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,
  }
}