Function substitute_variables 

pub fn substitute_variables<S: BuildHasher>(
    content: &str,
    values: &HashMap<String, String, S>,
    variables: &[PromptVariable],
) -> Result<String>

Substitutes variables in prompt content.

Arguments

• content - The template content with {{variable}} placeholders.
• values - A map of variable names to their values.
• variables - Variable definitions for defaults and required checks.

Security

All user-provided variable values are sanitized via sanitize_variable_value to prevent template injection attacks:

• Nested {{...}} patterns in values are escaped
• Control characters are removed
• Excessively long values are truncated

Errors

Returns an error if a required variable is missing and has no default.