Estimate: Data Visualization Dashboard

Problem Description

We have an internal analytics platform built with Python and FastAPI. The backend serves JSON endpoints for business metrics (revenue, user signups, churn rate) aggregated from a PostgreSQL database. Currently, all data is consumed via API calls by downstream tools — there is no visualization layer in the app itself.

The product team wants to add an interactive dashboard page with charts showing metrics over time (line charts, bar charts), a date range picker for filtering, plan-type filters (free vs paid), and a button to export the currently displayed data as CSV. The frontend is served by FastAPI's Jinja2 templates with plain HTML/CSS and vanilla JavaScript — there is no React, Vue, or any frontend framework. There is no chart library installed.

Output Specification

Produce a complete estimation document and save it to estimate.md. The estimate should cover all work needed to build this dashboard feature, broken into sub-tasks with time estimates calibrated for an AI coding agent.

Input Files

The following files describe the current state of the project. Extract them before beginning.

=============== FILE: inputs/pyproject.toml =============== [project] name = "analytics-platform" version = "1.4.0" requires-python = ">=3.11" dependencies = [ "fastapi>=0.111.0", "uvicorn>=0.30.0", "sqlalchemy>=2.0.30", "psycopg2-binary>=2.9.9", "pydantic>=2.7.0", "jinja2>=3.1.4", "python-dotenv>=1.0.0", "alembic>=1.13.0", ]

[project.optional-dependencies] dev = [ "pytest>=8.2.0", "httpx>=0.27.0", "ruff>=0.4.0", ]

=============== FILE: inputs/file-tree.txt =============== app/ ├── main.py ├── config.py ├── models/ │ ├── user.py │ ├── subscription.py │ └── event.py ├── routers/ │ ├── auth.py │ ├── metrics.py │ └── admin.py ├── services/ │ ├── analytics.py │ └── export.py ├── templates/ │ ├── base.html │ ├── login.html │ └── admin.html ├── static/ │ ├── css/style.css │ └── js/admin.js tests/ ├── test_metrics.py └── test_auth.py alembic/ └── versions/

=============== FILE: inputs/analytics.py =============== from sqlalchemy import func, select from sqlalchemy.ext.asyncio import AsyncSession from app.models.event import Event from app.models.subscription import Subscription from datetime import date

async def get_revenue_by_month(db: AsyncSession, start: date, end: date): query = ( select( func.date_trunc('month', Event.created_at).label('month'), func.sum(Event.amount).label('total') ) .where(Event.type == 'payment') .where(Event.created_at.between(start, end)) .group_by('month') .order_by('month') ) result = await db.execute(query) return result.all()

async def get_signups_by_month(db: AsyncSession, start: date, end: date): query = ( select( func.date_trunc('month', Subscription.created_at).label('month'), func.count().label('count') ) .where(Subscription.created_at.between(start, end)) .group_by('month') .order_by('month') ) result = await db.execute(query) return result.all()