Add RequestCached and RequestCachedBytes functions for caching HTTP requests

go.mod

@@ -1,3 +1,5 @@
 module git.site.quack-lab.dev/dave/cyutils
 
 go 1.23.6
+
+require golang.org/x/time v0.12.0

go.sum

@@ -0,0 +1,2 @@
+golang.org/x/time v0.12.0 h1:ScB/8o8olJvc+CQPWrK3fPZNfh7qgwCrY0zJmoEQLSE=
+golang.org/x/time v0.12.0/go.mod h1:CDIdPxbZBQxdj6cxyCIdrNogrJKMJ7pr37NYpMcMDSg=

main.go

@@ -1,7 +1,15 @@
 package cyutils
 
 import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
 	"sync"
+
+	"golang.org/x/time/rate"
 )
 
 func WithWorkers[T any](workers int, arr []T, fn func(worker int, item T)) {
@@ -40,3 +48,84 @@ func Batched[T any](arr []T, batchSize int, fn func(batch []T)) {
 		fn(batch)
 	}
 }
+
+type RateLimitedTransport struct {
+	base    http.RoundTripper // Underlying transport
+	limiter *rate.Limiter     // Rate limiter
+}
+
+// RoundTrip enforces rate limiting before executing the request
+func (t *RateLimitedTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	ctx := req.Context()
+	if err := t.limiter.Wait(ctx); err != nil {
+		return nil, err // Handle context cancellation/timeout
+	}
+	return t.base.RoundTrip(req)
+}
+func LimitedHttp(rps float64, burst int) *http.Client {
+	baseTransport := &http.Transport{
+		MaxIdleConns:        100,
+		MaxIdleConnsPerHost: 10,
+	}
+
+	// Initialize rate limiter
+	limiter := rate.NewLimiter(rate.Limit(rps), burst)
+
+	// Wrap transport with rate limiting
+	transport := &RateLimitedTransport{
+		base:    baseTransport,
+		limiter: limiter,
+	}
+
+	// Return configured client
+	return &http.Client{
+		Transport: transport,
+	}
+}
+
+func RequestCached[T any](req *http.Request, filename string) (T, error) {
+	var zero T
+
+	data, err := os.ReadFile(filename)
+	if err != nil {
+		if !os.IsNotExist(err) {
+			return zero, fmt.Errorf("failed to read cache: %w", err)
+		}
+
+		resp, httpErr := http.DefaultClient.Do(req)
+		if httpErr != nil {
+			return zero, fmt.Errorf("HTTP request failed: %w", httpErr)
+		}
+		defer resp.Body.Close()
+
+		body, readErr := io.ReadAll(resp.Body)
+		if readErr != nil {
+			return zero, fmt.Errorf("failed to read response body: %w", readErr)
+		}
+
+		dir := filepath.Dir(filename)
+		if dir != "." && dir != "" {
+			if mkErr := os.MkdirAll(dir, 0o755); mkErr != nil {
+				return zero, fmt.Errorf("failed to create cache dir %s: %w", dir, mkErr)
+			}
+		}
+		if writeErr := os.WriteFile(filename, body, 0o644); writeErr != nil {
+			return zero, fmt.Errorf("failed to write cache %s: %w", filename, writeErr)
+		}
+		data = body
+	}
+
+	if _, ok := any(zero).([]byte); ok {
+		return any(data).(T), nil
+	}
+
+	var out T
+	if err := json.Unmarshal(data, &out); err != nil {
+		return zero, fmt.Errorf("failed to unmarshal cached response: %w", err)
+	}
+	return out, nil
+}
+
+func RequestCachedBytes(req *http.Request, filename string) ([]byte, error) {
+	return RequestCached[[]byte](req, filename)
+}