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File Content: parse.js

'use strict'

// The ABNF grammar in the spec is totally ambiguous.
//
// This parser follows the operator precedence defined in the
// `Order of Precedence and Parentheses` section.

module.exports = function (tokens) {
  var index = 0

function hasMore () {
    return index < tokens.length
  }

function token () {
    return hasMore() ? tokens[index] : null
  }

function next () {
    if (!hasMore()) {
      throw new Error()
    }
    index++
  }

function parseOperator (operator) {
    var t = token()
    if (t && t.type === 'OPERATOR' && operator === t.string) {
      next()
      return t.string
    }
  }

function parseWith () {
    if (parseOperator('WITH')) {
      var t = token()
      if (t && t.type === 'EXCEPTION') {
        next()
        return t.string
      }
      throw new Error('Expected exception after `WITH`')
    }
  }

function parseLicenseRef () {
    // TODO: Actually, everything is concatenated into one string
    // for backward-compatibility but it could be better to return
    // a nice structure.
    var begin = index
    var string = ''
    var t = token()
    if (t.type === 'DOCUMENTREF') {
      next()
      string += 'DocumentRef-' + t.string + ':'
      if (!parseOperator(':')) {
        throw new Error('Expected `:` after `DocumentRef-...`')
      }
    }
    t = token()
    if (t.type === 'LICENSEREF') {
      next()
      string += 'LicenseRef-' + t.string
      return {license: string}
    }
    index = begin
  }

function parseLicense () {
    var t = token()
    if (t && t.type === 'LICENSE') {
      next()
      var node = {license: t.string}
      if (parseOperator('+')) {
        node.plus = true
      }
      var exception = parseWith()
      if (exception) {
        node.exception = exception
      }
      return node
    }
  }

function parseParenthesizedExpression () {
    var left = parseOperator('(')
    if (!left) {
      return
    }

var expr = parseExpression()

if (!parseOperator(')')) {
      throw new Error('Expected `)`')
    }

return expr
  }

function parseAtom () {
    return (
      parseParenthesizedExpression() ||
      parseLicenseRef() ||
      parseLicense()
    )
  }

function makeBinaryOpParser (operator, nextParser) {
    return function parseBinaryOp () {
      var left = nextParser()
      if (!left) {
        return
      }

if (!parseOperator(operator)) {
        return left
      }

var right = parseBinaryOp()
      if (!right) {
        throw new Error('Expected expression')
      }
      return {
        left: left,
        conjunction: operator.toLowerCase(),
        right: right
      }
    }
  }

var parseAnd = makeBinaryOpParser('AND', parseAtom)
  var parseExpression = makeBinaryOpParser('OR', parseAnd)

var node = parseExpression()
  if (!node || hasMore()) {
    throw new Error('Syntax error')
  }
  return node
}

Name	Size	Permission
AUTHORS	203 bytes	0644
LICENSE	1111 bytes	0644
README.md	3826 bytes	0644
index.js	143 bytes	0644
package.json	2619 bytes	0644
parse.js	2897 bytes	0644
scan.js	2750 bytes	0644