require('bare-process/global')
const EventEmitter = require('bare-events')
const b4a = require('b4a')
const { assertNonEmpty } = require('../../_shared/lib/errors.js')
const { initModuleSwarm, gossipSend } = require('../../_shared/p2p-bare.js')

const PROTOCOL = 'inverted-index/v1'

function normalizeTerm (term) {
  return String(term).toLowerCase().trim()
}

class HyperP2PInvertedIndex extends EventEmitter {
  constructor (opts = {}) {
    super()
    this.topic = opts.topic || null
    this.keyPair = opts.keyPair || require('hypercore-crypto').keyPair()
    this.peerHex = b4a.toString(this.keyPair.publicKey, 'hex')
    this._terms = new Map()
    this._docs = new Map()
    this._stats = { indexed: 0, removed: 0, queries: 0, gossipIn: 0, gossipOut: 0 }
    this.swarm = null
    this._peerMsgs = null
  }

  index (docId, terms) {
    assertNonEmpty(docId, 'docId')
    const normalized = (terms || []).map(normalizeTerm).filter(Boolean)
    const prev = this._docs.get(docId) || new Set()
    for (const term of normalized) {
      const set = this._terms.get(term) || new Set()
      set.add(docId)
      this._terms.set(term, set)
      if (!prev.has(term)) {
        this._gossip({ type: 'term-index-sync', op: 'add', term, docId, peer: this.peerHex, at: Date.now() })
      }
    }
    this._docs.set(docId, new Set(normalized))
    this._stats.indexed++
    this.emit('index', { docId, terms: normalized })
    return { docId, terms: normalized }
  }

  search (term) {
    this._stats.queries++
    const set = this._terms.get(normalizeTerm(term))
    return set ? [...set].sort() : []
  }

  searchAll (terms, mode = 'and') {
    if (!Array.isArray(terms) || !terms.length) return []
    const normalized = terms.map(normalizeTerm).filter(Boolean)
    if (!normalized.length) return []
    this._stats.queries++
    if (mode === 'or') {
      const out = new Set()
      for (const term of normalized) {
        for (const docId of this.search(term)) out.add(docId)
      }
      return [...out].sort()
    }
    let hits = null
    for (const term of normalized) {
      const set = this._terms.get(term)
      const ids = set ? [...set] : []
      if (hits === null) hits = new Set(ids)
      else {
        const next = new Set()
        for (const id of ids) if (hits.has(id)) next.add(id)
        hits = next
      }
    }
    return hits ? [...hits].sort() : []
  }

  getDocTerms (docId) {
    const terms = this._docs.get(docId)
    return terms ? [...terms].sort() : []
  }

  removeDoc (docId) {
    assertNonEmpty(docId, 'docId')
    const terms = this._docs.get(docId)
    if (!terms) return false
    for (const term of terms) {
      const set = this._terms.get(term)
      if (set) {
        set.delete(docId)
        if (!set.size) this._terms.delete(term)
      }
      this._gossip({ type: 'term-index-sync', op: 'remove', term, docId, peer: this.peerHex, at: Date.now() })
    }
    this._docs.delete(docId)
    this._stats.removed++
    this.emit('remove', { docId })
    return true
  }

  listTerms () {
    return [...this._terms.keys()].sort()
  }

  docCount () {
    return this._docs.size
  }

  hasDoc (docId) {
    return this._docs.has(String(docId))
  }

  topTerms (limit = 10) {
    const ranked = [...this._terms.entries()]
      .map(([term, set]) => ({ term, docs: set.size }))
      .sort((a, b) => b.docs - a.docs)
    return ranked.slice(0, Math.max(0, limit | 0))
  }

  _gossip (data) {
    if (!this._peerMsgs) return
    gossipSend(this, data)
    this._stats.gossipOut++
  }

  _onGossip (data) {
    if (!data || data.type !== 'term-index-sync') return
    this._stats.gossipIn++
    const term = normalizeTerm(data.term)
    const docId = data.docId
    if (!term || !docId) return

    if (data.op === 'remove') {
      const set = this._terms.get(term)
      if (set) {
        set.delete(docId)
        if (!set.size) this._terms.delete(term)
      }
      const docTerms = this._docs.get(docId)
      if (docTerms) docTerms.delete(term)
      this.emit('remote-remove', { term, docId, peer: data.peer })
      return
    }

    const set = this._terms.get(term) || new Set()
    set.add(docId)
    this._terms.set(term, set)
    const docTerms = this._docs.get(docId) || new Set()
    docTerms.add(term)
    this._docs.set(docId, docTerms)
    this.emit('remote-index', { term, docId, peer: data.peer })
  }

  getStats () {
    return {
      ...this._stats,
      terms: this._terms.size,
      docs: this._docs.size,
      protocol: PROTOCOL
    }
  }

  async ready () {
    if (this.swarm || !this.topic) return this
    await initModuleSwarm(this, {
      keyPair: this.keyPair,
      topic: this.topic,
      protocol: PROTOCOL,
      onmessage: (data) => this._onGossip(data)
    })
    return this
  }

  async close () {
    this._terms.clear()
    this._docs.clear()
    if (this.swarm) await this.swarm.destroy().catch(() => {})
    this.swarm = null
    this.emit('closed')
  }
}

module.exports = { HyperP2PInvertedIndex, PROTOCOL }