const errors = require('@tryghost/errors');
const DomainEvents = require('@tryghost/domain-events');
const {MemberSubscribeEvent} = require('@tryghost/member-events');

const messages = {
    emailVerificationNeeded: `We're hard at work processing your import. To make sure you get great deliverability on a list of that size, we'll need to enable some extra features for your account. A member of our team will be in touch with you by email to review your account make sure everything is configured correctly so you're ready to go.`,
    emailVerificationEmailSubject: `Email needs verification`,
    emailVerificationEmailMessage: `Email verification needed for site: {siteUrl}, just imported: {importedNumber} members.`
};

class VerificationTrigger {
    /**
     * 
     * @param {object} deps
     * @param {number} deps.configThreshold Threshold for triggering verification as defined in config
     * @param {() => boolean} deps.isVerified Check Ghost config to see if we are already verified
     * @param {() => boolean} deps.isVerificationRequired Check Ghost settings to see whether verification has been requested
     * @param {(content: {subject: string, message: string, amountImported: number}) => {}} deps.sendVerificationEmail Sends an email to the escalation address to confirm that customer needs to be verified
     * @param {any} deps.membersStats MemberStats service
     * @param {any} deps.Settings Ghost Settings model
     * @param {any} deps.eventRepository For querying events
     */
    constructor({
        configThreshold,
        isVerified,
        isVerificationRequired,
        sendVerificationEmail,
        membersStats,
        Settings,
        eventRepository
    }) {
        this._configThreshold = configThreshold;
        this._isVerified = isVerified;
        this._isVerificationRequired = isVerificationRequired;
        this._sendVerificationEmail = sendVerificationEmail;
        this._membersStats = membersStats;
        this._Settings = Settings;
        this._eventRepository = eventRepository;

        DomainEvents.subscribe(MemberSubscribeEvent, async (event) => {
            if (event.data.source === 'api' && isFinite(this._configThreshold)) {
                const createdAt = new Date();
                createdAt.setDate(createdAt.getDate() - 30);
                const events = await this._eventRepository.getNewsletterSubscriptionEvents({
                    // Date in last 30 days, source is API
                    filter: `source:api+created_at:>'${createdAt.toISOString().replace('T', ' ').substring(0, 19)}'`
                });

                if (events.meta.pagination.total > this._configThreshold) {
                    await this.startVerificationProcess({
                        amountImported: events.meta.pagination.total,
                        throwOnTrigger: false
                    });
                }
            }
        });
    }

    async getImportThreshold() {
        const volumeThreshold = this._configThreshold;
        if (isFinite(volumeThreshold)) {
            const membersTotal = await this._membersStats.getTotalMembers();
            return Math.max(membersTotal, volumeThreshold);
        } else {
            return volumeThreshold;
        }
    }

    /** @typedef IVerificationResult
     * @property {boolean} needsVerification Whether the verification workflow was triggered
     */

    /**
     * 
     * @param {object} config
     * @param {number} config.amountImported Amount of members which were imported
     * @param {boolean} config.throwOnTrigger Whether to throw if verification is needed
     * @returns {Promise<IVerificationResult>} Object containing property "needsVerification" - true when triggered 
     */
    async startVerificationProcess({
        amountImported,
        throwOnTrigger
    }) {
        if (!this._isVerified()) {
            // Only trigger flag change and escalation email the first time
            if (!this._isVerificationRequired()) {
                await this._Settings.edit([{
                    key: 'email_verification_required',
                    value: true
                }], {context: {internal: true}});

                this._sendVerificationEmail({
                    message: messages.emailVerificationEmailMessage,
                    subject: messages.emailVerificationEmailSubject,
                    amountImported
                });

                if (throwOnTrigger) {
                    throw new errors.ValidationError({
                        message: messages.emailVerificationNeeded
                    });
                }

                return {
                    needsVerification: true
                };
            }
        }

        return {
            needsVerification: false
        };
    }
}

module.exports = VerificationTrigger;