// tslint:disable ban-types
import Ast, { SourceFile, ts } from 'ts-simple-ast';

import appRootDir from 'app-root-dir';
import * as fs from 'fs-extra';
import * as path from 'path';

const findRoot = async (
  dir: string | string[],
  filename: string,
): Promise<string> => {
  let start = dir;

  if (typeof start === 'string') {
    if (start[start.length - 1] !== path.sep) {
      start += path.sep;
    }
    start = start.split(path.sep);
  }
  if (!start.length) {
    throw new Error('tsconfig.json not found in path');
  }

  start.pop();
  const currentDir = start.join(path.sep);
  const file = path.join(currentDir, filename);
  const exists = await fs.pathExists(file);
  if (exists) {
    return file;
  }

  return findRoot(start, filename);
};

export const makeAst = async (dir: string): Promise<Ast> => {
  const tsConfigFilePath = await findRoot(dir, 'tsconfig.json');
  const res = ts.readConfigFile(tsConfigFilePath, (value) =>
    fs.readFileSync(value, 'utf8'),
  );
  const parseConfigHost = {
    fileExists: fs.existsSync,
    readDirectory: ts.sys.readDirectory,
    readFile: ts.sys.readFile,
    useCaseSensitiveFileNames: true,
  };
  const parsed = ts.parseJsonConfigFileContent(
    res.config,
    parseConfigHost,
    path.dirname(tsConfigFilePath),
  );

  return new Ast({ compilerOptions: parsed.options });
};

export const getAst = async (dir: string): Promise<Ast> => {
  const ast = await makeAst(dir);
  ast.addExistingSourceFiles(path.join(dir, '**', '*.ts'));
  // For some reason this forces Ast to resolve references. Do not remove.
  ast.getPreEmitDiagnostics();
  return ast;
};

export const getAstForSnippet = async (
  code: string,
): Promise<{ ast: Ast; sourceFile: SourceFile }> => {
  const ast = await makeAst(appRootDir.get());
  const sourceFile = ast.createSourceFile('code.ts', code);
  // For some reason this forces Ast to resolve references. Do not remove.
  ast.getPreEmitDiagnostics();
  return { ast, sourceFile };
};

export function notNull<TValue>(
  value: TValue | null | undefined,
): value is TValue {
  return value != null;
}