Feature: Chart primitives for views.rules

[davidfowl]

Summary

Add charting capabilities to views.rules so spending patterns can be visualized directly in HTML and TXT reports.

Motivation

Tables are great for detailed data, but some patterns are only visible through charts:

• Spending trends over time (increasing/decreasing)
• Category concentration (where does 80% go?)
• Seasonality and timing patterns
• Comparison across dimensions (weekday vs weekend, cardholder, etc.)

Proposed Syntax

[Food Delivery]
filter: category == "Food" and subcategory == "Delivery"
chart: trend                    # line chart over time

[Spending by Category]  
filter: not is_excluded
chart: bar
group_by: category              # aggregate by this field
limit: 10                       # top N

[Monthly Bills]
filter: is_monthly
chart: stacked
group_by: subcategory

Chart Types

Type	HTML Render	TXT Render
trend	SVG line chart (monthly)	ASCII sparkline ▁▃▅▇▅▃▁
bar	Horizontal SVG bars	████████░░ $5,000
pie	SVG donut chart	Percentage table
stacked	Stacked bar by month	Grouped ASCII bars
heatmap	Calendar grid	ASCII calendar
histogram	Distribution bars	Bucket counts

Chart Properties

chart: trend | bar | pie | stacked | heatmap | histogram
group_by: category | subcategory | merchant | month | dayofweek | cardholder
limit: 10                       # max items (default: 10)
sort_by: total | cv | count     # ordering
period: month | week | day      # x-axis grouping for trend
buckets: [0, 50, 100, 500]      # for histogram

Example Queries (New Insights)

Spending Velocity

[Spending Acceleration]
description: Categories where spending is increasing month-over-month
filter: slope(sum(by("month"))) > 0.1
chart: trend

Weekend vs Weekday

[Weekend Splurge]
filter: dayofweek(date) in [6, 7]
chart: bar
group_by: category

Late Night Spending

[Late Night Spending]
filter: hour(time) >= 21 or hour(time) <= 5
chart: bar
group_by: subcategory

Subscription Creep

[Subscription Growth]
filter: category == "Subscriptions"
chart: stacked
group_by: month

Merchant Concentration

[Top 10 Concentration]
filter: total > 1000
chart: pie
group_by: merchant
limit: 10

Transaction Size Distribution

[Transaction Sizes]
filter: amount > 0
chart: histogram
buckets: [0, 25, 50, 100, 250, 500, 1000, 5000]

Family Member Comparison

[By Cardholder]
filter: not is_excluded
chart: stacked
group_by: cardholder

New Primitives Needed

Primitive	Description
slope(list)	Linear regression slope (is spending increasing?)
dayofweek(date)	1-7 for filtering/grouping
hour(time)	0-23 for time-of-day analysis
cardholder	Card member field from transactions

HTML Output

Inline SVG, no external dependencies:

<section class="monthly-section">
  <div class="section-header">...</div>
  <div class="section-chart">
    <svg viewBox="0 0 400 150">
      <!-- pure SVG bars/lines, styled with CSS vars -->
    </svg>
  </div>
  <div class="section-content">...</div>
</section>

TXT Output

[Monthly] $6,805/yr · $567/mo
├─ Pro Club      ████████████████████ $6,805
├─ Augusta Lawn  ████████████░░░░░░░░ $5,289
└─ Puget Sound   ████████░░░░░░░░░░░░ $4,215

Trend: ▂▃▅▇▆▅▄▃▂▂▃▄ (Jan-Dec)

Value

Query Type	What It Reveals
Late Night Spending	Hidden impulse purchases
Weekend Splurge	Lifestyle vs necessity split
Spending Acceleration	Habits getting out of control
Subscription Growth	Creeping monthly commitments
Top 10 Concentration	Dependency on few merchants
By Cardholder	Family spending comparison