Fork Gauge

The fork gauge is the primary visual indicator of Augur fork risk on the site. It consists of an SVG half-circle arc with a needle, a gradient color track, and a risk label — all driven by live blockchain data fetched from /data/fork-risk.json.

Component Architecture

ForkMonitor (island entry point, client:load)
└── ForkDataProvider (React Context — loads live data)
    └── ForkMockProvider (React Context — demo overrides, dev-only)
        └── ForkDisplay (subscribes to contexts + animation store)
            └── ForkGauge (pure SVG renderer, takes percentage prop)

• ForkMonitor — The Astro island. Always use client:load so the gauge hydrates immediately.
• ForkDataProvider — Fetches /data/fork-risk.json on mount, refreshes every 5 minutes. Exposes data via useForkData().
• ForkMockProvider — Dev-only demo layer. Wraps ForkDataProvider and can override data via generateScenario(). Guarded by import.meta.env.PROD.
• ForkDisplay — Composes the full UI. Subscribes to $appStore (animation state) and useForkData() (risk data).
• ForkGauge — Pure SVG component. Receives percentage prop (0–100). No data fetching, no context.

Risk Levels

Risk levels flow from the JSON data through the provider to the gauge:

JSON riskLevel	Display label	Color
none	NO RISK	--color-green-400
low	LOW	--color-green-400
moderate	MEDIUM	--color-yellow-400
high	HIGH	--color-orange-400
critical	EXTREME	--color-red-500

The arc uses a linearGradient (green → yellow → orange → red) regardless of current level. The needle and center hub use the color for the current risk level.

Visual Percentage Mapping

The gauge uses a non-linear scale to make risk visually intuitive. The getVisualPercentage() function in ForkGauge.tsx maps actual fork threshold percentage to visual gauge fill:

Fork threshold %	Visual gauge %	Zone
0%	0%	No risk
0–10%	0–25%	Low
10–25%	25–50%	Medium
25–75%	50–90%	High
75%+	90–100%	Extreme

When modifying risk thresholds or visual ranges, update getVisualPercentage() in src/components/ForkGauge.tsx.

Common Workflows

Update risk colors

Colors are defined in getRiskColor() in ForkGauge.tsx. Use CSS custom properties from the global theme:

const getRiskColor = (forkThresholdPercent: number): string => {
  if (forkThresholdPercent < 10) return 'var(--color-green-400)'
  if (forkThresholdPercent < 25) return 'var(--color-yellow-400)'
  if (forkThresholdPercent < 75) return 'var(--color-orange-400)'
  return 'var(--color-red-500)'
}

The arc gradient is defined in the <linearGradient id="forkMeterGradient"> SVG element. Update both if changing colors.

Add glow effects

The arc path uses className="fx-glow". For stronger or weaker glow, use size variants: fx-glow-sm, fx-glow-lg. The needle uses inline filter: drop-shadow(...) with the current risk color.

Modify the arc geometry

The arc is a semicircle from left (180°) to right (0°). Key dimensions in ForkGauge.tsx:

• Center: (200, 200)
• Arc radius: 120
• Needle radius: 100 (slightly shorter than arc)
• ViewBox: "60 60 280 160" (crops to the semicircle only)

Test risk scenarios

Use demo mode — press F2 in the browser during development to cycle through scenarios (None, Low, Moderate, High, Critical). This is guarded by import.meta.env.PROD and will not appear in production builds.

Alternatively, temporarily edit /public/data/fork-risk.json to test a specific state locally.

Update the data pipeline

Live data flows from GitHub Actions → /public/data/fork-risk.json → ForkDataProvider → ForkDisplay → ForkGauge. The JSON is fetched client-side after hydration to avoid build-time failures.

See references/data-pipeline.md for the full JSON schema and pipeline details.

Additional Resources

• references/data-pipeline.md — JSON schema, data flow, GitHub Actions update cycle
• references/svg-geometry.md — Arc math, needle calculation, coordinate system details