import browser from "webextension-polyfill";
import {createValue, type Value} from "@holllo/webextension-storage";

/** A queued item. */
export type Item = {
  /** The date when the item was added. */
  dateAdded: Date;

  /** The unique ID for this item. */
  id: number;

  /**
   * The display text of the item.
   *
   * This can be undefined when the context menu doesn't have access to the text
   * like when a tab's context menu is used.
   */
  text: string | undefined;

  /** The URL of the item. */
  url: string;
};

/** A serialized representation of {@link Item} for use in storage. */
export type SerializedItem = {
  // Create an index signature with every key from Item and the type for each
  // as `string`.
  [k in keyof Item]: string;
};

/** The key prefix for {@link Item}s. */
export type ItemKeyPrefix = "item-" | "history-";

export function storageForPrefix(
  prefix: ItemKeyPrefix,
): browser.Storage.StorageArea {
  return prefix === "item-" ? browser.storage.sync : browser.storage.local;
}

/**
 * Serialize and JSON-stringify an {@link Item}.
 *
 * @param input The {@link Item} to serialize.
 * @returns The serialized {@link Item} string.
 */
export const serializeItem: Value<Item>["serialize"] = (
  input: Item,
): string => {
  const serialized: SerializedItem = {
    dateAdded: input.dateAdded.toISOString(),
    id: input.id.toString(),
    text: input.text ?? "",
    url: input.url,
  };

  return JSON.stringify(serialized);
};

/**
 * Deserialize and JSON-parse an {@link Item} from a string.
 *
 * This function should only ever be used with {@link Value} as this
 * doesn't do any validation. With {@link Value} it's reasonable to assume
 * the input will actually deserialize to an {@link Item}.
 *
 * @param input The {@link Item} string to deserialize.
 * @returns The deserialized {@link Item}.
 */
export const deserializeItem: Value<Item>["deserialize"] = (
  input: string,
): Item => {
  const parsed = JSON.parse(input) as SerializedItem;

  return {
    dateAdded: new Date(parsed.dateAdded),
    id: Number(parsed.id),
    // In `serializeItem()` the item text is set to an empty string when
    // undefined, so revert it back to undefined here if that's the case.
    text: parsed.text === "" ? undefined : parsed.text,
    url: parsed.url,
  };
};

/**
 * Create a new {@link Item} in the default storage.
 *
 * @param text The text of the {@link Item} to create.
 * @param url The URL of the {@link Item} to create.
 * @param itemKeyPrefix The prefix for the {@link Item} key.
 * @returns The created {@link Value} with inner {@link Item}.
 */
export async function createItem(
  text: Item["text"],
  url: Item["url"],
  itemKeyPrefix: ItemKeyPrefix = "item-",
): Promise<Value<Item>> {
  const nextId = await nextItemId();

  const item = await createValue<Item>({
    deserialize: deserializeItem,
    serialize: serializeItem,
    storage: storageForPrefix(itemKeyPrefix),
    key: `${itemKeyPrefix}${nextId}`,
    value: {
      dateAdded: new Date(),
      id: nextId,
      text,
      url,
    },
  });

  return item;
}

/**
 * Get all keys from storage that start with the {@link ItemKeyPrefix}.
 *
 * @returns The keys as a string array.
 */
export async function getItemKeys(
  itemKeyPrefix: ItemKeyPrefix,
): Promise<string[]> {
  const storage = storageForPrefix(itemKeyPrefix);
  const stored = Object.keys(await storage.get());
  const keys = stored.filter((key) => key.startsWith(itemKeyPrefix));
  return keys;
}

/**
 * Get the next unique {@link Item} ID.
 *
 * @returns The next ID as a number.
 */
export async function nextItemId(
  itemKeyPrefix: ItemKeyPrefix = "item-",
): Promise<number> {
  // Get all the item keys and sort them so the highest ID is first.
  const keys = await getItemKeys(itemKeyPrefix);
  keys.sort((a, b) => b.localeCompare(a));

  // Get the first key or use 0 if no items exist yet.
  const highestKey = keys[0] ?? `${itemKeyPrefix}0`;

  // Create the next ID by removing the item key prefix and adding 1.
  return Number(highestKey.slice(itemKeyPrefix.length)) + 1;
}

/**
 * Get the next queued {@link Item}.
 *
 * @returns The {@link Value} with inner {@link Item} or `undefined` if the
 * queue is empty.
 */
export async function nextItem(): Promise<Value<Item> | undefined> {
  const itemKeyPrefix: ItemKeyPrefix = "item-";

  // Get all the item keys and sort them so the lowest ID is first.
  const keys = await getItemKeys(itemKeyPrefix);
  keys.sort((a, b) => a.localeCompare(b));

  // If no keys exist then exit early.
  const key = keys[0];
  if (key === undefined) {
    return undefined;
  }

  return createValue<Item>({
    deserialize: deserializeItem,
    key,
    // We know that an item exists in storage since there is a key for it, which
    // means passing undefined here is fine as it won't be used.
    value: undefined!,
    serialize: serializeItem,
  });
}

/**
 * Set the WebExtension's badge text to show the current {@link Item} count.
 */
export async function setBadgeText(): Promise<void> {
  const itemKeyPrefix: ItemKeyPrefix = "item-";
  const keys = await getItemKeys(itemKeyPrefix);
  const count = keys.length;
  const action: browser.Action.Static =
    $browser === "firefox" ? browser.browserAction : browser.action;

  await action.setBadgeBackgroundColor({color: "#2a2041"});
  await action.setBadgeText({text: count === 0 ? "" : count.toString()});

  // Only Firefox supports the `setBadgeTextColor` function.
  if ($browser === "firefox") {
    action.setBadgeTextColor({color: "#f2efff"});
  }
}