import Module from 'node:module';

import {
  type ResolutionResult,
  type DependencyResolution,
  DependencyResolutionSource,
} from './types';
import {
  type PackageJson,
  defaultShouldIncludeDependency,
  mergeResolutionResults,
  loadPackageJson,
  maybeRealpath,
  fastJoin,
} from './utils';

declare module 'node:module' {
  export function _nodeModulePaths(base: string): readonly string[];
}

// NOTE(@kitten): There's no need to search very deep for modules
// We don't expect native modules to be excessively nested in the dependency tree
const MAX_DEPTH = 8;

const createNodeModulePathsCreator = () => {
  const _nodeModulePathCache = new Map<string, string | null>();
  return async function getNodeModulePaths(packagePath: string) {
    const outputPaths: string[] = [];
    const nodeModulePaths = Module._nodeModulePaths(packagePath);
    for (let idx = 0; idx < nodeModulePaths.length; idx++) {
      const nodeModulePath = nodeModulePaths[idx];
      let target = _nodeModulePathCache.get(nodeModulePath);
      if (target === undefined) {
        target = await maybeRealpath(nodeModulePath);
        if (idx !== 0) {
          _nodeModulePathCache.set(nodeModulePath, target);
        }
      }
      if (target != null) {
        outputPaths.push(target);
      }
    }
    return outputPaths;
  };
};

async function resolveDependencies(
  packageJson: PackageJson,
  nodeModulePaths: readonly string[],
  depth: number,
  shouldIncludeDependency: (dependencyName: string) => boolean
): Promise<DependencyResolution[]> {
  const dependencies: Record<string, string> = Object.create(null);
  if (packageJson.dependencies != null && typeof packageJson.dependencies === 'object') {
    Object.assign(dependencies, packageJson.dependencies);
  }
  // NOTE(@kitten): Also traverse devDependencies for top-level package.json
  if (
    depth === 0 &&
    packageJson.devDependencies != null &&
    typeof packageJson.devDependencies === 'object'
  ) {
    Object.assign(dependencies, packageJson.devDependencies);
  }
  if (packageJson.peerDependencies != null && typeof packageJson.peerDependencies === 'object') {
    const peerDependenciesMeta =
      packageJson.peerDependenciesMeta != null &&
      typeof packageJson.peerDependenciesMeta === 'object'
        ? (packageJson.peerDependenciesMeta as Record<string, unknown>)
        : undefined;
    for (const dependencyName in packageJson.peerDependencies) {
      // NOTE(@kitten): We only check peer dependencies because some package managers auto-install them
      // which would mean they'd have no reference in any dependencies. However, optional peer dependencies
      // don't auto-install and we can skip them
      if (!isOptionalPeerDependencyMeta(peerDependenciesMeta, dependencyName)) {
        dependencies[dependencyName] = '';
      }
    }
  }

  const resolveDependency = async (
    dependencyName: string
  ): Promise<DependencyResolution | null> => {
    for (let idx = 0; idx < nodeModulePaths.length; idx++) {
      const originPath = fastJoin(nodeModulePaths[idx], dependencyName);
      const nodeModulePath = await maybeRealpath(originPath);
      if (nodeModulePath != null) {
        return {
          source: DependencyResolutionSource.RECURSIVE_RESOLUTION,
          name: dependencyName,
          version: '',
          path: nodeModulePath,
          originPath,
          duplicates: null,
          depth,
        };
      }
    }
    return null;
  };

  const modules = await Promise.all(
    Object.keys(dependencies)
      .filter((dependencyName) => shouldIncludeDependency(dependencyName))
      .map((dependencyName) => resolveDependency(dependencyName))
  );

  return modules.filter((resolution) => resolution != null);
}

interface ResolutionOptions {
  shouldIncludeDependency?(name: string): boolean;
  limitDepth?: number;
}

export async function scanDependenciesRecursively(
  rawPath: string,
  { shouldIncludeDependency = defaultShouldIncludeDependency, limitDepth }: ResolutionOptions = {}
): Promise<ResolutionResult> {
  const rootPath = await maybeRealpath(rawPath);
  if (!rootPath) {
    return {};
  }

  const _visitedPackagePaths = new Set();
  const getNodeModulePaths = createNodeModulePathsCreator();
  const maxDepth = limitDepth != null ? limitDepth : MAX_DEPTH;

  const recurse = async (
    resolution: DependencyResolution,
    depth = 0
  ): Promise<ResolutionResult> => {
    const searchResults: ResolutionResult = Object.create(null);
    if (_visitedPackagePaths.has(resolution.path)) {
      return searchResults;
    } else {
      _visitedPackagePaths.add(resolution.path);
    }
    const [nodeModulePaths, packageJson] = await Promise.all([
      getNodeModulePaths(resolution.path),
      loadPackageJson(fastJoin(resolution.path, 'package.json')),
    ]);
    if (!packageJson) {
      return searchResults;
    } else {
      resolution.version = packageJson.version || '';
    }

    const modules = await resolveDependencies(
      packageJson,
      nodeModulePaths,
      depth,
      shouldIncludeDependency
    );
    for (let idx = 0; idx < modules.length; idx++) {
      searchResults[modules[idx].name] = modules[idx];
    }

    if (depth + 1 < maxDepth) {
      const childResults = await Promise.all(
        modules.map((resolution) => recurse(resolution, depth + 1))
      );
      return mergeResolutionResults(childResults, searchResults);
    } else {
      return searchResults;
    }
  };

  const searchResults = await recurse({
    source: DependencyResolutionSource.RECURSIVE_RESOLUTION,
    name: '',
    version: '',
    path: rootPath,
    originPath: rawPath,
    duplicates: null,
    depth: -1,
  });

  return searchResults;
}

const isOptionalPeerDependencyMeta = (
  peerDependenciesMeta: Record<string, unknown> | undefined,
  packageName: string
) => {
  return (
    peerDependenciesMeta &&
    peerDependenciesMeta[packageName] != null &&
    typeof peerDependenciesMeta[packageName] === 'object' &&
    'optional' in peerDependenciesMeta[packageName] &&
    !!peerDependenciesMeta[packageName].optional
  );
};