refactor(ui): isolate session components (#33670)

packages/session-ui/src/components/session-diff.ts

@@ -0,0 +1,144 @@
+import { parseDiffFromFile, parsePatchFiles, type FileDiffMetadata } from "@pierre/diffs"
+import { parsePatch } from "diff"
+import type { SnapshotFileDiff, VcsFileDiff } from "@opencode-ai/sdk/v2"
+
+type LegacyDiff = {
+  file: string
+  patch?: string
+  before?: string
+  after?: string
+  additions: number
+  deletions: number
+  status?: "added" | "deleted" | "modified"
+}
+
+type SnapshotDiff = SnapshotFileDiff & { file: string }
+type ReviewDiff = SnapshotDiff | VcsFileDiff | LegacyDiff
+export type DiffSource = Pick<LegacyDiff, "file" | "patch" | "before" | "after">
+
+export type ViewDiff = {
+  file: string
+  additions: number
+  deletions: number
+  status?: "added" | "deleted" | "modified"
+  fileDiff: FileDiffMetadata
+}
+
+const diffCacheLimit = 16
+const patchFileDiffCache = new Map<string, FileDiffMetadata>()
+
+export function resolveFileDiff(diff: DiffSource) {
+  if (typeof diff.patch === "string") return fileDiffFromPatch(diff.file, diff.patch)
+  return fileDiffFromContent(
+    diff.file,
+    typeof diff.before === "string" ? diff.before : "",
+    typeof diff.after === "string" ? diff.after : "",
+  )
+}
+
+export function normalize(diff: ReviewDiff): ViewDiff {
+  return {
+    file: diff.file,
+    additions: diff.additions,
+    deletions: diff.deletions,
+    status: diff.status,
+    fileDiff: resolveFileDiff(diff),
+  }
+}
+
+export function text(diff: ViewDiff, side: "deletions" | "additions") {
+  if (side === "deletions") return diff.fileDiff.deletionLines.join("")
+  return diff.fileDiff.additionLines.join("")
+}
+
+function fileDiffFromPatch(file: string, patch: string) {
+  const key = `${file}\0${patch}`
+  const hit = patchFileDiffCache.get(key)
+  if (hit) {
+    patchFileDiffCache.delete(key)
+    patchFileDiffCache.set(key, hit)
+    return hit
+  }
+
+  const contents = completePatchContents(patch)
+  const input = contents ? undefined : patchInput(file, patch)
+  const value = contents
+    ? fileDiffFromContent(file, contents.before, contents.after)
+    : ((input ? parsePatchFiles(input)[0]?.files[0] : undefined) ?? emptyFileDiff(file))
+  patchFileDiffCache.set(key, value)
+  while (patchFileDiffCache.size > diffCacheLimit) patchFileDiffCache.delete(patchFileDiffCache.keys().next().value!)
+  return value
+}
+
+function completePatchContents(patch: string) {
+  try {
+    const parsed = parsePatch(patch)[0]
+    if (!parsed || (!parsed.index && !parsed.oldFileName && !parsed.newFileName)) return
+    // Snapshot and VCS producers request full context. Tool patches use jsdiff's shorter default context.
+    if (!patch.startsWith("diff --git ") && !/^--- [^\n]*\t\r?\n\+\+\+ [^\n]*\t(?:\r?\n|$)/m.test(patch)) return
+    // Full patches collapse into one leading hunk. Separated hunks omit ranges and must stay partial.
+    if (parsed.hunks.length !== 1) return
+
+    const hunk = parsed.hunks[0]
+    if (!hunk || hunk.oldStart > 1 || hunk.newStart > 1) return
+
+    const before: Array<{ text: string; newline: boolean }> = []
+    const after: Array<{ text: string; newline: boolean }> = []
+    let previous: "-" | "+" | " " | undefined
+
+    for (const line of hunk.lines) {
+      if (line.startsWith("\\")) {
+        if (previous === "-" || previous === " ") {
+          const value = before.at(-1)
+          if (value) value.newline = false
+        }
+        if (previous === "+" || previous === " ") {
+          const value = after.at(-1)
+          if (value) value.newline = false
+        }
+        continue
+      }
+      if (line.startsWith("-")) {
+        before.push({ text: line.slice(1), newline: true })
+        previous = "-"
+        continue
+      }
+      if (line.startsWith("+")) {
+        after.push({ text: line.slice(1), newline: true })
+        previous = "+"
+        continue
+      }
+      if (!line.startsWith(" ")) return
+      before.push({ text: line.slice(1), newline: true })
+      after.push({ text: line.slice(1), newline: true })
+      previous = " "
+    }
+
+    const text = (lines: Array<{ text: string; newline: boolean }>) =>
+      lines.map((line) => line.text + (line.newline ? "\n" : "")).join("")
+    return { before: text(before), after: text(after) }
+  } catch {
+    return
+  }
+}
+
+function patchInput(file: string, patch: string) {
+  try {
+    const parsed = parsePatch(patch)[0]
+    if (!parsed) return
+    if (parsed.index || parsed.oldFileName || parsed.newFileName) return patch
+    if (!parsed.hunks.length) return
+    return `Index: ${file}\n===================================================================\n--- ${file}\t\n+++ ${file}\t\n${patch}`
+  } catch {
+    return
+  }
+}
+
+function fileDiffFromContent(file: string, before: string, after: string) {
+  if (!before && !after) return emptyFileDiff(file)
+  return parseDiffFromFile({ name: file, contents: before }, { name: file, contents: after })
+}
+
+function emptyFileDiff(file: string) {
+  return parseDiffFromFile({ name: file, contents: "" }, { name: file, contents: "" })
+}