### Start Development Environment

Source: https://github.com/mgm-tp/a12-expression/blob/main/README.md

Start the development server and TypeScript compilers in watch mode. This is the recommended way to begin development.

```sh
pnpm start
```

--------------------------------

### Install Dependencies with pnpm

Source: https://github.com/mgm-tp/a12-expression/blob/main/README.md

Install all project dependencies and link local packages using pnpm. This command is necessary before building the project.

```sh
pnpm install
```

--------------------------------

### Expression AST Example

Source: https://github.com/mgm-tp/a12-expression/blob/main/documentation/src/0400_modules.adoc

This example shows the Abstract Syntax Tree (AST) generated from a sample expression string. The AST represents the structure of the expression, including fields, strings, and groups.

```json
{
  "type": "root",
  "children": [
    {
      "type": "group",
      "name": "PersonalInfo",
      "children": [
        {
          "type": "field",
          "name": "LastName"
        },
        {
          "type": "string",
          "content": " "
        },
        {
          "type": "field",
          "name": "FirstName"
        }
      ]
    }
  ]
}
```

--------------------------------

### Install expression-core NPM Package

Source: https://github.com/mgm-tp/a12-expression/blob/main/documentation/src/0200_installation.adoc

Use this command to install the expression-core package from NPM. This command installs ES5 CommonJS modules.

```bash
npm install @com.mgmtp.a12.expression/expression-core
```

--------------------------------

### Compile All Packages

Source: https://github.com/mgm-tp/a12-expression/blob/main/README.md

Build all packages within the repository after installing dependencies. This command compiles the project's code.

```sh
pnpm compile
```

--------------------------------

### Main Usage Example

Source: https://github.com/mgm-tp/a12-expression/blob/main/documentation/src/0300_usage.adoc

This snippet demonstrates the main usage of the Expression package. It requires document, documentModel, localizer, and fieldFormatter to create an Expression resolver.

```typescript
import {
  Expression,
  ExpressionResolver,
  ExpressionContext,
} from "@mgm/a12-expression";

// Assume these are provided by the A12 environment
const document = {};
const documentModel = {};
const localizer = {};
const fieldFormatter = (value: any) => String(value);

// Create an Expression context
const context: ExpressionContext = {
  document,
  documentModel,
  localizer,
  fieldFormatter,
};

// Create an Expression resolver
const resolver = new ExpressionResolver(context);

// Example usage of the resolver
const expression = new Expression("user.name");
const value = resolver.resolve(expression);

console.log(value);

```

--------------------------------

### MultilingualTextValue Example

Source: https://github.com/mgm-tp/a12-expression/blob/main/documentation/src/0500_language.adoc

Defines localized text values using locale codes and corresponding strings, enclosed in parentheses and separated by commas.

```bash
(en: "women", de: "frauen", fr: "femmes")
```

--------------------------------

### ExpressionInterpreter HTML Output Example

Source: https://github.com/mgm-tp/a12-expression/blob/main/documentation/src/0400_modules.adoc

Demonstrates the HTML output generated by the ExpressionInterpreter.format function when processing a given AST. The output is typically a structured HTML string.

```html
<div>
    <p>John Doe</p>
</div>
```

--------------------------------

### StringValue Example

Source: https://github.com/mgm-tp/a12-expression/blob/main/documentation/src/0500_language.adoc

Represents a string literal enclosed in double quotes.

```bash
"Fullname:"
```

--------------------------------

### FieldValue Example

Source: https://github.com/mgm-tp/a12-expression/blob/main/documentation/src/0500_language.adoc

References a field within the current scope, enclosed in square brackets. Only available within GroupOperation.

```bash
[FirstName]
```

--------------------------------

### GroupOperation with Custom Delimiter

Source: https://github.com/mgm-tp/a12-expression/blob/main/documentation/src/0500_language.adoc

Concatenates results of repeatable groups using a specified delimiter. This example uses ', ' to separate multiple addresses.

```bash
kontext (PersonalInfo) {
  kontext (Address, delimiter = ", ") {
   [City] " (" [Country] ")"
  }
}
```

--------------------------------

### Markdown Formatting in Expressions

Source: https://github.com/mgm-tp/a12-expression/blob/main/documentation/src/0500_language.adoc

This example shows how to use Markdown syntax within expressions for text formatting like bold and italics. Markdown characters must be wrapped in double quotes.

```expression
"**Bold Text**"
"*Italic Text*"
"~~StrikeThrough~~
"My name is: **" [FirstName] "**" " " *" [LastName] *"
```

--------------------------------

### GroupOperation Basic Usage

Source: https://github.com/mgm-tp/a12-expression/blob/main/documentation/src/0500_language.adoc

Accesses nested document model elements. The example shows accessing FirstName and LastName, and then City and Country within a nested Address group.

```bash
kontext (PersonalInfo) {
  [FirstName] " " [LastName]
  " from "
  kontext (Address) {
   [City] "," [Country]
  }
}
```

--------------------------------

### Run Unit Tests

Source: https://github.com/mgm-tp/a12-expression/blob/main/README.md

Execute unit tests across all packages in the repository. This command verifies the correctness of the code.

```sh
pnpm test
```

--------------------------------

### Run Linting

Source: https://github.com/mgm-tp/a12-expression/blob/main/README.md

Execute linting checks on the entire project. This command helps maintain code quality and consistency.

```sh
pnpm lint
```

--------------------------------

### ExpressionBuilder.build

Source: https://github.com/mgm-tp/a12-expression/blob/main/documentation/src/0400_modules.adoc

The ExpressionBuilder module exposes the `build` function to create an abstract syntax tree (AST) from a raw expression string. It accepts the expression string and an optional context object.

```APIDOC
## ExpressionBuilder.build

### Description
Builds an abstract syntax tree (AST) from a raw expression string. This is useful for customizations.

### Parameters

#### Path Parameters
None

#### Query Parameters
None

#### Request Body
* **expression** (string) - Required - The string expression to be parsed.
* **context** (object) - Optional - Contains additional information for the builder.
```

--------------------------------

### Format Code

Source: https://github.com/mgm-tp/a12-expression/blob/main/README.md

Automatically fix linting issues and format the code according to project standards. This command ensures code style consistency.

```sh
pnpm format
```

--------------------------------

### CaseOperation Syntax

Source: https://github.com/mgm-tp/a12-expression/blob/main/documentation/src/0500_language.adoc

Provides branching logic based on field comparison. Supports equality ('=') and inequality ('!=') operators.

```bash
case [<field_name>] <operator> <string_value> { <list_of_elements> }
```

--------------------------------

### Clean Build Artifacts

Source: https://github.com/mgm-tp/a12-expression/blob/main/README.md

Remove all build artifacts from the project. Use this command to clean the project before a fresh build.

```sh
pnpm clean
```

--------------------------------

### ExpressionBuilder API

Source: https://github.com/mgm-tp/a12-expression/blob/main/documentation/src/0400_modules.adoc

The ExpressionBuilder module exposes the build function for creating an Abstract Syntax Tree (AST) from a raw string expression. It takes the expression string and an optional context object.

```typescript
/**
 * Builds an AST from a raw expression string.
 *
 * @param expression The expression string to parse.
 * @param context Optional context information for the builder.
 * @returns The generated AST.
 */
export function build(expression: string, context?: unknown): AST {
  // Implementation omitted for brevity
  return { type: "root", children: [] };
}

```

--------------------------------

### ExpressionInterpreter Parameters

Source: https://github.com/mgm-tp/a12-expression/blob/main/documentation/src/0400_modules.adoc

Defines the parameters accepted by the ExpressionInterpreter module for formatting an AST into HTML. It includes the AST itself and optional configuration for output.

```typescript
interface Parameters {
  ast: AST;
  // Optional: wrap output by a span instead of div
  asSpan?: boolean;
  // Optional: additional CSS class name
  className?: string;
}

```

--------------------------------

### ExpressionInterpreter.format

Source: https://github.com/mgm-tp/a12-expression/blob/main/documentation/src/0400_modules.adoc

The ExpressionInterpreter module transforms an expression AST into an HTML string. It takes a single parameter object conforming to the Interpreter.Parameters interface.

```APIDOC
## ExpressionInterpreter.format

### Description
Transforms an expression AST into an HTML string.

### Parameters

#### Path Parameters
None

#### Query Parameters
None

#### Request Body
* **(object)** (Interpreter.Parameters) - Required - An object containing parameters for formatting the AST into HTML. The specific fields depend on the `Interpreter.Parameters` interface.

### Response
#### Success Response (200)
* **(string)** - The HTML string representation of the expression.

### Response Example
```html
<div>
    <p>John Doe</p>
</div>
```
```

--------------------------------

### ExpressionOutput Component

Source: https://github.com/mgm-tp/a12-expression/blob/main/documentation/src/0400_modules.adoc

The ExpressionOutput is a React component that wraps the ExpressionInterpreter. It is recommended for integrating HTML output into applications, providing a safer alternative to React's `dangerouslySetInnerHTML`.

```APIDOC
## ExpressionOutput Component

### Description
A React component that renders HTML output from an expression AST, wrapping the `ExpressionInterpreter`.

### Props

* **(Interpreter.Parameters)** - Required - Same parameters as `ExpressionInterpreter.format`.
* **asSpan** (boolean) - Optional - If true, wraps the output in a `span` element instead of the default `div`.
* **className** (string) - Optional - Additional CSS class name to apply to the wrapper element.
```

--------------------------------

### Expression with Conditional Title

Source: https://github.com/mgm-tp/a12-expression/blob/main/documentation/src/0500_language.adoc

This expression demonstrates how to conditionally add a title based on a boolean field. It reuses the document model from the GroupOperation section.

```expression
kontext (PersonalInfo) {
  case [IsMale] = "true"  { "Mr." }
  case [IsMale] != "true" { "Mrs." }
  [LastName]
}
```

--------------------------------

### Expression Language Grammar

Source: https://github.com/mgm-tp/a12-expression/blob/main/documentation/src/0500_language.adoc

This is the ANTLR grammar definition for the Expression language, used by the ANTLR library to generate the lexer and parser.

```g4
grammar Expression;


//
// Parser rules
//


expression
    : value
    | operation
    ;


operation
    : LPAREN expression RPAREN
    | NOT expression
    | expression BINOP expression
    | expression QUESTION expression COLON expression
    | expression CASE expression LCURLY expression RCURLY
    | expression IS expression
    | expression ISNOT expression
    | expression EQ expression
    | expression NEQ expression
    | expression GT expression
    | expression GTE expression
    | expression LT expression
    | expression LTE expression
    ;


value
    : STRING
    | NUMBER
    | BOOLEAN
    | NULL
    | field
    | list
    | kontext
    ;


field 
    : LBRACKET ID RBRACKET
    ;


list
    : LBRACKET value (COMMA value)* RBRACKET
    ;


kontext
    : KONTEXT ID LCURLY expression RCURLY
    ;


//
// Lexer rules
//


STRING
    : '"' ( ESCAPED_STRING | . )* '"'
    ;


fragment
ESCAPED_STRING
    : '\\' ( '"' | '\\' )
    ;


NUMBER
    : SIGNED_NUMBER
    | UNSIGNED_NUMBER
    ;


fragment
SIGNED_NUMBER
    : (PLUS | MINUS) UNSIGNED_NUMBER
    ;


fragment
UNSIGNED_NUMBER
    : INT ( (DOT INT?)? | DOT INT )
    ;


fragment
INT
    : [0-9]+ 
    ;


BOOLEAN
    : 'true' | 'false'
    ;


NULL
    : 'null'
    ;


BINOP
    : EQ | NEQ | GT | GTE | LT | LTE | IS | ISNOT
    ;


EQ
    : '='
    ;

NEQ
    : '!='
    ;

GT
    : '>'
    ;

GTE
    : '>='
    ;

LT
    : '<'
    ;

LTE
    : '<='
    ;

IS
    : 'is'
    ;

ISNOT
    : 'is not'
    ;

NOT
    : '!'
    ;

QUESTION
    : '?'
    ;

COLON
    : ':'
    ;

CASE
    : 'case'
    ;

KONTEXT
    : 'kontext'
    ;

LPAREN
    : '(' 
    ;

RPAREN
    : ')' 
    ;

LCURLY
    : '{'
    ;

RCURLY
    : '}'
    ;

LBRACKET
    : '['
    ;

RBRACKET
    : ']'
    ;

COMMA
    : ','
    ;

PLUS
    : '+'
    ;

MINUS
    : '-'
    ;

DOT
    : '.'
    ;

WS
    : ( ' ' | '\t' | '\r' | '\n' )+ -> skip
    ;


```

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