//! `cargo doc2readme` is a cargo subcommand to create a readme file to display on [GitHub] or [crates.io],
//! containing the rustdoc comments from your code.
//!
//! # Usage
//!
//! ```bash
//! cargo install cargo-doc2readme
//! cargo doc2readme --out README.md
//! ```
//!
//! If you want to run this using GitHub Actions, you can use the pre-built docker image:
//!
//! ```yaml
//! readme:
//!   runs-on: ubuntu-latest
//!   steps:
//!     - uses: actions/checkout@v2
//!     - uses: docker://ghcr.io/msrd0/cargo-doc2readme
//!       with:
//!         entrypoint: cargo
//!         args: doc2readme
//!     - run: git diff --exit-code README.md
//! ```
//!
//! # Features
//!
//!  - parse markdown from your rustdoc comments and embed it into your readme
//!  - use existing crates to parse Rust and Markdown
//!  - support your `[CustomType]` rustdoc links
//!  - default, minimalistic readme template with some useful badges
//!  - custom readme templates
//!
//! # Non-Goals
//!
//!  - verbatim copy of your markdown
//!  - easy readability of the generated markdown source code
//!
//! # Similar tools
//!
//! [`cargo readme`][cargo-readme] is a similar tool. However, it brings its own Rust code parser that only covers the 95% use case. Also, it does not support Rust path links introduced in Rust 1.48, making your readme ugly due to GitHub showing the unsupported links as raw markdown, and being less convenient for the reader that has to search [docs.rs] instead of clicking on a link.
//!
//! # Stability Guarantees
//!
//! This project adheres to semantic versioning. All versions will be tested against the latest stable rust version
//! at the time of the release. All non-bugfix changes to the rustdoc input processing and markdown output or the
//! default readme template are considered breaking changes, as well as any non-backwards-compatible changes to the
//! command-line arguments or to these stability guarantees. All other changes, including any changes to the Rust
//! code, or bumping the MSRV, are not considered breaking changes.
//!
//!  [crates.io]: https://crates.io
//!  [GitHub]: https://github.com
//!  [cargo-readme]: https://github.com/livioribeiro/cargo-readme
//!  [docs.rs]: https://docs.rs

use cargo::{
	core::{
		registry::{LockedPatchDependency, PackageRegistry},
		Dependency, EitherManifest, SourceId, Verbosity
	},
	util::{important_paths::find_root_manifest_for_wd, toml::read_manifest},
	Config as CargoConfig
};
use clap::Clap;
use std::{borrow::Cow, env, fs::File, io::Read, path::PathBuf};

mod input;
mod output;

#[derive(Clap)]
enum Subcommand {
	Doc2readme(Args)
}

#[derive(Clap)]
struct Args {
	/// Path to Cargo.toml.
	#[clap(long)]
	manifest_path: Option<PathBuf>,

	/// Output File.
	#[clap(short, long, default_value = "README.md")]
	out: PathBuf,

	/// Template File. This is processed by Tera. Look at the source code for cargo-doc2readme for
	/// an example.
	#[clap(short, long, default_value = "README.j2")]
	template: PathBuf
}

#[derive(Clap)]
struct CmdLine {
	#[clap(subcommand)]
	cmd: Subcommand
}

fn main() {
	let args = match env::args().nth(1) {
		Some(subcmd) if subcmd == "doc2readme" => match CmdLine::parse().cmd {
			Subcommand::Doc2readme(args) => args
		},
		_ => Args::parse()
	};

	// get the cargo manifest path
	let manifest_path = match args.manifest_path {
		Some(path) if path.is_relative() => env::current_dir().unwrap().join(path),
		Some(path) => path,
		None => find_root_manifest_for_wd(&env::current_dir().unwrap()).expect("Unable to find Cargo.toml")
	};

	// parse the cargo manifest
	let cargo_cfg = CargoConfig::default().expect("Failed to initialize cargo");
	let src_id = SourceId::for_path(&manifest_path).expect("Failed to obtain source id");
	let manifest = match read_manifest(&manifest_path, src_id, &cargo_cfg).expect("Failed to read Cargo.toml") {
		(EitherManifest::Real(manifest), _) => manifest,
		(EitherManifest::Virtual(_), _) => panic!("What on earth is a virtual manifest?")
	};

	// fix cargo being extremely verbose by default
	match env::var("RUST_LOG") {
		Ok(log) if log == "debug" => cargo_cfg.shell().set_verbosity(Verbosity::Verbose),
		_ => cargo_cfg.shell().set_verbosity(Verbosity::Normal)
	}

	// find the target whose rustdoc comment we'll use.
	// this uses a library target if exists, otherwise a binary target with the same name as the
	// package, or otherwise the first binary target
	let targets = manifest.targets();
	let target = targets
		.iter()
		.find(|target| target.is_lib())
		.or_else(|| {
			targets
				.iter()
				.find(|target| target.is_bin() && target.name() == manifest.name().as_str())
		})
		.or_else(|| targets.iter().find(|target| target.is_bin()))
		.expect("Failed to find a library or binary target");

	// initialize the crate registry
	let _guard = cargo_cfg
		.acquire_package_cache_lock()
		.expect("Failed to aquire package cache lock");
	let mut registry = PackageRegistry::new(&cargo_cfg).expect("Failed to initialize crate registry");
	for (url, deps) in manifest.patch() {
		let deps: Vec<(&Dependency, Option<LockedPatchDependency>)> = deps.iter().map(|dep| (dep, None)).collect();
		registry.patch(url, &deps).expect("Failed to apply patches");
	}
	registry.lock_patches();

	// resolve the template
	let template: Cow<'static, str> = if args.template.exists() {
		let mut buf = String::new();
		File::open(args.template)
			.expect("Failed to open template")
			.read_to_string(&mut buf)
			.expect("Failed to read template");
		buf.into()
	} else {
		include_str!("README.j2").into()
	};

	// Configure git transport ( makes cargo compatible with HTTP proxies )
	init_git_transports(&cargo_cfg);

	// process the target
	let file = target.src_path().path().expect("Target does not have a source file");
	cargo_cfg.shell().status("Reading", file.display()).ok();
	let input_file = input::read_file(&manifest, &mut registry, file).expect("Unable to read file");
	cargo_cfg
		.shell()
		.verbose(|shell| shell.status("Processing", format!("{:?}", input_file)))
		.ok();
	if input_file.scope.has_glob_use {
		cargo_cfg.shell().warn("Your code contains glob use statements (e.g. `use std::io::prelude::*;`). Those can lead to incomplete link generation.").ok();
	}
	let out = if args.out.is_relative() {
		env::current_dir().unwrap().join(args.out)
	} else {
		args.out
	};
	cargo_cfg.shell().status("Writing", out.display()).ok();
	let mut out = File::create(out).expect("Unable to create output file");
	output::emit(input_file, &template, &mut out).expect("Unable to write output file");

	cargo_cfg.release_package_cache_lock();
}

/// Copied from cargo crate:
/// https://github.com/rust-lang/cargo/blob/e870eac9967b132825116525476d6875c305e4d8/src/bin/cargo/main.rs#L199
fn init_git_transports(config: &CargoConfig) {
	// Only use a custom transport if any HTTP options are specified,
	// such as proxies or custom certificate authorities. The custom
	// transport, however, is not as well battle-tested.

	match cargo::ops::needs_custom_http_transport(config) {
		Ok(true) => {},
		_ => return
	}

	let handle = match cargo::ops::http_handle(config) {
		Ok(handle) => handle,
		Err(..) => return
	};

	// The unsafety of the registration function derives from two aspects:
	//
	// 1. This call must be synchronized with all other registration calls as
	//    well as construction of new transports.
	// 2. The argument is leaked.
	//
	// We're clear on point (1) because this is only called at the start of this
	// binary (we know what the state of the world looks like) and we're mostly
	// clear on point (2) because we'd only free it after everything is done
	// anyway
	unsafe {
		git2_curl::register(handle);
	}
}