import type { Database } from 'sql.js'
import type { Entry } from './types'
import { getMeta, persistDb, setMeta, upsertEntries } from './db'

const LAST_SYNC_KEY = 'last_sync_at'

export async function syncEntries(db: Database) {
  const lastSyncAt = getMeta(db, LAST_SYNC_KEY)
  const url = new URL('https://sanasto.wiki/api/entries')
  if (lastSyncAt) {
    url.searchParams.set('since', lastSyncAt)
  }

  const response = await fetch(url.toString(), {
    headers: {
      'X-Sanasto-App': 'app.sanasto',
    },
  })
  if (!response.ok) {
    throw new Error(`Sync failed with ${response.status}`)
  }

  const entries = (await response.json()) as Entry[]
  if (entries.length === 0) {
    return { updated: 0, lastSyncAt }
  }

  upsertEntries(db, entries)

  const newest = entries.reduce<Date | null>((current, entry) => {
    if (!entry.updated_at) {
      return current
    }
    const date = new Date(entry.updated_at)
    if (!current || date > current) {
      return date
    }
    return current
  }, lastSyncAt ? new Date(lastSyncAt) : null)

  if (newest) {
    setMeta(db, LAST_SYNC_KEY, newest.toISOString())
  }

  await persistDb(db)

  return { updated: entries.length, lastSyncAt: newest?.toISOString() ?? lastSyncAt }
}