feat(node-runtime): extract FTS5 index operations to shared package

Move core FTS operations (create, build, rebuild, insert, search) to
@openchatlab/node-runtime working with DatabaseAdapter. Electron fts.ts
becomes a thin adapter that adds session-level DB connection management.

Reduces Electron fts.ts from ~207 lines to ~90 lines of pure wrappers.

packages/node-runtime/src/fts/index.ts

@@ -0,0 +1,140 @@
+/**
+ * FTS5 full-text search index operations (platform-agnostic).
+ *
+ * Extracted from electron/main/worker/query/fts.ts.
+ * Works with DatabaseAdapter + NLP tokenizer from this package.
+ */
+
+import type { DatabaseAdapter } from '@openchatlab/core'
+import { FTS_TABLE_SCHEMA } from '@openchatlab/core'
+import { tokenizeForFts, tokenizeQueryForFts } from '../nlp'
+
+const BATCH_SIZE = 5000
+
+/**
+ * Check if FTS virtual table exists in the database.
+ */
+export function hasFtsTable(db: DatabaseAdapter): boolean {
+  try {
+    const row = db.prepare("SELECT name FROM sqlite_master WHERE type='table' AND name='message_fts'").get()
+    return !!row
+  } catch {
+    return false
+  }
+}
+
+/**
+ * Create FTS virtual table if it doesn't exist.
+ */
+export function createFtsTable(db: DatabaseAdapter): void {
+  db.exec(FTS_TABLE_SCHEMA)
+}
+
+/**
+ * Build FTS index from all text messages in the database.
+ * Processes in batches for memory efficiency.
+ */
+export function buildFtsIndex(db: DatabaseAdapter): { indexed: number } {
+  createFtsTable(db)
+
+  const insertFts = db.prepare('INSERT INTO message_fts(rowid, content) VALUES (?, ?)')
+
+  const countRow = db
+    .prepare("SELECT COUNT(*) as total FROM message WHERE type = 0 AND content IS NOT NULL AND content != ''")
+    .get() as { total: number } | undefined
+  const total = countRow?.total ?? 0
+
+  let indexed = 0
+  let offset = 0
+
+  while (offset < total) {
+    const rows = db
+      .prepare(
+        `SELECT id, content FROM message
+         WHERE type = 0 AND content IS NOT NULL AND content != ''
+         ORDER BY id ASC LIMIT ? OFFSET ?`
+      )
+      .all(BATCH_SIZE, offset) as Array<{ id: number; content: string }>
+
+    if (rows.length === 0) break
+
+    db.transaction(() => {
+      for (const row of rows) {
+        const tokens = tokenizeForFts(row.content)
+        if (tokens) {
+          insertFts.run(row.id, tokens)
+        }
+      }
+    })
+
+    indexed += rows.length
+    offset += BATCH_SIZE
+  }
+
+  return { indexed }
+}
+
+/**
+ * Rebuild FTS index by dropping and recreating.
+ */
+export function rebuildFtsIndex(db: DatabaseAdapter): { indexed: number } {
+  if (hasFtsTable(db)) {
+    db.exec('DROP TABLE message_fts')
+  }
+  return buildFtsIndex(db)
+}
+
+/**
+ * Insert FTS entries for a batch of messages.
+ * Used during incremental import to sync new messages.
+ */
+export function insertFtsEntries(db: DatabaseAdapter, entries: Array<{ id: number; content: string | null }>): void {
+  if (!hasFtsTable(db)) return
+
+  const insertFts = db.prepare('INSERT INTO message_fts(rowid, content) VALUES (?, ?)')
+
+  db.transaction(() => {
+    for (const entry of entries) {
+      if (entry.content) {
+        const tokens = tokenizeForFts(entry.content)
+        if (tokens) {
+          insertFts.run(entry.id, tokens)
+        }
+      }
+    }
+  })
+}
+
+/**
+ * Search messages using FTS5, returning matching rowids.
+ */
+export function searchByFts(
+  db: DatabaseAdapter,
+  keywords: string[],
+  limit = 1000,
+  offset = 0
+): { rowids: number[]; total: number } {
+  if (keywords.length === 0) return { rowids: [], total: 0 }
+
+  const matchQuery = tokenizeQueryForFts(keywords)
+  if (!matchQuery) return { rowids: [], total: 0 }
+
+  try {
+    const countRow = db.prepare('SELECT COUNT(*) as total FROM message_fts WHERE content MATCH ?').get(matchQuery) as
+      | { total: number }
+      | undefined
+    const total = countRow?.total ?? 0
+
+    const rows = db
+      .prepare(`SELECT rowid FROM message_fts WHERE content MATCH ? ORDER BY rank LIMIT ? OFFSET ?`)
+      .all(matchQuery, limit, offset) as Array<{ rowid: number }>
+
+    return {
+      rowids: rows.map((r) => r.rowid),
+      total,
+    }
+  } catch (error) {
+    console.error('[FTS] Search failed, query:', matchQuery, error)
+    return { rowids: [], total: 0 }
+  }
+}

packages/node-runtime/src/index.ts

@@ -11,6 +11,9 @@ export { BetterSqliteAdapter, openBetterSqliteDatabase } from './better-sqlite3-
 export { writeParseResultToDb } from './import'
 export type { ImportMeta, WriteParseResultStats } from './import'
 
+// FTS5 full-text search operations
+export { hasFtsTable, createFtsTable, buildFtsIndex, rebuildFtsIndex, insertFtsEntries, searchByFts } from './fts'
+
 // AI Logger
 export { AiLogger, extractErrorInfo, extractErrorStack } from './ai'
 export { NodePathProvider } from './node-path-provider'