1 files changed, 364 insertions, 0 deletions
diff --git a/src/main/fileSyncBridge.ts b/src/main/fileSyncBridge.ts
new file mode 100644
index 0000000..e0529cb
--- /dev/null
+++ b/src/main/fileSyncBridge.ts
@@ -0,0 +1,364 @@
+// Bidirectional file sync bridge: temp dir ↔ Overleaf via OT
+import { join } from 'path'
+import { readFile, writeFile, mkdir } from 'fs/promises'
+import { createHash } from 'crypto'
+import * as chokidar from 'chokidar'
+import { diff_match_patch } from 'diff-match-patch'
+import type { BrowserWindow } from 'electron'
+import type { OverleafSocket } from './overleafSocket'
+import { OtClient } from './otClient'
+import type { OtOp } from './otTypes'
+import { isInsert, isDelete } from './otTypes'
+
+const dmp = new diff_match_patch()
+
+export class FileSyncBridge {
+  private lastKnownContent = new Map<string, string>()   // relPath → content
+  private writesInProgress = new Set<string>()            // relPaths being written by bridge
+  private debounceTimers = new Map<string, ReturnType<typeof setTimeout>>()
+  private otClients = new Map<string, OtClient>()         // docId → OtClient (non-editor docs)
+  private editorDocs = new Set<string>()                  // docIds owned by renderer
+  private watcher: chokidar.FSWatcher | null = null
+
+  private socket: OverleafSocket
+  private tmpDir: string
+  private docPathMap: Record<string, string>    // docId → relPath
+  private pathDocMap: Record<string, string>    // relPath → docId
+  private mainWindow: BrowserWindow
+
+  private serverEventHandler: ((name: string, args: unknown[]) => void) | null = null
+  private stopped = false
+
+  constructor(
+    socket: OverleafSocket,
+    tmpDir: string,
+    docPathMap: Record<string, string>,
+    pathDocMap: Record<string, string>,
+    mainWindow: BrowserWindow
+  ) {
+    this.socket = socket
+    this.tmpDir = tmpDir
+    this.docPathMap = docPathMap
+    this.pathDocMap = pathDocMap
+    this.mainWindow = mainWindow
+  }
+
+  async start(): Promise<void> {
+    // Join ALL docs, fetch content, write to disk
+    await mkdir(this.tmpDir, { recursive: true })
+
+    const docIds = Object.keys(this.docPathMap)
+    for (const docId of docIds) {
+      const relPath = this.docPathMap[docId]
+      try {
+        const result = await this.socket.joinDoc(docId)
+        const content = (result.docLines || []).join('\n')
+        this.lastKnownContent.set(relPath, content)
+
+        // Create OtClient for this doc (bridge owns it initially)
+        const otClient = new OtClient(
+          result.version,
+          (ops, version) => this.sendOps(docId, ops, version),
+          (ops) => this.onRemoteApply(docId, ops)
+        )
+        this.otClients.set(docId, otClient)
+
+        // Write to disk
+        await this.writeToDisk(relPath, content)
+      } catch (e) {
+        console.log(`[FileSyncBridge] failed to join doc ${relPath}:`, e)
+      }
+    }
+
+    // Listen for server events (remote ops on non-editor docs)
+    this.serverEventHandler = (name: string, args: unknown[]) => {
+      if (name === 'otUpdateApplied') {
+        const update = args[0] as { doc?: string; op?: OtOp[]; v?: number } | undefined
+        if (!update?.doc) return
+        const docId = update.doc
+
+        // For non-editor docs, process remote ops through bridge's OtClient
+        if (!this.editorDocs.has(docId) && update.op && update.v !== undefined) {
+          const otClient = this.otClients.get(docId)
+          if (otClient) {
+            otClient.onRemoteOps(update.op, update.v)
+          }
+        }
+
+        // For non-editor docs, handle ack (op with no ops array = ack for our own op)
+        if (!this.editorDocs.has(docId) && !update.op) {
+          const otClient = this.otClients.get(docId)
+          if (otClient) {
+            otClient.onAck()
+          }
+        }
+      }
+    }
+    this.socket.on('serverEvent', this.serverEventHandler)
+
+    // Start watching the temp dir
+    this.watcher = chokidar.watch(this.tmpDir, {
+      ignoreInitial: true,
+      awaitWriteFinish: { stabilityThreshold: 100, pollInterval: 50 },
+      ignored: [
+        /(^|[/\\])\../, // dotfiles
+        /\.(aux|log|pdf|fls|fdb_latexmk|synctex\.gz|bbl|blg|out|toc|lof|lot|nav|snm|vrb)$/ // LaTeX output files
+      ]
+    })
+
+    this.watcher.on('change', (absPath: string) => {
+      const relPath = absPath.replace(this.tmpDir + '/', '')
+      this.onFileChanged(relPath)
+    })
+
+    this.watcher.on('add', (absPath: string) => {
+      const relPath = absPath.replace(this.tmpDir + '/', '')
+      // Only process if it's a known doc
+      if (this.pathDocMap[relPath]) {
+        this.onFileChanged(relPath)
+      }
+    })
+
+    console.log(`[FileSyncBridge] started, watching ${this.tmpDir}, ${docIds.length} docs synced`)
+  }
+
+  async stop(): Promise<void> {
+    this.stopped = true
+
+    // Clear all debounce timers
+    for (const timer of this.debounceTimers.values()) {
+      clearTimeout(timer)
+    }
+    this.debounceTimers.clear()
+
+    // Remove server event handler
+    if (this.serverEventHandler) {
+      this.socket.removeListener('serverEvent', this.serverEventHandler)
+      this.serverEventHandler = null
+    }
+
+    // Close watcher
+    if (this.watcher) {
+      await this.watcher.close()
+      this.watcher = null
+    }
+
+    this.otClients.clear()
+    this.lastKnownContent.clear()
+    this.writesInProgress.clear()
+    this.editorDocs.clear()
+
+    console.log('[FileSyncBridge] stopped')
+  }
+
+  // ── Disk change handler ──────────────────────────────────────
+
+  private onFileChanged(relPath: string): void {
+    if (this.stopped) return
+
+    // Layer 1: Skip if bridge is currently writing this file
+    if (this.writesInProgress.has(relPath)) return
+
+    // Layer 3: Debounce 300ms per file
+    const existing = this.debounceTimers.get(relPath)
+    if (existing) clearTimeout(existing)
+
+    this.debounceTimers.set(relPath, setTimeout(() => {
+      this.debounceTimers.delete(relPath)
+      this.processChange(relPath)
+    }, 300))
+  }
+
+  private async processChange(relPath: string): Promise<void> {
+    if (this.stopped) return
+
+    const docId = this.pathDocMap[relPath]
+    if (!docId) return
+
+    let newContent: string
+    try {
+      newContent = await readFile(join(this.tmpDir, relPath), 'utf-8')
+    } catch {
+      return // file deleted or unreadable
+    }
+
+    const lastKnown = this.lastKnownContent.get(relPath)
+
+    // Layer 2: Content equality check
+    if (newContent === lastKnown) return
+
+    console.log(`[FileSyncBridge] disk change detected: ${relPath} (${(newContent.length)} chars)`)
+
+    if (this.editorDocs.has(docId)) {
+      // Doc is open in editor → send to renderer via IPC
+      this.lastKnownContent.set(relPath, newContent)
+      this.mainWindow.webContents.send('sync:externalEdit', { docId, content: newContent })
+    } else {
+      // Doc NOT open in editor → bridge handles OT directly
+      const oldContent = lastKnown ?? ''
+      this.lastKnownContent.set(relPath, newContent)
+
+      const diffs = dmp.diff_main(oldContent, newContent)
+      dmp.diff_cleanupEfficiency(diffs)
+      const ops = diffsToOtOps(diffs)
+
+      if (ops.length > 0) {
+        const otClient = this.otClients.get(docId)
+        if (otClient) {
+          otClient.onLocalOps(ops)
+        }
+      }
+    }
+  }
+
+  // ── Send OT ops to Overleaf (for non-editor docs) ───────────
+
+  private sendOps(docId: string, ops: OtOp[], version: number): void {
+    const relPath = this.docPathMap[docId]
+    const content = relPath ? this.lastKnownContent.get(relPath) ?? '' : ''
+    const hash = createHash('sha1').update(content).digest('hex')
+    this.socket.applyOtUpdate(docId, ops, version, hash)
+  }
+
+  // ── Apply remote ops (for non-editor docs) ──────────────────
+
+  private onRemoteApply(docId: string, ops: OtOp[]): void {
+    const relPath = this.docPathMap[docId]
+    if (!relPath) return
+
+    const currentContent = this.lastKnownContent.get(relPath) ?? ''
+    const newContent = applyOpsToText(currentContent, ops)
+    this.lastKnownContent.set(relPath, newContent)
+    this.writeToDisk(relPath, newContent)
+  }
+
+  // ── Called by main process when editor/remote changes content ─
+
+  /** Called when renderer notifies bridge that editor content changed */
+  onEditorContentChanged(docId: string, content: string): void {
+    const relPath = this.docPathMap[docId]
+    if (!relPath) return
+
+    // Update last known content
+    this.lastKnownContent.set(relPath, content)
+
+    // Write to disk so external tools can see the change
+    this.writeToDisk(relPath, content)
+  }
+
+  // ── Editor doc tracking ──────────────────────────────────────
+
+  /** Renderer opened this doc in the editor — bridge stops owning OT */
+  addEditorDoc(docId: string): void {
+    this.editorDocs.add(docId)
+    // Bridge's OtClient for this doc is no longer used (renderer has its own)
+    // But we keep the doc joined in the socket
+  }
+
+  /** Renderer closed this doc from the editor — bridge takes over OT */
+  removeEditorDoc(docId: string): void {
+    this.editorDocs.delete(docId)
+
+    // Re-join the doc to get fresh version, since renderer's OtClient was tracking it
+    const relPath = this.docPathMap[docId]
+    if (!relPath) return
+
+    this.socket.joinDoc(docId).then((result) => {
+      const content = (result.docLines || []).join('\n')
+      this.lastKnownContent.set(relPath, content)
+
+      // Create fresh OtClient with current version
+      const otClient = new OtClient(
+        result.version,
+        (ops, version) => this.sendOps(docId, ops, version),
+        (ops) => this.onRemoteApply(docId, ops)
+      )
+      this.otClients.set(docId, otClient)
+
+      // Write latest content to disk
+      this.writeToDisk(relPath, content)
+    }).catch((e) => {
+      console.log(`[FileSyncBridge] failed to re-join doc ${relPath}:`, e)
+    })
+  }
+
+  // ── Helpers ──────────────────────────────────────────────────
+
+  private async writeToDisk(relPath: string, content: string): Promise<void> {
+    const fullPath = join(this.tmpDir, relPath)
+    const dir = fullPath.substring(0, fullPath.lastIndexOf('/'))
+
+    // Set write guard
+    this.writesInProgress.add(relPath)
+
+    try {
+      await mkdir(dir, { recursive: true })
+      await writeFile(fullPath, content, 'utf-8')
+    } catch (e) {
+      console.log(`[FileSyncBridge] write error for ${relPath}:`, e)
+    }
+
+    // Clear write guard after 150ms (chokidar needs time to fire & be ignored)
+    setTimeout(() => {
+      this.writesInProgress.delete(relPath)
+    }, 150)
+  }
+
+  /** Get the temp dir path */
+  get dir(): string {
+    return this.tmpDir
+  }
+
+  /** Get content for a doc (used by compilation manager) */
+  getDocContent(relPath: string): string | undefined {
+    return this.lastKnownContent.get(relPath)
+  }
+
+  /** Check if a doc's content is known */
+  hasDoc(relPath: string): boolean {
+    return this.lastKnownContent.has(relPath)
+  }
+}
+
+// ── Utility functions ────────────────────────────────────────
+
+/** Convert diff-match-patch diffs to OT ops */
+function diffsToOtOps(diffs: [number, string][]): OtOp[] {
+  const ops: OtOp[] = []
+  let pos = 0
+
+  for (const [type, text] of diffs) {
+    switch (type) {
+      case 0: // DIFF_EQUAL
+        pos += text.length
+        break
+      case 1: // DIFF_INSERT
+        ops.push({ i: text, p: pos })
+        pos += text.length
+        break
+      case -1: // DIFF_DELETE
+        ops.push({ d: text, p: pos })
+        // Don't advance pos — deletion doesn't move cursor forward
+        break
+    }
+  }
+
+  return ops
+}
+
+/** Apply OT ops to a text string */
+function applyOpsToText(text: string, ops: OtOp[]): string {
+  // Sort ops by position descending so we can apply without position shifting
+  const sortedOps = [...ops].sort((a, b) => b.p - a.p)
+
+  for (const op of sortedOps) {
+    if (isInsert(op)) {
+      text = text.slice(0, op.p) + op.i + text.slice(op.p)
+    } else if (isDelete(op)) {
+      text = text.slice(0, op.p) + text.slice(op.p + op.d.length)
+    }
+    // Comment ops don't modify text
+  }
+
+  return text
+}