#!/usr/bin/env -S cargo +nightly -Zscript
---cargo
[package]
edition = "2021"
---

use std::{env, fs};

const README: &str = "README.md";
const FILE_TO_INSERT: &str = "examples/example-json.rs";
const START_PATTERN: &str = "<!-- START_INSERT: examples/example-json.rs -->\n";
const END_PATTERN: &str = "<!-- END_INSERT: examples/example-json.rs -->\n";

fn main() -> Result<(), ()> {
    let only_check = match env::args().nth(1).as_deref() {
        Some("--check") => true,
        Some(_) => panic!("invalid first CLI argument"),
        None => false,
    };

    let mut file_to_insert = fs::read_to_string(FILE_TO_INSERT)
        .expect("could not read file to insert");
    let crate_manifest = fs::read_to_string("Cargo.toml").unwrap();
    let version_line = crate_manifest
        .lines()
        .find(|l| l.starts_with("version = "))
        .unwrap();
    file_to_insert = file_to_insert.replace(r#"path = "..""#, &version_line);

    let readme_file = fs::read_to_string(README).expect("could not read the README.md file");

    let mut output = readme_file.clone();
    let start_bytes = output.find(START_PATTERN).unwrap();
    let end_bytes = output.find(END_PATTERN).unwrap();
    output.replace_range(
        start_bytes..end_bytes,
        &format!("{START_PATTERN}```rust\n{file_to_insert}```\n"),
    );

    if only_check {
        if output == readme_file {
            Ok(())
        } else {
            panic!("README.md is not up to date");
        }
    } else {
      fs::write(README, output).map_err(|_| ())
    }
}