first (BIG) commit

middlewares/middlewares.go

@@ -0,0 +1,141 @@
+/*
+Package middlewares implements all handlers of the application.
+
+Those handlers manage requests coming from the unique entry point (aka "/").
+*/
+package middlewares
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+
+	"github.com/gulien/gotenberg/context"
+	"github.com/gulien/gotenberg/converters"
+	"github.com/gulien/gotenberg/helpers"
+	"github.com/gulien/gotenberg/logger"
+
+	"github.com/justinas/alice"
+	"github.com/satori/go.uuid"
+)
+
+// LoggingHandler identifies the request.
+func LoggingHandler(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		transactionID := uuid.NewV4().String()
+		r = r.WithContext(context.WithTransactionID(r.Context(), transactionID))
+		logger.InfoR(context.GetTransactionID(r.Context()), fmt.Sprintf("Handling new request from %s", r.RemoteAddr))
+		next.ServeHTTP(w, r)
+	})
+}
+
+// GetMiddlewaresChain builds and returns the chaining of handlers
+// using the alice library.
+func GetMiddlewaresChain() http.Handler {
+	return alice.New(enforceContentLengthHandler, enforceContentTypeHandler, convertHandler, serveHandler).ThenFunc(clearHandler)
+}
+
+// enforeContentLengthHandler checks if the request has content.
+func enforceContentLengthHandler(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.ContentLength == 0 {
+			http.Error(w, http.StatusText(http.StatusBadRequest), http.StatusBadRequest)
+			logger.ErrorR(context.GetTransactionID(r.Context()), fmt.Errorf("%s", http.StatusText(http.StatusBadRequest)), http.StatusBadRequest, "Request has no content")
+			return
+		}
+
+		next.ServeHTTP(w, r)
+	})
+}
+
+// enforceContentTypeHandler checks if the "Content-Type" entry
+// from the request's header matches one of the allowed content types.
+func enforceContentTypeHandler(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		contentType := helpers.GetMatchingContentType(r.Header.Get("Content-Type"))
+		if contentType == "" {
+			http.Error(w, http.StatusText(http.StatusUnsupportedMediaType), http.StatusUnsupportedMediaType)
+			logger.ErrorR(context.GetTransactionID(r.Context()), fmt.Errorf("%s", http.StatusText(http.StatusUnsupportedMediaType)), http.StatusUnsupportedMediaType, "No matching content type found")
+			return
+		}
+
+		r = r.WithContext(context.WithContentType(r.Context(), contentType))
+		next.ServeHTTP(w, r)
+	})
+}
+
+// convertHandler is in charge of converting the file(s) from the request to PDF.
+func convertHandler(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		contentType := context.GetContentType(r.Context())
+
+		c, err := converters.NewConverter(contentType, r)
+		if err != nil {
+			if converterUnprocessableEntityError, ok := err.(*converters.ConverterUnprocessableEntityError); ok {
+				// a file from the request has a content type which does not match with one of the allowed
+				// content types.
+				http.Error(w, converterUnprocessableEntityError.Error(), http.StatusUnprocessableEntity)
+				logger.ErrorR(context.GetTransactionID(r.Context()), converterUnprocessableEntityError, http.StatusUnprocessableEntity, "A file has a content type which does not match with one of the allowed content types")
+			} else {
+				// something bad happened during the creation of the converter...
+				http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
+				logger.ErrorR(context.GetTransactionID(r.Context()), err, http.StatusInternalServerError, "Something bad happened during the creation of the converter")
+			}
+
+			return
+		}
+
+		resultFilePath, err := c.Convert()
+		if err != nil {
+			// an error occured during conversion...
+			http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
+			logger.ErrorR(context.GetTransactionID(r.Context()), err, http.StatusInternalServerError, "An error occured during conversion")
+			return
+		}
+
+		r = r.WithContext(context.WithResultFilePath(r.Context(), resultFilePath))
+		r = r.WithContext(context.WithConverter(r.Context(), c))
+		next.ServeHTTP(w, r)
+	})
+}
+
+// serveHandler simply serves the created PDF.
+func serveHandler(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		resultFilePath := context.GetResultFilePath(r.Context())
+
+		reader, err := os.Open(resultFilePath)
+		if err != nil {
+			http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
+			logger.ErrorR(context.GetTransactionID(r.Context()), err, http.StatusInternalServerError, fmt.Sprintf("An error occured while opening result file \"%s\"", resultFilePath))
+			return
+		}
+
+		defer reader.Close()
+
+		resultFileInfo, err := reader.Stat()
+		if err != nil {
+			http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
+			logger.ErrorR(context.GetTransactionID(r.Context()), err, http.StatusInternalServerError, fmt.Sprintf("An error occured while retrieving info from result file \"%s\"", resultFilePath))
+			return
+		}
+
+		w.Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename=\"%s\"", resultFileInfo.Name()))
+		w.Header().Set("Content-Type", "application/pdf")
+		w.Header().Set("Content-Length", fmt.Sprintf("%d", resultFileInfo.Size()))
+		io.Copy(w, reader)
+
+		next.ServeHTTP(w, r)
+	})
+}
+
+// clearHandler removes all files created during the conversion.
+func clearHandler(w http.ResponseWriter, r *http.Request) {
+	c := context.GetConverter(r.Context())
+
+	if err := c.Clear(); err != nil {
+		logger.WarnR(context.GetTransactionID(r.Context()), err.Error())
+	}
+	logger.InfoR(context.GetTransactionID(r.Context()), "Request handled")
+}