feat: Start refactoring code base to be testable

Implement a spreadsheet service abstraction, GAS integration, and Jest testing setup.

src/services/GASSpreadsheetService.ts

@@ -0,0 +1,85 @@
+import { ISpreadsheetService } from "../interfaces/ISpreadsheetService";
+
+export class GASSpreadsheetService implements ISpreadsheetService {
+  private getSheet(sheetName: string): GoogleAppsScript.Spreadsheet.Sheet {
+    const sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName(sheetName);
+    if (!sheet) {
+      throw new Error(`Sheet '${sheetName}' not found`);
+    }
+    return sheet;
+  }
+
+  private getColumnIndex(sheet: GoogleAppsScript.Spreadsheet.Sheet, columnName: string): number {
+    const headers = sheet.getRange(1, 1, 1, sheet.getLastColumn()).getValues()[0];
+    return headers.indexOf(columnName);
+  }
+
+  getHeaders(sheetName: string): string[] {
+    const sheet = this.getSheet(sheetName);
+    return sheet.getRange(1, 1, 1, sheet.getLastColumn()).getValues()[0];
+  }
+
+  getRowData(sheetName: string, row: number): any[] {
+    const sheet = this.getSheet(sheetName);
+    const lastCol = sheet.getLastColumn();
+    // getRange(row, column, numRows, numColumns)
+    return sheet.getRange(row, 1, 1, lastCol).getValues()[0];
+  }
+
+  getRowNumberByColumnValue(sheetName: string, columnName: string, value: any): number | undefined {
+    const sheet = this.getSheet(sheetName);
+    const colIndex = this.getColumnIndex(sheet, columnName);
+    if (colIndex === -1) return undefined;
+
+    // Get all values in the column. Note: calling getValues() on a large sheet might be slow,
+    // but this matches the previous implementation's performance characteristics more or less.
+    // Ideally we would cache this or use a more efficient find.
+    // offset(1, colIndex) to skip header, but actually getColumnValuesByName usually gets everything including header or handles it.
+    // Original implementation: getColumnValuesByName gets range from row 2.
+
+    const data = sheet.getRange(2, colIndex + 1, sheet.getLastRow() - 1, 1).getValues();
+    const flatData = data.map(r => r[0]);
+    const index = flatData.indexOf(value);
+
+    if (index === -1) return undefined;
+    return index + 2; // +1 for 0-based index, +1 for header row
+  }
+
+  setCellValueByColumnName(sheetName: string, row: number, columnName: string, value: any): void {
+    const sheet = this.getSheet(sheetName);
+    const colIndex = this.getColumnIndex(sheet, columnName);
+    if (colIndex !== -1) {
+      sheet.getRange(row, colIndex + 1).setValue(value);
+    }
+  }
+
+  getCellValueByColumnName(sheetName: string, row: number, columnName: string): any {
+    const sheet = this.getSheet(sheetName);
+    const colIndex = this.getColumnIndex(sheet, columnName);
+    if (colIndex !== -1) {
+      return sheet.getRange(row, colIndex + 1).getValue();
+    }
+    return null;
+  }
+
+  getCellHyperlink(sheetName: string, row: number, columnName: string): string | null {
+    const sheet = this.getSheet(sheetName);
+    const colIndex = this.getColumnIndex(sheet, columnName);
+    if (colIndex !== -1) {
+      return sheet.getRange(row, colIndex + 1).getRichTextValue().getLinkUrl();
+    }
+    return null;
+  }
+
+  setCellHyperlink(sheetName: string, row: number, columnName: string, displayText: string, url: string): void {
+    const sheet = this.getSheet(sheetName);
+    const colIndex = this.getColumnIndex(sheet, columnName);
+    if (colIndex !== -1) {
+      const richText = SpreadsheetApp.newRichTextValue()
+        .setText(displayText)
+        .setLinkUrl(url)
+        .build();
+      sheet.getRange(row, colIndex + 1).setRichTextValue(richText);
+    }
+  }
+}