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RuleSetCompiler.js
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Mon, Jun 16, 08:54

RuleSetCompiler.js
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/*
MIT License http://www.opensource.org/licenses/mit-license.php
Author Tobias Koppers @sokra
*/
"use strict";
const { SyncHook } = require("tapable");
/**
* @typedef {Object} RuleCondition
* @property {string | string[]} property
* @property {boolean} matchWhenEmpty
* @property {function(string): boolean} fn
*/
/**
* @typedef {Object} Condition
* @property {boolean} matchWhenEmpty
* @property {function(string): boolean} fn
*/
/**
* @typedef {Object} CompiledRule
* @property {RuleCondition[]} conditions
* @property {(Effect|function(object): Effect[])[]} effects
* @property {CompiledRule[]=} rules
* @property {CompiledRule[]=} oneOf
*/
/**
* @typedef {Object} Effect
* @property {string} type
* @property {any} value
*/
/**
* @typedef {Object} RuleSet
* @property {Map<string, any>} references map of references in the rule set (may grow over time)
* @property {function(object): Effect[]} exec execute the rule set
*/
class RuleSetCompiler {
constructor(plugins) {
this.hooks = Object.freeze({
/** @type {SyncHook<[string, object, Set<string>, CompiledRule, Map<string, any>]>} */
rule: new SyncHook([
"path",
"rule",
"unhandledProperties",
"compiledRule",
"references"
])
});
if (plugins) {
for (const plugin of plugins) {
plugin.apply(this);
}
}
}
/**
* @param {object[]} ruleSet raw user provided rules
* @returns {RuleSet} compiled RuleSet
*/
compile(ruleSet) {
const refs = new Map();
const rules = this.compileRules("ruleSet", ruleSet, refs);
/**
* @param {object} data data passed in
* @param {CompiledRule} rule the compiled rule
* @param {Effect[]} effects an array where effects are pushed to
* @returns {boolean} true, if the rule has matched
*/
const execRule = (data, rule, effects) => {
for (const condition of rule.conditions) {
const p = condition.property;
if (Array.isArray(p)) {
let current = data;
for (const subProperty of p) {
if (
current &&
typeof current === "object" &&
Object.prototype.hasOwnProperty.call(current, subProperty)
) {
current = current[subProperty];
} else {
current = undefined;
break;
}
}
if (current !== undefined) {
if (!condition.fn(current)) return false;
continue;
}
} else if (p in data) {
const value = data[p];
if (value !== undefined) {
if (!condition.fn(value)) return false;
continue;
}
}
if (!condition.matchWhenEmpty) {
return false;
}
}
for (const effect of rule.effects) {
if (typeof effect === "function") {
const returnedEffects = effect(data);
for (const effect of returnedEffects) {
effects.push(effect);
}
} else {
effects.push(effect);
}
}
if (rule.rules) {
for (const childRule of rule.rules) {
execRule(data, childRule, effects);
}
}
if (rule.oneOf) {
for (const childRule of rule.oneOf) {
if (execRule(data, childRule, effects)) {
break;
}
}
}
return true;
};
return {
references: refs,
exec: data => {
/** @type {Effect[]} */
const effects = [];
for (const rule of rules) {
execRule(data, rule, effects);
}
return effects;
}
};
}
/**
* @param {string} path current path
* @param {object[]} rules the raw rules provided by user
* @param {Map<string, any>} refs references
* @returns {CompiledRule[]} rules
*/
compileRules(path, rules, refs) {
return rules.map((rule, i) =>
this.compileRule(`${path}[${i}]`, rule, refs)
);
}
/**
* @param {string} path current path
* @param {object} rule the raw rule provided by user
* @param {Map<string, any>} refs references
* @returns {CompiledRule} normalized and compiled rule for processing
*/
compileRule(path, rule, refs) {
const unhandledProperties = new Set(
Object.keys(rule).filter(key => rule[key] !== undefined)
);
/** @type {CompiledRule} */
const compiledRule = {
conditions: [],
effects: [],
rules: undefined,
oneOf: undefined
};
this.hooks.rule.call(path, rule, unhandledProperties, compiledRule, refs);
if (unhandledProperties.has("rules")) {
unhandledProperties.delete("rules");
const rules = rule.rules;
if (!Array.isArray(rules))
throw this.error(path, rules, "Rule.rules must be an array of rules");
compiledRule.rules = this.compileRules(`${path}.rules`, rules, refs);
}
if (unhandledProperties.has("oneOf")) {
unhandledProperties.delete("oneOf");
const oneOf = rule.oneOf;
if (!Array.isArray(oneOf))
throw this.error(path, oneOf, "Rule.oneOf must be an array of rules");
compiledRule.oneOf = this.compileRules(`${path}.oneOf`, oneOf, refs);
}
if (unhandledProperties.size > 0) {
throw this.error(
path,
rule,
`Properties ${Array.from(unhandledProperties).join(", ")} are unknown`
);
}
return compiledRule;
}
/**
* @param {string} path current path
* @param {any} condition user provided condition value
* @returns {Condition} compiled condition
*/
compileCondition(path, condition) {
if (!condition) {
throw this.error(
path,
condition,
"Expected condition but got falsy value"
);
}
if (typeof condition === "string") {
return {
matchWhenEmpty: condition.length === 0,
fn: str => str.startsWith(condition)
};
}
if (typeof condition === "function") {
try {
return {
matchWhenEmpty: condition(""),
fn: condition
};
} catch (err) {
throw this.error(
path,
condition,
"Evaluation of condition function threw error"
);
}
}
if (condition instanceof RegExp) {
return {
matchWhenEmpty: condition.test(""),
fn: v => condition.test(v)
};
}
if (Array.isArray(condition)) {
const items = condition.map((c, i) =>
this.compileCondition(`${path}[${i}]`, c)
);
return this.combineConditionsOr(items);
}
if (typeof condition !== "object") {
throw this.error(
path,
condition,
`Unexpected ${typeof condition} when condition was expected`
);
}
const conditions = [];
for (const key of Object.keys(condition)) {
const value = condition[key];
switch (key) {
case "or":
if (value) {
if (!Array.isArray(value)) {
throw this.error(
`${path}.or`,
condition.and,
"Expected array of conditions"
);
}
conditions.push(this.compileCondition(`${path}.or`, value));
}
break;
case "and":
if (value) {
if (!Array.isArray(value)) {
throw this.error(
`${path}.and`,
condition.and,
"Expected array of conditions"
);
}
let i = 0;
for (const item of value) {
conditions.push(this.compileCondition(`${path}.and[${i}]`, item));
i++;
}
}
break;
case "not":
if (value) {
const matcher = this.compileCondition(`${path}.not`, value);
const fn = matcher.fn;
conditions.push({
matchWhenEmpty: !matcher.matchWhenEmpty,
fn: v => !fn(v)
});
}
break;
default:
throw this.error(
`${path}.${key}`,
condition[key],
`Unexpected property ${key} in condition`
);
}
}
if (conditions.length === 0) {
throw this.error(
path,
condition,
"Expected condition, but got empty thing"
);
}
return this.combineConditionsAnd(conditions);
}
/**
* @param {Condition[]} conditions some conditions
* @returns {Condition} merged condition
*/
combineConditionsOr(conditions) {
if (conditions.length === 0) {
return {
matchWhenEmpty: false,
fn: () => false
};
} else if (conditions.length === 1) {
return conditions[0];
} else {
return {
matchWhenEmpty: conditions.some(c => c.matchWhenEmpty),
fn: v => conditions.some(c => c.fn(v))
};
}
}
/**
* @param {Condition[]} conditions some conditions
* @returns {Condition} merged condition
*/
combineConditionsAnd(conditions) {
if (conditions.length === 0) {
return {
matchWhenEmpty: false,
fn: () => false
};
} else if (conditions.length === 1) {
return conditions[0];
} else {
return {
matchWhenEmpty: conditions.every(c => c.matchWhenEmpty),
fn: v => conditions.every(c => c.fn(v))
};
}
}
/**
* @param {string} path current path
* @param {any} value value at the error location
* @param {string} message message explaining the problem
* @returns {Error} an error object
*/
error(path, value, message) {
return new Error(
`Compiling RuleSet failed: ${message} (at ${path}: ${value})`
);
}
}
module.exports = RuleSetCompiler;

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