// Thin client for the OTIVM save and map APIs
// Backend: GET /api/save/:token  — load state
//          POST /api/save/:token — write state
//          GET /api/map/:h5/:epoch — H7 land/sea cells for one waypoint at one epoch

const BASE_SAVE = '/api/save'
const BASE_MAP  = '/api/map'

// Generate a random 8-character hex token
export function generateToken() {
  return Array.from(crypto.getRandomValues(new Uint8Array(4)))
    .map((b) => b.toString(16).padStart(2, '0'))
    .join('')
}

// Load state from server — returns parsed state object or null
export async function loadState(token) {
  try {
    const res = await fetch(`${BASE_SAVE}/${token}`)
    if (!res.ok) return null
    return await res.json()
  } catch {
    return null
  }
}

// Save state to server — returns true on success
export async function saveState(token, state) {
  try {
    const res = await fetch(`${BASE_SAVE}/${token}`, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' },
      body: JSON.stringify(state),
    })
    return res.ok
  } catch {
    return false
  }
}

// Fetch H7 land/sea classification for one H5 waypoint at one named epoch.
// h5: H3 res-5 hex string (e.g. '851e805bfffffff')
// epochKey: named epoch from paleo_epochs (e.g. 'roman_14bce')
// Returns: { epoch_key, sl_offset_cm, h5, cells: [{ h7, h7_land, h9_total, is_land }] }
// Returns null on any error.
export async function fetchMapCells(h5, epochKey) {
  try {
    const res = await fetch(`${BASE_MAP}/${h5}/${epochKey}`)
    if (!res.ok) return null
    return await res.json()
  } catch {
    return null
  }
}