added golangci-linting, refactor, simplified error msgs and fixed some error handling

internal/api/v1/errorpage/error_page.go

@@ -0,0 +1,90 @@
+package errorpage
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"path"
+	"sync"
+
+	. "github.com/yusing/go-proxy/internal/api/v1/utils"
+	"github.com/yusing/go-proxy/internal/common"
+	U "github.com/yusing/go-proxy/internal/utils"
+	F "github.com/yusing/go-proxy/internal/utils/functional"
+	W "github.com/yusing/go-proxy/internal/watcher"
+	"github.com/yusing/go-proxy/internal/watcher/events"
+)
+
+const errPagesBasePath = common.ErrorPagesBasePath
+
+var (
+	dirWatcher     W.Watcher
+	fileContentMap = F.NewMapOf[string, []byte]()
+)
+
+var setup = sync.OnceFunc(func() {
+	dirWatcher = W.NewDirectoryWatcher(context.Background(), errPagesBasePath)
+	loadContent()
+	go watchDir()
+})
+
+func GetStaticFile(filename string) ([]byte, bool) {
+	return fileContentMap.Load(filename)
+}
+
+// try <statusCode>.html -> 404.html -> not ok.
+func GetErrorPageByStatus(statusCode int) (content []byte, ok bool) {
+	content, ok = fileContentMap.Load(fmt.Sprintf("%d.html", statusCode))
+	if !ok && statusCode != 404 {
+		return fileContentMap.Load("404.html")
+	}
+	return
+}
+
+func loadContent() {
+	files, err := U.ListFiles(errPagesBasePath, 0)
+	if err != nil {
+		Logger.Error(err)
+		return
+	}
+	for _, file := range files {
+		if fileContentMap.Has(file) {
+			continue
+		}
+		content, err := os.ReadFile(file)
+		if err != nil {
+			Logger.Errorf("failed to read error page resource %s: %s", file, err)
+			continue
+		}
+		file = path.Base(file)
+		Logger.Infof("error page resource %s loaded", file)
+		fileContentMap.Store(file, content)
+	}
+}
+
+func watchDir() {
+	eventCh, errCh := dirWatcher.Events(context.Background())
+	for {
+		select {
+		case event, ok := <-eventCh:
+			if !ok {
+				return
+			}
+			filename := event.ActorName
+			switch event.Action {
+			case events.ActionFileWritten:
+				fileContentMap.Delete(filename)
+				loadContent()
+			case events.ActionFileDeleted:
+				fileContentMap.Delete(filename)
+				Logger.Infof("error page resource %s deleted", filename)
+			case events.ActionFileRenamed:
+				Logger.Infof("error page resource %s deleted", filename)
+				fileContentMap.Delete(filename)
+				loadContent()
+			}
+		case err := <-errCh:
+			Logger.Errorf("error watching error page directory: %s", err)
+		}
+	}
+}

internal/api/v1/errorpage/http_handler.go

@@ -0,0 +1,31 @@
+package errorpage
+
+import (
+	"net/http"
+
+	. "github.com/yusing/go-proxy/internal/api/v1/utils"
+)
+
+func GetHandleFunc() http.HandlerFunc {
+	setup()
+	return serveHTTP
+}
+
+func serveHTTP(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodGet {
+		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+	if r.URL.Path == "/" {
+		http.Error(w, "invalid path", http.StatusNotFound)
+		return
+	}
+	content, ok := fileContentMap.Load(r.URL.Path)
+	if !ok {
+		http.Error(w, "404 not found", http.StatusNotFound)
+		return
+	}
+	if _, err := w.Write(content); err != nil {
+		HandleErr(w, r, err)
+	}
+}