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import { acl } from "../constants";
import {
  createSolidDataset,
  getSolidDataset,
  saveSolidDatasetAt,
} from "../resource/solidDataset";
import type {
  WithResourceInfo,
  File,
  WithServerResourceInfo,
  UrlString,
  Url,
  SolidDataset,
  Thing,
} from "../interfaces";
import { setThing } from "../thing/thing";
import { removeAll } from "../thing/remove";
import { setIri } from "../thing/set";
import { getResourceInfo, getSourceUrl } from "../resource/resource";
import { getFile } from "../resource/file";
import { internal_cloneResource } from "../resource/resource.internal";
import {
  internal_fetchAcl,
  internal_getAclRules,
  internal_getDefaultAclRulesForResource,
  internal_setAcl,
} from "./acl.internal";
import { freeze } from "../rdf.internal";

/**
 * ```{note} The Web Access Control specification is not yet finalised. As such, this
 * function is still experimental and subject to change, even in a non-major release.
 * ```
 *
 * Verify whether a given SolidDataset was fetched together with its Access Control List.
 *
 * @param dataset A [[SolidDataset]] that may have its ACLs attached.
 * @returns True if `dataset` was fetched together with its ACLs.
 */
export function hasAcl<T extends object>(dataset: T): dataset is T & WithAcl {
  const potentialAcl = dataset as T & WithAcl;
  return typeof potentialAcl.internal_acl === "object";
}

/**
 * ```{note} The Web Access Control specification is not yet finalised. As such, this
 * function is still experimental and subject to change, even in a non-major release.
 * ```
 *
 * Verifies whether the given Resource has a resource ACL (Access Control List) attached.
 *
 * The [[hasResourceAcl]] function checks that:
 * - a given Resource has a resource ACL attached, and
 * - the user calling [[hasResourceAcl]] has Control access to the Resource.
 *
 * To retrieve a Resource with its ACLs, see [[getSolidDatasetWithAcl]].
 *
 * @param resource A Resource that might have an ACL attached.
 * @returns `true` if the Resource has a resource ACL attached that is accessible by the user.
 */
export function hasResourceAcl<
  Resource extends WithAcl & WithServerResourceInfo,
>(
  resource: Resource,
): resource is Resource & WithResourceAcl & WithAccessibleAcl {
  return (
    resource.internal_acl.resourceAcl !== null &&
    getSourceUrl(resource) ===
      resource.internal_acl.resourceAcl.internal_accessTo &&
    resource.internal_resourceInfo.aclUrl ===
      getSourceUrl(resource.internal_acl.resourceAcl)
  );
}

/**
 * Experimental: fetch a SolidDataset and its associated Access Control List.
 *
 * This is an experimental function that fetches both a Resource, the linked ACL Resource (if
 * available), and the ACL that applies to it if the linked ACL Resource is not available. This can
 * result in many HTTP requests being executed, in lieu of the Solid spec mandating servers to
 * provide this info in a single request. Therefore, and because this function is still
 * experimental, prefer [[getSolidDataset]] instead.
 *
 * If the Resource does not advertise the ACL Resource (because the authenticated user does not have
 * access to it), the `acl` property in the returned value will be null. `acl.resourceAcl` will be
 * undefined if the Resource's linked ACL Resource could not be fetched (because it does not exist),
 * and `acl.fallbackAcl` will be null if the applicable Container's ACL is not accessible to the
 * authenticated user.
 *
 * @param url URL of the SolidDataset to fetch.
 * @param options Optional parameter `options.fetch`: An alternative `fetch` function to make the HTTP request, compatible with the browser-native [fetch API](https://developer.mozilla.org/docs/Web/API/WindowOrWorkerGlobalScope/fetch#parameters).
 * @returns A SolidDataset and the ACLs that apply to it, if available to the authenticated user.
 */
export async function getSolidDatasetWithAcl(
  url: UrlString | Url,
  options?: { fetch?: typeof fetch },
): Promise<SolidDataset & WithServerResourceInfo & WithAcl> {
  const solidDataset = await getSolidDataset(url, options);
  const acl = await internal_fetchAcl(solidDataset, options);
  return internal_setAcl(solidDataset, acl);
}

/**
 * ```{note} This function is still experimental and subject to change, even in a non-major release.
 * ```
 *
 * Retrieves a file, its resource ACL (Access Control List) if available,
 * and its fallback ACL from a URL and returns them as a blob.
 *
 * If the user calling the function does not have access to the file's resource ACL,
 * [[hasAccessibleAcl]] on the returned blob returns false.
 * If the user has access to the file's resource ACL but the resource ACL does not exist,
 * [[getResourceAcl]] on the returned blob returns null.
 * If the fallback ACL is inaccessible by the user,
 * [[getFallbackAcl]] on the returned blob returns null.
 *
 * ```{tip}
 * To retrieve the ACLs, the function results in multiple HTTP requests rather than a single
 * request as mandated by the Solid spec. As such, prefer [[getFile]] instead if you do not need the ACL.
 * ```
 *
 * @param url The URL of the fetched file
 * @param options Fetching options: a custom fetcher and/or headers.
 * @returns A file and its ACLs, if available to the authenticated user, as a blob.
 * @since 0.2.0
 */
export async function getFileWithAcl(
  input: Url | UrlString,
  options?: { fetch?: typeof fetch },
): Promise<File & WithServerResourceInfo & WithAcl> {
  const file = await getFile(input, options);
  const acl = await internal_fetchAcl(file, options);
  return internal_setAcl(file, acl);
}

/**
 * Experimental: fetch a Resource's metadata and its associated Access Control List.
 *
 * This is an experimental function that fetches both a Resource's metadata, the linked ACL Resource (if
 * available), and the ACL that applies to it if the linked ACL Resource is not available (if accessible). This can
 * result in many HTTP requests being executed, in lieu of the Solid spec mandating servers to
 * provide this info in a single request.
 *
 * If the Resource's linked ACL Resource could not be fetched (because it does not exist, or because
 * the authenticated user does not have access to it), `acl.resourceAcl` will be `null`. If the
 * applicable Container's ACL is not accessible to the authenticated user, `acl.fallbackAcl` will be
 * `null`.
 *
 * @param url URL of the SolidDataset to fetch.
 * @param options Optional parameter `options.fetch`: An alternative `fetch` function to make the HTTP request, compatible with the browser-native [fetch API](https://developer.mozilla.org/docs/Web/API/WindowOrWorkerGlobalScope/fetch#parameters).
 * @returns A Resource's metadata and the ACLs that apply to the Resource, if available to the authenticated user.
 */
export async function getResourceInfoWithAcl(
  url: UrlString,
  options?: { fetch?: typeof fetch },
): Promise<WithServerResourceInfo & WithAcl> {
  const resourceInfo = await getResourceInfo(url, options);
  const acl = await internal_fetchAcl(resourceInfo, options);
  return internal_setAcl(resourceInfo, acl);
}

/**
 * ```{note} The Web Access Control specification is not yet finalised. As such, this
 * function is still experimental and subject to change, even in a non-major release.
 * ```
 * Returns the resource ACL (Access Control List) attached to a Resource.
 *
 * If the Resource has its resource ACL attached and is accessible by the user
 * (see [[hasResourceAcl]]), the function returns the resource ACL.
 * If the Resource does not have a resource ACL attached or is inaccessible by the user,
 * the function returns `null`.
 *
 * @param resource A Resource with potentially an ACL attached.
 * @returns The resource ACL if available and `null` if not.
 */
export function getResourceAcl(
  resource: WithAcl & WithServerResourceInfo & WithResourceAcl,
): AclDataset;
export function getResourceAcl(
  resource: WithAcl & WithServerResourceInfo,
): AclDataset | null;
export function getResourceAcl(
  resource: WithAcl & WithServerResourceInfo,
): AclDataset | null {
  if (!hasResourceAcl(resource)) {
    return null;
  }
  return resource.internal_acl.resourceAcl;
}

/**
 * ```{note} The Web Access Control specification is not yet finalised. As such, this
 * function is still experimental and subject to change, even in a non-major release.
 * ```
 *
 * Verifies whether the given Resource has a fallback ACL (Access Control List) attached.
 *
 * A fallback ACL for a Resource is inherited from the Resource's parent Container
 * (or another of its ancestor Containers) and applies if the Resource does
 * not have its own resource ACL.
 *
 * The [[hasFallbackAcl]] function checks that:
 * - a given Resource has a fallback ACL attached, and
 * - the user calling [[hasFallbackAcl]] has Control access to the Container
 * from which the Resource inherits its ACL.
 *
 * To retrieve a Resource with its ACLs, see [[getSolidDatasetWithAcl]].
 *
 * @param resource A [[SolidDataset]] that might have a fallback ACL attached.
 *
 * @returns `true` if the Resource has a fallback ACL attached that is accessible to the user.
 */
export function hasFallbackAcl<Resource extends WithAcl>(
  resource: Resource,
): resource is Resource & WithFallbackAcl {
  return resource.internal_acl.fallbackAcl !== null;
}

/**
 * ```{note} The Web Access Control specification is not yet finalised. As such, this
 * function is still experimental and subject to change, even in a non-major release.
 * ```
 *
 * Returns the fallback ACL (Access Control List) attached to a Resource.
 *
 * If the Resource has a fallback ACL attached and is accessible by the user
 * (see [[hasFallbackAcl]]), the function returns the fallback ACL.
 * If the Resource does not hava a fallback ACL attached or is inaccessible by the user,
 * the function returns `null`.
 *
 * @param resource A Resource with potentially a fallback ACL attached.
 * @returns The fallback ACL if available or `null` if not.
 */
export function getFallbackAcl(resource: WithFallbackAcl): AclDataset;
export function getFallbackAcl(dataset: WithAcl): AclDataset | null;
export function getFallbackAcl(dataset: WithAcl): AclDataset | null {
  if (!hasFallbackAcl(dataset)) {
    return null;
  }
  return dataset.internal_acl.fallbackAcl;
}

/**
 * ```{note} The Web Access Control specification is not yet finalised. As such, this
 * function is still experimental and subject to change, even in a non-major release.
 * ```
 *
 * Creates an empty resource ACL (Access Control List) for a given Resource.
 *
 * @param targetResource A Resource that does not have its own ACL yet (see [[hasResourceAcl]]).
 * @returns An empty resource ACL for the given Resource.
 */
export function createAcl(
  targetResource: WithResourceInfo & WithAccessibleAcl,
): AclDataset {
  const emptyResourceAcl: AclDataset = freeze({
    ...createSolidDataset(),
    internal_accessTo: getSourceUrl(targetResource),
    internal_resourceInfo: {
      sourceIri: targetResource.internal_resourceInfo.aclUrl,
      isRawData: false,
      linkedResources: {},
    },
  });

  return emptyResourceAcl;
}

/**
 * ```{note} The Web Access Control specification is not yet finalised. As such, this
 * function is still experimental and subject to change, even in a non-major release.
 * ```
 *
 * Creates a resource ACL (Access Control List), initialised from the fallback ACL
 * inherited from the given Resource's Container (or another of its ancestor Containers).
 * That is, the new ACL has the same rules/entries as the fallback ACL that currently
 * applies to the Resource.
 *
 * @param resource A Resource without its own resource ACL (see [[hasResourceAcl]]) but with an accessible fallback ACL (see [[hasFallbackAcl]]).
 * @returns A resource ACL initialised with the rules/entries from the Resource's fallback ACL.
 */
export function createAclFromFallbackAcl(
  resource: WithFallbackAcl & WithServerResourceInfo & WithAccessibleAcl,
): AclDataset {
  const emptyResourceAcl: AclDataset = createAcl(resource);

  const fallbackAclRules = internal_getAclRules(
    resource.internal_acl.fallbackAcl,
  );
  const defaultAclRules = internal_getDefaultAclRulesForResource(
    fallbackAclRules,
    resource.internal_acl.fallbackAcl.internal_accessTo,
  );
  const newAclRules = defaultAclRules.map((rule) => {
    rule = removeAll(rule, acl.default);
    rule = removeAll(rule, acl.defaultForNew);
    rule = setIri(rule, acl.accessTo, getSourceUrl(resource));
    rule = setIri(rule, acl.default, getSourceUrl(resource));
    return rule;
  });

  // Iterate over every ACL Rule we want to import, inserting them into `emptyResourceAcl` one by one:
  const initialisedResourceAcl = newAclRules.reduce(setThing, emptyResourceAcl);

  return initialisedResourceAcl;
}

/**
 * ```{note} The Web Access Control specification is not yet finalised. As such, this
 * function is still experimental and subject to change, even in a non-major release.
 * ```
 *
 * Saves the resource ACL for a Resource.
 *
 * @param resource The Resource to which the given resource ACL applies.
 * @param resourceAcl An [[AclDataset]] whose ACL Rules will apply to `resource`.
 * @param options Optional parameter `options.fetch`: An alternative `fetch` function to make the HTTP request, compatible with the browser-native [fetch API](https://developer.mozilla.org/docs/Web/API/WindowOrWorkerGlobalScope/fetch#parameters).
 */
export async function saveAclFor(
  resource: WithAccessibleAcl,
  resourceAcl: SolidDataset,
  options?: { fetch?: typeof fetch },
): Promise<AclDataset & WithResourceInfo> {
  if (!hasAccessibleAcl(resource)) {
    throw new Error(
      `Could not determine the location of the ACL for the Resource at [${getSourceUrl(
        resource,
      )}]; possibly the current user does not have Control access to that Resource. Try calling \`hasAccessibleAcl()\` before calling \`saveAclFor()\`.`,
    );
  }
  const savedDataset = await saveSolidDatasetAt(
    resource.internal_resourceInfo.aclUrl,
    resourceAcl,
    options,
  );
  const savedAclDataset: AclDataset & typeof savedDataset = {
    ...savedDataset,
    internal_accessTo: getSourceUrl(resource),
  };

  return savedAclDataset;
}

/**
 * ```{note} The Web Access Control specification is not yet finalised. As such, this
 * function is still experimental and subject to change, even in a non-major release.
 * ```
 *
 * Removes the resource ACL (Access Control List) from a Resource.
 *
 * Once the resource ACL is removed from the Resource, the Resource relies on the
 * fallback ACL inherited from the Resource's parent Container (or another of its ancestor Containers).
 *
 * @param resource The Resource for which you want to delete the ACL.
 * @param options Optional parameter `options.fetch`: An alternative `fetch` function to make the HTTP request, compatible with the browser-native [fetch API](https://developer.mozilla.org/docs/Web/API/WindowOrWorkerGlobalScope/fetch#parameters).
 */
export async function deleteAclFor<
  Resource extends WithResourceInfo & WithAccessibleAcl,
>(
  resource: Resource,
  options?: { fetch?: typeof fetch },
): Promise<Resource & { acl: { resourceAcl: null } }> {
  const response = await (options?.fetch ?? fetch)(
    resource.internal_resourceInfo.aclUrl,
    {
      method: "DELETE",
    },
  );

  if (!response.ok) {
    throw new Error(
      `Deleting the ACL of the Resource at [${getSourceUrl(
        resource,
      )}] failed: [${response.status}] [${response.statusText}].`,
    );
  }

  const storedResource = Object.assign(internal_cloneResource(resource), {
    acl: {
      resourceAcl: null,
    },
  });

  return storedResource;
}

/**
 * A [[SolidDataset]] containing Access Control rules for another SolidDataset.
 *
 * Please note that the Web Access Control specification is not yet finalised, and hence, this
 * function is still experimental and can change in a non-major release.
 */
export type AclDataset = SolidDataset &
  WithResourceInfo & { internal_accessTo: UrlString };

/**
 * @hidden Developers shouldn't need to directly access ACL rules. Instead, we provide our own functions that verify what access someone has.
 */
export type AclRule = Thing;

/**
 * An object with the boolean properties `read`, `append`, `write` and `control`, representing the
 * respective Access Modes defined by the Web Access Control specification.
 *
 * Since that specification is not finalised yet, this interface is still experimental.
 */
export type Access =
  // If someone has write permissions, they also have append permissions:
  {
    read: boolean;
    append: boolean;
    write: boolean;
    control: boolean;
  };

/**
 * Please note that the Web Access Control specification is not yet finalised, and hence, this
 * function is still experimental and can change in a non-major release.
 *
 * @hidden Developers should use [[getResourceAcl]] and [[getFallbackAcl]] to access these.
 */
export type WithAcl = {
  internal_acl:
    | {
        resourceAcl: AclDataset;
        fallbackAcl: null;
      }
    | {
        resourceAcl: null;
        fallbackAcl: AclDataset | null;
      };
};

/**
 * If this type applies to a Resource, an Access Control List that applies to it exists and is accessible to the currently authenticated user.
 *
 * Please note that the Web Access Control specification is not yet finalised, and hence, this
 * function is still experimental and can change in a non-major release.
 */
export type WithResourceAcl<ResourceExt extends WithAcl = WithAcl> =
  ResourceExt & {
    internal_acl: {
      resourceAcl: Exclude<WithAcl["internal_acl"]["resourceAcl"], null>;
    };
  };

/**
 * If this type applies to a Resource, the Access Control List that applies to its nearest Container with an ACL is accessible to the currently authenticated user.
 *
 * Please note that the Web Access Control specification is not yet finalised, and hence, this
 * function is still experimental and can change in a non-major release.
 */
export type WithFallbackAcl<ResourceExt extends WithAcl = WithAcl> =
  ResourceExt & {
    internal_acl: {
      fallbackAcl: Exclude<WithAcl["internal_acl"]["fallbackAcl"], null>;
    };
  };

/**
 * If this type applies to a Resource, its Access Control List, if it exists, is accessible to the currently authenticated user.
 *
 * Please note that the Web Access Control specification is not yet finalised, and hence, this
 * function is still experimental and can change in a non-major release.
 */
export type WithAccessibleAcl<
  ResourceExt extends WithServerResourceInfo = WithServerResourceInfo,
> = ResourceExt & {
  internal_resourceInfo: {
    aclUrl: Exclude<
      WithServerResourceInfo["internal_resourceInfo"]["aclUrl"],
      undefined
    >;
  };
};

/**
 * Given a [[SolidDataset]], verify whether its Access Control List is accessible to the current user.
 *
 * This should generally only be true for SolidDatasets fetched by
 * [[getSolidDatasetWithAcl]].
 *
 * Please note that the Web Access Control specification is not yet finalised, and hence, this
 * function is still experimental and can change in a non-major release.
 *
 * @param dataset A [[SolidDataset]].
 * @returns Whether the given `dataset` has a an ACL that is accessible to the current user.
 */
export function hasAccessibleAcl<ResourceExt extends WithServerResourceInfo>(
  dataset: ResourceExt,
): dataset is WithAccessibleAcl<ResourceExt> {
  return typeof dataset.internal_resourceInfo.aclUrl === "string";
}