'use strict';

const BbPromise = require('bluebird');
const validate = require('./lib/validate');
const fetch = require('node-fetch');

class AwsRollbackFunction {
  constructor(serverless, options) {
    this.serverless = serverless;
    this.options = options || {};
    this.provider = this.serverless.getProvider('aws');

    Object.assign(this, validate);

    this.hooks = {
      'rollback:function:rollback': async () =>
        BbPromise.bind(this)
          .then(this.validate)
          .then(this.getFunctionToBeRestored)
          .then(this.fetchFunctionCode)
          .then(this.restoreFunction),
    };
  }

  async getFunctionToBeRestored() {
    const funcName = this.options.function;
    let funcVersion = this.options['function-version'];

    // versions need to be string so that AWS understands it
    funcVersion = String(this.options['function-version']);

    this.serverless.cli.log(`Rolling back function "${funcName}" to version "${funcVersion}"...`);

    const funcObj = this.serverless.service.getFunction(funcName);

    const params = {
      FunctionName: funcObj.name,
      Qualifier: funcVersion,
    };

    return this.provider
      .request('Lambda', 'getFunction', params)
      .then((func) => func)
      .catch((error) => {
        if (error.message.match(/not found/)) {
          const errorMessage = [
            `Function "${funcName}" with version "${funcVersion}" not found.`,
            ` Please check if you've deployed "${funcName}"`,
            ` and version "${funcVersion}" is available for this function.`,
            ' Please check the docs for more info.',
          ].join('');
          throw new Error(errorMessage);
        }
        throw new Error(error.message);
      });
  }

  async fetchFunctionCode(func) {
    const codeUrl = func.Code.Location;

    return fetch(codeUrl).then((response) => response.buffer());
  }

  async restoreFunction(zipBuffer) {
    const funcName = this.options.function;

    this.serverless.cli.log('Restoring function...');

    const funcObj = this.serverless.service.getFunction(funcName);

    const params = {
      FunctionName: funcObj.name,
      ZipFile: zipBuffer,
    };

    return this.provider.request('Lambda', 'updateFunctionCode', params).then(() => {
      this.serverless.cli.log(`Successfully rolled back function "${this.options.function}"`);
    });
  }
}

module.exports = AwsRollbackFunction;