import errors from '@tryghost/errors';
import type {GiftCadence} from './gift-schema';

export type {GiftCadence} from './gift-schema';

export interface GiftCheckoutTier {
    status: string;
    visibility: string;
    type: string;
    currency: string | null;
    monthlyPrice: number | null;
    yearlyPrice: number | null;
}

interface GiftDurationDefinition {
    cadence: GiftCadence;
    billingDuration: number;
    portalPlan: 'monthly' | 'yearly';
    priceProperty: 'monthlyPrice' | 'yearlyPrice';
    multiplier: number;
}

export interface ResolvedGiftDuration extends GiftDurationDefinition {
    totalMonths: number;
    isCadenceOnly: boolean;
}

export interface GiftCheckoutPlan {
    cadence: GiftCadence;
    duration: number;
    totalMonths: number;
    amount: number;
}

// Mirrored by the Portal catalogue in apps/portal/src/utils/gift-subscriptions.ts
// until later customization work makes durations server-provided
const GIFT_DURATION_CATALOGUE = new Map<number, GiftDurationDefinition>([
    [1, {cadence: 'month', billingDuration: 1, portalPlan: 'monthly', priceProperty: 'monthlyPrice', multiplier: 1}],
    [3, {cadence: 'month', billingDuration: 3, portalPlan: 'monthly', priceProperty: 'monthlyPrice', multiplier: 3}],
    [6, {cadence: 'month', billingDuration: 6, portalPlan: 'monthly', priceProperty: 'monthlyPrice', multiplier: 6}],
    [12, {cadence: 'year', billingDuration: 1, portalPlan: 'yearly', priceProperty: 'yearlyPrice', multiplier: 1}]
]);

function invalidGiftOffer(context: string) {
    return new errors.BadRequestError({
        message: 'Bad Request.',
        context
    });
}

export function resolveGiftDuration({
    duration,
    cadence
}: {
    duration?: number;
    cadence?: string;
}): ResolvedGiftDuration {
    let totalMonths = duration;

    if (totalMonths === undefined) {
        if (cadence === 'month') {
            totalMonths = 1;
        } else if (cadence === 'year') {
            totalMonths = 12;
        } else {
            throw invalidGiftOffer('Expected a supported gift duration or legacy cadence');
        }
    }

    if (typeof totalMonths !== 'number' || !Number.isInteger(totalMonths)) {
        throw invalidGiftOffer(`Unsupported gift duration "${totalMonths}"`);
    }

    const offer = GIFT_DURATION_CATALOGUE.get(totalMonths);

    if (!offer) {
        throw invalidGiftOffer(`Unsupported gift duration "${totalMonths}"`);
    }

    if (cadence !== undefined && cadence !== offer.cadence) {
        throw invalidGiftOffer(`Gift duration "${totalMonths}" conflicts with cadence "${cadence}"`);
    }

    return {
        ...offer,
        totalMonths,
        isCadenceOnly: duration === undefined
    };
}

export function validateGiftCheckoutOffer({
    tier,
    portalPlans,
    offer
}: {
    tier: GiftCheckoutTier;
    portalPlans: unknown;
    offer: ResolvedGiftDuration;
}): GiftCheckoutPlan {
    if (tier.status !== 'active' || tier.visibility !== 'public' || tier.type !== 'paid') {
        throw invalidGiftOffer('The requested tier is not available for gift purchases');
    }

    // legacy cadence-only requests predate the Portal plan gate, keep them working
    if (!offer.isCadenceOnly && (!Array.isArray(portalPlans) || !portalPlans.includes(offer.portalPlan))) {
        throw invalidGiftOffer(`The ${offer.portalPlan} Portal plan is not available`);
    }

    const unitAmount = tier[offer.priceProperty];

    if (typeof unitAmount !== 'number' || !Number.isSafeInteger(unitAmount) || unitAmount <= 0 || typeof tier.currency !== 'string' || !tier.currency) {
        throw invalidGiftOffer('The requested tier does not have a valid gift price');
    }

    const amount = unitAmount * offer.multiplier;

    if (!Number.isSafeInteger(amount)) {
        throw invalidGiftOffer('The requested gift amount is invalid');
    }

    return {
        cadence: offer.cadence,
        duration: offer.billingDuration,
        totalMonths: offer.totalMonths,
        amount
    };
}