// Copyright 2015-2018 Parity Technologies (UK) Ltd.
// This file is part of Parity.

// Parity is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Parity is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Parity.  If not, see <http://www.gnu.org/licenses/>.

//! Custom panic hook with bug report link

extern crate backtrace;

use std::io::{self, Write};
use std::panic::{self, PanicInfo};
use std::thread;
use std::process;
use backtrace::Backtrace;

/// Set the panic hook to write to stderr and abort the process when a panic happens.
pub fn set_abort() {
	set_with(|msg| {
		let _ = io::stderr().write_all(msg.as_bytes());
		process::abort()
	});
}

/// Set the panic hook with a closure to be called. The closure receives the panic message.
///
/// Depending on how Parity was compiled, after the closure has been executed, either the process
/// aborts or unwinding starts.
///
/// If you panic within the closure, a double panic happens and the process will stop.
pub fn set_with<F>(f: F)
where F: Fn(&str) + Send + Sync + 'static
{
	panic::set_hook(Box::new(move |info| {
		let msg = gen_panic_msg(info);
		f(&msg);
	}));
}

static ABOUT_PANIC: &str = "
This is a bug. Please report it at:

    https://github.com/paritytech/parity-ethereum/issues/new
";

fn gen_panic_msg(info: &PanicInfo) -> String {
	let location = info.location();
	let file = location.as_ref().map(|l| l.file()).unwrap_or("<unknown>");
	let line = location.as_ref().map(|l| l.line()).unwrap_or(0);

	let msg = match info.payload().downcast_ref::<&'static str>() {
		Some(s) => *s,
		None => match info.payload().downcast_ref::<String>() {
			Some(s) => &s[..],
			None => "Box<Any>",
		}
	};

	let thread = thread::current();
	let name = thread.name().unwrap_or("<unnamed>");

	let backtrace = Backtrace::new();

	format!(r#"

====================

{backtrace:?}

Thread '{name}' panicked at '{msg}', {file}:{line}
{about}
"#, backtrace = backtrace, name = name, msg = msg, file = file, line = line, about = ABOUT_PANIC)
}