Stacked Bar Chart

[nhatt-dev]

Changes

preview.mov

Backend

• New endpoint: GET /transactions/getMonthlyByCategory/:user_id?startDate=<>&endDate=<>
• Sanitize and validate inputs.
• Aggregate transactions by month, yielding the total expense for each and all categories in a given month.
• Optional query parameters can be used to limit retrieval period.

Frontend

• Show monthly expense as bars with each bar further separated by category.
• Responsive: bars resize based on width (of window/device) and height (height of tallest bar). Number of bars vary depending on screen size.
• Absolute/relative: can toggle between both monthly absolute expense in dollars (or cents) and relative expense as a percentage.
• Transition animation: bars shift smoothly between absolute and relative modes.

Testing

• Various combinations of backend invocations including both meaningful and spurious inputs.
• Different screen sizes.
• Different randomly generated transaction data.

[himansig7]

Looks great, appreciate the detail in the pull request!