const selfClosingTags = require("./util/selfClosingTags");

module.exports = class Compiler {
  constructor(tree, context) {
    this.tree = tree;
    this.context = context;
    this.pos = 0;
    this.result = "";
  }

  compile() {
    this.tree.forEach(node => {
      switch (node.constructor.name) {
        case "Application":
          this.result += this.application(node);
          break;
        case "Identifier":
          this.result += this.lookup(node);
          break;
        case "String":
          this.result += node.value;
          break;
      }
    });

    return this.result;
  }

  application(node) {
    let result = `<${node.functionName.name}`;

    node.args
      .filter(arg => arg.constructor.name === "Attribute")
      .forEach(arg => {
        result += ` ${arg.name}`;

        let compiler = new Compiler([arg.value], this.context);
        let attrValue = compiler.compile();

        if (attrValue) {
          result += `="${attrValue}"`;
        }
      });

    result += ">";

    node.args
      .filter(arg => arg.constructor.name !== "Attribute")
      .forEach(arg => {
        let compiler = new Compiler([arg], this.context);
        result += compiler.compile();
      });

    if (!selfClosingTags.includes(node.functionName.name)) {
      result += `</${node.functionName.name}>`;
    }

    return result;
  }

  lookup(identifier) {
    let result = this.context[identifier.name];

    if (!result) {
      throw `Undefined variable '${identifier.name}'`;
    }

    return result;
  }
};