dashback/src/tools/net-gross-calc.js

import { defineTool, ToolError } from 'libllmorbiter';

const DEFAULT_TAX_RATE = 19;
const DEFAULT_PRECISION = 6;

/**
 * Calculates net-to-gross or gross-to-net for a single price.
 *
 * @param {object} params
 * @param {number} [params.net]
 * @param {number} [params.gross]
 * @param {number} [params.amount]
 * @param {'net'|'gross'} [params.from]
 * @param {number} [params.taxRate=19]
 * @param {number} [params.precision=6]
 * @returns {object}
 */
export function calculatePrice({ net, gross, amount, from, taxRate = DEFAULT_TAX_RATE, precision = DEFAULT_PRECISION }) {
    const rate = taxRate != null ? Number(taxRate) : DEFAULT_TAX_RATE;
    if (!Number.isFinite(rate) || rate < 0) {
        throw new ToolError(`Invalid taxRate: ${taxRate}. Must be a non-negative number.`);
    }

    const prec = precision != null ? Math.min(8, Math.max(2, Number(precision) || DEFAULT_PRECISION)) : DEFAULT_PRECISION;
    const factor = 1 + rate / 100;

    let inputType = null;
    let inputValue = null;

    if (net != null && gross == null) {
        inputType = 'net';
        inputValue = Number(net);
    } else if (gross != null && net == null) {
        inputType = 'gross';
        inputValue = Number(gross);
    } else if (amount != null) {
        inputValue = Number(amount);
        inputType = from === 'net' ? 'net' : 'gross';
    } else if (net != null && gross != null) {
        // Both provided: validate consistency
        const n = Number(net);
        const g = Number(gross);
        const calculatedGross = +(n * factor).toFixed(2);
        const effectiveRate = n > 0 ? +(((g - n) / n) * 100).toFixed(2) : 0;
        return {
            direction: 'verify',
            net: +n.toFixed(2),
            gross: +g.toFixed(2),
            taxRate: rate,
            effectiveTaxRate: effectiveRate,
            isConsistent: Math.abs(calculatedGross - g) <= 0.02,
            taxAmount: +(g - n).toFixed(2),
        };
    } else {
        throw new ToolError('net_gross_calc requires "net", "gross", or "amount".');
    }

    if (!Number.isFinite(inputValue) || inputValue < 0) {
        throw new ToolError(`Invalid price amount: ${inputValue}. Must be a non-negative number.`);
    }

    if (inputType === 'gross') {
        const grossVal = +inputValue.toFixed(2);
        const exactNet = inputValue / factor;
        const netRounded = +exactNet.toFixed(2);
        const netPrecision = +exactNet.toFixed(prec);
        const taxAmount = +(grossVal - netRounded).toFixed(2);

        return {
            direction: 'gross_to_net',
            gross: grossVal,
            net: netRounded,
            netPrecision,
            netPrecise: exactNet,
            taxRate: rate,
            taxAmount,
            apiNetValue: netPrecision,
            formatted: {
                gross: `${grossVal.toFixed(2)} €`,
                net: `${netRounded.toFixed(2)} €`,
                tax: `${taxAmount.toFixed(2)} €`,
            },
        };
    } else {
        const netVal = +inputValue.toFixed(2);
        const exactGross = inputValue * factor;
        const grossRounded = +exactGross.toFixed(2);
        const taxAmount = +(grossRounded - netVal).toFixed(2);

        return {
            direction: 'net_to_gross',
            net: netVal,
            gross: grossRounded,
            grossPrecise: exactGross,
            taxRate: rate,
            taxAmount,
            formatted: {
                net: `${netVal.toFixed(2)} €`,
                gross: `${grossRounded.toFixed(2)} €`,
                tax: `${taxAmount.toFixed(2)} €`,
            },
        };
    }
}

/**
 * Creates the net_gross_calc tool.
 */
export function createNetGrossCalcTool() {
    return defineTool({
        name: 'net_gross_calc',
        description:
            'Convert between net and gross prices (net to gross, gross to net) with VAT/tax rate (default 19%). ' +
            'Computes 2-decimal rounded display values and 6-decimal high-precision net values for API article creation.',
        strict: false,
        parameters: {
            type: 'object',
            additionalProperties: false,
            properties: {
                note: {
                    type: 'string',
                    description: 'A note explaining what this price calculation is doing. This note will be displayed to the user while executing.',
                },
                gross: {
                    type: ['number', 'null'],
                    description: 'Gross price (incl. VAT) or null. When provided, computes net price and tax amount.',
                },
                net: {
                    type: ['number', 'null'],
                    description: 'Net price (excl. VAT) or null. When provided, computes gross price and tax amount.',
                },
                taxRate: {
                    type: ['number', 'null'],
                    description: `Tax/VAT rate percentage (e.g. 19 for 19%, 7 for 7%) or null. Default ${DEFAULT_TAX_RATE}.`,
                },
                amount: {
                    type: ['number', 'null'],
                    description: 'Generic price amount or null when used with "from" ("gross" or "net").',
                },
                from: {
                    type: ['string', 'null'],
                    enum: ['gross', 'net', null],
                    description: 'Direction when using "amount": "gross" (default) or "net".',
                },
                precision: {
                    type: ['number', 'null'],
                    description: `Decimal precision for net price API value or null (default ${DEFAULT_PRECISION}, between 2 and 8).`,
                },
                items: {
                    type: ['array', 'null'],
                    description: 'Optional array of prices or objects for batch calculation: [19.99, 49.95] or [{ gross: 19.99, taxRate: 7 }].',
                    items: {
                        type: 'object',
                        additionalProperties: false,
                        properties: {
                            gross: { type: ['number', 'null'] },
                            net: { type: ['number', 'null'] },
                            amount: { type: ['number', 'null'] },
                            from: { type: ['string', 'null'], enum: ['gross', 'net', null] },
                            taxRate: { type: ['number', 'null'] },
                        },
                    },
                },
            },
        },
        invoke: async ({ note, gross, net, amount, from, taxRate = DEFAULT_TAX_RATE, precision = DEFAULT_PRECISION, items } = {}) => {
            if (Array.isArray(items) && items.length > 0) {
                const results = items.map((item, idx) => {
                    const itemRate = item.taxRate != null ? item.taxRate : taxRate;
                    try {
                        return calculatePrice({
                            net: item.net,
                            gross: item.gross,
                            amount: item.amount,
                            from: item.from || from,
                            taxRate: itemRate,
                            precision,
                        });
                    } catch (err) {
                        return { itemIndex: idx, error: err.message };
                    }
                });
                return JSON.stringify({ count: results.length, results }, null, 2);
            }

            const result = calculatePrice({ net, gross, amount, from, taxRate, precision });
            return JSON.stringify(result, null, 2);
        },
    });
}