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| 1 | +'use strict' |
| 2 | + |
| 3 | +// The ABNF grammar in the spec is totally ambiguous. |
| 4 | +// |
| 5 | +// This parser follows the operator precedence defined in the |
| 6 | +// `Order of Precedence and Parentheses` section. |
| 7 | + |
| 8 | +module.exports = function (tokens) { |
| 9 | + var index = 0 |
| 10 | + |
| 11 | + function hasMore () { |
| 12 | + return index < tokens.length |
| 13 | + } |
| 14 | + |
| 15 | + function token () { |
| 16 | + return hasMore() ? tokens[index] : null |
| 17 | + } |
| 18 | + |
| 19 | + function next () { |
| 20 | + if (!hasMore()) { |
| 21 | + throw new Error() |
| 22 | + } |
| 23 | + index++ |
| 24 | + } |
| 25 | + |
| 26 | + function parseOperator (operator) { |
| 27 | + var t = token() |
| 28 | + if (t && t.type === 'OPERATOR' && operator === t.string) { |
| 29 | + next() |
| 30 | + return t.string |
| 31 | + } |
| 32 | + } |
| 33 | + |
| 34 | + function parseWith () { |
| 35 | + if (parseOperator('WITH')) { |
| 36 | + var t = token() |
| 37 | + if (t && t.type === 'EXCEPTION') { |
| 38 | + next() |
| 39 | + return t.string |
| 40 | + } |
| 41 | + throw new Error('Expected exception after `WITH`') |
| 42 | + } |
| 43 | + } |
| 44 | + |
| 45 | + function parseLicenseRef () { |
| 46 | + // TODO: Actually, everything is concatenated into one string |
| 47 | + // for backward-compatibility but it could be better to return |
| 48 | + // a nice structure. |
| 49 | + var begin = index |
| 50 | + var string = '' |
| 51 | + var t = token() |
| 52 | + if (t.type === 'DOCUMENTREF') { |
| 53 | + next() |
| 54 | + string += 'DocumentRef-' + t.string + ':' |
| 55 | + if (!parseOperator(':')) { |
| 56 | + throw new Error('Expected `:` after `DocumentRef-...`') |
| 57 | + } |
| 58 | + } |
| 59 | + t = token() |
| 60 | + if (t.type === 'LICENSEREF') { |
| 61 | + next() |
| 62 | + string += 'LicenseRef-' + t.string |
| 63 | + return { license: string } |
| 64 | + } |
| 65 | + index = begin |
| 66 | + } |
| 67 | + |
| 68 | + function parseLicense () { |
| 69 | + var t = token() |
| 70 | + if (t && t.type === 'LICENSE') { |
| 71 | + next() |
| 72 | + var node = { license: t.string } |
| 73 | + if (parseOperator('+')) { |
| 74 | + node.plus = true |
| 75 | + } |
| 76 | + var exception = parseWith() |
| 77 | + if (exception) { |
| 78 | + node.exception = exception |
| 79 | + } |
| 80 | + return node |
| 81 | + } |
| 82 | + } |
| 83 | + |
| 84 | + function parseParenthesizedExpression () { |
| 85 | + var left = parseOperator('(') |
| 86 | + if (!left) { |
| 87 | + return |
| 88 | + } |
| 89 | + |
| 90 | + var expr = parseExpression() |
| 91 | + |
| 92 | + if (!parseOperator(')')) { |
| 93 | + throw new Error('Expected `)`') |
| 94 | + } |
| 95 | + |
| 96 | + return expr |
| 97 | + } |
| 98 | + |
| 99 | + function parseAtom () { |
| 100 | + return ( |
| 101 | + parseParenthesizedExpression() || |
| 102 | + parseLicenseRef() || |
| 103 | + parseLicense() |
| 104 | + ) |
| 105 | + } |
| 106 | + |
| 107 | + function makeBinaryOpParser (operator, nextParser) { |
| 108 | + return function parseBinaryOp () { |
| 109 | + var left = nextParser() |
| 110 | + if (!left) { |
| 111 | + return |
| 112 | + } |
| 113 | + |
| 114 | + if (!parseOperator(operator)) { |
| 115 | + return left |
| 116 | + } |
| 117 | + |
| 118 | + var right = parseBinaryOp() |
| 119 | + if (!right) { |
| 120 | + throw new Error('Expected expression') |
| 121 | + } |
| 122 | + return { |
| 123 | + left: left, |
| 124 | + conjunction: operator.toLowerCase(), |
| 125 | + right: right |
| 126 | + } |
| 127 | + } |
| 128 | + } |
| 129 | + |
| 130 | + var parseAnd = makeBinaryOpParser('AND', parseAtom) |
| 131 | + var parseExpression = makeBinaryOpParser('OR', parseAnd) |
| 132 | + |
| 133 | + var node = parseExpression() |
| 134 | + if (!node || hasMore()) { |
| 135 | + throw new Error('Syntax error') |
| 136 | + } |
| 137 | + return node |
| 138 | +} |
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