1# `bibel` - Bible Verse CLI Utility
  2
  3A Go utility for displaying Bible verses. This tool shows Bible verses based on
  4the current date, displaying 12 verses per day through the four Gospels.
  5
  6## Features
  7
  8- **Date-Based Progression**: Automatically calculates position based on day of
  9year (1 January = Matthew 1:1-12)
 10- **Smart Sizing**: Default snippet size is 12 verses, extends to end of
 11chapter if less than 12 verses remain
 12- **Colour Output**: ANSI color-coded output (green for book/chapter, yellow
 13for verse range)
 14- **Yearly Cycle**: Progresses through all four Gospels each year, restarting
 15on 1 January
 16- **Simple CLI**: Run to display today's Bible snippet
 17
 18## Installation
 19
 20```bash
 21go build ./cmd/bibel.go
 22```
 23
 24## Usage
 25
 26```bash
 27./bibel
 28```
 29
 30The program will:
 311. Calculate today's date and day of year
 322. Determine Bible position: day_of_year × 12 verses
 333. Find corresponding verses in the Gospels
 344. Display the Bible snippet with colored headers
 35
 36No bookmark file is needed or created - the position is calculated from the
 37date alone.
 38
 39## Data Format
 40
 41The Bible data is in JSON format (`books/pol_nbg.json`) with the following structure:
 42```json
 43{
 44  "metadata": { ... },
 45  "verses": [
 46    {
 47      "book_name": "Mateusza",
 48      "book": 40,
 49      "chapter": 1,
 50      "verse": 1,
 51      "text": "¶ KSIĘGA początku Jezusa Chrystusa..."
 52    },
 53    ...
 54  ]
 55}
 56```
 57
 58Books 40-43 correspond to the four Gospels:
 59- 40: Matthew (Mateusza)
 60- 41: Mark (Marek)
 61- 42: Luke (Łukasz)
 62- 43: John (Jana)
 63
 64## Date-Based Algorithm
 65
 66The program calculates reading position as follows:
 67
 681. **Day of Year**: Get current day number (1-366)
 692. **Verse Offset**: Multiply by 12 verses per day: `offset = (day_of_year - 1) × 12`
 703. **Modulo Wrap**: Apply modulo with total Gospel verses (3779) to cycle yearly
 714. **Position Mapping**: Walk through Gospels to find corresponding verses
 725. **Lookahead Rule**: Extend to chapter end if less than 12 verses remain
 73
 74## Project Structure
 75
 76```
 77.
 78├── cmd/bibel.go                 # Main CLI entry point
 79├── internal/bible/
 80│   ├── verse.go                 # Data structures
 81│   ├── loader.go                # JSON loading and indexing
 82│   ├── dateprogression.go       # Date-based position calculation
 83│   ├── formatter.go             # Output formatting
 84│   └── bookmark.go              # Legacy bookmark management (optional)
 85├── books/pol_nbg.json           # Bible data
 86└── old_code.ml                  # Original OCaml implementation
 87```
 88
 89## Examples
 90
 91- **1 January**: Matthew 1:1-12
 92- **2 January**: Matthew 1:13-25 (extends to end of chapter)
 93- **16 April**: Mark 5:41-43
 94- **31 December**: Matthew 18:7-18 (year wraps around)
 95
 96## Development
 97
 98```bash
 99# Build
100go build ./cmd/bibel.go
101
102# Run with today's date
103./bibel
104
105# Test with specific date (environment variable)
106GOOSE_TEST_DATE=2026-01-01 ./bibel
107```