const moment = require('moment');

class SubscriptionStatsService {
    /**
     * @param {object} deps
     * @param {import('knex').Knex} deps.knex*/
    constructor({knex}) {
        this.knex = knex;
    }

    /**
     * @returns {Promise<{data: SubscriptionHistoryEntry[]}>}
     **/
    async getSubscriptionHistory() {
        const subscriptionDeltaEntries = await this.fetchAllSubscriptionDeltas();
        const counts = await this.fetchSubscriptionCounts();

        /** @type {Object.<string, Object.<string, number>>} */
        const countData = {};
        counts.forEach((count) => {
            if (!countData[count.tier]) {
                countData[count.tier] = {};
            }
            countData[count.tier][count.cadence] = count.count;
        });

        /** @type {SubscriptionHistoryEntry[]} */
        let subscriptionHistoryEntries = [];

        /** @type {string[]} */
        let cadences = [];
        /** @type {string[]} */
        let tiers = [];

        for (let index = subscriptionDeltaEntries.length - 1; index >= 0; index -= 1) {
            const entry = subscriptionDeltaEntries[index];
            if (!countData[entry.tier]) {
                countData[entry.tier] = {};
            }
            if (!countData[entry.tier][entry.cadence]) {
                countData[entry.tier][entry.cadence] = 0;
            }

            subscriptionHistoryEntries.unshift({
                ...entry,
                date: moment(entry.date).format('YYYY-MM-DD'),
                count: countData[entry.tier][entry.cadence]
            });

            countData[entry.tier][entry.cadence] += entry.negative_delta;
            countData[entry.tier][entry.cadence] -= entry.positive_delta;

            if (!cadences.includes(entry.cadence)) {
                cadences.push(entry.cadence);
            }
            if (!tiers.includes(entry.tier)) {
                tiers.push(entry.tier);
            }
        }

        return {
            data: subscriptionHistoryEntries,
            meta: {
                cadences,
                tiers,
                totals: counts
            }
        };
    }

    /**
     * @returns {Promise<SubscriptionDelta[]>}
     **/
    async fetchAllSubscriptionDeltas() {
        const knex = this.knex;
        const rows = await knex('members_paid_subscription_events')
            .join('stripe_prices AS price', function () {
                this.on('price.stripe_price_id', '=', 'members_paid_subscription_events.from_plan')
                    .orOn('price.stripe_price_id', '=', 'members_paid_subscription_events.to_plan');
            })
            .join('stripe_products AS product', 'product.stripe_product_id', '=', 'price.stripe_product_id')
            .join('products AS tier', 'tier.id', '=', 'product.product_id')
            .leftJoin('stripe_prices AS from_price', 'from_price.stripe_price_id', '=', 'members_paid_subscription_events.from_plan')
            .leftJoin('stripe_prices AS to_price', 'to_price.stripe_price_id', '=', 'members_paid_subscription_events.to_plan')
            .select(knex.raw(`
                DATE(members_paid_subscription_events.created_at) as date
            `))
            .select(knex.raw(`
                tier.id as tier
            `))
            .select(knex.raw(`
                price.interval as cadence
            `))
            .select(knex.raw(`SUM(
                CASE
                    WHEN members_paid_subscription_events.type IN ('created','reactivated') AND members_paid_subscription_events.mrr_delta != 0 THEN 1
                    WHEN members_paid_subscription_events.type='updated' AND price.id = to_price.id THEN 1
                    ELSE 0
                END
            ) as positive_delta`))
            .select(knex.raw(`SUM(
                CASE
                    WHEN members_paid_subscription_events.type IN ('canceled', 'expired') AND members_paid_subscription_events.mrr_delta != 0 THEN 1
                    WHEN members_paid_subscription_events.type='updated' AND price.id = from_price.id THEN 1
                    ELSE 0
                END
            ) as negative_delta`))
            .select(knex.raw(`SUM(
                CASE
                    WHEN members_paid_subscription_events.type IN ('created','reactivated') AND members_paid_subscription_events.mrr_delta != 0 THEN 1
                    ELSE 0
                END
            ) as signups`))
            .select(knex.raw(`SUM(
                CASE
                    WHEN members_paid_subscription_events.type IN ('canceled', 'expired') AND members_paid_subscription_events.mrr_delta != 0 THEN 1
                    ELSE 0
                END
            ) as cancellations`))
            .groupBy('date', 'tier', 'cadence')
            .orderBy('date');

        return rows;
    }

    /**
      * Get the current total subscriptions grouped by Cadence and Tier
      * @returns {Promise<SubscriptionCount[]>}
      **/
    async fetchSubscriptionCounts() {
        const knex = this.knex;

        const data = await knex('members_stripe_customers_subscriptions')
            .select(knex.raw(`
                  COUNT(members_stripe_customers_subscriptions.id) AS count,
                  products.id AS tier,
                  stripe_prices.interval AS cadence
             `))
            .join('stripe_prices', 'stripe_prices.stripe_price_id', '=', 'members_stripe_customers_subscriptions.stripe_price_id')
            .join('stripe_products', 'stripe_products.stripe_product_id', '=', 'stripe_prices.stripe_product_id')
            .join('products', 'products.id', '=', 'stripe_products.product_id')
            .whereNot('members_stripe_customers_subscriptions.mrr', 0)
            .groupBy('tier', 'cadence');

        return data;
    }
}

/** @typedef {object} SubscriptionCount
  * @prop {string} tier
  * @prop {string} cadence
  * @prop {number} count
  **/

/**
 * @typedef {object} SubscriptionDelta
 * @prop {string} tier
 * @prop {string} cadence
 * @prop {string} date
 * @prop {number} positive_delta
 * @prop {number} negative_delta
 * @prop {number} signups
 * @prop {number} cancellations
 **/

/**
 * @typedef {object} SubscriptionHistoryEntry
 * @prop {string} tier
 * @prop {string} cadence
 * @prop {string} date
 * @prop {number} positive_delta
 * @prop {number} negative_delta
 * @prop {number} signups
 * @prop {number} cancellations
 * @prop {number} count
 **/

module.exports = SubscriptionStatsService;