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

import { EvaluateExpressionDelegate, ExpressionEvaluator } from '../expressionEvaluator';
import { ExpressionType } from '../expressionType';
import { FunctionUtils } from '../functionUtils';
import { ReturnType } from '../returnType';
import bigInt from 'big-integer';

/**
 * Convert the string version of a floating-point number to a floating-point number.
 */
export class Float extends ExpressionEvaluator {
    /**
     * Initializes a new instance of the [Float](xref:adaptive-expressions.Float) class.
     */
    constructor() {
        super(ExpressionType.Float, Float.evaluator(), ReturnType.Number, FunctionUtils.validateUnary);
    }

    /**
     * @private
     */
    private static evaluator(): EvaluateExpressionDelegate {
        return FunctionUtils.applyWithError((args: any[]): any => {
            const firstChild = args[0];
            let error: string;
            let value: unknown;
            if (bigInt.isInstance(firstChild)) {
                return { value: firstChild.toJSNumber(), error };
            }
            if (typeof firstChild === 'string') {
                value = parseFloat(firstChild);
                if (!FunctionUtils.isNumber(value)) {
                    error = `parameter ${args[0]} is not a valid number string.`;
                }
            } else if (FunctionUtils.isNumber(firstChild)) {
                value = firstChild;
            }

            return { value, error };
        });
    }
}