Make WithWorkers support slices and maps with generic key-value pairs

main.go

@@ -1,40 +1,58 @@
 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)) {
+func WithWorkers[K comparable, V any, C []V | map[K]V](
-	workersChan := make(chan struct{}, workers)
+	workers int,
-	ingestChan := make(chan T, len(arr))
+	items C,
+	fn func(worker int, key K, value V),
+) {
+	type KV struct {
+		// A bit of type weaving...
+		Key   any
+		Value V
+	}
 
-	for _, item := range arr {
+	n := len(items)
-		ingestChan <- item
+	ingestChan := make(chan KV, n)
+
+	go func() {
+		switch v := any(items).(type) {
+		case []V:
+			for i, it := range v {
+				ingestChan <- KV{Key: i, Value: it}
+			}
+		case map[K]V:
+			for key, it := range v {
+				ingestChan <- KV{Key: key, Value: it}
+			}
 		}
 		close(ingestChan)
+	}()
 
-	wg := sync.WaitGroup{}
+	var wg sync.WaitGroup
+	wg.Add(workers)
 	for i := 0; i < workers; i++ {
-		workersChan <- struct{}{}
-		wg.Add(1)
 		go func(worker int) {
 			defer wg.Done()
-			defer func() { <-workersChan }()
+			for v := range ingestChan {
-			for {
+				fn(worker, v.Key.(K), v.Value)
-				item, ok := <-ingestChan
-				// We're done processing totally
-				if !ok {
-					return
-				}
-				fn(worker, item)
 			}
 		}(i)
 	}
 	wg.Wait()
 }
+
 func Batched[T any](arr []T, batchSize int, fn func(batch []T)) {
 	for i := 0; i < len(arr); i += batchSize {
 		start := i
@@ -77,3 +95,50 @@ func LimitedHttp(rps float64, burst int) *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)
+}