• The top input text field only displays the cell value and cannot be used to modify the cell.
• On initial page load, cells that contain formulas will be changed to numerical values. The formulas in the cells may appear for a split second. This was done on purpose to simplify the code and make it easier to read. This can be easily solved by computing the numerical value with a server side scripting language.
• Subtraction works as long as the formula is separated by "+". For example, =-2+A1+B1+-3
• Notable files:
  • /app/HTTP/Controllers/Controller.php (Controller: displays spreadsheet and saves spreadsheet cell values)
  • /resources/views/spreadsheet.php (View: displays spreadsheet)
  • /public/js/spreadsheet.js (Makes spreadsheet interactive)
  • /routes/web.php (Construct URLs, nothing much here)
  • /app/Cell.php (Model: database table declaration, nothing much here)
• Database structure:
  • Table name: cells
  • Columns:
    • Name: id Type: varchar(255) Null: No PRIMARY KEY
    • Name: content Type: varchar(255) Null: Yes
    • Name: created_at Type: timestamp Null: Yes
    • Name: updated_at Type: timestamp Null: Yes

Building an Interactive Spreadsheet

Today, the vast majority of businesses implement their commission plan models in Microsoft Excel, Google Sheets, or some other spreadsheet software. In this problem, you will implement a simplified browser-based spreadsheet that can be used to implement an extremely simple financial model.

Requirements

• For simplicity, the size of the spreadsheet is fixed to 10 rows and 10 columns.
  • Columns are named after capital letters, starting with "A".
  • Rows are numbered and increasing, starting from "1".
• The state of the spreadsheet should be maintained in a backend service that is mutatable via API calls.
• The frontend should be interactive: saving data after a cell in the spreadsheet changes, and updating any affected cells with their newly computed values.
• The state of the spreadsheet should be persisted across server restarts.
• Cell values should support either an integer or a simple formula that references other cells and only needs to support addition.
  • For example, -1 and 123 should be able to be stored in a cell.
  • =A1+B1 should be able to be stored in a cell, and the display value should be the result of evaluating the sum of the value in A1 and the value in B1.

Out-of-scope

• Don't worry about handling multiple concurrent users viewing and editing the spreadsheet at the same time.