match-graph.cjs•12.7 kB
'use strict';
const parse = require('../definition-syntax/parse.cjs');
const MATCH = { type: 'Match' };
const MISMATCH = { type: 'Mismatch' };
const DISALLOW_EMPTY = { type: 'DisallowEmpty' };
const LEFTPARENTHESIS = 40; // (
const RIGHTPARENTHESIS = 41; // )
function createCondition(match, thenBranch, elseBranch) {
// reduce node count
if (thenBranch === MATCH && elseBranch === MISMATCH) {
return match;
}
if (match === MATCH && thenBranch === MATCH && elseBranch === MATCH) {
return match;
}
if (match.type === 'If' && match.else === MISMATCH && thenBranch === MATCH) {
thenBranch = match.then;
match = match.match;
}
return {
type: 'If',
match,
then: thenBranch,
else: elseBranch
};
}
function isFunctionType(name) {
return (
name.length > 2 &&
name.charCodeAt(name.length - 2) === LEFTPARENTHESIS &&
name.charCodeAt(name.length - 1) === RIGHTPARENTHESIS
);
}
function isEnumCapatible(term) {
return (
term.type === 'Keyword' ||
term.type === 'AtKeyword' ||
term.type === 'Function' ||
term.type === 'Type' && isFunctionType(term.name)
);
}
function buildGroupMatchGraph(combinator, terms, atLeastOneTermMatched) {
switch (combinator) {
case ' ': {
// Juxtaposing components means that all of them must occur, in the given order.
//
// a b c
// =
// match a
// then match b
// then match c
// then MATCH
// else MISMATCH
// else MISMATCH
// else MISMATCH
let result = MATCH;
for (let i = terms.length - 1; i >= 0; i--) {
const term = terms[i];
result = createCondition(
term,
result,
MISMATCH
);
}
return result;
}
case '|': {
// A bar (|) separates two or more alternatives: exactly one of them must occur.
//
// a | b | c
// =
// match a
// then MATCH
// else match b
// then MATCH
// else match c
// then MATCH
// else MISMATCH
let result = MISMATCH;
let map = null;
for (let i = terms.length - 1; i >= 0; i--) {
let term = terms[i];
// reduce sequence of keywords into a Enum
if (isEnumCapatible(term)) {
if (map === null && i > 0 && isEnumCapatible(terms[i - 1])) {
map = Object.create(null);
result = createCondition(
{
type: 'Enum',
map
},
MATCH,
result
);
}
if (map !== null) {
const key = (isFunctionType(term.name) ? term.name.slice(0, -1) : term.name).toLowerCase();
if (key in map === false) {
map[key] = term;
continue;
}
}
}
map = null;
// create a new conditonal node
result = createCondition(
term,
MATCH,
result
);
}
return result;
}
case '&&': {
// A double ampersand (&&) separates two or more components,
// all of which must occur, in any order.
// Use MatchOnce for groups with a large number of terms,
// since &&-groups produces at least N!-node trees
if (terms.length > 5) {
return {
type: 'MatchOnce',
terms,
all: true
};
}
// Use a combination tree for groups with small number of terms
//
// a && b && c
// =
// match a
// then [b && c]
// else match b
// then [a && c]
// else match c
// then [a && b]
// else MISMATCH
//
// a && b
// =
// match a
// then match b
// then MATCH
// else MISMATCH
// else match b
// then match a
// then MATCH
// else MISMATCH
// else MISMATCH
let result = MISMATCH;
for (let i = terms.length - 1; i >= 0; i--) {
const term = terms[i];
let thenClause;
if (terms.length > 1) {
thenClause = buildGroupMatchGraph(
combinator,
terms.filter(function(newGroupTerm) {
return newGroupTerm !== term;
}),
false
);
} else {
thenClause = MATCH;
}
result = createCondition(
term,
thenClause,
result
);
}
return result;
}
case '||': {
// A double bar (||) separates two or more options:
// one or more of them must occur, in any order.
// Use MatchOnce for groups with a large number of terms,
// since ||-groups produces at least N!-node trees
if (terms.length > 5) {
return {
type: 'MatchOnce',
terms,
all: false
};
}
// Use a combination tree for groups with small number of terms
//
// a || b || c
// =
// match a
// then [b || c]
// else match b
// then [a || c]
// else match c
// then [a || b]
// else MISMATCH
//
// a || b
// =
// match a
// then match b
// then MATCH
// else MATCH
// else match b
// then match a
// then MATCH
// else MATCH
// else MISMATCH
let result = atLeastOneTermMatched ? MATCH : MISMATCH;
for (let i = terms.length - 1; i >= 0; i--) {
const term = terms[i];
let thenClause;
if (terms.length > 1) {
thenClause = buildGroupMatchGraph(
combinator,
terms.filter(function(newGroupTerm) {
return newGroupTerm !== term;
}),
true
);
} else {
thenClause = MATCH;
}
result = createCondition(
term,
thenClause,
result
);
}
return result;
}
}
}
function buildMultiplierMatchGraph(node) {
let result = MATCH;
let matchTerm = buildMatchGraphInternal(node.term);
if (node.max === 0) {
// disable repeating of empty match to prevent infinite loop
matchTerm = createCondition(
matchTerm,
DISALLOW_EMPTY,
MISMATCH
);
// an occurrence count is not limited, make a cycle;
// to collect more terms on each following matching mismatch
result = createCondition(
matchTerm,
null, // will be a loop
MISMATCH
);
result.then = createCondition(
MATCH,
MATCH,
result // make a loop
);
if (node.comma) {
result.then.else = createCondition(
{ type: 'Comma', syntax: node },
result,
MISMATCH
);
}
} else {
// create a match node chain for [min .. max] interval with optional matches
for (let i = node.min || 1; i <= node.max; i++) {
if (node.comma && result !== MATCH) {
result = createCondition(
{ type: 'Comma', syntax: node },
result,
MISMATCH
);
}
result = createCondition(
matchTerm,
createCondition(
MATCH,
MATCH,
result
),
MISMATCH
);
}
}
if (node.min === 0) {
// allow zero match
result = createCondition(
MATCH,
MATCH,
result
);
} else {
// create a match node chain to collect [0 ... min - 1] required matches
for (let i = 0; i < node.min - 1; i++) {
if (node.comma && result !== MATCH) {
result = createCondition(
{ type: 'Comma', syntax: node },
result,
MISMATCH
);
}
result = createCondition(
matchTerm,
result,
MISMATCH
);
}
}
return result;
}
function buildMatchGraphInternal(node) {
if (typeof node === 'function') {
return {
type: 'Generic',
fn: node
};
}
switch (node.type) {
case 'Group': {
let result = buildGroupMatchGraph(
node.combinator,
node.terms.map(buildMatchGraphInternal),
false
);
if (node.disallowEmpty) {
result = createCondition(
result,
DISALLOW_EMPTY,
MISMATCH
);
}
return result;
}
case 'Multiplier':
return buildMultiplierMatchGraph(node);
case 'Type':
case 'Property':
return {
type: node.type,
name: node.name,
syntax: node
};
case 'Keyword':
return {
type: node.type,
name: node.name.toLowerCase(),
syntax: node
};
case 'AtKeyword':
return {
type: node.type,
name: '@' + node.name.toLowerCase(),
syntax: node
};
case 'Function':
return {
type: node.type,
name: node.name.toLowerCase() + '(',
syntax: node
};
case 'String':
// convert a one char length String to a Token
if (node.value.length === 3) {
return {
type: 'Token',
value: node.value.charAt(1),
syntax: node
};
}
// otherwise use it as is
return {
type: node.type,
value: node.value.substr(1, node.value.length - 2).replace(/\\'/g, '\''),
syntax: node
};
case 'Token':
return {
type: node.type,
value: node.value,
syntax: node
};
case 'Comma':
return {
type: node.type,
syntax: node
};
default:
throw new Error('Unknown node type:', node.type);
}
}
function buildMatchGraph(syntaxTree, ref) {
if (typeof syntaxTree === 'string') {
syntaxTree = parse.parse(syntaxTree);
}
return {
type: 'MatchGraph',
match: buildMatchGraphInternal(syntaxTree),
syntax: ref || null,
source: syntaxTree
};
}
exports.DISALLOW_EMPTY = DISALLOW_EMPTY;
exports.MATCH = MATCH;
exports.MISMATCH = MISMATCH;
exports.buildMatchGraph = buildMatchGraph;