siimee/backend/lib/services/match.js

const Schmervice = require('@hapipal/schmervice')

function engageEveryone(guys) {
    let done
    do {
        done = true
        for (let i = 0; i < guys.length; i++) {
            const guy = guys[i]
            if (!guy.fiance) {
                done = false
                const gal = guy.nextCandidate()
                if (!gal.fiance || gal.prefers(guy)) {
                    guy.engageTo(gal)
                }
            }
        }
    } while (!done)
}

class Person {
    constructor(name) {
        let candidateIndex = 0
        this.name = name
        this.fiance = null
        this.candidates = []
        this.rank = p => {
            for (let i = 0; i < this.candidates.length; i++) {
                if (this.candidates[i] === p) return i
            }
            return this.candidates.length + 1
        }
        this.prefers = p => {
            return this.rank(p) < this.rank(this.fiance)
        }
        this.nextCandidate = () => {
            if (candidateIndex >= this.candidates.length) {
                return null
            }
            return this.candidates[candidateIndex++]
        }

        this.engageTo = p => {
            if (p.fiance) {
                p.fiance.fiance = null
            }
            p.fiance = this
            if (this.fiance) {
                this.fiance.fiance = null
            }
            this.fiance = p
        }

        this.swapWith = p => {
            const thisFiance = this.fiance
            const pFiance = p.fiance
            this.engageTo(pFiance)
            p.engageTo(thisFiance)
        }
    }
}

module.exports = class MatchService extends Schmervice.Service {
    constructor(...args) {
        super(...args)
    }
    async calcMatches(allQueuesByType) {
        const seekers = Object.keys(allQueuesByType['seeker']).map(id => ({
            profile_id: parseInt(id),
            queue: allQueuesByType['seeker'][id],
        }))
        const posters = Object.keys(allQueuesByType['poster']).map(id => ({
            profile_id: parseInt(id),
            queue: allQueuesByType['poster'][id],
        }))

        const diff = Math.abs(posters.length - seekers.length)
        const smallerList = posters.length < seekers.length ? posters : seekers
        // ADD DUMMY IDS TO THE SMALLER LIST
        for (let d = 0; d < diff; d++) {
            smallerList.push({ profile_id: `${d}-dummy`, queue: [] })
        }
        let allPeople = [...seekers, ...posters]
        const queuesById = allPeople.reduce((queuesById, profile) => {
            queuesById[profile.profile_id] = profile.queue
            return queuesById
        }, {})
        let allIds = allPeople.map(profile => profile.profile_id)
        seekers.forEach(profile => {
            profile.queue.forEach(id => allIds.push(id))
        })
        posters.forEach(profile => {
            profile.queue.forEach(id => allIds.push(id))
        })
        allIds = [...new Set(allIds)]
        const peopleById = allIds.reduce((peopleById, id) => {
            peopleById[id] = new Person(id)
            if (queuesById[id]) {
                peopleById[id].candidates = queuesById[id].map(
                    queueId => new Person(queueId),
                )
            }
            return peopleById
        }, {})
        const seekerPeople = seekers.map(
            profile => peopleById[profile.profile_id],
        )
        const posterPeople = posters.map(
            profile => peopleById[profile.profile_id],
        )
        // You only need to engage from one side
        engageEveryone(seekerPeople)
        engageEveryone(posterPeople)
        // TODO: Test this, probably bug

        Object.values(peopleById).forEach(person => {
            if (person.fiance) {
                person.fiance.fiance = null
            }
        })
        return Object.values(peopleById).map(person => ({
            id: person.name,
            otp: person?.fiance?.name ?? null,
        }))
    }
}