		for i := 0; i < len(ids); i++ {
-			if ids[i] == p.MinID {
-				// Hit the boundary.
-				// Reslice to be:
-				// "up to here"
-				ids = ids[:i]
-				break
-			}
-		}
-	}
-
-	if asc && len(ids) > 1 {
-		var (
-			// Start at front.
-			i = 0
-
-			// Start at back.
-			j = len(ids) - 1
-		)
-
-		// Clone input IDs before
-		// we perform modifications.
-		ids = slices.Clone(ids)
-
-		for i < j {
-			// Swap i,j index values in slice.
-			ids[i], ids[j] = ids[j], ids[i]
-
-			// incr + decr,
-			// looping until
-			// they meet in
-			// the middle.
-			i++
-			j--
-		}
-	}
-
-	if p.Limit > 0 && p.Limit < len(ids) {
-		// Reslice IDs to given limit.
-		ids = ids[:p.Limit]
-	}
-
-	return ids
-}

internal/paging/paging_test.go

@@ -1,171 +0,0 @@
-// 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 paging_test
-
-import (
-	"testing"
-
-	"github.com/superseriousbusiness/gotosocial/internal/paging"
-	"golang.org/x/exp/slices"
-)
-
-type Case struct {
-	// Name is the test case name.
-	Name string
-
-	// Input contains test case input ID slice.
-	Input []string
-
-	// Expect contains expected test case output.
-	Expect []string
-
-	// Page contains the paging function to use.
-	Page func([]string) []string
-}
-
-var cases = []Case{
-	{
-		Name: "min_id and max_id set",
-		Input: []string{
-			"064Q5D7VG6TPPQ46T09MHJ96FW",
-			"064Q5D7VGPTC4NK5T070VYSSF8",
-			"064Q5D7VH5F0JXG6W5NCQ3JCWW",
-			"064Q5D7VHMSW9DF3GCS088VAZC",
-			"064Q5D7VJ073XG9ZTWHA2KHN10",
-			"064Q5D7VJADJTPA3GW8WAX10TW",
-			"064Q5D7VJMWXZD3S1KT7RD51N8",
-			"064Q5D7VJYFBYSAH86KDBKZ6AC",
-			"064Q5D7VK8H7WMJS399SHEPCB0",
-			"064Q5D7VKG5EQ43TYP71B4K6K0",
-		},
-		Expect: []string{
-			"064Q5D7VGPTC4NK5T070VYSSF8",
-			"064Q5D7VH5F0JXG6W5NCQ3JCWW",
-			"064Q5D7VHMSW9DF3GCS088VAZC",
-			"064Q5D7VJ073XG9ZTWHA2KHN10",
-			"064Q5D7VJADJTPA3GW8WAX10TW",
-			"064Q5D7VJMWXZD3S1KT7RD51N8",
-			"064Q5D7VJYFBYSAH86KDBKZ6AC",
-			"064Q5D7VK8H7WMJS399SHEPCB0",
-		},
-		Page: (&paging.Pager{
-			MinID: "064Q5D7VG6TPPQ46T09MHJ96FW",
-			MaxID: "064Q5D7VKG5EQ43TYP71B4K6K0",
-		}).PageAsc,
-	},
-	{
-		Name: "min_id, max_id and limit set",
-		Input: []string{
-			"064Q5D7VG6TPPQ46T09MHJ96FW",
-			"064Q5D7VGPTC4NK5T070VYSSF8",
-			"064Q5D7VH5F0JXG6W5NCQ3JCWW",
-			"064Q5D7VHMSW9DF3GCS088VAZC",
-			"064Q5D7VJ073XG9ZTWHA2KHN10",
-			"064Q5D7VJADJTPA3GW8WAX10TW",
-			"064Q5D7VJMWXZD3S1KT7RD51N8",
-			"064Q5D7VJYFBYSAH86KDBKZ6AC",
-			"064Q5D7VK8H7WMJS399SHEPCB0",
-			"064Q5D7VKG5EQ43TYP71B4K6K0",
-		},
-		Expect: []string{
-			"064Q5D7VGPTC4NK5T070VYSSF8",
-			"064Q5D7VH5F0JXG6W5NCQ3JCWW",
-			"064Q5D7VHMSW9DF3GCS088VAZC",
-			"064Q5D7VJ073XG9ZTWHA2KHN10",
-			"064Q5D7VJADJTPA3GW8WAX10TW",
-		},
-		Page: (&paging.Pager{
-			MinID: "064Q5D7VG6TPPQ46T09MHJ96FW",
-			MaxID: "064Q5D7VKG5EQ43TYP71B4K6K0",
-			Limit: 5,
-		}).PageAsc,
-	},
-	{
-		Name: "min_id, max_id and too-large limit set",
-		Input: []string{
-			"064Q5D7VG6TPPQ46T09MHJ96FW",
-			"064Q5D7VGPTC4NK5T070VYSSF8",
-			"064Q5D7VH5F0JXG6W5NCQ3JCWW",
-			"064Q5D7VHMSW9DF3GCS088VAZC",
-			"064Q5D7VJ073XG9ZTWHA2KHN10",
-			"064Q5D7VJADJTPA3GW8WAX10TW",
-			"064Q5D7VJMWXZD3S1KT7RD51N8",
-			"064Q5D7VJYFBYSAH86KDBKZ6AC",
-			"064Q5D7VK8H7WMJS399SHEPCB0",
-			"064Q5D7VKG5EQ43TYP71B4K6K0",
-		},
-		Expect: []string{
-			"064Q5D7VGPTC4NK5T070VYSSF8",
-			"064Q5D7VH5F0JXG6W5NCQ3JCWW",
-			"064Q5D7VHMSW9DF3GCS088VAZC",
-			"064Q5D7VJ073XG9ZTWHA2KHN10",
-			"064Q5D7VJADJTPA3GW8WAX10TW",
-			"064Q5D7VJMWXZD3S1KT7RD51N8",
-			"064Q5D7VJYFBYSAH86KDBKZ6AC",
-			"064Q5D7VK8H7WMJS399SHEPCB0",
-		},
-		Page: (&paging.Pager{
-			MinID: "064Q5D7VG6TPPQ46T09MHJ96FW",
-			MaxID: "064Q5D7VKG5EQ43TYP71B4K6K0",
-			Limit: 100,
-		}).PageAsc,
-	},
-	{
-		Name: "since_id and max_id set",
-		Input: []string{
-			"064Q5D7VG6TPPQ46T09MHJ96FW",
-			"064Q5D7VGPTC4NK5T070VYSSF8",
-			"064Q5D7VH5F0JXG6W5NCQ3JCWW",
-			"064Q5D7VHMSW9DF3GCS088VAZC",
-			"064Q5D7VJ073XG9ZTWHA2KHN10",
-			"064Q5D7VJADJTPA3GW8WAX10TW",
-			"064Q5D7VJMWXZD3S1KT7RD51N8",
-			"064Q5D7VJYFBYSAH86KDBKZ6AC",
-			"064Q5D7VK8H7WMJS399SHEPCB0",
-			"064Q5D7VKG5EQ43TYP71B4K6K0",
-		},
-		Expect: []string{
-			"064Q5D7VK8H7WMJS399SHEPCB0",
-			"064Q5D7VJYFBYSAH86KDBKZ6AC",
-			"064Q5D7VJMWXZD3S1KT7RD51N8",
-			"064Q5D7VJADJTPA3GW8WAX10TW",
-			"064Q5D7VJ073XG9ZTWHA2KHN10",
-			"064Q5D7VHMSW9DF3GCS088VAZC",
-			"064Q5D7VH5F0JXG6W5NCQ3JCWW",
-			"064Q5D7VGPTC4NK5T070VYSSF8",
-		},
-		Page: (&paging.Pager{
-			SinceID: "064Q5D7VG6TPPQ46T09MHJ96FW",
-			MaxID:   "064Q5D7VKG5EQ43TYP71B4K6K0",
-		}).PageAsc,
-	},
-}
-
-func TestPage(t *testing.T) {
-	for _, c := range cases {
-		t.Run(c.Name, func(t *testing.T) {
-			// Page the input slice.
-			out := c.Page(c.Input)
-
-			// Check paged output is as expected.
-			if !slices.Equal(out, c.Expect) {
-				t.Errorf("\nreceived=%v\nexpect%v\n", out, c.Expect)
-			}
-		})
-	}
-}

internal/paging/parse.go

@@ -0,0 +1,111 @@
+// 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 paging
+
+import (
+	"strconv"
+
+	"github.com/gin-gonic/gin"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+)
+
+// ParseIDPage parses an ID Page from a request context, returning BadRequest on error parsing.
+// The min, max and default parameters define the page size limit minimum, maximum and default
+// value, where a non-zero default will enforce paging for the endpoint on which this is called.
+// While conversely, a zero default limit will not enforce paging, returning a nil page value.
+func ParseIDPage(c *gin.Context, min, max, _default int) (*Page, gtserror.WithCode) {
+	// Extract request query params.
+	sinceID := c.Query("since_id")
+	minID := c.Query("min_id")
+	maxID := c.Query("max_id")
+
+	// Extract request limit parameter.
+	limit, errWithCode := ParseLimit(c, min, max, _default)
+	if errWithCode != nil {
+		return nil, errWithCode
+	}
+
+	if sinceID == "" &&
+		minID == "" &&
+		maxID == "" &&
+		limit == 0 {
+		// No ID paging params provided, and no default
+		// limit value which indicates paging not enforced.
+		return nil, nil
+	}
+
+	return &Page{
+		Min:   MinID(minID, sinceID),
+		Max:   MaxID(maxID),
+		Limit: limit,
+	}, nil
+}
+
+// ParseShortcodeDomainPage parses an emoji shortcode domain Page from a request context, returning BadRequest
+// on error parsing. The min, max and default parameters define the page size limit minimum, maximum and default
+// value where a non-zero default will enforce paging for the endpoint on which this is called. While conversely,
+// a zero default limit will not enforce paging, returning a nil page value.
+func ParseShortcodeDomainPage(c *gin.Context, min, max, _default int) (*Page, gtserror.WithCode) {
+	// Extract request query parameters.
+	minShortcode := c.Query("min_shortcode_domain")
+	maxShortcode := c.Query("max_shortcode_domain")
+
+	// Extract request limit parameter.
+	limit, errWithCode := ParseLimit(c, min, max, _default)
+	if errWithCode != nil {
+		return nil, errWithCode
+	}
+
+	if minShortcode == "" &&
+		maxShortcode == "" &&
+		limit == 0 {
+		// No ID paging params provided, and no default
+		// limit value which indicates paging not enforced.
+		return nil, nil
+	}
+
+	return &Page{
+		Min:   MinShortcodeDomain(minShortcode),
+		Max:   MaxShortcodeDomain(maxShortcode),
+		Limit: limit,
+	}, nil
+}
+
+// ParseLimit parses the limit query parameter from a request context, returning BadRequest on error parsing and _default if zero limit given.
+func ParseLimit(c *gin.Context, min, max, _default int) (int, gtserror.WithCode) {
+	// Get limit query param.
+	str := c.Query("limit")
+
+	// Attempt to parse limit int.
+	i, err := strconv.Atoi(str)
+	if err != nil {
+		const help = "bad integer limit value"
+		return 0, gtserror.NewErrorBadRequest(err, help)
+	}
+
+	switch {
+	case i == 0:
+		return _default, nil
+	case i < min:
+		return min, nil
+	case i > max:
+		return max, nil
+	default:
+		return i, nil
+	}
+}

internal/paging/response.go

@@ -0,0 +1,91 @@
+// 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 paging
+
+import (
+	"strings"
+
+	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
+	"github.com/superseriousbusiness/gotosocial/internal/config"
+)
+
+// ResponseParams models the parameters to pass to PageableResponse.
+//
+// The given items will be provided in the paged response.
+//
+// The other values are all used to create the Link header so that callers know
+// which endpoint to query next and previously in order to do paging.
+type ResponseParams struct {
+	Items []interface{} // Sorted slice of items (statuses, notifications, etc)
+	Path  string        // path to use for next/prev queries in the link header
+	Next  *Page         // page details for the next page
+	Prev  *Page         // page details for the previous page
+	Query []string      // any extra query parameters to provide in the link header, should be in the format 'example=value'
+}
+
+// PackageResponse is a convenience function for returning
+// a bunch of pageable items (notifications, statuses, etc), as well
+// as a Link header to inform callers of where to find next/prev items.
+func PackageResponse(params ResponseParams) *apimodel.PageableResponse {
+	if len(params.Items) == 0 {
+		// No items to page through.
+		return EmptyResponse()
+	}
+
+	var (
+		// Extract paging params.
+		nextPg = params.Next
+		prevPg = params.Prev
+
+		// Host app configuration.
+		proto = config.GetProtocol()
+		host  = config.GetHost()
+
+		// Combined next/prev page link header parts.
+		linkHeaderParts = make([]string, 0, 2)
+	)
+
+	// Build the next / previous page links from page and host config.
+	nextLink := nextPg.ToLink(proto, host, params.Path, params.Query)
+	prevLink := prevPg.ToLink(proto, host, params.Path, params.Query)
+
+	if nextLink != "" {
+		// Append page "next" link to header parts.
+		linkHeaderParts = append(linkHeaderParts, `<`+nextLink+`>; rel="next"`)
+	}
+
+	if prevLink != "" {
+		// Append page "prev" link to header parts.
+		linkHeaderParts = append(linkHeaderParts, `<`+prevLink+`>; rel="prev"`)
+	}
+
+	return &apimodel.PageableResponse{
+		Items:      params.Items,
+		NextLink:   nextLink,
+		PrevLink:   prevLink,
+		LinkHeader: strings.Join(linkHeaderParts, ", "),
+	}
+}
+
+// EmptyResponse just returns an empty
+// PageableResponse with no link header or items.
+func EmptyResponse() *apimodel.PageableResponse {
+	return &apimodel.PageableResponse{
+		Items: []interface{}{},
+	}
+}

internal/paging/response_test.go

@@ -0,0 +1,134 @@
+// 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 paging_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/suite"
+	"github.com/superseriousbusiness/gotosocial/internal/config"
+	"github.com/superseriousbusiness/gotosocial/internal/paging"
+)
+
+type PagingSuite struct {
+	suite.Suite
+}
+
+func (suite *PagingSuite) TestPagingStandard() {
+	config.SetHost("example.org")
+
+	params := paging.ResponseParams{
+		Items: make([]interface{}, 10, 10),
+		Path:  "/api/v1/accounts/01H11KA68PM4NNYJEG0FJQ90R3/statuses",
+		Next:  nextPage("01H11KA1DM2VH3747YDE7FV5HN", 10),
+		Prev:  prevPage("01H11KBBVRRDYYC5KEPME1NP5R", 10),
+	}
+
+	resp := paging.PackageResponse(params)
+
+	suite.Equal(make([]interface{}, 10, 10), resp.Items)
+	suite.Equal(`<https://example.org/api/v1/accounts/01H11KA68PM4NNYJEG0FJQ90R3/statuses?max_id=01H11KA1DM2VH3747YDE7FV5HN&limit=10>; rel="next", <https://example.org/api/v1/accounts/01H11KA68PM4NNYJEG0FJQ90R3/statuses?min_id=01H11KBBVRRDYYC5KEPME1NP5R&limit=10>; rel="prev"`, resp.LinkHeader)
+	suite.Equal(`https://example.org/api/v1/accounts/01H11KA68PM4NNYJEG0FJQ90R3/statuses?max_id=01H11KA1DM2VH3747YDE7FV5HN&limit=10`, resp.NextLink)
+	suite.Equal(`https://example.org/api/v1/accounts/01H11KA68PM4NNYJEG0FJQ90R3/statuses?min_id=01H11KBBVRRDYYC5KEPME1NP5R&limit=10`, resp.PrevLink)
+}
+
+func (suite *PagingSuite) TestPagingNoLimit() {
+	config.SetHost("example.org")
+
+	params := paging.ResponseParams{
+		Items: make([]interface{}, 10, 10),
+		Path:  "/api/v1/accounts/01H11KA68PM4NNYJEG0FJQ90R3/statuses",
+		Next:  nextPage("01H11KA1DM2VH3747YDE7FV5HN", 0),
+		Prev:  prevPage("01H11KBBVRRDYYC5KEPME1NP5R", 0),
+	}
+
+	resp := paging.PackageResponse(params)
+
+	suite.Equal(make([]interface{}, 10, 10), resp.Items)
+	suite.Equal(`<https://example.org/api/v1/accounts/01H11KA68PM4NNYJEG0FJQ90R3/statuses?max_id=01H11KA1DM2VH3747YDE7FV5HN>; rel="next", <https://example.org/api/v1/accounts/01H11KA68PM4NNYJEG0FJQ90R3/statuses?min_id=01H11KBBVRRDYYC5KEPME1NP5R>; rel="prev"`, resp.LinkHeader)
+	suite.Equal(`https://example.org/api/v1/accounts/01H11KA68PM4NNYJEG0FJQ90R3/statuses?max_id=01H11KA1DM2VH3747YDE7FV5HN`, resp.NextLink)
+	suite.Equal(`https://example.org/api/v1/accounts/01H11KA68PM4NNYJEG0FJQ90R3/statuses?min_id=01H11KBBVRRDYYC5KEPME1NP5R`, resp.PrevLink)
+}
+
+func (suite *PagingSuite) TestPagingNoNextID() {
+	config.SetHost("example.org")
+
+	params := paging.ResponseParams{
+		Items: make([]interface{}, 10, 10),
+		Path:  "/api/v1/accounts/01H11KA68PM4NNYJEG0FJQ90R3/statuses",
+		Prev:  prevPage("01H11KBBVRRDYYC5KEPME1NP5R", 10),
+	}
+
+	resp := paging.PackageResponse(params)
+
+	suite.Equal(make([]interface{}, 10, 10), resp.Items)
+	suite.Equal(`<https://example.org/api/v1/accounts/01H11KA68PM4NNYJEG0FJQ90R3/statuses?min_id=01H11KBBVRRDYYC5KEPME1NP5R&limit=10>; rel="prev"`, resp.LinkHeader)
+	suite.Equal(``, resp.NextLink)
+	suite.Equal(`https://example.org/api/v1/accounts/01H11KA68PM4NNYJEG0FJQ90R3/statuses?min_id=01H11KBBVRRDYYC5KEPME1NP5R&limit=10`, resp.PrevLink)
+}
+
+func (suite *PagingSuite) TestPagingNoPrevID() {
+	config.SetHost("example.org")
+
+	params := paging.ResponseParams{
+		Items: make([]interface{}, 10, 10),
+		Path:  "/api/v1/accounts/01H11KA68PM4NNYJEG0FJQ90R3/statuses",
+		Next:  nextPage("01H11KA1DM2VH3747YDE7FV5HN", 10),
+	}
+
+	resp := paging.PackageResponse(params)
+
+	suite.Equal(make([]interface{}, 10, 10), resp.Items)
+	suite.Equal(`<https://example.org/api/v1/accounts/01H11KA68PM4NNYJEG0FJQ90R3/statuses?max_id=01H11KA1DM2VH3747YDE7FV5HN&limit=10>; rel="next"`, resp.LinkHeader)
+	suite.Equal(`https://example.org/api/v1/accounts/01H11KA68PM4NNYJEG0FJQ90R3/statuses?max_id=01H11KA1DM2VH3747YDE7FV5HN&limit=10`, resp.NextLink)
+	suite.Equal(``, resp.PrevLink)
+}
+
+func (suite *PagingSuite) TestPagingNoItems() {
+	config.SetHost("example.org")
+
+	params := paging.ResponseParams{
+		Next: nextPage("01H11KA1DM2VH3747YDE7FV5HN", 10),
+		Prev: prevPage("01H11KBBVRRDYYC5KEPME1NP5R", 10),
+	}
+
+	resp := paging.PackageResponse(params)
+
+	suite.Empty(resp.Items)
+	suite.Empty(resp.LinkHeader)
+	suite.Empty(resp.NextLink)
+	suite.Empty(resp.PrevLink)
+}
+
+func TestPagingSuite(t *testing.T) {
+	suite.Run(t, &PagingSuite{})
+}
+
+func nextPage(id string, limit int) *paging.Page {
+	return &paging.Page{
+		Max:   paging.MaxID(id),
+		Limit: limit,
+	}
+}
+
+func prevPage(id string, limit int) *paging.Page {
+	return &paging.Page{
+		Min:   paging.MinID(id, ""),
+		Limit: limit,
+	}
+}

internal/paging/util.go

@@ -0,0 +1,49 @@
+// 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 paging
+
+// Reverse will reverse the given input slice.
+func Reverse(in []string) []string {
+	var (
+		// Start at front.
+		i = 0
+
+		// Start at back.
+		j = len(in) - 1
+	)
+
+	for i < j {
+		// Swap i,j index values in slice.
+		in[i], in[j] = in[j], in[i]
+
+		// incr + decr,
+		// looping until
+		// they meet in
+		// the middle.
+		i++
+		j--
+	}
+
+	return in
+}
+
+// zero is a shorthand to check a generic value is its zero value.
+func zero[T comparable](t T) bool {
+	var z T
+	return t == z
+}

internal/processing/blocks.go

@@ -34,11 +34,11 @@
 func (p *Processor) BlocksGet(
 	ctx context.Context,
 	requestingAccount *gtsmodel.Account,
-	page paging.Pager,
+	page *paging.Page,
 ) (*apimodel.PageableResponse, gtserror.WithCode) {
 	blocks, err := p.state.DB.GetAccountBlocks(ctx,
 		requestingAccount.ID,
-		&page,
+		page,
 	)
 	if err != nil && !errors.Is(err, db.ErrNoEntries) {
 		return nil, gtserror.NewErrorInternalError(err)
@@ -77,13 +77,10 @@ func (p *Processor) BlocksGet(
 		items = append(items, account)
 	}
 
-	return util.PackagePageableResponse(util.PageableResponseParams{
+	return paging.PackageResponse(paging.ResponseParams{
-		Items:          items,
+		Items: items,
-		Path:           "/api/v1/blocks",
+		Path:  "/api/v1/blocks",
-		NextMaxIDKey:   "max_id",
+		Next:  page.Next(nextMaxIDValue),
-		PrevMinIDKey:   "since_id",
+		Prev:  page.Prev(prevMinIDValue),
-		NextMaxIDValue: nextMaxIDValue,
+	}), nil
-		PrevMinIDValue: prevMinIDValue,
-		Limit:          page.Limit,
-	})
 }