// Commission calculation service. Single source of truth used by all provision endpoints.
//
// Hierarchy for shop commission (highest priority wins):
//   1. Tariff-specific rule (provisionsregeln, active, gueltig_ab <= schaltungs_datum)
//   2. Global provider rule (anbieter_provisionsregeln, active, gueltig_ab <= schaltungs_datum)
//   3. Direct tariff amount (tarife.provision_euro)
//
// For type='prozent' the rule's basis_euro field is the base amount the percentage
// applies to. If basis_euro is missing on a percent rule, the contribution is 0
// (rule is effectively unusable - caller should validate at write time).
//
// Tarifoptionen are added on top (signed: rebates are negative).
// Hardware logic: when hardware is set, shop = shop - hardware_ek + kundenverkaufspreis_netto.
//
// Employee commission follows the same hierarchy but uses verkaeufer_* fields.
// For type='prozent' the base is the computed shop commission.

function num(value) {
    const n = parseFloat(value);
    return Number.isFinite(n) ? n : 0;
}

function pickRule(context) {
    // Returns the active rule that should apply, or null.
    // context: { tarifRule, anbieterRule, tarif }
    if (context.tarifRule) {
        return { source: 'Tarif-spezifische Regel', rule: context.tarifRule };
    }
    if (context.anbieterRule) {
        return { source: 'Globale Anbieter-Regel', rule: context.anbieterRule };
    }
    if (context.tarif && context.tarif.provision_euro != null && num(context.tarif.provision_euro) !== 0) {
        return {
            source: 'Direkte Tarif-Provision',
            rule: {
                provision_typ: 'fix',
                betrag: num(context.tarif.provision_euro),
                basis_euro: null,
                beschreibung: context.tarif.beschreibung || null,
                verkaeufer_provision_typ: null,
                verkaeufer_provision_betrag: null,
                verkaeufer_provision_beschreibung: null,
            },
        };
    }
    return null;
}

function applyShopRule(rule) {
    if (!rule) return 0;
    if (rule.provision_typ === 'fix') {
        return num(rule.betrag);
    }
    if (rule.provision_typ === 'prozent') {
        const basis = num(rule.basis_euro);
        return (num(rule.betrag) / 100) * basis;
    }
    return 0;
}

function applyEmployeeRule(rule, shopProvision) {
    if (!rule) return 0;
    if (rule.verkaeufer_provision_typ === 'fix') {
        return num(rule.verkaeufer_provision_betrag);
    }
    if (rule.verkaeufer_provision_typ === 'prozent') {
        return (num(rule.verkaeufer_provision_betrag) / 100) * shopProvision;
    }
    return 0;
}

function sumTarifoptionen(tarifoptionen) {
    if (!Array.isArray(tarifoptionen)) return { sum: 0, names: [] };
    let sum = 0;
    const names = [];
    for (const opt of tarifoptionen) {
        const v = num(opt.provision_euro);
        if (v !== 0) {
            sum += v;
            names.push(opt.name);
        }
    }
    return { sum, names };
}

// Main entry. Inputs are plain data (already loaded from DB by the route).
// `schaltung` is the schaltungen row (joined with tarif basics).
// `tarif` is the full tarif row.
// `tarifRule` is the active provisionsregeln row (or null).
// `anbieterRule` is the active anbieter_provisionsregeln row (or null).
// `tarifoptionen` is an array of tarifoption rows linked to this schaltung.
// `mitarbeiterProzentsatz` is a number (0-100) — used only when there is no
// employee-specific rule and the tariff defines mitarbeiter_provision.
function calculate({ schaltung, tarif, tarifRule, anbieterRule, tarifoptionen, mitarbeiterProzentsatz }) {
    const picked = pickRule({ tarifRule, anbieterRule, tarif });
    const ruleSource = picked ? picked.source : 'Keine Shop-Provision definiert';
    const rule = picked ? picked.rule : null;

    let shopProvision = applyShopRule(rule);

    const { sum: tarifoptionenSum, names: tarifoptionenNames } = sumTarifoptionen(tarifoptionen);
    shopProvision += tarifoptionenSum;

    let hardwareGewinn = 0;
    if (schaltung && schaltung.hardware && String(schaltung.hardware).trim() !== '') {
        hardwareGewinn = num(schaltung.kundenverkaufspreis_netto) - num(schaltung.hardware_ek);
        shopProvision += hardwareGewinn;
    }

    let employeeProvision = applyEmployeeRule(rule, shopProvision);
    let employeeSource = picked ? `${picked.source} (Verkäufer)` : 'Keine Mitarbeiter-Provision definiert';

    // Fallback: if no rule defines an employee commission, use the per-anbieter
    // mitarbeiter_prozentsatz against the computed shop commission.
    if (employeeProvision === 0 && (!rule || !rule.verkaeufer_provision_typ)) {
        const p = num(mitarbeiterProzentsatz);
        if (p !== 0) {
            employeeProvision = (p / 100) * shopProvision;
            employeeSource = `${p}% Mitarbeiter-Anteil von ${shopProvision.toFixed(2)}€`;
        }
    }

    return {
        shop: {
            betrag: round2(shopProvision),
            quelle: ruleSource,
            typ: rule ? rule.provision_typ : null,
            regel_betrag: rule ? num(rule.betrag) : null,
            basis_euro: rule ? (rule.basis_euro != null ? num(rule.basis_euro) : null) : null,
            beschreibung: rule ? rule.beschreibung : null,
        },
        mitarbeiter: {
            betrag: round2(employeeProvision),
            quelle: employeeSource,
            typ: rule ? rule.verkaeufer_provision_typ : null,
            regel_betrag: rule ? (rule.verkaeufer_provision_betrag != null ? num(rule.verkaeufer_provision_betrag) : null) : null,
            beschreibung: rule ? rule.verkaeufer_provision_beschreibung : null,
            prozentsatz: num(mitarbeiterProzentsatz),
        },
        tarifoptionen: {
            betrag: round2(tarifoptionenSum),
            namen: tarifoptionenNames,
        },
        hardware_gewinn: round2(hardwareGewinn),
    };
}

function round2(n) {
    return Math.round(n * 100) / 100;
}

module.exports = { calculate, num, round2 };