// Copyright 2015-2020 Parity Technologies (UK) Ltd.
// This file is part of OpenEthereum.

// OpenEthereum 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.

// OpenEthereum 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 OpenEthereum.  If not, see <http://www.gnu.org/licenses/>.

//! Wasm Interpreter

extern crate byteorder;
extern crate ethereum_types;
#[macro_use]
extern crate log;
extern crate libc;
extern crate parity_wasm;
extern crate pwasm_utils as wasm_utils;
extern crate vm;
extern crate wasmi;

#[cfg(test)]
extern crate env_logger;

mod env;
mod panic_payload;
mod parser;
mod runtime;

use vm::{ActionParams, GasLeft, ReturnData};
use wasmi::{Error as InterpreterError, Trap};

use runtime::{Runtime, RuntimeContext};

use ethereum_types::U256;

/// Wrapped interpreter error
#[derive(Debug)]
pub enum Error {
    Interpreter(InterpreterError),
    Trap(Trap),
}

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

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

impl From<Error> for vm::Error {
    fn from(e: Error) -> Self {
        match e {
            Error::Interpreter(e) => vm::Error::Wasm(format!("Wasm runtime error: {:?}", e)),
            Error::Trap(e) => vm::Error::Wasm(format!("Wasm contract trap: {:?}", e)),
        }
    }
}

/// Wasm interpreter instance
pub struct WasmInterpreter {
    params: ActionParams,
}

impl WasmInterpreter {
    pub fn new(params: ActionParams) -> Self {
        WasmInterpreter { params }
    }
}

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

enum ExecutionOutcome {
    Suicide,
    Return,
    NotSpecial,
}

impl WasmInterpreter {
    pub fn run(self: Box<WasmInterpreter>, ext: &mut dyn vm::Ext) -> vm::Result<GasLeft> {
        let (module, data) = parser::payload(&self.params, ext.schedule().wasm())?;

        let loaded_module =
            wasmi::Module::from_parity_wasm_module(module).map_err(Error::Interpreter)?;

        let instantiation_resolver = env::ImportResolver::with_limit(16, ext.schedule().wasm());

        let module_instance = wasmi::ModuleInstance::new(
            &loaded_module,
            &wasmi::ImportsBuilder::new().with_resolver("env", &instantiation_resolver),
        )
        .map_err(Error::Interpreter)?;

        let adjusted_gas = self.params.gas * U256::from(ext.schedule().wasm().opcodes_div)
            / U256::from(ext.schedule().wasm().opcodes_mul);

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

        let initial_memory = instantiation_resolver
            .memory_size()
            .map_err(Error::Interpreter)?;
        trace!(target: "wasm", "Contract requested {:?} pages of initial memory", initial_memory);

        let (gas_left, result) = {
            let mut runtime = Runtime::with_params(
                ext,
                instantiation_resolver.memory_ref(),
                // cannot overflow, checked above
                adjusted_gas.low_u64(),
                data.to_vec(),
                RuntimeContext {
                    address: self.params.address,
                    sender: self.params.sender,
                    origin: self.params.origin,
                    code_address: self.params.code_address,
                    value: self.params.value.value(),
                },
            );

            // cannot overflow if static_region < 2^16,
            // initial_memory ∈ [0..2^32)
            // total_charge <- static_region * 2^32 * 2^16
            // total_charge ∈ [0..2^64) if static_region ∈ [0..2^16)
            // qed
            assert!(runtime.schedule().wasm().initial_mem < 1 << 16);
            runtime.charge(|s| initial_memory as u64 * s.wasm().initial_mem as u64)?;

            let module_instance = module_instance
                .run_start(&mut runtime)
                .map_err(Error::Trap)?;

            let invoke_result = module_instance.invoke_export("call", &[], &mut runtime);

            let mut execution_outcome = ExecutionOutcome::NotSpecial;
            if let Err(InterpreterError::Trap(ref trap)) = invoke_result {
                if let wasmi::TrapKind::Host(ref boxed) = *trap.kind() {
                    let ref runtime_err = boxed
                        .downcast_ref::<runtime::Error>()
                        .expect("Host errors other than runtime::Error never produced; qed");

                    match **runtime_err {
                        runtime::Error::Suicide => {
                            execution_outcome = ExecutionOutcome::Suicide;
                        }
                        runtime::Error::Return => {
                            execution_outcome = ExecutionOutcome::Return;
                        }
                        _ => {}
                    }
                }
            }

            if let (ExecutionOutcome::NotSpecial, Err(e)) = (execution_outcome, invoke_result) {
                trace!(target: "wasm", "Error executing contract: {:?}", e);
                return Err(vm::Error::from(Error::from(e)));
            }

            (
                runtime
                    .gas_left()
                    .expect("Cannot fail since it was not updated since last charge"),
                runtime.into_result(),
            )
        };

        let gas_left = U256::from(gas_left) * U256::from(ext.schedule().wasm().opcodes_mul)
            / U256::from(ext.schedule().wasm().opcodes_div);

        if result.is_empty() {
            trace!(target: "wasm", "Contract execution result is empty.");
            Ok(GasLeft::Known(gas_left))
        } else {
            let len = result.len();
            Ok(GasLeft::NeedsReturn {
                gas_left: gas_left,
                data: ReturnData::new(result, 0, len),
                apply_state: true,
            })
        }
    }
}

impl vm::Exec for WasmInterpreter {
    fn exec(self: Box<WasmInterpreter>, ext: &mut dyn vm::Ext) -> vm::ExecTrapResult<GasLeft> {
        Ok(self.run(ext))
    }
}