const debug = require('debug')('ipfs-pinner');

async function promiseAllInBatches(task, items, batchSize) {
  let position = 0;
  let results = [];
  while (position < items.length) {
    const itemsForBatch = items.slice(position, position + batchSize);
    results = [...results, ...await Promise.allSettled(itemsForBatch.map(item => task(item)))];
    position += batchSize;
  }
  return results;
}

class IpfsPinner {
  constructor (kredits, ipfsApi) {
    this.kredits = kredits;
    this.ipfsApi = ipfsApi || this.kredits.ipfs;
  }

  async pinAll () {
    const contributorHashes   = await this._pinAllFromContract(this.kredits.Contributor);
    const contributionHashes  = await this._pinAllFromContract(this.kredits.Contribution);
    const reimbursementHashes = await this._pinAllFromContract(this.kredits.Reimbursement);

    return contributorHashes.concat(contributionHashes)
                            .concat(reimbursementHashes);
  }

  monitor (callback) {
    this.kredits.Contribution.on('ContributionAdded', (id) => {
      this.kredits.Contribution.getData(id)
        .then(data => { return this.ipfsApi.pin(data); })
        .then(callback);
    });
    this.kredits.Contributor.on('ContributorAdded', (id) => {
      this.kredits.Contribution.getData(id)
        .then(data => { return this.ipfsApi.pin(data); })
        .then(callback);
    });
    this.kredits.Contributor.on('ContributorProfileUpdated', (id) => {
      this.kredits.Contributor.getData(id)
        .then(data => { return this.ipfsApi.pin(data); })
        .then(callback);
    });
  }

  async _pinAllFromContract (contract) {
    debug(`Pinning data from ${contract.constructor.name}...`);
    const count = await contract.count;
    debug('Item count:', count);
    const ids = [...Array(count).keys()].map(i => i+1);
    const cids = [];

    async function loadAndPin (id) {
     debug(`Loading ${contract.constructor.name} #${id}`);
      return contract.getData(id).then(data => {
        debug(`Pinning ${contract.constructor.name} #${id}`);
        return this.ipfsApi.pin(data).then(cid => cids.push(cid));
      });
    }

    await promiseAllInBatches(loadAndPin.bind(this), ids, 100);

    return cids;
  }
}

module.exports = IpfsPinner;