Refactor CLI tool to give room for growth (#667)

* refactor CLI commands for easier expansion

* add license headers

* cargo fmt

cli/src/commands/codegen.rs

@@ -0,0 +1,88 @@
+// Copyright 2019-2022 Parity Technologies (UK) Ltd.
+// This file is dual-licensed as Apache-2.0 or GPL-3.0.
+// see LICENSE for license details.
+
+use clap::Parser as ClapParser;
+use color_eyre::eyre;
+use frame_metadata::RuntimeMetadataPrefixed;
+use jsonrpsee::client_transport::ws::Uri;
+use scale::{
+    Decode,
+    Input,
+};
+use std::{
+    fs,
+    io::Read,
+    path::PathBuf,
+};
+use subxt_codegen::DerivesRegistry;
+
+/// Generate runtime API client code from metadata.
+///
+/// # Example (with code formatting)
+///
+/// `subxt codegen | rustfmt --edition=2018 --emit=stdout`
+#[derive(Debug, ClapParser)]
+pub struct Opts {
+    /// The url of the substrate node to query for metadata for codegen.
+    #[clap(name = "url", long, parse(try_from_str))]
+    url: Option<Uri>,
+    /// The path to the encoded metadata file.
+    #[clap(short, long, parse(from_os_str))]
+    file: Option<PathBuf>,
+    /// Additional derives
+    #[clap(long = "derive")]
+    derives: Vec<String>,
+    /// The `subxt` crate access path in the generated code.
+    /// Defaults to `::subxt`.
+    #[clap(long = "crate")]
+    crate_path: Option<String>,
+}
+
+pub async fn run(opts: Opts) -> color_eyre::Result<()> {
+    if let Some(file) = opts.file.as_ref() {
+        if opts.url.is_some() {
+            eyre::bail!("specify one of `--url` or `--file` but not both")
+        };
+
+        let mut file = fs::File::open(file)?;
+        let mut bytes = Vec::new();
+        file.read_to_end(&mut bytes)?;
+        codegen(&mut &bytes[..], opts.derives, opts.crate_path)?;
+        return Ok(())
+    }
+
+    let url = opts.url.unwrap_or_else(|| {
+        "http://localhost:9933"
+            .parse::<Uri>()
+            .expect("default url is valid")
+    });
+    let (_, bytes) = super::metadata::fetch_metadata(&url).await?;
+    codegen(&mut &bytes[..], opts.derives, opts.crate_path)?;
+    Ok(())
+}
+
+fn codegen<I: Input>(
+    encoded: &mut I,
+    raw_derives: Vec<String>,
+    crate_path: Option<String>,
+) -> color_eyre::Result<()> {
+    let metadata = <RuntimeMetadataPrefixed as Decode>::decode(encoded)?;
+    let generator = subxt_codegen::RuntimeGenerator::new(metadata);
+    let item_mod = syn::parse_quote!(
+        pub mod api {}
+    );
+
+    let p = raw_derives
+        .iter()
+        .map(|raw| syn::parse_str(raw))
+        .collect::<Result<Vec<_>, _>>()?;
+
+    let crate_path = crate_path.map(Into::into).unwrap_or_default();
+    let mut derives = DerivesRegistry::new(&crate_path);
+    derives.extend_for_all(p.into_iter());
+
+    let runtime_api = generator.generate_runtime(item_mod, derives, crate_path);
+    println!("{}", runtime_api);
+    Ok(())
+}