# all files / src/audits/performance/ input-readiness-metric.js

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     /**
     * @license
     * Copyright 2016 Google Inc. All rights reserved.
     *
     * Licensed under the Apache License, Version 2.0 (the "License");
     * you may not use this file except in compliance with the License.
     * You may obtain a copy of the License at
     *
     *     http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed under the License is distributed on an "AS IS" BASIS,
     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */

    'use strict';

    const Audit = require('../audit');
    const TracingProcessor = require('../../lib/traces/tracing-processor');

    class InputReadinessMetric extends Audit {
      static get meta() {
        return {
          category: 'Performance',
          name: 'input-readiness',
          description: 'Input readiness - main thread availability',
          optimalValue: '100',
          requiredArtifacts: ['traceContents']
        };
      }

      /**
       * Audits the page to give a score for Input Readiness.
       * @see https://github.com/GoogleChrome/lighthouse/issues/26
       * @param {!Artifacts} artifacts The artifacts from the gather phase.
       * @return {!AuditResult} The score from the audit, ranging from 0-100.
       */
      static audit(artifacts) {
        try {
          const tracingProcessor = new TracingProcessor();
          const model = tracingProcessor.init(artifacts.traceContents);
          const hazardMetric = tracingProcessor.getInputReadiness(model);

          const readinessScore = Math.round(100 - (hazardMetric.numeric.value * 100));
          const rawValue = hazardMetric.numeric.value.toFixed(4);

          return InputReadinessMetric.generateAuditResult({
            value: readinessScore,
            rawValue: rawValue,
            optimalValue: this.meta.optimalValue
          });
        } catch (err) {
          return InputReadinessMetric.generateAuditResult({
            value: -1,
            debugString: 'Unable to parse trace contents: ' + err.message
          });
        }
      }
    }

    module.exports = InputReadinessMetric;