# AGENTS.md - SCL Language Server (Unified)

This is a unified Neovim/LazyVim plugin for Siemens SCL language support.

## Project Overview

The unified `scl_lsp` project provides:
- **LSP Server** - Language Server Protocol implementation
- **Linter** - Diagnostics and code validation
- **Formatter** - Document formatting
- **Syntax Highlighting** - Tree-sitter based
- **Auto-completion** - blink.cmp integration with smart context-aware completions
- **Auto-prefix** - Automatic `#` prefixing for variables
- **Workspace Scanning** - Automatic scanning of UDTs (.udt) and Global DBs (.db)

## Reference Project for Testing

For testing and referencing SCL, UDT, DB, and XML files, use the reference project at:
```
~/dev/siemens/projects/scl_lang_support_lazyvim_ref_project
```

This project contains example SCL files, UDT definitions, and global data blocks.

## Project Structure

```
scl_lsp/
├── src/                        # LSP server implementation
│   ├── main.lua               # Entry point, protocol handling
│   ├── parser.lua             # Regex-based SCL parser
│   ├── treesitter.lua         # Tree-sitter integration
│   ├── diagnostics.lua        # Linter diagnostics
│   ├── formatter.lua          # Document formatter
│   ├── json.lua               # JSON encoder/decoder
│   └── plc_json.lua           # External UDT loading
├── lua/
│   ├── scl/                   # Neovim plugin modules
│   │   ├── init.lua          # Main plugin setup
│   │   ├── auto_prefix.lua    # Auto-prefix variables with #
│   │   ├── blink_cmp_source.lua    # blink.cmp completion source
│   │   ├── db_parser.lua           # Global DB (.db) parser
│   │   ├── fb_parser.lua           # Function Block parser
│   │   ├── udt_parser.lua         # UDT (.udt) parser
│   │   ├── variables.lua          # Local variable extraction
│   │   ├── workspace_types.lua     # Workspace scanning (UDTs, DBs, FBs)
│   │   └── multiline_params.lua   # Multiline parameter filling
│   └── scl_lsp/
│       ├── init.lua           # Unified plugin setup
│       └── plugins/
│           └── scl.lua        # LazyVim plugin spec
├── queries/                   # Tree-sitter queries
│   ├── highlights.scm
│   ├── indents.scm
│   ├── folds.scm
│   ├── locals.scm
│   └── tags.scm
├── grammar.js                # Tree-sitter grammar
└── tree-sitter.json         # Parser config
```

## Key Modules

### Parser Modules

| Module | Purpose |
|--------|---------|
| `udt_parser.lua` | Parses `.udt` files to extract TYPE definitions and STRUCT members |
| `db_parser.lua` | Parses `.db` files to extract DATA_BLOCK definitions and VAR members |
| `fb_parser.lua` | Parses `.scl` files to extract FUNCTION_BLOCK and FUNCTION interfaces |
| `variables.lua` | Extracts local variables from VAR sections |

### Completion System

| Module | Purpose |
|--------|---------|
| `blink_cmp_source.lua` | Main completion source for blink.cmp. Handles: |
| | - Local variables (with # prefix after BEGIN) |
| | - UDT types (quoted: "MyUDT") |
| | - UDT members (after dot: #var.member) |
| | - Global DB names (available in general completion) |
| | - Global DB members (after quote+dot: "DBName".member) |
| | - FB parameter completions (inside FB calls) |
| | - Basic SCL types |

### Workspace Scanner

| Module | Purpose |
|--------|---------|
| `workspace_types.lua` | Scans project for: |
| | - `.udt` files (UDT types) |
| | - `.db` files (Global Data Blocks) |
| | - `.scl` files (Function Blocks/Functions) |
| | - Uses project markers to find project root |

## Auto-Completion Features

### Trigger Characters
- `#` - Local variables (after BEGIN)
- `.` - Member access (UDT/DB members)
- `"` - Global DB names and member access
- `(` - FB/Function parameter completion
- ` ` (space) - General completion (variables, UDTs, DBs, types)

### Completion Contexts

1. **Variable Completion** (after space or at start)
   - Local variables from VAR sections
   - UDT type names (quoted)
   - Global DB names (wrapped in quotes automatically)
   - Basic SCL types

2. **Member Completion** (after `.`)
   - UDT members (resolves through nested types)
   - DB members (resolves through nested types)
   - Supports multi-level nesting: `#var.member.submember`

3. **Global DB Completion**
   - Type `"` then select DB → shows DB members
   - Or type space → select DB from list → automatically wrapped in quotes

4. **FB Parameter Completion** (after `fbName(`)
   - Input parameters (`:=`)
   - InOut parameters (`:=`)
   - Output parameters (`=>`)

### Special Features

- **Auto-Prefix**: Adds `#` to variables automatically after BEGIN
- **Quote Wrapping**: DB names selected from general completion are automatically wrapped in quotes
- **Nested Resolution**: Multi-level member path resolution for both UDTs and DBs

## Development

### Running the LSP Server

```bash
# Direct execution
lua src/main.lua

# Via shell script
./scl_lsp.sh

# With test mode
lua src/main.lua --test
```

### Testing

```bash
# Tree-sitter parser
npm test
tree-sitter generate

# Test file parsing
tree-sitter parse corpus/test/main_org_block.scl
```

### Key Patterns

- **LSP Protocol**: JSON-RPC over stdin/stdout in `src/main.lua`
- **Diagnostics**: `src/diagnostics.lua` - validates SCL code
- **Formatter**: `src/formatter.lua` - formats SCL documents
- **Syntax**: Tree-sitter queries in `queries/`
- **Plugin Setup**: `lua/scl_lsp/init.lua` - LazyVim integration

## Configuration

See `README.md` for configuration options and usage.

## Commands

| Command | Description |
|---------|-------------|
| `:SCLShowVariables` | Show local variables in current file |
| `:SCLShowWorkspaceTypes` | Show workspace UDTs, FBs, and Global DBs count |
| `:SCLRescanWorkspaceTypes` | Rescan workspace for types and DBs |
| `:SCLPrefixWord` | Manually prefix current word with `#` |
| `:SCLMultilineParams` | Fill multiline parameters for FB/Function call |
| `:LspSCLFormat` | Format current SCL file |
| `:SCLGeneratePlcJson` | Generate plc.data.json from data_types/ |