sexp-template/src/compiler.js

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
  }
}