extract ring buffer logic to new package

mattdholloway · mattdholloway · commit 4e43327dae35 · 2025-08-15T16:01:02.000+01:00
diff --git a/pkg/buffer/buffer.go b/pkg/buffer/buffer.go
@@ -0,0 +1,51 @@
+package buffer
+
+import (
+	"bufio"
+	"fmt"
+	"net/http"
+	"strings"
+)
+
+func ProcessAsRingBufferToEnd(httpResp *http.Response, maxJobLogLines int) (string, int, *http.Response, error) {
+	lines := make([]string, maxJobLogLines)
+	validLines := make([]bool, maxJobLogLines)
+	totalLines := 0
+	writeIndex := 0
+
+	scanner := bufio.NewScanner(httpResp.Body)
+	scanner.Buffer(make([]byte, 0, 64*1024), 1024*1024)
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		totalLines++
+
+		lines[writeIndex] = line
+		validLines[writeIndex] = true
+		writeIndex = (writeIndex + 1) % maxJobLogLines
+	}
+
+	if err := scanner.Err(); err != nil {
+		return "", 0, httpResp, fmt.Errorf("failed to read log content: %w", err)
+	}
+
+	var result []string
+	linesInBuffer := totalLines
+	if linesInBuffer > maxJobLogLines {
+		linesInBuffer = maxJobLogLines
+	}
+
+	startIndex := 0
+	if totalLines > maxJobLogLines {
+		startIndex = writeIndex
+	}
+
+	for i := 0; i < linesInBuffer; i++ {
+		idx := (startIndex + i) % maxJobLogLines
+		if validLines[idx] {
+			result = append(result, lines[idx])
+		}
+	}
+
+	return strings.Join(result, "\n"), totalLines, httpResp, nil
+}
diff --git a/pkg/github/actions.go b/pkg/github/actions.go
@@ -1,14 +1,13 @@
 package github
 
 import (
-	"bufio"
 	"context"
 	"encoding/json"
 	"fmt"
 	"net/http"
 	"strconv"
-	"strings"
 
+	buffer "github.com/github/github-mcp-server/pkg/buffer"
 	ghErrors "github.com/github/github-mcp-server/pkg/errors"
 	"github.com/github/github-mcp-server/pkg/translations"
 	"github.com/google/go-github/v74/github"
@@ -758,50 +757,13 @@ func downloadLogContent(logURL string, tailLines int) (string, int, *http.Respon
 		tailLines = 1000
 	}
 
-	lines := make([]string, maxJobLogLines)
-	validLines := make([]bool, maxJobLogLines)
-	totalLines := 0
-	writeIndex := 0
+	processedInput, totalLines, httpResp, err := buffer.ProcessAsRingBufferToEnd(httpResp, tailLines)
 
-	scanner := bufio.NewScanner(httpResp.Body)
-	scanner.Buffer(make([]byte, 0, 64*1024), 1024*1024)
-
-	for scanner.Scan() {
-		line := scanner.Text()
-		totalLines++
-
-		lines[writeIndex] = line
-		validLines[writeIndex] = true
-		writeIndex = (writeIndex + 1) % maxJobLogLines
-	}
-
-	if err := scanner.Err(); err != nil {
-		return "", 0, httpResp, fmt.Errorf("failed to read log content: %w", err)
-	}
-
-	var result []string
-	linesInBuffer := totalLines
-	if linesInBuffer > maxJobLogLines {
-		linesInBuffer = maxJobLogLines
-	}
-
-	startIndex := 0
-	if totalLines > maxJobLogLines {
-		startIndex = writeIndex
-	}
-
-	for i := 0; i < linesInBuffer; i++ {
-		idx := (startIndex + i) % maxJobLogLines
-		if validLines[idx] {
-			result = append(result, lines[idx])
-		}
-	}
-
-	if len(result) > tailLines {
-		result = result[len(result)-tailLines:]
+	if len(processedInput) > tailLines {
+		processedInput = processedInput[len(processedInput)-tailLines:]
 	}
 
-	finalResult := strings.Join(result, "\n")
+	finalResult := processedInput
 
 	return finalResult, totalLines, httpResp, nil
 }
