Figura 🃏

A lightweight, flexible template formatting engine for Rust with support for custom delimiters and extensible directive parsing.

Features

• Variable Substitution: {name} → context values
• Repetition: {pattern:count} → repeat patterns
• Conditionals: {condition?true_part:false_part} → conditional rendering
• Custom Delimiters: Use any characters as template boundaries
• Extensible Parsers: Create custom directive handlers
• Escape Sequences: {{ and }} for literal delimiters
• Alignment Support: {value<}, {value>}, {value^} for formatting hints

Quick Start

use figura::{Template, Context, Value};
use std::collections::HashMap;

// Basic variable substitution
let template = Template::parse("Hello, {name}!")?;
let mut ctx = HashMap::new();
ctx.insert("name", Value::String("World".into()));
assert_eq!(template.format(&ctx)?, "Hello, World!");

// Repetition
let template = Template::parse("Echo: {word:3}")?;
let mut ctx = HashMap::new();
ctx.insert("word", Value::String("hi".into()));
assert_eq!(template.format(&ctx)?, "Echo: hihihi");

// Conditionals
let template = Template::parse("{logged_in?Welcome back!:Please log in}")?;
let mut ctx = HashMap::new();
ctx.insert("logged_in", Value::Bool(true));
assert_eq!(template.format(&ctx)?, "Welcome back!");

// Custom delimiters
let template = Template::<'[', ']'>::parse("Hello [name]!")?;

Value Types

The engine supports multiple value types:

ctx.insert("name", Value::String("Alice".into()));
ctx.insert("age", Value::Int(30));
ctx.insert("score", Value::Float(95.5));
ctx.insert("active", Value::Bool(true));

Custom Parsers

Extend functionality by implementing the Parser trait:

struct CustomParser;

impl Parser for CustomParser {
    fn parse(tokens: &[Token], content: &str) -> Option<Box<dyn Directive>> {
        // Your custom parsing logic
        // Fall back to DefaultParser if needed
        DefaultParser::parse(tokens, content)
    }
}

let template = Template::with_parser::<CustomParser>("Your template")?;

Error Handling

The engine provides detailed error information:

• MissingDelimiter: Unmatched template delimiters
• NoValueFound: Referenced variable not in context
• ExecutionError: Runtime directive execution failures
• DirectiveParsing: Parser unable to handle directive

License

MIT