btc

Bitcoin price tracker written in Haskell. Includes a CLI tool and a browser-based GUI dashboard.

Repository: github.com/johan-martensson/btc

Uses the CoinGecko free API with automatic fallback to Binance public API. No API keys required.

Building

Requires GHC with the time library (included in standard GHC installations).

make

Or individually:

ghc -O2 -o btcprice btcprice.hs
ghc -O2 -o btcgui btcgui.hs

Usage

CLI (btcprice)

# Current price in USD, EUR, GBP
./btcprice

# Daily price stats for a date range
./btcprice 2025-10-01 2026-01-01

Example output:

=== Bitcoin Daily Prices: 2025-12-01 to 2026-01-15 ===

Date        Price (USD)     Volume (USD)          Change
------------------------------------------------------------
2025-12-01  $90,359.87      $37,064,742,380
2025-12-02  $86,281.50      $21,163,124,465       -4.51%
2025-12-03  $91,320.08      $50,705,395,176       +5.84%
...
------------------------------------------------------------

=== Summary ===
  High:       $96,933.53
  Low:        $85,450.33
  Average:    $89,832.48
  Change:     +7.27%
  Total Vol:  $1,443,270,103,254
  Avg Vol:    $45,102,190,727

Standalone GUI (btcgui.html)

open btcgui.html     # macOS
# or: make open-gui

A standalone HTML file that runs entirely in the browser — no compilation needed. Just open it directly. It fetches current price and historical data client-side on page load (default: last 90 days, 3M highlighted).

GUI (btcgui) — Haskell binary

# Default: last 90 days
./btcgui

# Custom date range
./btcgui 2025-10-01 2026-01-01

Compiles with GHC. Fetches initial data server-side, generates an HTML dashboard, and opens it in the browser. Features (shared with btcgui.html):

• Current price (USD, EUR, GBP) and 24h trading volume
• Preset range buttons: 1D, 1W, 1M, 3M, 1Y, All
• Interactive date range picker — change the period and click Fetch to reload data live from the browser
• Line chart with hover tooltips (Chart.js) and volume bars on secondary Y-axis
• Bitcoin Power Law overlay — support, near support (historical low), fair value, and resistance corridor lines with 20% forward projection
• Log Scale toggle (Y-axis logarithmic)
• Log-Log chart mode — days since genesis on X-axis (log) vs. price (log), where the power law appears as straight lines; tooltips show actual date, fair value, support, and resistance prices
• Automatic hourly granularity — ranges of 30 days or less (1D, 1W, 1M) show hourly data points; longer ranges show daily
• Period statistics (high, low, average, change %, avg volume, total volume)
• Scrollable price table with volume and color-coded changes
• Dark theme

Data Sources

Both tools try CoinGecko first. If it fails (rate limit, timeout, or error), they automatically fall back to Binance public endpoints. This applies to:

• Current price and 24h volume fetching (CLI and GUI startup)
• Historical price and daily volume fetching (CLI and GUI startup)
• Live date range updates in the GUI (client-side JavaScript)

CoinGecko's free tier is limited to the last 365 days. The Binance fallback has no such limit — long ranges are fetched automatically via pagination (1000-day chunks).