import type { ComponentType } from "react";

/**
 * Type guard to check if a value is a React component
 */
const isReactComponent = (value: unknown): value is ComponentType => {
  return typeof value === "function";
};

/**
 * Type guard to check if a value is an object with a default property
 */
const hasDefaultProperty = (value: unknown): value is { default: unknown } => {
  return (
    value !== null &&
    typeof value === "object" &&
    "default" in value &&
    value.default !== undefined
  );
};

/**
 * Extract MDX component from a module (for both .md and .mdx files)
 * Handles both direct component exports and default exports
 */
const extractMDXComponent = (module: unknown): ComponentType | null => {
  if (isReactComponent(module)) {
    return module;
  }

  if (hasDefaultProperty(module)) {
    const defaultExport = module.default;
    if (isReactComponent(defaultExport)) {
      return defaultExport;
    }
  }

  return null;
};

/**
 * Auto-discovered markdown and MDX files as MDX components
 * Both .md and .mdx files are processed by the MDX plugin
 * Lazy loading enabled for better performance
 */
const mdxModules = import.meta.glob("../../content/**/*.{md,mdx}", {
  eager: false,
});

/**
 * Get the MDX component for a given documentation slug
 *
 * Normalizes the slug and searches for matching files in the content directory.
 * Handles README files as index files (e.g., "api/readme" matches slug "api").
 * Returns a promise that resolves to the component for lazy loading.
 *
 * @param slug - The documentation slug (e.g., "docs/architecture", "components/button")
 * @returns Promise that resolves to the React component for the documentation page, or null if not found
 */
export const getDocComponent = async (
  slug: string,
): Promise<ComponentType | null> => {
  const normalizedSlug = slug.toLowerCase().replace(/^\/+|\/+$/g, "");

  for (const [path, moduleLoader] of Object.entries(mdxModules)) {
    const normalizedPath = path
      .replace(/^\.\.\/\.\.\/content\//, "")
      .replace(/\.(md|mdx)$/, "")
      .toLowerCase();

    let matches = normalizedPath === normalizedSlug;

    if (!matches && normalizedPath.endsWith("/readme")) {
      const dirPath = normalizedPath.replace(/\/readme$/, "");
      matches =
        dirPath === normalizedSlug || dirPath === `${normalizedSlug}/readme`;
    }

    if (!matches && normalizedPath === `${normalizedSlug}/readme`) {
      matches = true;
    }

    if (matches) {
      const module = await moduleLoader();
      const component = extractMDXComponent(module);

      if (component) {
        return component;
      }
    }
  }

  return null;
};

/**
 * Get a list of all available documentation slugs
 *
 * Extracts slugs from all discovered markdown and MDX files,
 * excluding README files and empty slugs.
 *
 * @returns Array of normalized documentation slugs
 */
export const getAvailableDocs = (): string[] => {
  return Object.keys(mdxModules)
    .map((path) => {
      const normalizedPath = path
        .replace(/^\.\.\/\.\.\/content\//, "")
        .replace(/\.(md|mdx)$/, "");
      return normalizedPath.toLowerCase();
    })
    .filter((slug) => {
      const filename = slug.split("/").pop() ?? "";
      return filename !== "readme" && slug.length > 0;
    });
};