3 files changed, 264 insertions, 12 deletions
diff --git a/internal/cache/domain/domain.go b/internal/cache/domain/domain.go
new file mode 100644
index 000000000..4697f05a6
--- /dev/null
+++ b/internal/cache/domain/domain.go
@@ -0,0 +1,170 @@
+/*
+   GoToSocial
+   Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org
+
+   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 domain
+
+import (
+	"fmt"
+	"time"
+
+	"codeberg.org/gruf/go-cache/v3/ttl"
+	"github.com/miekg/dns"
+)
+
+// BlockCache provides a means of caching domain blocks in memory to reduce load
+// on an underlying storage mechanism, e.g. a database.
+//
+// It consists of a TTL primary cache that stores calculated domain string to block results,
+// that on cache miss is filled by calculating block status by iterating over a list of all of
+// the domain blocks stored in memory. This reduces CPU usage required by not need needing to
+// iterate through a possible 100-1000s long block list, while saving memory by having a primary
+// cache of limited size that evicts stale entries. The raw list of all domain blocks should in
+// most cases be negligible when it comes to memory usage.
+//
+// The in-memory block list is kept up-to-date by means of a passed loader function during every
+// call to .IsBlocked(). In the case of a nil internal block list, the loader function is called to
+// hydrate the cache with the latest list of domain blocks. The .Clear() function can be used to invalidate
+// the cache, e.g. when a domain block is added / deleted from the database. It will drop the current
+// list of domain blocks and clear all entries from the primary cache.
+type BlockCache struct {
+	pcache *ttl.Cache[string, bool] // primary cache of domains -> block results
+	blocks []block                  // raw list of all domain blocks, nil => not loaded.
+}
+
+// New returns a new initialized BlockCache instance with given primary cache capacity and TTL.
+func New(pcap int, pttl time.Duration) *BlockCache {
+	c := new(BlockCache)
+	c.pcache = new(ttl.Cache[string, bool])
+	c.pcache.Init(0, pcap, pttl)
+	return c
+}
+
+// Start will start the cache background eviction routine with given sweep frequency. If already running or a freq <= 0 provided, this is a no-op. This will block until the eviction routine has started.
+func (b *BlockCache) Start(pfreq time.Duration) bool {
+	return b.pcache.Start(pfreq)
+}
+
+// Stop will stop cache background eviction routine. If not running this is a no-op. This will block until the eviction routine has stopped.
+func (b *BlockCache) Stop() bool {
+	return b.pcache.Stop()
+}
+
+// IsBlocked checks whether domain is blocked. If the cache is not currently loaded, then the provided load function is used to hydrate it.
+// NOTE: be VERY careful using any kind of locking mechanism within the load function, as this itself is ran within the cache mutex lock.
+func (b *BlockCache) IsBlocked(domain string, load func() ([]string, error)) (bool, error) {
+	var blocked bool
+
+	// Acquire cache lock
+	b.pcache.Lock()
+	defer b.pcache.Unlock()
+
+	// Check primary cache for result
+	entry, ok := b.pcache.Cache.Get(domain)
+	if ok {
+		return entry.Value, nil
+	}
+
+	if b.blocks == nil {
+		// Cache is not hydrated
+		//
+		// Load domains from callback
+		domains, err := load()
+		if err != nil {
+			return false, fmt.Errorf("error reloading cache: %w", err)
+		}
+
+		// Drop all domain blocks and recreate
+		b.blocks = make([]block, len(domains))
+
+		for i, domain := range domains {
+			// Store pre-split labels for each domain block
+			b.blocks[i].labels = dns.SplitDomainName(domain)
+		}
+	}
+
+	// Split domain into it separate labels
+	labels := dns.SplitDomainName(domain)
+
+	// Compare this to our stored blocks
+	for _, block := range b.blocks {
+		if block.Blocks(labels) {
+			blocked = true
+			break
+		}
+	}
+
+	// Store block result in primary cache
+	b.pcache.Cache.Set(domain, &ttl.Entry[string, bool]{
+		Key:    domain,
+		Value:  blocked,
+		Expiry: time.Now().Add(b.pcache.TTL),
+	})
+
+	return blocked, nil
+}
+
+// Clear will drop the currently loaded domain list, and clear the primary cache.
+// This will trigger a reload on next call to .IsBlocked().
+func (b *BlockCache) Clear() {
+	// Drop all blocks.
+	b.pcache.Lock()
+	b.blocks = nil
+	b.pcache.Unlock()
+
+	// Clear needs to be done _outside_ of
+	// lock, as also acquires a mutex lock.
+	b.pcache.Clear()
+}
+
+// block represents a domain block, and stores the
+// deconstructed labels of a singular domain block.
+// e.g. []string{"gts", "superseriousbusiness", "org"}.
+type block struct {
+	labels []string
+}
+
+// Blocks checks whether the separated domain labels of an
+// incoming domain matches the stored (receiving struct) block.
+func (b block) Blocks(labels []string) bool {
+	// Calculate length difference
+	d := len(labels) - len(b.labels)
+	if d < 0 {
+		return false
+	}
+
+	// Iterate backwards through domain block's
+	// labels, omparing against the incoming domain's.
+	//
+	// So for the following input:
+	// labels   = []string{"mail", "google", "com"}
+	// b.labels = []string{"google", "com"}
+	//
+	// These would be matched in reverse order along
+	// the entirety of the block object's labels:
+	// "com"    => match
+	// "google" => match
+	//
+	// And so would reach the end and return true.
+	for i := len(b.labels) - 1; i >= 0; i-- {
+		if b.labels[i] != labels[i+d] {
+			return false
+		}
+	}
+
+	return true
+}
diff --git a/internal/cache/domain/domain_test.go b/internal/cache/domain/domain_test.go
new file mode 100644
index 000000000..416ce5012
--- /dev/null
+++ b/internal/cache/domain/domain_test.go
@@ -0,0 +1,85 @@
+/*
+   GoToSocial
+   Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org
+
+   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 domain_test
+
+import (
+	"errors"
+	"testing"
+	"time"
+
+	"github.com/superseriousbusiness/gotosocial/internal/cache/domain"
+)
+
+func TestBlockCache(t *testing.T) {
+	c := domain.New(100, time.Second)
+
+	blocks := []string{
+		"google.com",
+		"google.co.uk",
+		"pleroma.bad.host",
+	}
+
+	loader := func() ([]string, error) {
+		t.Log("load: returning blocked domains")
+		return blocks, nil
+	}
+
+	// Check a list of known blocked domains.
+	for _, domain := range []string{
+		"google.com",
+		"mail.google.com",
+		"google.co.uk",
+		"mail.google.co.uk",
+		"pleroma.bad.host",
+		"dev.pleroma.bad.host",
+	} {
+		t.Logf("checking domain is blocked: %s", domain)
+		if b, _ := c.IsBlocked(domain, loader); !b {
+			t.Errorf("domain should be blocked: %s", domain)
+		}
+	}
+
+	// Check a list of known unblocked domains.
+	for _, domain := range []string{
+		"askjeeves.com",
+		"ask-kim.co.uk",
+		"google.ie",
+		"mail.google.ie",
+		"gts.bad.host",
+		"mastodon.bad.host",
+	} {
+		t.Logf("checking domain isn't blocked: %s", domain)
+		if b, _ := c.IsBlocked(domain, loader); b {
+			t.Errorf("domain should not be blocked: %s", domain)
+		}
+	}
+
+	// Clear the cache
+	c.Clear()
+
+	knownErr := errors.New("known error")
+
+	// Check that reload is actually performed and returns our error
+	if _, err := c.IsBlocked("", func() ([]string, error) {
+		t.Log("load: returning known error")
+		return nil, knownErr
+	}); !errors.Is(err, knownErr) {
+		t.Errorf("is blocked did not return expected error: %v", err)
+	}
+}
diff --git a/internal/cache/gts.go b/internal/cache/gts.go
index 6083b8693..3fa25ddef 100644
--- a/internal/cache/gts.go
+++ b/internal/cache/gts.go
@@ -20,6 +20,7 @@ package cache
 
 import (
 	"codeberg.org/gruf/go-cache/v3/result"
+	"github.com/superseriousbusiness/gotosocial/internal/cache/domain"
 	"github.com/superseriousbusiness/gotosocial/internal/config"
 	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
 )
@@ -41,8 +42,8 @@ type GTSCaches interface {
 	// Block provides access to the gtsmodel Block (account) database cache.
 	Block() *result.Cache[*gtsmodel.Block]
 
-	// DomainBlock provides access to the gtsmodel DomainBlock database cache.
-	DomainBlock() *result.Cache[*gtsmodel.DomainBlock]
+	// DomainBlock provides access to the domain block database cache.
+	DomainBlock() *domain.BlockCache
 
 	// Emoji provides access to the gtsmodel Emoji database cache.
 	Emoji() *result.Cache[*gtsmodel.Emoji]
@@ -74,7 +75,7 @@ func NewGTS() GTSCaches {
 type gtsCaches struct {
 	account       *result.Cache[*gtsmodel.Account]
 	block         *result.Cache[*gtsmodel.Block]
-	domainBlock   *result.Cache[*gtsmodel.DomainBlock]
+	domainBlock   *domain.BlockCache
 	emoji         *result.Cache[*gtsmodel.Emoji]
 	emojiCategory *result.Cache[*gtsmodel.EmojiCategory]
 	mention       *result.Cache[*gtsmodel.Mention]
@@ -151,7 +152,7 @@ func (c *gtsCaches) Block() *result.Cache[*gtsmodel.Block] {
 	return c.block
 }
 
-func (c *gtsCaches) DomainBlock() *result.Cache[*gtsmodel.DomainBlock] {
+func (c *gtsCaches) DomainBlock() *domain.BlockCache {
 	return c.domainBlock
 }
 
@@ -212,14 +213,10 @@ func (c *gtsCaches) initBlock() {
 }
 
 func (c *gtsCaches) initDomainBlock() {
-	c.domainBlock = result.NewSized([]result.Lookup{
-		{Name: "Domain"},
-	}, func(d1 *gtsmodel.DomainBlock) *gtsmodel.DomainBlock {
-		d2 := new(gtsmodel.DomainBlock)
-		*d2 = *d1
-		return d2
-	}, config.GetCacheGTSDomainBlockMaxSize())
-	c.domainBlock.SetTTL(config.GetCacheGTSDomainBlockTTL(), true)
+	c.domainBlock = domain.New(
+		config.GetCacheGTSDomainBlockMaxSize(),
+		config.GetCacheGTSDomainBlockTTL(),
+	)
 }
 
 func (c *gtsCaches) initEmoji() {