You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: parser.rs
    path of file: ./repos/fluent-rs/fluent-syntax/src/bin
    
    the code of the file until where you have to start completion: //! This is a simple CLI utility to take in an FTL file and output the AST.
//!
//! ## View the `Debug` representation:
//!
//! From the root directory of the `fluent-rs` repo:
//!
//! ```sh
//! cargo run --bin parser -- ./fluent-syntax/tests/fixtures/literal_expressions.ftl
//! ```
//!
//! ## View the `json` representation:
//!
//! ```sh
//! cargo run --bin parser --features json -- ./fluent-syntax/tests/fixtures/literal_expressions.ftl
//! ```

use fluent_syntax::parser::parse;
use std::env;
use std::fs::File;
use std::io;
use std::io::Read;

fn read_file(path: &str) -> Result<String, io::Error> {
    let mut f = File::open(path)?;
    let mut s = String::new();
    f.read_to_string(&mut s)?;
    Ok(s)
}

fn main() {
    let args: Vec<String> = env::args().collect();
    let source
    
fn main() {
    let args: Vec<String> = env::args().collect();
    let source = read_file(args.get(1).expect("Pass a file path as the first argument"))
        .expect("Failed to fetch file");

    let (ast, errors) = match parse(source.as_str()) {
        Ok(ast) => (ast, None),
        Err((ast, err)) => (ast, Some(err)),
    };

    #[cfg(feature = "json")]
    {
        let target_json = serde_json::to_string_pretty(&ast).unwrap();
        println!("{}", target_json);
    }
    #[cfg(not(feature = "json"))]
    {
        use std::fmt::Write;
        let mut result = String::new();
        write!(result, "{:#?}", ast).unwrap();
        println!("{}", result);
    }

    if let Some(errors) = errors {
        println!("\n======== Errors ========== \n");
        for err in errors {
            println!("Err: {:#?}", err);
        }
    }
}