const javascriptStringify = require("javascript-stringify");
const TemplateEngine = require("./TemplateEngine");
const EleventyBaseError = require("../EleventyBaseError");

class JavaScriptTemplateLiteralCompileError extends EleventyBaseError {}

class JavaScriptTemplateLiteral extends TemplateEngine {
  // add ` around template if it doesn’t exist.
  static normalizeTicks(str) {
    // TODO make this work with tagged templates html``
    let trimmedStr = str.trim();
    if (
      trimmedStr.charAt(0) === "`" &&
      trimmedStr.charAt(trimmedStr.length - 1) === "`"
    ) {
      str =
        "`" +
        trimmedStr.substr(1, trimmedStr.length - 2).replace(/`/g, "\\`") +
        "`";
    } else {
      str =
        "`" +
        str.replace(/`/g, "\\`") +
        (trimmedStr.charAt(trimmedStr.length - 1) === "`" ? "\n" : "") +
        "`";
    }

    return str;
  }

  async compile(str, inputPath) {
    return function(data) {
      // avoid `with`
      let dataStr = "";
      for (let j in data) {
        dataStr += `let ${j} = ${javascriptStringify.stringify(
          data[j],
          null,
          null,
          {
            references: true
          }
        )};\n`;
      }

      let evalStr = `${dataStr}\n${JavaScriptTemplateLiteral.normalizeTicks(
        str
      )};`;
      try {
        // TODO switch to https://www.npmjs.com/package/es6-template-strings
        let val = eval(evalStr);
        return val;
      } catch (e) {
        throw new JavaScriptTemplateLiteralCompileError(
          `Broken ES6 template:\n${evalStr}`,
          e
        );
      }
    };
  }
}

module.exports = JavaScriptTemplateLiteral;