> ## Documentation Index
> Fetch the complete documentation index at: https://www.c1.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# CEL expressions

> Common Expression Language reference for baton-http and baton-sql data transformation.

Both meta-connectors use the Common Expression Language (CEL) for data transformation. CEL is a simple, fast, and secure expression language - a safer alternative to embedding arbitrary code in your config.

## Basic field mapping

```yaml theme={"theme":{"light":"css-variables","dark":"css-variables"}}
map:
  id: ".id"                                           # Direct field access
  display_name: ".first_name + ' ' + .last_name"      # String concatenation
  status: ".is_active ? 'enabled' : 'disabled'"       # Ternary
```

## Available functions

| Function       | Purpose              | Example                                    |
| -------------- | -------------------- | ------------------------------------------ |
| `lowercase()`  | Convert to lowercase | `lowercase(.email)`                        |
| `uppercase()`  | Convert to uppercase | `uppercase(.code)`                         |
| `titlecase()`  | Title case           | `titlecase(.name)`                         |
| `trim()`       | Remove whitespace    | `trim(.value)`                             |
| `match()`      | Regex matching       | `match(.email, ".*@corp\\.com")`           |
| `extract()`    | Extract regex group  | `extract(.urn, "user-([0-9]+)")`           |
| `replace()`    | String replacement   | `replace(.name, {"old": "_", "new": "-"})` |
| `get()`        | Get with default     | `get(.optional, "default")`                |
| `has()`        | Check field exists   | `has(input.employee_id)`                   |
| `parse_json()` | Parse JSON string    | `parse_json(.metadata).type`               |
| `json_path()`  | Extract from JSON    | `json_path(.data, "user.name")`            |

## Context variables

Available variables depend on context:

| Variable            | Available in         | Purpose                    |
| ------------------- | -------------------- | -------------------------- |
| `item` or `.column` | List/Grants          | Current row/item           |
| `resource`          | Grants, Provisioning | Current resource           |
| `principal`         | Provisioning         | User being granted/revoked |
| `entitlement`       | Provisioning         | Entitlement being modified |
| `input`             | Account creation     | User-provided form values  |
| `password`          | Account creation     | Generated password         |

## Common patterns

### Conditional field mapping

```yaml theme={"theme":{"light":"css-variables","dark":"css-variables"}}
account_type: ".type == 'employee' ? 'human' : 'service'"
```

### Null handling

```yaml theme={"theme":{"light":"css-variables","dark":"css-variables"}}
last_login: ".last_login != null ? string(.last_login) : ''"
```

### String operations

```yaml theme={"theme":{"light":"css-variables","dark":"css-variables"}}
# Lowercase email
email: "lowercase(.email)"

# Build full name
display_name: ".first_name + ' ' + .last_name"

# Extract username from email
username: "extract(.email, '([^@]+)@.*')"
```

### Type conversion

```yaml theme={"theme":{"light":"css-variables","dark":"css-variables"}}
# Convert numeric ID to string
id: "string(.numeric_id)"
```

### Field existence check

```yaml theme={"theme":{"light":"css-variables","dark":"css-variables"}}
# Use optional field with fallback
department: "has(input.department) ? input.department : 'Unknown'"
```

### Skip conditions in grants

```yaml theme={"theme":{"light":"css-variables","dark":"css-variables"}}
grants:
  - query: "SELECT * FROM role_members WHERE role_id = ?<role_id>"
    map:
      - skip_if: ".user_type == 'system'"    # Skip system accounts
        principal_id: ".user_id"
        principal_type: "user"
        entitlement_id: "member"
```

## Quick reference

```yaml theme={"theme":{"light":"css-variables","dark":"css-variables"}}
# Direct field access
".field_name"

# String concatenation
".first + ' ' + .last"

# Ternary
".active ? 'enabled' : 'disabled'"

# Null check
".value != null ? .value : 'default'"

# Type conversion
"string(.numeric_id)"

# Field existence check
"has(input.optional_field)"

# Lowercase/uppercase
"lowercase(.email)"
"uppercase(.code)"
```