added csv exporting logic

web/src/lib/Day.ts

@@ -0,0 +1,31 @@
+export type Day = number;
+
+export interface AttendanceDay {
+  date: Day,
+  ids: string[],
+}
+
+export function dayToDate(day: Day): Date {
+  const SEC_PER_DAY = 86_400;
+
+  return new Date(day * SEC_PER_DAY * 1000);
+}
+
+export async function fetchDay(day: Day): Promise<AttendanceDay> {
+  let res = await fetch("/api/day?" + (new URLSearchParams({ day: day.toString() }).toString()));
+
+  let json = await res.json();
+
+  return json;
+}
+
+export async function fetchDays(from: Date, to: Date): Promise<Day[]> {
+  let q = new URLSearchParams({ from: (from.getTime() / 1000).toString(), to: (to.getTime() / 1000).toString() });
+
+  let res = await fetch("/api/days?" + q);
+
+  let json = await res.json();
+
+  return json;
+}
+

web/src/lib/csv.ts

@@ -0,0 +1,106 @@
+interface CSVOptions {
+  delimiter?: string;             // default: ","
+  includeHeader?: boolean;        // default: true for object input, false for array-of-arrays unless headers provided
+  headerOrder?: string[];         // explicit ordering for columns that should come first
+  eol?: string;                   // default: "\r\n"
+  includeBOM?: boolean;           // default: false (useful for Excel)
+  nullString?: string;            // default: "" (how to render null/undefined)
+}
+
+type RowObject = Record<string, any>;
+type InputRows = RowObject[];
+
+export function generateCSVString(input: InputRows, opts: CSVOptions = {}): string {
+  const {
+    delimiter = ",",
+    includeHeader,
+    headerOrder,
+    eol = "\r\n",
+    includeBOM = false,
+    nullString = "",
+  } = opts;
+
+  // Check if the value need quoting
+  // Usually not needed in our use case but still in case
+  const needsQuoting = (s: string) =>
+    s.includes(delimiter) || s.includes('"') || s.includes("\n") || s.includes("\r") || /^\s|\s$/.test(s);
+
+  // Transform the value of a cell in a SAFE string
+  const escapeCell = (raw: any): string => {
+    if (raw === null || raw === undefined) return nullString;
+
+    let s = defaultStringify(raw);
+
+    // Replace quotes 
+    if (s.includes('"')) s = s.replace(/"/g, '""');
+
+    return needsQuoting(s) ? `"${s}"` : s;
+  };
+
+  // Transform the value of a cell into a string
+  function defaultStringify(v: any): string {
+    if (v === null || v === undefined) return nullString;
+    if (v instanceof Date) return v.toLocaleDateString();
+    if (typeof v === "boolean") return v ? "X" : "";
+
+    if (typeof v === "object") {
+      // CHeck if array and join with "|"
+      if (Array.isArray(v)) return v.map(item => (item === null || item === undefined ? nullString : String(item))).join("|");
+
+      // If all fails parse it via json
+      // Should also not happen in our use case
+      try { return JSON.stringify(v); } catch { return String(v); }
+    }
+    return String(v);
+  }
+
+  const objs = (input as RowObject[]) || [];
+
+  // Derive headers in the order keys are first encountered (fixed: no reduce)
+  const seen = new Set<string>();
+  const derivedOrder: string[] = [];
+  for (const obj of objs) {
+    if (!obj || typeof obj !== "object") continue;
+    for (const k of Object.keys(obj)) {
+      if (!seen.has(k)) {
+        seen.add(k);
+        derivedOrder.push(k);
+      }
+    }
+  }
+
+  // Apply headerOrder if provided: put listed columns first (in the order provided),
+  // then append the remaining derived headers in their derived order.
+  let finalHeaders = derivedOrder.slice();
+  if (Array.isArray(headerOrder) && headerOrder.length > 0) {
+    const headSet = new Set(headerOrder);
+    const first = headerOrder.filter(h => seen.has(h)); // keep only headers that actually exist
+    const rest = derivedOrder.filter(h => !headSet.has(h));
+    finalHeaders = first.concat(rest);
+  }
+
+  const shouldIncludeHeader = typeof includeHeader === "boolean" ? includeHeader : finalHeaders.length > 0;
+  const rowsOut: string[] = [];
+
+  if (shouldIncludeHeader && finalHeaders.length) {
+    rowsOut.push(finalHeaders.map(h => escapeCell(h)).join(delimiter));
+  }
+
+  // Parse every row 
+  for (const obj of objs) {
+
+    // Check if obj is null or somthing else we can't convert
+    if (!obj || typeof obj !== "object") {
+
+      // produce empty row with same number of columns 
+      rowsOut.push(finalHeaders.map(() => escapeCell(null)).join(delimiter));
+      continue;
+    }
+
+    // For every header check if a value on our row exist and print it
+    const row = finalHeaders.map(col => escapeCell(col in obj ? (obj as any)[col] : null)).join(delimiter);
+    rowsOut.push(row);
+  }
+
+  return (includeBOM ? "\uFEFF" : "") + rowsOut.join(eol);
+}

web/src/lib/exporting.ts

@@ -0,0 +1,53 @@
+import { generateCSVString } from "./csv";
+import { dayToDate, fetchDay, fetchDays, type AttendanceDay, type Day } from "./Day";
+import type { IDMap } from "./IDMapping";
+
+interface CSVRow {
+  ID: string
+  Vorname: string
+  Nachname: string
+  [key: string]: string | boolean
+}
+
+function prepareRows(mapping: IDMap, days: AttendanceDay[]): CSVRow[] {
+  let csvData: CSVRow[] = [];
+
+  const allIDs = Object.keys(mapping);
+
+  for (const id of allIDs) {
+    const name = mapping[id];
+    const row: CSVRow = {
+      ID: id,
+      Vorname: name.first,
+      Nachname: name.last,
+    };
+
+    for (const day of days) {
+      const dayKey = dayToDate(day.date).toLocaleDateString();
+      row[dayKey] = day.ids.includes(id);
+    }
+
+    csvData.push(row);
+  }
+
+  return csvData;
+}
+
+async function getDays(from: Date, to: Date): Promise<AttendanceDay[]> {
+  const recordedDays: Day[] = await fetchDays(from, to);
+  let days: AttendanceDay[] = [];
+
+  for (const day of recordedDays) {
+    days.push(await fetchDay(day))
+  }
+
+  return days;
+}
+
+export async function generateCSVFile(from: Date, to: Date, mapping: IDMap): Promise<string> {
+  const days = await getDays(from, to);
+  const rows = prepareRows(mapping, days);
+  const csvString = generateCSVString(rows);
+
+  return csvString;
+}