fix(tui): handle Zed selection byte offsets (#24825)

2 files changed, 135 insertions, 5 deletions

diff --git a/packages/opencode/src/cli/cmd/tui/context/editor-zed.ts b/packages/opencode/src/cli/cmd/tui/context/editor-zed.ts
index 40063dc70..00f90857c 100644
--- a/packages/opencode/src/cli/cmd/tui/context/editor-zed.ts
+++ b/packages/opencode/src/cli/cmd/tui/context/editor-zed.ts
@@ -20,6 +20,8 @@ const ZedEditorContentsSchema = z.object({
   contents: z.string().nullable(),
 })
 
+const utf8 = new TextEncoder()
+
 type ZedEditorRow = z.infer<typeof ZedEditorRowSchema>
 type ZedActiveEditorRow = ZedEditorRow & { item_kind: "Editor"; editor_id: number }
 
@@ -45,8 +47,8 @@ export async function resolveZedSelection(dbPath: string, cwd = process.cwd()):
           .catch(() => undefined)
   if (text == null) return { type: "unavailable" }
 
-  const startOffset = Math.min(row.selection_start, row.selection_end)
-  const endOffset = Math.max(row.selection_start, row.selection_end)
+  const startOffset = utf8ByteOffsetToStringIndex(text, Math.min(row.selection_start, row.selection_end))
+  const endOffset = utf8ByteOffsetToStringIndex(text, Math.max(row.selection_start, row.selection_end))
 
   return {
     type: "selection",
@@ -158,7 +160,25 @@ function zedWorkspacePaths(value: string | null) {
 }
 
 export function offsetToPosition(text: string, offset: number) {
-  return offsetsToSelection(text, offset, offset).start
+  const stringOffset = utf8ByteOffsetToStringIndex(text, offset)
+  return offsetsToSelection(text, stringOffset, stringOffset).start
+}
+
+function utf8ByteOffsetToStringIndex(text: string, byteOffset: number) {
+  if (byteOffset <= 0) return 0
+
+  let bytes = 0
+  for (let index = 0; index < text.length; ) {
+    const codePoint = text.codePointAt(index)
+    if (codePoint === undefined) return text.length
+
+    const nextIndex = index + (codePoint > 0xffff ? 2 : 1)
+    bytes += utf8.encode(text.slice(index, nextIndex)).length
+    if (bytes >= byteOffset) return nextIndex
+    index = nextIndex
+  }
+
+  return text.length
 }
 
 function offsetsToSelection(text: string, startOffset: number, endOffset: number) {
diff --git a/packages/opencode/test/cli/tui/editor-context.test.ts b/packages/opencode/test/cli/tui/editor-context.test.ts
index 767eeb8ec..4c5491461 100644
--- a/packages/opencode/test/cli/tui/editor-context.test.ts
+++ b/packages/opencode/test/cli/tui/editor-context.test.ts
@@ -10,12 +10,14 @@ type ZedFixtureOptions = {
   editor?: boolean
   selectionStart?: number | null
   selectionEnd?: number | null
+  contents?: string
 }
 
 async function writeZedFixture(dir: string, options: ZedFixtureOptions = {}) {
   const dbPath = path.join(dir, "zed.sqlite")
   const filePath = path.join(dir, "file.ts")
-  await Bun.write(filePath, "one\ntwo\nthree")
+  const contents = options.contents ?? "one\ntwo\nthree"
+  await Bun.write(filePath, contents)
 
   const db = new Database(dbPath)
   db.run("create table workspaces (workspace_id integer, paths text, timestamp text)")
@@ -27,7 +29,7 @@ async function writeZedFixture(dir: string, options: ZedFixtureOptions = {}) {
   db.run("insert into panes values (1, 1, 1)")
   db.run("insert into items values (1, 1, 1, 1, ?)", [options.itemKind ?? "Editor"])
   if (options.editor !== false) {
-    db.run("insert into editors values (1, 1, ?, ?)", [filePath, "one\ntwo\nthree"])
+    db.run("insert into editors values (1, 1, ?, ?)", [filePath, contents])
     db.run("insert into editor_selections values (1, 1, ?, ?)", [
       options.selectionStart === undefined ? 4 : options.selectionStart,
       options.selectionEnd === undefined ? 7 : options.selectionEnd,
@@ -38,11 +40,23 @@ async function writeZedFixture(dir: string, options: ZedFixtureOptions = {}) {
   return { dbPath, filePath }
 }
 
+function utf8ByteOffset(text: string, offset: number) {
+  return new TextEncoder().encode(text.slice(0, offset)).length
+}
+
 test("offsetToPosition converts Zed offsets to 1-based editor positions", () => {
   expect(offsetToPosition("one\ntwo\nthree", 0)).toEqual({ line: 1, character: 1 })
   expect(offsetToPosition("one\ntwo\nthree", 4)).toEqual({ line: 2, character: 1 })
   expect(offsetToPosition("one\ntwo\nthree", 6)).toEqual({ line: 2, character: 3 })
   expect(offsetToPosition("one\ntwo\nthree", 100)).toEqual({ line: 3, character: 6 })
+  expect(offsetToPosition("Ж\nabc", utf8ByteOffset("Ж\nabc", "Ж\nabc".indexOf("a")))).toEqual({
+    line: 2,
+    character: 1,
+  })
+  expect(offsetToPosition("😀\nabc", utf8ByteOffset("😀\nabc", "😀\nabc".indexOf("a")))).toEqual({
+    line: 2,
+    character: 1,
+  })
 })
 
 test("resolveZedSelection returns active editor selection", async () => {
@@ -63,6 +77,102 @@ test("resolveZedSelection returns active editor selection", async () => {
   })
 })
 
+test("resolveZedSelection converts Zed UTF-8 byte offsets to string offsets", async () => {
+  await using tmp = await tmpdir()
+  const contents = "a\nЖЖЖЖЖЖЖЖЖЖ\nb\nTARGET\nz"
+  const start = contents.indexOf("TARGET")
+  const fixture = await writeZedFixture(tmp.path, {
+    contents,
+    selectionStart: utf8ByteOffset(contents, start),
+    selectionEnd: utf8ByteOffset(contents, start + "TARGET".length),
+  })
+
+  expect(await resolveZedSelection(fixture.dbPath, tmp.path)).toEqual({
+    type: "selection",
+    selection: {
+      text: "TARGET",
+      filePath: fixture.filePath,
+      source: "zed",
+      selection: {
+        start: { line: 4, character: 1 },
+        end: { line: 4, character: 7 },
+      },
+    },
+  })
+})
+
+test("resolveZedSelection handles non-ASCII text inside the selected range", async () => {
+  await using tmp = await tmpdir()
+  const contents = "a\npre\nвыбор\nz"
+  const start = contents.indexOf("выбор")
+  const fixture = await writeZedFixture(tmp.path, {
+    contents,
+    selectionStart: utf8ByteOffset(contents, start),
+    selectionEnd: utf8ByteOffset(contents, start + "выбор".length),
+  })
+
+  expect(await resolveZedSelection(fixture.dbPath, tmp.path)).toEqual({
+    type: "selection",
+    selection: {
+      text: "выбор",
+      filePath: fixture.filePath,
+      source: "zed",
+      selection: {
+        start: { line: 3, character: 1 },
+        end: { line: 3, character: 6 },
+      },
+    },
+  })
+})
+
+test("resolveZedSelection handles emoji before the selected range", async () => {
+  await using tmp = await tmpdir()
+  const contents = "😀\nTARGET\nz"
+  const start = contents.indexOf("TARGET")
+  const fixture = await writeZedFixture(tmp.path, {
+    contents,
+    selectionStart: utf8ByteOffset(contents, start),
+    selectionEnd: utf8ByteOffset(contents, start + "TARGET".length),
+  })
+
+  expect(await resolveZedSelection(fixture.dbPath, tmp.path)).toEqual({
+    type: "selection",
+    selection: {
+      text: "TARGET",
+      filePath: fixture.filePath,
+      source: "zed",
+      selection: {
+        start: { line: 2, character: 1 },
+        end: { line: 2, character: 7 },
+      },
+    },
+  })
+})
+
+test("resolveZedSelection handles reversed Zed byte offsets", async () => {
+  await using tmp = await tmpdir()
+  const contents = "a\nЖЖЖ\nTARGET\nz"
+  const start = contents.indexOf("TARGET")
+  const fixture = await writeZedFixture(tmp.path, {
+    contents,
+    selectionStart: utf8ByteOffset(contents, start + "TARGET".length),
+    selectionEnd: utf8ByteOffset(contents, start),
+  })
+
+  expect(await resolveZedSelection(fixture.dbPath, tmp.path)).toEqual({
+    type: "selection",
+    selection: {
+      text: "TARGET",
+      filePath: fixture.filePath,
+      source: "zed",
+      selection: {
+        start: { line: 3, character: 1 },
+        end: { line: 3, character: 7 },
+      },
+    },
+  })
+})
+
 test("resolveZedSelection returns empty when no workspace matches", async () => {
   await using tmp = await tmpdir()
   const fixture = await writeZedFixture(tmp.path, {