adaptive-expressions/src/triggerTrees/clause.ts

Common Expression Language

/**
 * @module adaptive-expressions
 */
/**
 * Copyright (c) Microsoft Corporation. All rights reserved.
 * Licensed under the MIT License.
 */

import { Expression } from '../expression';
import { ExpressionType } from '../expressionType';
import { MemoryInterface } from '../memory';
import { PredicateComparer, PredicateComparers } from './optimizer';
import { RelationshipType } from './relationshipType';

/**
 * A canonical normal form expression.
 */
export class Clause extends Expression {
    private _ignored: Expression;

    /**
     * Initializes a new instance of the `Clause` class.
     *
     * @param clauseOrExpression A clause, expression or an array of expressions to initialize a `Clause`.
     */
    constructor(clauseOrExpression?: Clause | Expression | Expression[]) {
        super(ExpressionType.And, undefined);
        if (clauseOrExpression) {
            if (Array.isArray(clauseOrExpression)) {
                const children: Expression[] = clauseOrExpression;
                this.children = children;
            } else if (clauseOrExpression instanceof Clause) {
                const fromClause: Clause = clauseOrExpression;
                this.children = [...fromClause.children];
                for (const [key, value] of fromClause.anyBindings.entries()) {
                    this.anyBindings.set(key, value);
                }
            } else if (clauseOrExpression instanceof Expression) {
                const expression: Expression = clauseOrExpression;
                this.children.push(expression);
            }
        }
    }

    /**
     * Gets or sets the anyBinding dictionary.
     */
    anyBindings: Map<string, string> = new Map<string, string>();

    /**
     * Gets or sets whether the clause is subsumed.
     */
    subsumed = false;

    /**
     * Gets a string that represents the current clause.
     *
     * @param builder An array of string to build the string of clause.
     * @param indent An integer represents the number of spaces at the start of a line.
     * @returns A string that represents the current clause.
     */
    toString(builder: string[] = [], indent = 0): string {
        builder.push(' '.repeat(indent));
        if (this.subsumed) {
            builder.push('*');
        }

        builder.push('(');
        let first = true;
        for (const child of this.children) {
            if (first) {
                first = false;
            } else {
                builder.push(' && ');
            }
            builder.push(child.toString());
        }

        builder.push(')');
        if (this._ignored) {
            builder.push(' ignored(');
            builder.push(this._ignored.toString());
            builder.push(')');
        }

        this.anyBindings.forEach((value: string, key: string) => {
            builder.push(` ${key}->${value}`);
        });
        return builder.join('');
    }

    /**
     * Compares the current `Clause` with another `Clause`.
     *
     * @param other The other `Clause` to compare.
     * @param comparers A comparer, which is a dictionary of `PredicateComparer` with string keys.
     * @returns A `RelationshipType` value between two `Clause` instances.
     */
    relationship(other: Clause, comparers: PredicateComparers): RelationshipType {
        let soFar: RelationshipType = RelationshipType.incomparable;
        let shorter = this as Clause;
        let shorterCount = shorter.children.length;
        let longer: Clause = other;
        let longerCount = longer.children.length;
        let swapped = false;
        if (longerCount < shorterCount) {
            longer = this as Clause;
            shorter = other;
            const tmp = longerCount;
            longerCount = shorterCount;
            shorterCount = tmp;
            swapped = true;
        }

        if (shorterCount === 0) {
            if (longerCount === 0) {
                soFar = RelationshipType.equal;
            } else {
                soFar = RelationshipType.generalizes;
            }
        } else {
            // If every one of shorter predicates is equal or superset of one in longer, then shorter is a superset of longer
            for (const shortPredicate of shorter.children) {
                let shorterRel = RelationshipType.incomparable;
                for (const longPredicate of longer.children) {
                    shorterRel = this._relationship(shortPredicate, longPredicate, comparers);
                    if (shorterRel !== RelationshipType.incomparable) {
                        // Found related predicates
                        break;
                    }
                }

                if (shorterRel === RelationshipType.incomparable) {
                    // Predicate in shorter is incomparable so done
                    soFar = RelationshipType.incomparable;
                    break;
                } else {
                    if (soFar === RelationshipType.incomparable) {
                        soFar = shorterRel;
                    }

                    if (soFar === RelationshipType.equal) {
                        if (
                            shorterRel === RelationshipType.generalizes ||
                            (shorterRel === RelationshipType.specializes && shorterCount === longerCount) ||
                            shorterRel === RelationshipType.equal
                        ) {
                            soFar = shorterRel;
                        } else {
                            break;
                        }
                    } else if (soFar != shorterRel) {
                        // Not continued with sub/super so incomparable
                        break;
                    }
                }
            }

            if (shorterCount !== longerCount) {
                switch (soFar) {
                    case RelationshipType.equal:
                    case RelationshipType.generalizes:
                        soFar = RelationshipType.generalizes;
                        break;
                    default:
                        soFar = RelationshipType.incomparable;
                        break;
                }
            }

            soFar = this._bindingRelationship(soFar, shorter, longer);
        }

        return this._swap(soFar, swapped);
    }

    /**
     * Determines whether the current `Clause` matches with another `Clause`.
     *
     * @param clause The other `Clause` instance to compare with.
     * @param memory The scope for looking up variables.
     * @returns A boolean value indicating whether the two clauses are matches.
     */
    matches(clause: Clause, memory: MemoryInterface | any): boolean {
        let matched = false;
        if (clause.deepEquals(this)) {
            matched = true;
            if (this._ignored) {
                const { value: match, error } = this._ignored.tryEvaluate(memory);
                matched = !error && match;
            }
        }

        return matched;
    }

    /**
     * Splits ignored child expressions.
     */
    splitIgnores(): void {
        const children: Expression[] = [];
        const ignores: Expression[] = [];
        for (let i = 0; i < this.children.length; i++) {
            const child = this.children[i];
            if (child.type === ExpressionType.Ignore) {
                ignores.push(child);
            } else {
                children.push(child);
            }
        }

        this.children = children;

        if (ignores.length > 0) {
            this._ignored = Expression.andExpression(...ignores);
        }
    }

    private _bindingRelationship(
        soFar: RelationshipType,
        shorterClause: Clause,
        longerClause: Clause,
    ): RelationshipType {
        if (soFar === RelationshipType.equal) {
            let swapped = false;
            let shorter = shorterClause.anyBindings;
            let longer = longerClause.anyBindings;
            if (shorterClause.anyBindings.size > longerClause.anyBindings.size) {
                shorter = longerClause.anyBindings;
                longer = shorterClause.anyBindings;
                swapped = true;
            }

            for (const [shorterKey, shorterValue] of shorter.entries()) {
                let found = false;
                for (const [longerKey, longerValue] of longer.entries()) {
                    if (shorterKey === longerKey && shorterValue === longerValue) {
                        found = true;
                        break;
                    }
                }

                if (!found) {
                    soFar = RelationshipType.incomparable;
                }
            }

            if (soFar === RelationshipType.equal && shorter.size < longer.size) {
                soFar = RelationshipType.specializes;
            }

            soFar = this._swap(soFar, swapped);
        }

        return soFar;
    }

    private _swap(soFar: RelationshipType, swapped: boolean): RelationshipType {
        let reln = soFar;
        if (swapped) {
            switch (soFar) {
                case RelationshipType.specializes:
                    reln = RelationshipType.generalizes;
                    break;
                case RelationshipType.generalizes:
                    reln = RelationshipType.specializes;
                    break;
            }
        }
        return reln;
    }

    private _relationship(expr: Expression, other: Expression, comparers: PredicateComparers): RelationshipType {
        let relationship = RelationshipType.incomparable;
        let root = expr;
        let rootOther = other;
        if (expr.type === ExpressionType.Not && other.type === ExpressionType.Not) {
            root = expr.children[0];
            rootOther = other.children[0];
        }

        let comparer: PredicateComparer;
        if (root.type === other.type) {
            comparer = comparers[root.type];
        }

        if (comparer) {
            relationship = comparer.relationship(root, rootOther);
        } else {
            relationship = expr.deepEquals(other) ? RelationshipType.equal : RelationshipType.incomparable;
        }

        return relationship;
    }
}