feat: modernise to Go 1.26 — slices.DeleteFunc, iterators, range

- Use slices.DeleteFunc in prune() for cleaner time-window filtering
- Add Models() iter.Seq[string] and Iter() iter.Seq2[string, ModelStats]
- Use range over int in benchmarks and tests
- Update docs example to modern range syntax

Co-Authored-By: Gemini <noreply@google.com>
Co-Authored-By: Virgil <virgil@lethean.io>

docs/development.md

@@ -102,7 +102,7 @@ assert anything beyond absence of data races (the race detector does the work):
 
 ```go
 var wg sync.WaitGroup
-for i := 0; i < 20; i++ {
+for i := range 20 {
     wg.Add(1)
     go func() {
         defer wg.Done()

ratelimit.go

@@ -6,10 +6,12 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"iter"
 	"maps"
 	"net/http"
 	"os"
 	"path/filepath"
+	"slices"
 	"sync"
 	"time"
 
@@ -276,24 +278,14 @@ func (rl *RateLimiter) prune(model string) {
 	window := now.Add(-1 * time.Minute)
 
 	// Prune requests
-	validReqs := 0
-	for _, t := range stats.Requests {
-		if t.After(window) {
-			stats.Requests[validReqs] = t
-			validReqs++
-		}
-	}
-	stats.Requests = stats.Requests[:validReqs]
+	stats.Requests = slices.DeleteFunc(stats.Requests, func(t time.Time) bool {
+		return !t.After(window)
+	})
 
 	// Prune tokens
-	validTokens := 0
-	for _, t := range stats.Tokens {
-		if t.Time.After(window) {
-			stats.Tokens[validTokens] = t
-			validTokens++
-		}
-	}
-	stats.Tokens = stats.Tokens[:validTokens]
+	stats.Tokens = slices.DeleteFunc(stats.Tokens, func(t TokenEntry) bool {
+		return !t.Time.After(window)
+	})
 
 	// Reset daily counter if day has passed
 	if now.Sub(stats.DayStart) >= 24*time.Hour {
@@ -412,6 +404,30 @@ type ModelStats struct {
 	DayStart time.Time
 }
 
+// Models returns an iterator over all model names tracked by the limiter.
+func (rl *RateLimiter) Models() iter.Seq[string] {
+	return func(yield func(string) bool) {
+		stats := rl.AllStats()
+		for m := range stats {
+			if !yield(m) {
+				return
+			}
+		}
+	}
+}
+
+// Iter returns an iterator over all model names and their current stats.
+func (rl *RateLimiter) Iter() iter.Seq2[string, ModelStats] {
+	return func(yield func(string, ModelStats) bool) {
+		stats := rl.AllStats()
+		for k, v := range stats {
+			if !yield(k, v) {
+				return
+			}
+		}
+	}
+}
+
 // Stats returns current stats for a model.
 func (rl *RateLimiter) Stats(model string) ModelStats {
 	rl.mu.Lock()
@@ -460,23 +476,12 @@ func (rl *RateLimiter) AllStats() map[string]ModelStats {
 	for m := range result {
 		// Prune inline
 		if s, ok := rl.State[m]; ok {
-			validReqs := 0
-			for _, t := range s.Requests {
-				if t.After(window) {
-					s.Requests[validReqs] = t
-					validReqs++
-				}
-			}
-			s.Requests = s.Requests[:validReqs]
-
-			validTokens := 0
-			for _, t := range s.Tokens {
-				if t.Time.After(window) {
-					s.Tokens[validTokens] = t
-					validTokens++
-				}
-			}
-			s.Tokens = s.Tokens[:validTokens]
+			s.Requests = slices.DeleteFunc(s.Requests, func(t time.Time) bool {
+				return !t.After(window)
+			})
+			s.Tokens = slices.DeleteFunc(s.Tokens, func(t TokenEntry) bool {
+				return !t.Time.After(window)
+			})
 
 			if now.Sub(s.DayStart) >= 24*time.Hour {
 				s.DayStart = now

ratelimit_test.go

@@ -768,7 +768,7 @@ func BenchmarkCanSend(b *testing.B) {
 	}
 
 	b.ResetTimer()
-	for i := 0; i < b.N; i++ {
+	for range b.N {
 		rl.CanSend(model, 100)
 	}
 }
@@ -779,7 +779,7 @@ func BenchmarkRecordUsage(b *testing.B) {
 	rl.Quotas[model] = ModelQuota{MaxRPM: 100000, MaxTPM: 1000000000, MaxRPD: 1000000}
 
 	b.ResetTimer()
-	for i := 0; i < b.N; i++ {
+	for range b.N {
 		rl.RecordUsage(model, 100, 100)
 	}
 }
@@ -1237,7 +1237,7 @@ func BenchmarkCanSendWithPrune(b *testing.B) {
 	rl.State[model].DayCount = 1000
 
 	b.ResetTimer()
-	for i := 0; i < b.N; i++ {
+	for range b.N {
 		rl.CanSend(model, 100)
 	}
 }
@@ -1256,7 +1256,7 @@ func BenchmarkStats(b *testing.B) {
 	}
 
 	b.ResetTimer()
-	for i := 0; i < b.N; i++ {
+	for range b.N {
 		rl.Stats(model)
 	}
 }
@@ -1277,7 +1277,7 @@ func BenchmarkAllStats(b *testing.B) {
 	}
 
 	b.ResetTimer()
-	for i := 0; i < b.N; i++ {
+	for range b.N {
 		rl.AllStats()
 	}
 }
@@ -1300,7 +1300,7 @@ func BenchmarkPersist(b *testing.B) {
 	}
 
 	b.ResetTimer()
-	for i := 0; i < b.N; i++ {
+	for range b.N {
 		_ = rl.Persist()
 	}
 }

sqlite_test.go

@@ -672,7 +672,7 @@ func BenchmarkSQLitePersist(b *testing.B) {
 	}
 
 	b.ResetTimer()
-	for i := 0; i < b.N; i++ {
+	for range b.N {
 		_ = rl.Persist()
 	}
 }
@@ -698,7 +698,7 @@ func BenchmarkSQLiteLoad(b *testing.B) {
 	_ = rl.Persist()
 
 	b.ResetTimer()
-	for i := 0; i < b.N; i++ {
+	for range b.N {
 		_ = rl.Load()
 	}
 }