/**
 * Per-project graph persistence (localStorage).
 * Used by CanvasPage to load/save and by ProjectsTablePage for export.
 */

export const PROJECT_FILE_EXT = '.zui.json'
export const PROJECT_VERSION = 1

const GRAPH_KEY_PREFIX = 'zui_graph_'

export function getGraphStorageKey(projectId: string): string {
  return `${GRAPH_KEY_PREFIX}${projectId}`
}

export type GraphState = { version: number; nodes: unknown[]; edges: unknown[] }

export function loadGraphFromStorage(projectId: string): GraphState | null {
  try {
    const raw = localStorage.getItem(getGraphStorageKey(projectId))
    if (!raw) return null
    const data = JSON.parse(raw) as unknown
    if (!data || typeof data !== 'object' || !Array.isArray((data as GraphState).nodes) || !Array.isArray((data as GraphState).edges))
      return null
    return data as GraphState
  } catch {
    return null
  }
}

export function saveGraphToStorage(projectId: string, state: GraphState): void {
  localStorage.setItem(getGraphStorageKey(projectId), JSON.stringify(state))
}

export function removeGraphFromStorage(projectId: string): void {
  localStorage.removeItem(getGraphStorageKey(projectId))
}