data-source-join.ts

/*
Feature: Data Source Join and Mapping

Scenario: Joining and mapping data from third-party API and local DB query in execute()

GIVEN two different data sources, one from a third-party API (call3partyAPI) and one from a local DB query (dbQuery)
AND the call3partyAPI() returns static "curriculum" data
AND the dbQuery() returns user learning progress data from our DB
WHEN the execute() function is called
THEN it should return an array of [{lessonName, readableStatus}]
AND the readableStatus for each lesson is defined as follows:
    1: pending
    2: submitted
    3: passed
    4: failed
definition of response:
[
    {
      userId: number
      userName: string
      
      lessons: {
        lessonName: string
        readableStatus: string
        curriculumId: number
        lessonId: number
      }[]
    }
]
*/

const StatusMap = {
  1: "pending",
  2: "submitted",
  3: "passed",
  4: "failed"
}

async function call3partyAPI() { //not enought data cases for unit testing
  return {
    status: 200, // could be 400 or 500 sometimes
    data: [ // data property may or may not exist
      {
        curriculum: {
          id: 1,
          title: 'Technology and Sustainability',
          lessons: [
            {
              id: 28,
              name: 'Multiple Choice',
            },
            {
              id: 76,
              name: 'True or False Questions',
            },
          ]
        }
      },
      {
        curriculum: {
          id: 2,
          title: 'Technology and Sustainability',
          lessons: [
            {
              id: 120,
              name: 'Chaos',
            },
            {
              id: 160,
              name: 'Order',
            },
          ]
        }
      },

    ]
  };
};

// Assume only one user will ever get returned
async function dbQuery() { //not enought data cases for unit testing
  return [
    {
      user: { id: 1, name: 'Tom' },
      progress: {
        lessons: [
          {
            lesson_id: 28,
            status: 2,
          },
          {
            lesson_id: 76,
            status: 1
          }
        ]
      },
    },
    {
      user: { id: 2, name: 'Dan' },
      progress: {
        lessons: [
          {
            lesson_id: 76,
            status: 1
          },
          {
            lesson_id: 120,
            status: 1
          }
        ]
      }
    }
  ]
}

async function execute() { 
  const [client_response, students] = await Promise.all([call3partyAPI(), dbQuery()])
  const curriculums = client_response.data
  const curriculumIds = []
  const curriculumsMap = curriculums.reduce((a, curriculum)=>{
    const curriculumId = curriculum.curriculum.id;
    curriculumIds.push(curriculumId)
    const lessons = curriculum.curriculum.lessons
    a[curriculumId] = {
      lessons:lessons.reduce((aggr, lesson)=>{
        aggr[lesson.id] = lesson.name
        return aggr
      }, {}),
      set: new Set(lessons.map(lesson=>lesson.id))
    }
    return a
  }, {})
  // console.info("curriculumsMap", curriculumsMap)
  const Response = [];
  if (client_response) {

    students.map(student => {
      const studentResult = {
        userId: student.user.id,
        userName: student.user.name,
        lessons: []
      }
      const studentLessonIds = []
      const studentLessonMap = student.progress.lessons.reduce((a,i)=>{
        studentLessonIds.push(i.lesson_id)
        a[i.lesson_id] = i.status
        return a
      }, {})

      // console.info("studentLessonMap", studentLessonMap)
      curriculumIds.map((curriculumId) => {
        const intersection = studentLessonIds.filter((x) => curriculumsMap[parseInt(curriculumId)].set.has(x));
        // console.info("intersection", intersection, studentLessonIds, curriculumIds)
        intersection.map(lessonId => {
          studentResult.lessons.push({
            lessonName: curriculumsMap[curriculumId].lessons[lessonId],
            readableStatus: StatusMap[studentLessonMap[lessonId]],
            curriculumId,
            lessonId
          });
        })
      })

      Response.push(studentResult)
    })
  }

  return Response;
}


execute().then((res) => console.log(JSON.stringify(res, 0, 2)))