query grade distributions working, and filtering by semesters working

src/views/lib/database/queryDistribution.ts

@@ -0,0 +1,115 @@
+import { Course, Semester } from 'src/shared/types/Course';
+import { CourseSQLRow, Distribution } from 'src/shared/types/Distribution';
+import { initializeDB } from './initializeDB';
+
+/**
+ * fetches the aggregate distribution of grades for a given course from the course db, and the semesters that we have data for
+ * @param course the course to fetch the distribution for
+ * @returns a Distribution object containing the distribution of grades for the course, and
+ * an array of semesters that we have the distribution for
+ */
+export async function queryAggregateDistribution(course: Course): Promise<[Distribution, Semester[]]> {
+    const db = await initializeDB();
+    const query = generateQuery(course, null);
+
+    const res = db.exec(query)?.[0];
+    if (!res?.columns?.length) {
+        throw new NoDataError(course);
+    }
+
+    let row: Required<CourseSQLRow> = {} as Required<CourseSQLRow>;
+    res.columns.forEach((col, i) => {
+        row[res.columns[i]] = res.values[0][i];
+    });
+
+    const distribution: Distribution = {
+        A: row.a2,
+        'A-': row.a3,
+        'B+': row.b1,
+        B: row.b2,
+        'B-': row.b3,
+        'C+': row.c1,
+        C: row.c2,
+        'C-': row.c3,
+        'D+': row.d1,
+        D: row.d2,
+        'D-': row.d3,
+        F: row.f,
+    };
+
+    const semesters: Semester[] = row.semesters.split(',').map((sem: string) => {
+        const [season, year] = sem.split(' ');
+        return { year: parseInt(year, 10), season: season as Semester['season'] };
+    });
+
+    return [distribution, semesters];
+}
+
+/**
+ * Creates a SQL query that we can execute on the database to get the distribution of grades for a given course in a given semester
+ * @param course the course to fetch the distribution for
+ * @param semester the semester to fetch the distribution for OR null if we want the aggregate distribution
+ * @returns a SQL query string
+ */
+function generateQuery(course: Course, semester: Semester | null): string {
+    const profName = course.instructors[0]?.fullName;
+
+    const query = `
+        select * from ${semester ? 'grades' : 'agg'}
+        where dept like '%${course.department}%'
+        ${profName ? `and prof like '%${profName}%'` : ''}
+        and course_nbr like '%${course.number}%'
+        ${semester ? `and sem like '%${semester.season} ${semester.year}%'` : ''}
+        order by a1+a2+a3+b1+b2+b3+c1+c2+c3+d1+d2+d3+f desc
+    `;
+
+    return query;
+}
+
+/**
+ * fetches the distribution of grades for a semester for a given course from the course db
+ * @param course the course to fetch the distribution for
+ * @param semester the semester to fetch the distribution for
+ * @returns a Distribution object containing the distribution of grades for the course
+ */
+export async function querySemesterDistribution(course: Course, semester: Semester): Promise<Distribution> {
+    const db = await initializeDB();
+    const query = generateQuery(course, semester);
+
+    const res = db.exec(query)?.[0];
+    if (!res?.columns?.length) {
+        throw new NoDataError(course);
+    }
+
+    let row: Required<CourseSQLRow> = {} as Required<CourseSQLRow>;
+    res.columns.forEach((col, i) => {
+        row[res.columns[i]] = res.values[0][i];
+    });
+
+    const distribution: Distribution = {
+        A: row.a2,
+        'A-': row.a3,
+        'B+': row.b1,
+        B: row.b2,
+        'B-': row.b3,
+        'C+': row.c1,
+        C: row.c2,
+        'C-': row.c3,
+        'D+': row.d1,
+        D: row.d2,
+        'D-': row.d3,
+        F: row.f,
+    };
+
+    return distribution;
+}
+
+/**
+ * A custom error class for when we don't have data for a course
+ */
+export class NoDataError extends Error {
+    constructor(course: Course) {
+        super(`No data for #${course.uniqueId} ${course.department} ${course.number}`);
+        this.name = 'NoDataError';
+    }
+}