Refactor/base layer message split

pkg/channels/discord.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"fmt"
 	"os"
-	"strings"
 	"time"
 
 	"github.com/bwmarrin/discordgo"
@@ -106,7 +105,7 @@ func (c *DiscordChannel) Send(ctx context.Context, msg bus.OutboundMessage) erro
 		return nil
 	}
 
-	chunks := splitMessage(msg.Content, 1500) // Discord has a limit of 2000 characters per message, leave 500 for natural split e.g. code blocks
+	chunks := utils.SplitMessage(msg.Content, 2000) // Split messages into chunks, Discord length limit: 2000 chars
 
 	for _, chunk := range chunks {
 		if err := c.sendChunk(ctx, channelID, chunk); err != nil {
@@ -117,132 +116,6 @@ func (c *DiscordChannel) Send(ctx context.Context, msg bus.OutboundMessage) erro
 	return nil
 }
 
-// splitMessage splits long messages into chunks, preserving code block integrity
-// Uses natural boundaries (newlines, spaces) and extends messages slightly to avoid breaking code blocks
-func splitMessage(content string, limit int) []string {
-	var messages []string
-
-	for len(content) > 0 {
-		if len(content) <= limit {
-			messages = append(messages, content)
-			break
-		}
-
-		msgEnd := limit
-
-		// Find natural split point within the limit
-		msgEnd = findLastNewline(content[:limit], 200)
-		if msgEnd <= 0 {
-			msgEnd = findLastSpace(content[:limit], 100)
-		}
-		if msgEnd <= 0 {
-			msgEnd = limit
-		}
-
-		// Check if this would end with an incomplete code block
-		candidate := content[:msgEnd]
-		unclosedIdx := findLastUnclosedCodeBlock(candidate)
-
-		if unclosedIdx >= 0 {
-			// Message would end with incomplete code block
-			// Try to extend to include the closing ``` (with some buffer)
-			extendedLimit := limit + 500 // Allow 500 char buffer for code blocks
-			if len(content) > extendedLimit {
-				closingIdx := findNextClosingCodeBlock(content, msgEnd)
-				if closingIdx > 0 && closingIdx <= extendedLimit {
-					// Extend to include the closing ```
-					msgEnd = closingIdx
-				} else {
-					// Can't find closing, split before the code block
-					msgEnd = findLastNewline(content[:unclosedIdx], 200)
-					if msgEnd <= 0 {
-						msgEnd = findLastSpace(content[:unclosedIdx], 100)
-					}
-					if msgEnd <= 0 {
-						msgEnd = unclosedIdx
-					}
-				}
-			} else {
-				// Remaining content fits within extended limit
-				msgEnd = len(content)
-			}
-		}
-
-		if msgEnd <= 0 {
-			msgEnd = limit
-		}
-
-		messages = append(messages, content[:msgEnd])
-		content = strings.TrimSpace(content[msgEnd:])
-	}
-
-	return messages
-}
-
-// findLastUnclosedCodeBlock finds the last opening ``` that doesn't have a closing ```
-// Returns the position of the opening ``` or -1 if all code blocks are complete
-func findLastUnclosedCodeBlock(text string) int {
-	count := 0
-	lastOpenIdx := -1
-
-	for i := 0; i < len(text); i++ {
-		if i+2 < len(text) && text[i] == '`' && text[i+1] == '`' && text[i+2] == '`' {
-			if count == 0 {
-				lastOpenIdx = i
-			}
-			count++
-			i += 2
-		}
-	}
-
-	// If odd number of ``` markers, last one is unclosed
-	if count%2 == 1 {
-		return lastOpenIdx
-	}
-	return -1
-}
-
-// findNextClosingCodeBlock finds the next closing ``` starting from a position
-// Returns the position after the closing ``` or -1 if not found
-func findNextClosingCodeBlock(text string, startIdx int) int {
-	for i := startIdx; i < len(text); i++ {
-		if i+2 < len(text) && text[i] == '`' && text[i+1] == '`' && text[i+2] == '`' {
-			return i + 3
-		}
-	}
-	return -1
-}
-
-// findLastNewline finds the last newline character within the last N characters
-// Returns the position of the newline or -1 if not found
-func findLastNewline(s string, searchWindow int) int {
-	searchStart := len(s) - searchWindow
-	if searchStart < 0 {
-		searchStart = 0
-	}
-	for i := len(s) - 1; i >= searchStart; i-- {
-		if s[i] == '\n' {
-			return i
-		}
-	}
-	return -1
-}
-
-// findLastSpace finds the last space character within the last N characters
-// Returns the position of the space or -1 if not found
-func findLastSpace(s string, searchWindow int) int {
-	searchStart := len(s) - searchWindow
-	if searchStart < 0 {
-		searchStart = 0
-	}
-	for i := len(s) - 1; i >= searchStart; i-- {
-		if s[i] == ' ' || s[i] == '\t' {
-			return i
-		}
-	}
-	return -1
-}
-
 func (c *DiscordChannel) sendChunk(ctx context.Context, channelID, content string) error {
 	// 使用传入的 ctx 进行超时控制
 	sendCtx, cancel := context.WithTimeout(ctx, sendTimeout)

pkg/utils/message.go

@@ -0,0 +1,173 @@
+package utils
+
+import (
+	"strings"
+)
+
+const defaultCodeBlockBuffer = 500
+
+// SplitMessage splits long messages into chunks, preserving code block integrity.
+// The function prefers to split at maxLen - defaultCodeBlockBuffer to leave room for code blocks,
+// but may extend up to maxLen when needed to avoid breaking incomplete code blocks.
+// Call SplitMessage with the full text content and the maximum allowed length of a single message;
+// it returns a slice of message chunks that each respect maxLen and avoid splitting fenced code blocks.
+func SplitMessage(content string, maxLen int) []string {
+	var messages []string
+	codeBlockBuffer := defaultCodeBlockBuffer
+
+	for len(content) > 0 {
+		if len(content) <= maxLen {
+			messages = append(messages, content)
+			break
+		}
+
+		// Effective split point: maxLen minus buffer, to leave room for code blocks
+		effectiveLimit := maxLen - codeBlockBuffer
+		if effectiveLimit < maxLen/2 {
+			effectiveLimit = maxLen / 2
+		}
+
+		// Find natural split point within the effective limit
+		msgEnd := findLastNewline(content[:effectiveLimit], 200)
+		if msgEnd <= 0 {
+			msgEnd = findLastSpace(content[:effectiveLimit], 100)
+		}
+		if msgEnd <= 0 {
+			msgEnd = effectiveLimit
+		}
+
+		// Check if this would end with an incomplete code block
+		candidate := content[:msgEnd]
+		unclosedIdx := findLastUnclosedCodeBlock(candidate)
+
+		if unclosedIdx >= 0 {
+			// Message would end with incomplete code block
+			// Try to extend up to maxLen to include the closing ```
+			if len(content) > msgEnd {
+				closingIdx := findNextClosingCodeBlock(content, msgEnd)
+				if closingIdx > 0 && closingIdx <= maxLen {
+					// Extend to include the closing ```
+					msgEnd = closingIdx
+				} else {
+					// Code block is too long to fit in one chunk or missing closing fence.
+					// Try to split inside by injecting closing and reopening fences.
+					headerEnd := strings.Index(content[unclosedIdx:], "\n")
+					if headerEnd == -1 {
+						headerEnd = unclosedIdx + 3
+					} else {
+						headerEnd += unclosedIdx
+					}
+					header := strings.TrimSpace(content[unclosedIdx:headerEnd])
+
+					// If we have a reasonable amount of content after the header, split inside
+					if msgEnd > headerEnd+20 {
+						// Find a better split point closer to maxLen
+						innerLimit := maxLen - 5 // Leave room for "\n```"
+						betterEnd := findLastNewline(content[:innerLimit], 200)
+						if betterEnd > headerEnd {
+							msgEnd = betterEnd
+						} else {
+							msgEnd = innerLimit
+						}
+						messages = append(messages, strings.TrimRight(content[:msgEnd], " \t\n\r")+"\n```")
+						content = strings.TrimSpace(header + "\n" + content[msgEnd:])
+						continue
+					}
+
+					// Otherwise, try to split before the code block starts
+					newEnd := findLastNewline(content[:unclosedIdx], 200)
+					if newEnd <= 0 {
+						newEnd = findLastSpace(content[:unclosedIdx], 100)
+					}
+					if newEnd > 0 {
+						msgEnd = newEnd
+					} else {
+						// If we can't split before, we MUST split inside (last resort)
+						if unclosedIdx > 20 {
+							msgEnd = unclosedIdx
+						} else {
+							msgEnd = maxLen - 5
+							messages = append(messages, strings.TrimRight(content[:msgEnd], " \t\n\r")+"\n```")
+							content = strings.TrimSpace(header + "\n" + content[msgEnd:])
+							continue
+						}
+					}
+				}
+			}
+		}
+
+		if msgEnd <= 0 {
+			msgEnd = effectiveLimit
+		}
+
+		messages = append(messages, content[:msgEnd])
+		content = strings.TrimSpace(content[msgEnd:])
+	}
+
+	return messages
+}
+
+// findLastUnclosedCodeBlock finds the last opening ``` that doesn't have a closing ```
+// Returns the position of the opening ``` or -1 if all code blocks are complete
+func findLastUnclosedCodeBlock(text string) int {
+	inCodeBlock := false
+	lastOpenIdx := -1
+
+	for i := 0; i < len(text); i++ {
+		if i+2 < len(text) && text[i] == '`' && text[i+1] == '`' && text[i+2] == '`' {
+			// Toggle code block state on each fence
+			if !inCodeBlock {
+				// Entering a code block: record this opening fence
+				lastOpenIdx = i
+			}
+			inCodeBlock = !inCodeBlock
+			i += 2
+		}
+	}
+
+	if inCodeBlock {
+		return lastOpenIdx
+	}
+	return -1
+}
+
+// findNextClosingCodeBlock finds the next closing ``` starting from a position
+// Returns the position after the closing ``` or -1 if not found
+func findNextClosingCodeBlock(text string, startIdx int) int {
+	for i := startIdx; i < len(text); i++ {
+		if i+2 < len(text) && text[i] == '`' && text[i+1] == '`' && text[i+2] == '`' {
+			return i + 3
+		}
+	}
+	return -1
+}
+
+// findLastNewline finds the last newline character within the last N characters
+// Returns the position of the newline or -1 if not found
+func findLastNewline(s string, searchWindow int) int {
+	searchStart := len(s) - searchWindow
+	if searchStart < 0 {
+		searchStart = 0
+	}
+	for i := len(s) - 1; i >= searchStart; i-- {
+		if s[i] == '\n' {
+			return i
+		}
+	}
+	return -1
+}
+
+// findLastSpace finds the last space character within the last N characters
+// Returns the position of the space or -1 if not found
+func findLastSpace(s string, searchWindow int) int {
+	searchStart := len(s) - searchWindow
+	if searchStart < 0 {
+		searchStart = 0
+	}
+	for i := len(s) - 1; i >= searchStart; i-- {
+		if s[i] == ' ' || s[i] == '\t' {
+			return i
+		}
+	}
+	return -1
+}