import { preprocess } from "@glimmer/syntax";
import TemplateCompiler, { CompileOptions } from "./template-compiler";
import { SerializedTemplateWithLazyBlock, TemplateJavascript } from "@glimmer/wire-format";

export interface TemplateIdFn {
  (src: string): string;
}

export interface PrecompileOptions<T> extends CompileOptions<T> {
  id?: TemplateIdFn;
}

declare function require(id: string): any;

const defaultId: () => TemplateIdFn = (() => {
  let idFn: TemplateIdFn;
  return () => {
    if (!idFn) {
      if (typeof require === 'function') {
        try {
          /* tslint:disable:no-require-imports */
          const crypto = require('crypto');
          /* tslint:enable:no-require-imports */
          idFn = src => {
            let hash = crypto.createHash('sha1');
            hash.update(src, 'utf8');
            // trim to 6 bytes of data (2^48 - 1)
            return hash.digest('base64').substring(0,8);
          };
          idFn("test");
        } catch (e) {
          idFn = null;
        }
      }
      if (!idFn) {
        idFn = () => null;
      }
    }
    return idFn;
  };
})();

/*
 * Compile a string into a template javascript string.
 *
 * Example usage:
 *     import { precompile } from '@glimmer/compiler';
 *     import { templateFactory } from 'glimer-runtime';
 *     let templateJs = precompile("Howdy {{name}}");
 *     let factory = templateFactory(new Function("return " + templateJs)());
 *     let template = factory.create(env);
 *
 * @method precompile
 * @param {string} string a Glimmer template string
 * @return {string} a template javascript string
 */
export function precompile<T>(string: string, options?: PrecompileOptions<T>): TemplateJavascript;
export function precompile(string: string, options?: PrecompileOptions<{}>): TemplateJavascript {
  let opts = options || {
    id: defaultId(),
    meta: {}
  };
  let ast = preprocess(string, opts);
  let { block, meta } = TemplateCompiler.compile(opts, ast);
  let idFn = opts.id || defaultId();
  let blockJSON = JSON.stringify(block.toJSON());
  let templateJSONObject: SerializedTemplateWithLazyBlock<{}> = {
    id: idFn(JSON.stringify(meta) + blockJSON),
    block: blockJSON,
    meta
  };

  // JSON is javascript
  return JSON.stringify(templateJSONObject);
}