import { INITIAL_EXERCISE_LIST_FILTERS, mergeExerciseListPrefsFromApi } from '../constants/exerciseListFilters'
import { normalizeSelectedEntries } from './exerciseListSelection'

const STORAGE_KEY = 'shinkan.exerciseList.session.v1'

function safeParse(raw) {
  if (!raw) return null
  try {
    return JSON.parse(raw)
  } catch {
    return null
  }
}

/** @returns {{ filters: object, searchInput: string, aiSearchInput: string, mineOnly: boolean, selectedEntries: object[] } | null} */
export function readExerciseListSessionState() {
  if (typeof sessionStorage === 'undefined') return null
  const parsed = safeParse(sessionStorage.getItem(STORAGE_KEY))
  if (!parsed || typeof parsed !== 'object') return null

  const filters =
    parsed.filters && typeof parsed.filters === 'object'
      ? mergeExerciseListPrefsFromApi(parsed.filters)
      : { ...INITIAL_EXERCISE_LIST_FILTERS }

  return {
    filters,
    searchInput: typeof parsed.searchInput === 'string' ? parsed.searchInput : '',
    aiSearchInput: typeof parsed.aiSearchInput === 'string' ? parsed.aiSearchInput : '',
    mineOnly: !!parsed.mineOnly,
    selectedEntries: normalizeSelectedEntries(parsed.selectedEntries),
  }
}

export function writeExerciseListSessionState(state) {
  if (typeof sessionStorage === 'undefined' || !state || typeof state !== 'object') return
  try {
    sessionStorage.setItem(
      STORAGE_KEY,
      JSON.stringify({
        filters: state.filters ?? { ...INITIAL_EXERCISE_LIST_FILTERS },
        searchInput: typeof state.searchInput === 'string' ? state.searchInput : '',
        aiSearchInput: typeof state.aiSearchInput === 'string' ? state.aiSearchInput : '',
        mineOnly: !!state.mineOnly,
        selectedEntries: normalizeSelectedEntries(state.selectedEntries),
      })
    )
  } catch {
    /* quota / private mode */
  }
}