From bc52b1a949d43b8c95b80ae57e8a4267539fbbcb Mon Sep 17 00:00:00 2001
From: Antoine Aflalo <197810+Belphemur@users.noreply.github.com>
Date: Tue, 27 Aug 2024 09:54:47 -0400
Subject: [PATCH] perf: improve error handling by having error channel

---
 cmd/convert_cbz_command.go       | 22 +++++++++++++++++-----
 converter/webp/webp_converter.go | 19 ++++++++++++++-----
 2 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/cmd/convert_cbz_command.go b/cmd/convert_cbz_command.go
index 74ac422..d9f2818 100644
--- a/cmd/convert_cbz_command.go
+++ b/cmd/convert_cbz_command.go
@@ -83,6 +83,8 @@ func ConvertCbzCommand(cmd *cobra.Command, args []string) error {
 	}
 	// Channel to manage the files to process
 	fileChan := make(chan string)
+	// Channel to collect errors
+	errorChan := make(chan error, parallelism)
 
 	// WaitGroup to wait for all goroutines to finish
 	var wg sync.WaitGroup
@@ -98,7 +100,7 @@ func ConvertCbzCommand(cmd *cobra.Command, args []string) error {
 				// Load the chapter
 				chapter, err := cbz.LoadChapter(path)
 				if err != nil {
-					fmt.Printf("Failed to load chapter: %v\n", err)
+					errorChan <- fmt.Errorf("failed to load chapter: %v", err)
 					continue
 				}
 
@@ -112,7 +114,7 @@ func ConvertCbzCommand(cmd *cobra.Command, args []string) error {
 					fmt.Println(msg)
 				})
 				if err != nil {
-					fmt.Printf("Failed to convert chapter: %v\n", err)
+					errorChan <- fmt.Errorf("failed to convert chapter: %v", err)
 					continue
 				}
 				convertedChapter.SetConverted()
@@ -124,7 +126,7 @@ func ConvertCbzCommand(cmd *cobra.Command, args []string) error {
 				}
 				err = cbz.WriteChapterToCBZ(convertedChapter, outputPath)
 				if err != nil {
-					fmt.Printf("Failed to write converted chapter: %v\n", err)
+					errorChan <- fmt.Errorf("failed to write converted chapter: %v", err)
 					continue
 				}
 
@@ -150,8 +152,18 @@ func ConvertCbzCommand(cmd *cobra.Command, args []string) error {
 		return fmt.Errorf("error walking the path: %w", err)
 	}
 
-	close(fileChan) // Close the channel to signal workers to stop
-	wg.Wait()       // Wait for all workers to finish
+	close(fileChan)  // Close the channel to signal workers to stop
+	wg.Wait()        // Wait for all workers to finish
+	close(errorChan) // Close the error channel
+
+	var errs []error
+	for err := range errorChan {
+		errs = append(errs, err)
+	}
+
+	if len(errs) > 0 {
+		return fmt.Errorf("encountered errors: %v", errs)
+	}
 
 	return nil
 }
diff --git a/converter/webp/webp_converter.go b/converter/webp/webp_converter.go
index 0455704..6fe0b12 100644
--- a/converter/webp/webp_converter.go
+++ b/converter/webp/webp_converter.go
@@ -12,7 +12,6 @@ import (
 	_ "image/jpeg"
 	"image/png"
 	"io"
-	"log"
 	"runtime"
 	"sync"
 	"sync/atomic"
@@ -59,6 +58,7 @@ func (converter *Converter) ConvertChapter(chapter *packer2.Chapter, quality uin
 	maxGoroutines := runtime.NumCPU()
 
 	pagesChan := make(chan *packer2.PageContainer, maxGoroutines)
+	errChan := make(chan error, maxGoroutines)
 
 	var wgPages sync.WaitGroup
 	wgPages.Add(len(chapter.Pages))
@@ -78,6 +78,7 @@ func (converter *Converter) ConvertChapter(chapter *packer2.Chapter, quality uin
 					buffer := new(bytes.Buffer)
 					err := png.Encode(buffer, convertedPage.Image)
 					if err != nil {
+						errChan <- err
 						<-guard
 						return
 					}
@@ -91,7 +92,6 @@ func (converter *Converter) ConvertChapter(chapter *packer2.Chapter, quality uin
 				pagesMutex.Unlock()
 				<-guard
 			}(page)
-
 		}
 	}()
 
@@ -101,7 +101,7 @@ func (converter *Converter) ConvertChapter(chapter *packer2.Chapter, quality uin
 
 			splitNeeded, img, format, err := converter.checkPageNeedsSplit(page)
 			if err != nil {
-				log.Fatalf("error checking if page %d d of chapter %s  needs split: %v", page.Index, chapter.FilePath, err)
+				errChan <- fmt.Errorf("error checking if page %d of chapter %s needs split: %v", page.Index, chapter.FilePath, err)
 				return
 			}
 
@@ -112,7 +112,7 @@ func (converter *Converter) ConvertChapter(chapter *packer2.Chapter, quality uin
 			}
 			images, err := converter.cropImage(img)
 			if err != nil {
-				log.Fatalf("error converting page %d of chapter %s to webp: %v", page.Index, chapter.FilePath, err)
+				errChan <- fmt.Errorf("error converting page %d of chapter %s to webp: %v", page.Index, chapter.FilePath, err)
 				return
 			}
 
@@ -123,12 +123,21 @@ func (converter *Converter) ConvertChapter(chapter *packer2.Chapter, quality uin
 				pagesChan <- packer2.NewContainer(page, img, "N/A")
 			}
 		}(page)
-
 	}
 
 	wgPages.Wait()
 	wgConvertedPages.Wait()
 	close(pagesChan)
+	close(errChan)
+
+	var errList []error
+	for err := range errChan {
+		errList = append(errList, err)
+	}
+
+	if len(errList) > 0 {
+		return nil, fmt.Errorf("encountered errors: %v", errList)
+	}
 
 	slices.SortFunc(pages, func(a, b *packer2.Page) int {
 		if a.Index == b.Index {