优化消息里读/写内容显示样式

src/lib/session-files.ts

@@ -1,5 +1,6 @@
 import type { MessageTurn } from "./types"
 import { normalizeToolName } from "./tool-call-normalization"
+import { generateUnifiedDiff } from "./unified-diff-generator"
 
 export type FileOperation = "read" | "edit" | "write" | "apply_patch"
 
@@ -266,32 +267,12 @@ function countDiffLines(text: string): DiffStat {
   return { additions, deletions }
 }
 
-function createHunkHeader(oldLineCount: number, newLineCount: number): string {
-  const oldStart = oldLineCount === 0 ? 0 : 1
-  const newStart = newLineCount === 0 ? 0 : 1
-  return `@@ -${oldStart},${oldLineCount} +${newStart},${newLineCount} @@`
-}
-
 function buildUnifiedDiff(
   filePath: string,
   oldText: string,
   newText: string
 ): string | null {
-  if (!oldText && !newText) return null
-
-  const oldLines = oldText ? oldText.split("\n") : []
-  const newLines = newText ? newText.split("\n") : []
-
-  const lines: string[] = [
-    `--- a/${filePath}`,
-    `+++ b/${filePath}`,
-    createHunkHeader(oldLines.length, newLines.length),
-  ]
-
-  for (const line of oldLines) lines.push(`-${line}`)
-  for (const line of newLines) lines.push(`+${line}`)
-
-  return lines.join("\n")
+  return generateUnifiedDiff(oldText, newText, filePath)
 }
 
 function parseEditChangeValue(value: unknown): EditChangePreview | null {

src/lib/unified-diff-generator.ts

@@ -0,0 +1,180 @@
+import { computeLineDiff, type DiffHunk } from "@/components/merge/merge-diff"
+
+/**
+ * Maximum product of line counts before falling back to naive diff.
+ * Avoids O(n*m) LCS blowup for very large inputs.
+ */
+const LCS_PAIR_BUDGET = 200_000
+
+/**
+ * Generate a unified diff string from old and new text.
+ *
+ * Uses LCS-based line diff when within budget, falls back to
+ * simple "all deletions then all additions" for very large inputs.
+ */
+export function generateUnifiedDiff(
+  oldText: string,
+  newText: string,
+  filePath?: string,
+  contextLines: number = 3
+): string | null {
+  if (!oldText && !newText) return null
+  if (oldText === newText) return null
+
+  const oldLines = oldText ? splitLines(oldText) : []
+  const newLines = newText ? splitLines(newText) : []
+
+  const path = filePath ?? "file"
+  const header = `--- a/${path}\n+++ b/${path}`
+
+  // Performance gate: fall back to naive diff for large inputs
+  if (oldLines.length * newLines.length > LCS_PAIR_BUDGET) {
+    return buildNaiveDiff(header, oldLines, newLines)
+  }
+
+  const hunks = computeLineDiff(oldLines, newLines)
+  if (hunks.length === 0) return null
+
+  const unifiedHunks = buildUnifiedHunks(oldLines, hunks, contextLines)
+
+  return `${header}\n${unifiedHunks}`
+}
+
+function splitLines(text: string): string[] {
+  const lines = text.split("\n")
+  // Remove trailing empty line from trailing newline
+  if (lines.length > 0 && lines[lines.length - 1] === "") {
+    lines.pop()
+  }
+  return lines
+}
+
+/**
+ * Naive diff: all deletions first, then all additions, with a single hunk header.
+ * Used as fallback when inputs are too large for LCS.
+ */
+function buildNaiveDiff(
+  header: string,
+  oldLines: string[],
+  newLines: string[]
+): string {
+  const oldStart = oldLines.length === 0 ? 0 : 1
+  const newStart = newLines.length === 0 ? 0 : 1
+  const hunkHeader = `@@ -${oldStart},${oldLines.length} +${newStart},${newLines.length} @@`
+
+  const parts = [header, hunkHeader]
+  for (const line of oldLines) parts.push(`-${line}`)
+  for (const line of newLines) parts.push(`+${line}`)
+  return parts.join("\n")
+}
+
+/**
+ * Convert DiffHunk[] into unified diff text with context lines and hunk headers.
+ *
+ * Groups nearby hunks that overlap in their context windows into a single
+ * unified hunk, producing output similar to `diff -u`.
+ */
+function buildUnifiedHunks(
+  oldLines: string[],
+  hunks: DiffHunk[],
+  contextLines: number
+): string {
+  // Build "change regions" with context, then merge overlapping ones
+  const regions = hunks.map((hunk) => ({
+    // Context-expanded range in old lines
+    ctxOldStart: Math.max(0, hunk.baseStart - contextLines),
+    ctxOldEnd: Math.min(
+      oldLines.length,
+      hunk.baseStart + hunk.baseCount + contextLines
+    ),
+    hunk,
+  }))
+
+  // Merge overlapping regions
+  const merged: {
+    ctxOldStart: number
+    ctxOldEnd: number
+    hunks: DiffHunk[]
+  }[] = []
+
+  for (const region of regions) {
+    const last = merged[merged.length - 1]
+    if (last && region.ctxOldStart <= last.ctxOldEnd) {
+      // Overlapping — extend and add hunk
+      last.ctxOldEnd = Math.max(last.ctxOldEnd, region.ctxOldEnd)
+      last.hunks.push(region.hunk)
+    } else {
+      merged.push({
+        ctxOldStart: region.ctxOldStart,
+        ctxOldEnd: region.ctxOldEnd,
+        hunks: [region.hunk],
+      })
+    }
+  }
+
+  // Render each merged region as a unified hunk
+  const output: string[] = []
+
+  for (const group of merged) {
+    const lines: string[] = []
+    let oldCursor = group.ctxOldStart
+    let newLineCount = 0
+    const oldLineCount = group.ctxOldEnd - group.ctxOldStart
+
+    for (const hunk of group.hunks) {
+      // Context lines before this change
+      while (oldCursor < hunk.baseStart) {
+        lines.push(` ${oldLines[oldCursor]}`)
+        newLineCount++
+        oldCursor++
+      }
+
+      // Deleted lines
+      for (let i = 0; i < hunk.baseCount; i++) {
+        lines.push(`-${oldLines[hunk.baseStart + i]}`)
+        oldCursor++
+      }
+
+      // Added lines
+      for (const newLine of hunk.newLines) {
+        lines.push(`+${newLine}`)
+        newLineCount++
+      }
+    }
+
+    // Trailing context
+    while (oldCursor < group.ctxOldEnd) {
+      lines.push(` ${oldLines[oldCursor]}`)
+      newLineCount++
+      oldCursor++
+    }
+
+    // Compute hunk header
+    const oldStart = oldLineCount === 0 ? 0 : group.ctxOldStart + 1
+    const newStart =
+      newLineCount === 0
+        ? 0
+        : group.ctxOldStart +
+          1 +
+          computeNewOffset(group.hunks, group.ctxOldStart)
+
+    output.push(
+      `@@ -${oldStart},${oldLineCount} +${newStart},${newLineCount} @@`
+    )
+    output.push(...lines)
+  }
+
+  return output.join("\n")
+}
+
+/**
+ * Compute the offset applied to new-line numbering by hunks before a given position.
+ */
+function computeNewOffset(hunks: DiffHunk[], beforeOldLine: number): number {
+  let offset = 0
+  for (const hunk of hunks) {
+    if (hunk.baseStart >= beforeOldLine) break
+    offset += hunk.newLines.length - hunk.baseCount
+  }
+  return offset
+}