import {
  discoverToolboxCatalog,
  type ToolboxDiscoveryOptions,
} from "./discovery.js";
import { parseToolboxApp, parseToolboxCatalog } from "./parse.js";
import {
  ToolboxError,
  type ResolvedToolboxCatalog,
  type ToolboxAppManifest,
  type ToolboxCatalog,
  type ToolboxContextResult,
  type ToolboxDiscoverySource,
} from "./types.js";
import { requireSameOrigin, resolveToolboxApp, resolveWebUrl } from "./urls.js";

export type ToolboxFetch = (
  input: string | URL | Request,
  init?: RequestInit,
) => Promise<Response>;

export interface ToolboxLoadOptions {
  fetch?: ToolboxFetch;
  signal?: AbortSignal;
  baseUrl?: string | URL;
  expectedOrigin?: string | URL;
}

function defaultFetch(): ToolboxFetch {
  if (typeof globalThis.fetch !== "function") {
    throw new ToolboxError(
      "fetch-failed",
      "No fetch implementation is available",
    );
  }
  return globalThis.fetch.bind(globalThis);
}

function absoluteUrl(reference: string | URL, base?: string | URL): URL {
  if (base !== undefined) return resolveWebUrl(reference, base);
  if (typeof reference !== "string" || /^[a-z][a-z\d+.-]*:/i.test(reference)) {
    return resolveWebUrl(reference);
  }
  if (typeof globalThis.location !== "undefined") {
    return resolveWebUrl(reference, globalThis.location.href);
  }
  throw new ToolboxError(
    "invalid-url",
    `A base URL is required for relative URL: ${reference}`,
  );
}

async function fetchJson(
  url: URL,
  options: ToolboxLoadOptions,
): Promise<unknown> {
  let response: Response;
  try {
    response = await (options.fetch ?? defaultFetch())(url, {
      headers: { accept: "application/json" },
      redirect: "error",
      ...(options.signal === undefined ? {} : { signal: options.signal }),
    });
  } catch (cause) {
    throw new ToolboxError("fetch-failed", `Could not fetch ${url.href}`, {
      cause,
    });
  }
  if (typeof response.url === "string" && response.url !== "") {
    requireSameOrigin(
      resolveWebUrl(response.url),
      url,
      `Final response for ${url.href}`,
    );
  }
  if (!response.ok) {
    throw new ToolboxError(
      "fetch-failed",
      `Could not fetch ${url.href}: HTTP ${response.status}`,
    );
  }
  try {
    return await response.json();
  } catch (cause) {
    throw new ToolboxError("fetch-failed", `${url.href} is not valid JSON`, {
      cause,
    });
  }
}

export async function fetchToolboxAppManifest(
  manifestUrl: string | URL,
  options: ToolboxLoadOptions = {},
): Promise<ToolboxAppManifest> {
  const url = absoluteUrl(manifestUrl, options.baseUrl);
  if (options.expectedOrigin !== undefined) {
    requireSameOrigin(
      url,
      absoluteUrl(options.expectedOrigin),
      "Application manifest",
    );
  }
  return parseToolboxApp(await fetchJson(url, options));
}

export async function fetchToolboxCatalog(
  catalogUrl: string | URL,
  options: ToolboxLoadOptions = {},
): Promise<ToolboxCatalog> {
  const url = absoluteUrl(catalogUrl, options.baseUrl);
  if (options.expectedOrigin !== undefined) {
    requireSameOrigin(
      url,
      absoluteUrl(options.expectedOrigin),
      "Toolbox catalog",
    );
  }
  return parseToolboxCatalog(await fetchJson(url, options));
}

export async function loadToolboxCatalog(
  catalogReference: string | URL,
  options: ToolboxLoadOptions = {},
): Promise<ResolvedToolboxCatalog> {
  const catalogUrl = absoluteUrl(catalogReference, options.baseUrl);
  const expectedOrigin =
    options.expectedOrigin === undefined
      ? catalogUrl
      : absoluteUrl(options.expectedOrigin);
  requireSameOrigin(catalogUrl, expectedOrigin, "Toolbox catalog");

  const catalog = await fetchToolboxCatalog(catalogUrl, {
    ...options,
    expectedOrigin,
  });
  const apps = await Promise.all(
    catalog.apps
      .filter((entry) => entry.enabled)
      .map(async (entry) => {
        if ("entry" in entry) {
          return {
            kind: "external" as const,
            enabled: entry.enabled,
            name: entry.name,
            entryUrl: resolveWebUrl(entry.entry, catalogUrl),
            launch: entry.launch,
          };
        }
        const manifestUrl = requireSameOrigin(
          resolveWebUrl(entry.manifest, catalogUrl),
          expectedOrigin,
          "Catalog application manifest",
        );
        const manifest = await fetchToolboxAppManifest(manifestUrl, {
          ...options,
          expectedOrigin,
        });
        return {
          kind: "manifest" as const,
          enabled: entry.enabled,
          app: resolveToolboxApp(manifest, manifestUrl, expectedOrigin),
        };
      }),
  );
  const homeUrl = requireSameOrigin(
    resolveWebUrl(catalog.home, catalogUrl),
    expectedOrigin,
    "Toolbox home",
  );

  return {
    catalog,
    catalogUrl,
    apps,
    homeUrl,
  };
}

export interface ToolboxContextLoadOptions
  extends
    ToolboxDiscoveryOptions,
    Omit<ToolboxLoadOptions, "baseUrl" | "expectedOrigin"> {
  catalogUrl?: string | URL;
}

function asToolboxError(error: unknown): ToolboxError {
  return error instanceof ToolboxError
    ? error
    : new ToolboxError(
        "fetch-failed",
        "The toolbox context could not be loaded",
        {
          cause: error,
        },
      );
}

export async function loadToolboxContext(
  options: ToolboxContextLoadOptions = {},
): Promise<ToolboxContextResult> {
  let source: ToolboxDiscoverySource;
  let catalogUrl: URL;
  let pageUrl: URL;

  if (options.catalogUrl !== undefined) {
    source = "explicit";
    try {
      pageUrl = resolveWebUrl(
        options.location ??
          (typeof globalThis.location === "undefined"
            ? options.catalogUrl
            : globalThis.location.href),
      );
      catalogUrl = requireSameOrigin(
        resolveWebUrl(options.catalogUrl, pageUrl),
        pageUrl,
        "Toolbox catalog",
      );
    } catch (error) {
      return { status: "error", error: asToolboxError(error) };
    }
  } else {
    const discovery = discoverToolboxCatalog(options);
    if (discovery.status === "none") return { status: "standalone" };
    if (discovery.status === "error") return discovery;
    source = discovery.source;
    catalogUrl = discovery.catalogUrl;
    pageUrl = resolveWebUrl(
      options.location ??
        (typeof globalThis.location === "undefined"
          ? catalogUrl
          : globalThis.location.href),
    );
  }

  try {
    const catalog = await loadToolboxCatalog(catalogUrl, {
      ...(options.fetch === undefined ? {} : { fetch: options.fetch }),
      ...(options.signal === undefined ? {} : { signal: options.signal }),
      expectedOrigin: pageUrl,
    });
    return { status: "ready", context: { source, catalog } };
  } catch (error) {
    return { status: "error", error: asToolboxError(error) };
  }
}