import * as path from 'path';
import * as fs from 'fs';
import * as JSON5 from 'json5';

export interface MappedPath {
  key: string;
  path: string;
}

export interface GetMappedPathsParams {
  rootTsConfigPath: string;
  sharedMappings?: string[];
  rootPath?: string;
}

export function getMappedPaths({
  rootTsConfigPath,
  sharedMappings = [],
  rootPath,
}: GetMappedPathsParams): MappedPath[] {
  const result: MappedPath[] = [];
  if (!path.isAbsolute(rootTsConfigPath)) {
    throw new Error(
      'SharedMappings.register: tsConfigPath needs to be an absolute path!',
    );
  }
  if (!rootPath) {
    rootPath = path.normalize(path.dirname(rootTsConfigPath));
  }
  const shareAll = sharedMappings.length === 0;
  const tsConfig = JSON5.parse(
    fs.readFileSync(rootTsConfigPath, { encoding: 'utf-8' }),
  );
  const mappings = tsConfig?.compilerOptions?.paths;
  if (!mappings) {
    return result;
  }
  for (const key in mappings) {
    if (Object.prototype.hasOwnProperty.call(mappings, key)) {
      const libPath = path.normalize(path.join(rootPath, mappings[key][0]));
      if (sharedMappings.includes(key) || shareAll) {
        result.push({
          key,
          path: libPath,
        });
      }
    }
  }
  return result;
}