// Copyright 2015-2017 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/>.

//! Wasm Interpreter

extern crate vm;
extern crate ethcore_util as util;
extern crate ethcore_bigint as bigint;
#[macro_use] extern crate log;
extern crate ethcore_logger;
extern crate byteorder;
extern crate parity_wasm;
extern crate wasm_utils;

mod runtime;
mod ptr;
mod result;
#[cfg(test)]
mod tests;
mod env;

const DEFAULT_STACK_SPACE: u32 = 5 * 1024 * 1024;

use parity_wasm::{interpreter, elements};
use parity_wasm::interpreter::ModuleInstanceInterface;

use vm::{GasLeft, ReturnData, ActionParams};
use self::runtime::{Runtime, RuntimeContext, UserTrap};

pub use self::runtime::InterpreterError;

const DEFAULT_RESULT_BUFFER: usize = 1024;

/// Wrapped interpreter error
#[derive(Debug)]
pub struct Error(InterpreterError);

impl From<InterpreterError> for Error {
	fn from(e: InterpreterError) -> Self {
		Error(e)
	}
}

impl From<Error> for vm::Error {
	fn from(e: Error) -> Self {
		vm::Error::Wasm(format!("Wasm runtime error: {:?}", e.0))
	}
}

impl From<UserTrap> for vm::Error {
	fn from(e: UserTrap) -> Self { e.into() }
}

/// Wasm interpreter instance
pub struct WasmInterpreter {
	program: runtime::InterpreterProgramInstance,
	result: Vec<u8>,
}

impl WasmInterpreter {
	/// New wasm interpreter instance
	pub fn new() -> Result<WasmInterpreter, Error> {
		Ok(WasmInterpreter {
			program: interpreter::ProgramInstance::new()?,
			result: Vec::with_capacity(DEFAULT_RESULT_BUFFER),
		})
	}
}

impl vm::Vm for WasmInterpreter {

	fn exec(&mut self, params: ActionParams, ext: &mut vm::Ext) -> vm::Result<GasLeft> {
		use parity_wasm::elements::Deserialize;

		let code = params.code.expect("exec is only called on contract with code; qed");

		trace!(target: "wasm", "Started wasm interpreter with code.len={:?}", code.len());

		let env_instance = self.program.module("env")
			// prefer explicit panic here
			.expect("Wasm program to contain env module");

		let env_memory = env_instance.memory(interpreter::ItemIndex::Internal(0))
			// prefer explicit panic here
			.expect("Linear memory to exist in wasm runtime");

		if params.gas > ::std::u64::MAX.into() {
			return Err(vm::Error::Wasm("Wasm interpreter cannot run contracts with gas >= 2^64".to_owned()));
		}

		let mut runtime = Runtime::with_params(
			ext,
			env_memory,
			DEFAULT_STACK_SPACE,
			params.gas.low_u64(),
			RuntimeContext {
				address: params.address,
				sender: params.sender,
				origin: params.origin,
				value: params.value.value(),
			},
			&self.program,
		);

		let mut cursor = ::std::io::Cursor::new(&*code);

		let contract_module = wasm_utils::inject_gas_counter(
			elements::Module::deserialize(
				&mut cursor
			).map_err(|err| {
				vm::Error::Wasm(format!("Error deserializing contract code ({:?})", err))
			})?
		);

		let d_ptr = runtime.write_descriptor(&params.data.unwrap_or_default())
			.map_err(Error)?;

		{
			let execution_params = runtime.execution_params()
				.add_argument(interpreter::RuntimeValue::I32(d_ptr.as_raw() as i32));

			let module_instance = self.program.add_module("contract", contract_module, Some(&execution_params.externals))
				.map_err(|err| {
					trace!(target: "wasm", "Error adding contract module: {:?}", err);
					vm::Error::from(Error(err))
				})?;

			match module_instance.execute_export("_call", execution_params) {
				Ok(_) => { },
				Err(interpreter::Error::User(UserTrap::Suicide)) => { },
				Err(err) => {
					trace!(target: "wasm", "Error executing contract: {:?}", err);
					return Err(vm::Error::from(Error(err)))
				}
			}
		}

		let result = result::WasmResult::new(d_ptr);
		if result.peek_empty(&*runtime.memory()).map_err(|e| Error(e))? {
			trace!(target: "wasm", "Contract execution result is empty.");
			Ok(GasLeft::Known(runtime.gas_left()?.into()))
		} else {
			self.result.clear();
			// todo: use memory views to avoid copy
			self.result.extend(result.pop(&*runtime.memory()).map_err(|e| Error(e.into()))?);
			let len = self.result.len();
			Ok(GasLeft::NeedsReturn {
				gas_left: runtime.gas_left().map_err(|e| Error(e.into()))?.into(),
				data: ReturnData::new(
					::std::mem::replace(&mut self.result, Vec::with_capacity(DEFAULT_RESULT_BUFFER)),
					0,
					len,
				),
				apply_state: true,
			})
		}
	}
}