Struct VariableSubstitutor 

pub struct VariableSubstitutor;

Variable substitution engine

Provides methods for substituting variables in templates using event context. Supports:

• Simple variable substitution: {{variable_name}}
• Nested path substitution: {{metadata.size}}
• Literal text with variables: "path/{{file_path}}/subdir"
• Error handling for missing variables

Implementations

impl VariableSubstitutor

pub fn substitute(template: &str, context: &EventContext) -> Result<String>

Substitute variables in a template string

Replaces all {{variable_name}} placeholders with values from the event context. Supports nested paths like {{metadata.size}}.

Arguments

• template - Template string with placeholders
• context - Event context containing variables

Returns

Substituted string or error if variables are missing

Examples

let context = EventContext {
    data: json!({"file_path": "/path/to/file.rs"}),
    metadata: json!({}),
};
let result = VariableSubstitutor::substitute("File: {{file_path}}", &context)?;
assert_eq!(result, "File: /path/to/file.rs");

pub fn substitute_json(value: &Value, context: &EventContext) -> Result<Value>

Substitute variables in a JSON value

If the value is a string, performs variable substitution. If the value is an object or array, recursively substitutes in all string values. Other types are returned unchanged.

Arguments

• value - JSON value to substitute
• context - Event context containing variables

Returns

Substituted JSON value or error if variables are missing