import * as assert from 'assert';

import {CallCredentials, CallMetadataGenerator} from '../src/call-credentials';
import {Metadata} from '../src/metadata';

// Metadata generators

function makeGenerator(props: Array<string>): CallMetadataGenerator {
  return (options: {[propName: string]: string}, cb) => {
    const metadata: Metadata = new Metadata();
    props.forEach((prop) => {
      if (options[prop]) {
        metadata.add(prop, options[prop]);
      }
    });
    cb(null, metadata);
  };
}

function makeAfterMsElapsedGenerator(ms: number): CallMetadataGenerator {
  return (options, cb) => {
    const metadata = new Metadata();
    metadata.add('msElapsed', `${ms}`);
    setTimeout(() => cb(null, metadata), ms);
  };
}

const generateFromName: CallMetadataGenerator = makeGenerator(['name']);
const generateWithError: CallMetadataGenerator = (options, cb) =>
    cb(new Error());

// Tests

describe('CallCredentials', () => {
  describe('createFromMetadataGenerator', () => {
    it('should accept a metadata generator', () => {
      assert.doesNotThrow(
          () => CallCredentials.createFromMetadataGenerator(generateFromName));
    });
  });

  describe('compose', () => {
    it('should accept a CallCredentials object and return a new object', () => {
      const callCredentials1 =
          CallCredentials.createFromMetadataGenerator(generateFromName);
      const callCredentials2 =
          CallCredentials.createFromMetadataGenerator(generateFromName);
      const combinedCredentials = callCredentials1.compose(callCredentials2);
      assert.notEqual(combinedCredentials, callCredentials1);
      assert.notEqual(combinedCredentials, callCredentials2);
    });

    it('should be chainable', () => {
      const callCredentials1 =
          CallCredentials.createFromMetadataGenerator(generateFromName);
      const callCredentials2 =
          CallCredentials.createFromMetadataGenerator(generateFromName);
      assert.doesNotThrow(() => {
        callCredentials1.compose(callCredentials2)
            .compose(callCredentials2)
            .compose(callCredentials2);
      });
    });
  });

  describe('generateMetadata', () => {
    it('should call the function passed to createFromMetadataGenerator',
       async () => {
         const callCredentials =
             CallCredentials.createFromMetadataGenerator(generateFromName);
         let metadata: Metadata;
         try {
           metadata = await callCredentials.generateMetadata({name: 'foo'});
         } catch (err) {
           throw err;
         }
         assert.deepEqual(metadata.get('name'), ['foo']);
       });

    it('should emit an error if the associated metadataGenerator does',
       async () => {
         const callCredentials =
             CallCredentials.createFromMetadataGenerator(generateWithError);
         let metadata: Metadata|null = null;
         try {
           metadata = await callCredentials.generateMetadata({});
         } catch (err) {
           assert.ok(err instanceof Error);
         }
         assert.strictEqual(metadata, null);
       });

    it('should combine metadata from multiple generators', async () => {
      const [callCreds1, callCreds2, callCreds3, callCreds4] =
          [50, 100, 150, 200].map((ms) => {
            const generator: CallMetadataGenerator =
                makeAfterMsElapsedGenerator(ms);
            return CallCredentials.createFromMetadataGenerator(generator);
          });
      const testCases = [
        {
          credentials: callCreds1.compose(callCreds2)
                           .compose(callCreds3)
                           .compose(callCreds4),
          expected: ['50', '100', '150', '200']
        },
        {
          credentials: callCreds4.compose(
              callCreds3.compose(callCreds2.compose(callCreds1))),
          expected: ['200', '150', '100', '50']
        },
        {
          credentials: callCreds3.compose(
              callCreds4.compose(callCreds1).compose(callCreds2)),
          expected: ['150', '200', '50', '100']
        }
      ];
      const options = {};
      // Try each test case and make sure the msElapsed field is as expected
      await Promise.all(testCases.map(async (testCase) => {
        const {credentials, expected} = testCase;
        let metadata: Metadata;
        try {
          metadata = await credentials.generateMetadata(options);
        } catch (err) {
          throw err;
        }
        assert.deepEqual(metadata.get('msElapsed'), expected);
      }));
    });
  });
});