feat: add sync service with WebDAV merge logic

src/sync/syncService.ts

@@ -0,0 +1,90 @@
+import { Measurement } from '../types'
+import { initDatabase, getAllMeasurements, upsertMeasurement } from '../database/db'
+import { getWebDAVConfig } from '../screens/SettingsScreen'
+
+const WEBDAV_PATH = 'weegschaal/measurements.json'
+
+type SyncResult = { local: number; remote: number; merged: number }
+
+export function mergeMeasurements(local: Measurement[], remote: Measurement[]): Measurement[] {
+  const map = new Map<string, Measurement>()
+
+  for (const m of local) {
+    map.set(m.id, m)
+  }
+
+  for (const m of remote) {
+    const existing = map.get(m.id)
+    if (!existing || new Date(m.updatedAt) > new Date(existing.updatedAt)) {
+      map.set(m.id, { ...m, syncStatus: 'synced' })
+    }
+  }
+
+  return Array.from(map.values())
+}
+
+async function fetchRemote(config: { url: string; username: string; password: string }): Promise<Measurement[]> {
+  const url = `${config.url.replace(/\/+$/, '')}/${WEBDAV_PATH}`
+  const response = await fetch(url, {
+    headers: {
+      Authorization: 'Basic ' + btoa(`${config.username}:${config.password}`),
+    },
+  })
+
+  if (response.status === 404) {
+    return []
+  }
+
+  if (!response.ok) {
+    throw new Error(`WebDAV fetch failed: ${response.status}`)
+  }
+
+  return response.json()
+}
+
+async function uploadRemote(
+  config: { url: string; username: string; password: string },
+  measurements: Measurement[]
+): Promise<void> {
+  const url = `${config.url.replace(/\/+$/, '')}/${WEBDAV_PATH}`
+  const body = JSON.stringify(measurements)
+
+  const response = await fetch(url, {
+    method: 'PUT',
+    headers: {
+      Authorization: 'Basic ' + btoa(`${config.username}:${config.password}`),
+      'Content-Type': 'application/json',
+    },
+    body,
+  })
+
+  if (!response.ok) {
+    throw new Error(`WebDAV upload failed: ${response.status}`)
+  }
+}
+
+export async function syncAll(): Promise<SyncResult> {
+  const config = await getWebDAVConfig()
+  if (!config) {
+    throw new Error('Geen WebDAV configuratie. Stel deze eerst in in Instellingen.')
+  }
+
+  await initDatabase()
+
+  const local = await getAllMeasurements()
+  const remote = await fetchRemote(config)
+
+  const merged = mergeMeasurements(local, remote)
+
+  for (const m of merged) {
+    await upsertMeasurement(m)
+  }
+
+  await uploadRemote(config, merged)
+
+  return {
+    local: local.length,
+    remote: remote.length,
+    merged: merged.length,
+  }
+}