ts-budgie/src/nodes/visitors/forStatementVisitor.ts

Converts TypeScript code to Budgie.

import { CommandNames } from "budgie";
import * as ts from "typescript";

import { BudgieLine } from "../../output/budgieLine";
import { Transformation } from "../../output/transformation";
import { createUnsupportedBudgieLine } from "../../output/unsupported";
import { getNumericTypeNameFromUsages } from "../../parsing/numerics";
import { NodeVisitor } from "../visitor";

const forLoopsMustBeAdditiveComplaint = "For loops over numbers must change the iterator with addition.";

const irregularComplaint = "Could not parse irregular for loop.";

export class ForStatementVisitor extends NodeVisitor {
    public visit(node: ts.ForStatement) {
        return [Transformation.fromNode(node, this.sourceFile, this.getTransformationContents(node))];
    }

    private getTransformationContents(node: ts.ForStatement) {
        const { condition, incrementor, initializer } = node;
        if (
            condition === undefined ||
            incrementor === undefined ||
            initializer === undefined ||
            !ts.isVariableDeclarationList(initializer) ||
            initializer.declarations.length !== 1
        ) {
            return [createUnsupportedBudgieLine(irregularComplaint)];
        }

        const declaration = initializer.declarations[0];
        if (declaration.initializer === undefined) {
            return [createUnsupportedBudgieLine(irregularComplaint)];
        }

        const name = (declaration.name as ts.Identifier).text;
        const incrementorText = this.getIncrementorIfNotOne(name, incrementor);
        const end = this.getConditionEnd(name, condition);
        const start = declaration.initializer.getText(this.sourceFile);
        const realType = typeof end === "string" ? getNumericTypeNameFromUsages([start, end]) : "float";

        const bodyNodes = this.router.recurseIntoNode(node.statement);
        const parameters = [name, realType, start, end];
        if (incrementorText !== undefined) {
            parameters.push(incrementorText);
        }

        return [new BudgieLine(CommandNames.ForNumbersStart, ...parameters), ...bodyNodes, new BudgieLine(CommandNames.ForNumbersEnd)];
    }

    private getIncrementorIfNotOne(target: string, incrementor: ts.Expression) {
        if (ts.isPostfixUnaryExpression(incrementor) || ts.isPrefixUnaryExpression(incrementor)) {
            return undefined;
        }

        if (
            ts.isBinaryExpression(incrementor) &&
            incrementor.operatorToken.kind === ts.SyntaxKind.PlusEqualsToken &&
            (incrementor.left as ts.Identifier).text === target
        ) {
            const right = incrementor.right as ts.Identifier;

            return right.text === "1" ? undefined : right.text;
        }

        return createUnsupportedBudgieLine(forLoopsMustBeAdditiveComplaint);
    }

    private getConditionEnd(target: string, condition: ts.Expression) {
        if (
            !ts.isBinaryExpression(condition) ||
            (condition.left as ts.Identifier).text !== target ||
            condition.operatorToken.kind !== ts.SyntaxKind.LessThanToken
        ) {
            return createUnsupportedBudgieLine(irregularComplaint);
        }

        if (ts.isNumericLiteral(condition.right)) {
            return condition.right.text;
        }

        return this.router.recurseIntoValue(condition.right);
    }
}