import { LocalStorageUtility, StorageKey } from "Shared/StorageUtility";

// The component name whose state is being saved. Component name must not include special characters.
export type ComponentName = "DocumentsTab";

const SCHEMA_VERSION = 1;

// Export for testing purposes
export const MAX_ENTRY_NB = 100_000; // Limit number of entries to 100k

export interface StateData {
  schemaVersion: number;
  timestamp: number;
  data: unknown;
}

type StorePath = {
  componentName: string;
  subComponentName?: string;
  globalAccountName?: string;
  databaseName?: string;
  containerName?: string;
};

// Load and save state data
export const loadState = (path: StorePath): unknown => {
  const appState =
    LocalStorageUtility.getEntryObject<ApplicationState>(StorageKey.AppState) || ({} as ApplicationState);
  const key = createKeyFromPath(path);
  return appState[key]?.data;
};
export const saveState = (path: StorePath, state: unknown): void => {
  // Retrieve state object
  const appState =
    LocalStorageUtility.getEntryObject<ApplicationState>(StorageKey.AppState) || ({} as ApplicationState);
  const key = createKeyFromPath(path);
  appState[key] = {
    schemaVersion: SCHEMA_VERSION,
    timestamp: Date.now(),
    data: state,
  };

  if (Object.keys(appState).length > MAX_ENTRY_NB) {
    // Remove the oldest entry
    const oldestKey = Object.keys(appState).reduce((oldest, current) =>
      appState[current].timestamp < appState[oldest].timestamp ? current : oldest,
    );
    delete appState[oldestKey];
  }

  LocalStorageUtility.setEntryObject(StorageKey.AppState, appState);
};

export const deleteState = (path: StorePath): void => {
  // Retrieve state object
  const appState =
    LocalStorageUtility.getEntryObject<ApplicationState>(StorageKey.AppState) || ({} as ApplicationState);
  const key = createKeyFromPath(path);
  delete appState[key];
  LocalStorageUtility.setEntryObject(StorageKey.AppState, appState);
};

// This is for high-frequency state changes
let timeoutId: NodeJS.Timeout | undefined;
export const saveStateDebounced = (path: StorePath, state: unknown, debounceDelayMs = 1000): void => {
  if (timeoutId) {
    clearTimeout(timeoutId);
  }
  timeoutId = setTimeout(() => saveState(path, state), debounceDelayMs);
};

interface ApplicationState {
  [statePath: string]: StateData;
}

const orderedPathSegments: (keyof StorePath)[] = [
  "subComponentName",
  "globalAccountName",
  "databaseName",
  "containerName",
];

/**
 * /componentName/subComponentName/globalAccountName/databaseName/containerName/
 * Any of the path segments can be "" except componentName
 * Export for testing purposes
 * @param path
 */
export const createKeyFromPath = (path: StorePath): string => {
  if (path.componentName.includes("/")) {
    throw new Error(`Invalid component name: ${path.componentName}`);
  }
  let key = `/${path.componentName}`; // ComponentName is always there
  orderedPathSegments.forEach((segment) => {
    const segmentValue = path[segment as keyof StorePath];
    if (segmentValue.includes("/")) {
      throw new Error(`Invalid setting path segment: ${segment}`);
    }
    key += `/${segmentValue !== undefined ? segmentValue : ""}`;
  });
  return key;
};

/**
 * Remove the entire app state key from local storage
 */
export const deleteAllStates = (): void => {
  LocalStorageUtility.removeEntry(StorageKey.AppState);
};