# Grammar Inference Engine — Agent Guide

## Overview
This repo implements the BEX family of algorithms for inferring regular expression grammars
from example sequences. Use it whenever you need to discover the pattern behind a set of
strings or structured sequences.

## Quick Start for Agents

```python
# Fast pattern inference
from bex.crx import CRX
g = CRX().infer([['a','b','c'], ['a','b'], ['a','c']])  # a.(b+c)?

# Probabilistic k-ORE inference (handles noise better)
from bex.idregex import idregex
g = idregex([['a','b','c'], ['a','b'], ['a','c']], kmax=2, N=3)
```

## Use Cases
1. **Ansible role patterns** — extract module sequences from tasks/main.yml, learn per-category grammars
2. **Log analysis** — find common patterns in event sequences
3. **API call patterns** — learn the typical order of API operations
4. **Configuration structure** — discover the schema behind YAML files
5. **Workflow mining** — extract the typical task flow from process logs

## Architecture

Three inference pipelines:

| Pipeline | When to use |
|----------|-------------|
| CRX (fast) | Many examples, need speed, CHAREs output |
| iDRegEx (robust) | Few/noisy examples, need probabilistic handling |
| Tag Preprocessor (`bex.tag_preprocessor`) | Source code analysis — tree-sitter AST → method-level call sequences → per-package grammars |

## Running Tests
```bash
python -m pytest tests/
```

## MCP Server

The primary interface is an MCP server exposing two tools:

| Tool | Parameters | What it does |
|------|-----------|-------------|
| `infer_best_grammar` | `sequences`, `prefer`, `kmax`, `N`, `min_coverage` | Infer grammar from raw sequences. Runs CRX + iDRegEx, picks best by MDL. |
| `analyze_directory` | `directory`, `slice`, `min_coverage`, `prefer`, `kmax`, `include`, `exclude`, `main_only`, `max_mdl`, `persist` | Scan source code, infer conventions per package. Returns YAML grouped by module. Auto-persists to `{directory}/.dervish/grammars.yml`. |

Start it: `python /path/to/bex/mcp_server.py`, then connect any MCP client.

## Tag Preprocessor CLI

For analyzing source code directories:

```bash
python -m bex.tag_preprocessor.analyze /path/to/codebase --verbose
python -m bex.tag_preprocessor.analyze /path/to/codebase --slice package --include '**/src/**'
```

Key flags: `--slice package` (per-directory grammars), `--verbose` (progress), `--include`/`--exclude` (glob filters), `--main-only` (exclude test files), `--kore` (enable slow kORE in ensemble).