borderless-runtime 0.5.0

use std::sync::Arc;
use std::time::Instant;

use ahash::HashMap;
use borderless::__private::registers::*;
use borderless::agents::Init;
use borderless::common::{Introduction, Revocation, Symbols};
use borderless::events::Events;
use borderless::{events::CallAction, AgentId, BorderlessId};
use borderless_kv_store::backend::lmdb::Lmdb;
use borderless_kv_store::Db;
use http::StatusCode;
use parking_lot::Mutex as SyncMutex;
use tokio::sync::{mpsc, Mutex};
use wasmtime::{Caller, Config, Engine, ExternType, FuncType, Linker, Module};

use super::vm::{ActiveEntity, Commit};
use super::{
    code_store::CodeStore,
    vm::{self, VmState},
};
use crate::db::controller::Controller;
use crate::log_shim::*;
use crate::{
    error::{ErrorKind, Result},
    AGENT_SUB_DB, SUBSCRIPTION_REL_SUB_DB,
};

pub mod tasks;

pub type SharedRuntime<S> = Arc<Mutex<Runtime<S>>>;

pub struct Runtime<S = Lmdb>
where
    S: Db,
{
    linker: Linker<VmState<S>>,
    engine: Engine,
    agent_store: CodeStore<S>,
    mutability_lock: MutLock,
    executor: Option<Vec<u8>>,
}

impl<S: Db> Runtime<S> {
    pub fn new(storage: &S, agent_store: CodeStore<S>, lock: MutLock) -> Result<Self> {
        let start = Instant::now();
        // Create agent sub-db (in case it does not exist)
        let _ = storage.create_sub_db(AGENT_SUB_DB)?;
        let _ = storage.create_sub_db(SUBSCRIPTION_REL_SUB_DB)?;

        // Generate engine ( with async enabled )
        let mut config = Config::new();
        config.cranelift_opt_level(wasmtime::OptLevel::Speed);
        config.async_support(true); // <- BIG difference
        let engine = Engine::new(&config)?;

        let mut linker: Linker<VmState<S>> = Linker::new(&engine);

        // NOTE: We have to wrap the functions into a closure here, because they must be monomorphized
        // (as a generic function cannot be made into a function pointer)
        linker.func_wrap(
            "env",
            "print",
            |caller: Caller<'_, VmState<S>>, ptr, len, level| vm::print(caller, ptr, len, level),
        )?;
        linker.func_wrap(
            "env",
            "read_register",
            |caller: Caller<'_, VmState<S>>, register_id, ptr| {
                vm::read_register(caller, register_id, ptr)
            },
        )?;
        linker.func_wrap(
            "env",
            "register_len",
            |caller: Caller<'_, VmState<S>>, register_id| vm::register_len(caller, register_id),
        )?;
        linker.func_wrap(
            "env",
            "write_register",
            |caller: Caller<'_, VmState<S>>, register_id, wasm_ptr, wasm_ptr_len| {
                vm::write_register(caller, register_id, wasm_ptr, wasm_ptr_len)
            },
        )?;
        linker.func_wrap(
            "env",
            "storage_read",
            |caller: Caller<'_, VmState<S>>, base_key, sub_key, register_id| {
                vm::storage_read(caller, base_key, sub_key, register_id)
            },
        )?;
        linker.func_wrap(
            "env",
            "storage_write",
            |caller: Caller<'_, VmState<S>>, base_key, sub_key, value_ptr, value_len| {
                vm::storage_write(caller, base_key, sub_key, value_ptr, value_len)
            },
        )?;
        linker.func_wrap(
            "env",
            "storage_remove",
            |caller: Caller<'_, VmState<S>>, base_key, sub_key| {
                vm::storage_remove(caller, base_key, sub_key)
            },
        )?;
        linker.func_wrap(
            "env",
            "storage_has_key",
            |caller: Caller<'_, VmState<S>>, base_key, sub_key| {
                vm::storage_has_key(caller, base_key, sub_key)
            },
        )?;
        linker.func_wrap(
            "env",
            "storage_cursor",
            |caller: Caller<'_, VmState<S>>, base_key| vm::storage_cursor(caller, base_key),
        )?;

        linker.func_wrap(
            "env",
            "subscribe",
            |caller: Caller<'_, VmState<S>>, wasm_ptr, wasm_len| {
                vm::subscribe(caller, wasm_ptr, wasm_len)
            },
        )?;

        linker.func_wrap(
            "env",
            "unsubscribe",
            |caller: Caller<'_, VmState<S>>, wasm_ptr, wasm_len| {
                vm::unsubscribe(caller, wasm_ptr, wasm_len)
            },
        )?;

        // NOTE: Those functions introduce side-effects;
        // they should only be used by us or during development of a contract
        linker.func_wrap("env", "storage_gen_sub_key", vm::storage_gen_sub_key)?;
        linker.func_wrap("env", "tic", |caller: Caller<'_, VmState<S>>| {
            vm::tic(caller)
        })?;
        linker.func_wrap("env", "toc", |caller: Caller<'_, VmState<S>>| {
            vm::toc(caller)
        })?;
        linker.func_wrap("env", "rand", vm::rand)?;

        // --- TODO: Playground for the new async api
        linker.func_wrap_async(
            "env",
            "send_http_rq",
            |caller: Caller<'_, VmState<S>>, (rq_head, rq_body, rs_head, rs_body, err)| {
                Box::new(vm::async_abi::send_http_rq(
                    caller, rq_head, rq_body, rs_head, rs_body, err,
                ))
            },
        )?;
        linker.func_wrap_async(
            "env",
            "send_ws_msg",
            |caller: Caller<'_, VmState<S>>, (msg_ptr, msg_len)| {
                Box::new(vm::async_abi::send_ws_msg(caller, msg_ptr, msg_len))
            },
        )?;

        linker.func_wrap("env", "timestamp", |caller: Caller<'_, VmState<S>>| {
            vm::timestamp(caller)
        })?;

        info!("Initialized runtime in: {:?}", start.elapsed());

        Ok(Self {
            linker,
            engine,
            agent_store,
            mutability_lock: lock,
            executor: None,
        })
    }

    pub fn into_shared(self) -> Arc<Mutex<Self>> {
        Arc::new(Mutex::new(self))
    }

    /// Returns a copy of the underlying db handle
    pub fn get_db(&self) -> S {
        self.agent_store.get_db()
    }

    /// Check whether a sw-agent exists
    pub fn agent_exists(&self, aid: &AgentId) -> Result<bool> {
        let db = self.get_db();
        let controller = Controller::new(&db);
        controller.agent_exists(aid)
    }

    /// Check whether a sw-agent is revoked
    pub fn agent_revoked(&self, aid: &AgentId) -> Result<bool> {
        let db = self.get_db();
        let controller = Controller::new(&db);
        controller.agent_revoked(aid)
    }

    #[cfg_attr(feature = "tracing", tracing::instrument(skip_all, fields(%agent_id), err))]
    pub fn instantiate_sw_agent(&mut self, agent_id: AgentId, module_bytes: &[u8]) -> Result<()> {
        let module = Module::new(&self.engine, module_bytes)?;
        check_module(&self.engine, &module)?;
        self.agent_store.insert_swagent(agent_id, module)?;
        Ok(())
    }

    /// Sanity check for introductions
    #[cfg_attr(feature = "tracing", tracing::instrument(skip_all, err))]
    pub async fn check_module_and_state(
        &mut self,
        module_bytes: Vec<u8>,
        state: serde_json::Value,
    ) -> Result<(bool, Vec<String>)> {
        let module = Module::new(&self.engine, module_bytes)?;
        check_module(&self.engine, &module)?;
        let mut store = self.agent_store.create_store(&self.engine)?;
        let instance = self.linker.instantiate(&mut store, &module)?;

        // Prepare registers
        store
            .data_mut()
            .set_register(REGISTER_INPUT, state.to_string().into_bytes());

        // Get function
        let func = instance.get_typed_func::<(), ()>(&mut store, "parse_state")?;

        // Prepare execution
        store.data_mut().prepare_exec(ActiveEntity::None)?;

        // Call the actual function on the wasm side
        let success = match func.call_async(&mut store, ()).await {
            Ok(()) => true,
            Err(_e) => false,
        };
        let log = store.data_mut().finish_exec(None)?;
        Ok((success, log.into_iter().map(|l| l.msg).collect()))
    }

    /// Sets the currently active executor
    ///
    /// This buffers the [`BorderlessId`] of the executor, to later write it into the dedicated register,
    /// so that the wasm side can query it.
    #[cfg_attr(feature = "tracing", tracing::instrument(skip_all, fields(%executor_id), err))]
    pub fn set_executor(&mut self, executor_id: BorderlessId) -> Result<()> {
        let bytes = executor_id.into_bytes().to_vec();
        self.executor = Some(bytes);
        Ok(())
    }

    /// Registers a new websocket client
    #[cfg_attr(feature = "tracing", tracing::instrument(skip_all, fields(agent_id = %aid), err))]
    pub fn register_ws(&mut self, aid: AgentId) -> Result<mpsc::Receiver<Vec<u8>>> {
        let (tx, rx) = mpsc::channel(4);
        self.mutability_lock.insert_ws_sender(&aid, tx);
        Ok(rx)
    }

    #[cfg_attr(feature = "tracing", tracing::instrument(skip_all, fields(agent_id = %aid), err))]
    pub async fn initialize(&mut self, aid: &AgentId) -> Result<Init> {
        let (instance, mut store) = self
            .agent_store
            .get_agent(aid, &self.engine, &mut self.linker)
            .await?
            .ok_or_else(|| ErrorKind::MissingAgent { aid: *aid })?;

        // Buffered registers
        store
            .data_mut()
            .set_register(REGISTER_EXECUTOR, self.executor.clone().unwrap_or_default());

        // Call the actual function on the wasm side
        let func = instance.get_typed_func::<(), ()>(&mut store, "on_init")?;
        store
            .data_mut()
            .prepare_exec(ActiveEntity::agent(*aid, false))?;

        if let Err(e) = func.call_async(&mut store, ()).await {
            warn!("initialize failed with error: {e}");
        }
        let output = store.data().get_register(REGISTER_OUTPUT);
        store.data_mut().finish_exec(None)?;

        // Return output events
        let bytes = output.ok_or_else(|| ErrorKind::MissingRegisterValue("init-output"))?;
        let init = Init::from_bytes(&bytes)?;

        Ok(init)
    }

    #[cfg_attr(feature = "tracing", tracing::instrument(skip_all, fields(agent_id = %aid), err))]
    pub async fn process_ws_msg(&mut self, aid: &AgentId, msg: Vec<u8>) -> Result<Option<Events>> {
        self.call_mut(aid, msg, "on_ws_msg", Commit::Other).await
    }

    #[cfg_attr(feature = "tracing", tracing::instrument(skip_all, fields(agent_id = %aid), err))]
    pub async fn on_ws_open(&mut self, aid: &AgentId) -> Result<Option<Events>> {
        self.call_mut(aid, Vec::new(), "on_ws_open", Commit::Other)
            .await
    }

    #[cfg_attr(feature = "tracing", tracing::instrument(skip_all, fields(agent_id = %aid), err))]
    pub async fn on_ws_error(&mut self, aid: &AgentId) -> Result<Option<Events>> {
        self.call_mut(aid, Vec::new(), "on_ws_error", Commit::Other)
            .await
    }

    #[cfg_attr(feature = "tracing", tracing::instrument(skip_all, fields(agent_id = %aid), err))]
    pub async fn on_ws_close(&mut self, aid: &AgentId) -> Result<Option<Events>> {
        self.call_mut(aid, Vec::new(), "on_ws_close", Commit::Other)
            .await
    }

    // TODO: If the initial state from the introduction cannot be parsed, the agent should *not* be saved !!
    // Currently, this creates an agent, where decoding the state will constantly explode during runtime !!!
    #[cfg_attr(feature = "tracing", tracing::instrument(skip_all, fields(agent_id = %introduction.id), err))]
    pub async fn process_introduction(&mut self, introduction: Introduction) -> Result<()> {
        let aid = match introduction.id {
            borderless::prelude::Id::Contract { .. } => return Err(ErrorKind::InvalidIdType.into()),
            borderless::prelude::Id::Agent { agent_id } => agent_id,
        };
        // NOTE: The input for the introduction is not the introduction, but only the initial state!
        // The introduction itself is commited by the VmState
        let initial_state = introduction.initial_state.to_string().into_bytes();
        let res = self
            .call_mut(
                &aid,
                initial_state,
                "process_introduction",
                Commit::Introduction(introduction),
            )
            .await?;
        assert!(res.is_none(), "introductions should not write events");
        Ok(())
    }

    // TODO: Calling process revocation on an already revoked agent should generate an error
    #[cfg_attr(feature = "tracing", tracing::instrument(skip_all, fields(agent_id = %revocation.id), err))]
    pub async fn process_revocation(&mut self, revocation: Revocation) -> Result<()> {
        let aid = match revocation.id {
            borderless::prelude::Id::Contract { .. } => return Err(ErrorKind::InvalidIdType.into()),
            borderless::prelude::Id::Agent { agent_id } => agent_id,
        };
        let input = revocation.to_bytes()?;
        let res = self
            .call_mut(
                &aid,
                input,
                "process_revocation",
                Commit::Revocation(revocation),
            )
            .await?;
        assert!(res.is_none(), "revocations should not write events");
        Ok(())
    }

    // OK; Just to get some stuff going; I want to just simply call an action, and execute an http-request with it.
    // That's more than enough to test stuff out.
    // TODO: Logging ?
    #[must_use = "You have to handle the output events of this function"]
    #[cfg_attr(feature = "tracing", tracing::instrument(skip_all, fields(agent_id = %aid), err))]
    pub async fn process_action(
        &mut self,
        aid: &AgentId,
        action: CallAction,
    ) -> Result<Option<Events>> {
        // Parse action
        let input = action.to_bytes()?;
        self.call_mut(aid, input, "process_action", Commit::Other)
            .await
    }

    /// Helper function for mutable calls
    async fn call_mut(
        &mut self,
        aid: &AgentId,
        input: Vec<u8>,
        method: &'static str,
        commit: Commit,
    ) -> Result<Option<Events>> {
        let (instance, mut store) = self
            .agent_store
            .get_agent(aid, &self.engine, &mut self.linker)
            .await?
            .ok_or_else(|| ErrorKind::MissingAgent { aid: *aid })?;

        if self.agent_revoked(aid)? {
            return Err(ErrorKind::RevokedAgent { aid: *aid }.into());
        }

        let state = self.mutability_lock.get_lock_state(aid);
        let _guard = state.lock.lock().await;

        // Prepare registers
        store.data_mut().set_register(REGISTER_INPUT, input);

        // Buffered registers
        store
            .data_mut()
            .set_register(REGISTER_EXECUTOR, self.executor.clone().unwrap_or_default());

        // Inject ws-sender (if any)
        if let Some(tx) = state.ws_sender {
            store.data_mut().register_ws(tx)?;
        }

        // Call the actual function on the wasm side
        let func = instance.get_typed_func::<(), ()>(&mut store, method)?;
        store
            .data_mut()
            .prepare_exec(ActiveEntity::agent(*aid, true))?;

        let commit = match func.call_async(&mut store, ()).await {
            Ok(()) => Some(commit),
            Err(e) => {
                warn!("{method} failed with error: {e}");
                None
            }
        };
        let output = store.data().get_register(REGISTER_OUTPUT);
        let _logs = store.data_mut().finish_exec(commit)?;

        // Return output events
        match output {
            Some(bytes) => Ok(Some(Events::from_bytes(&bytes)?)),
            None => Ok(None),
        }
    }

    // --- NOTE: Maybe we should create a separate runtime for the HTTP handling ?

    #[cfg_attr(feature = "tracing", tracing::instrument(skip_all, fields(agent_id = %aid, %path), err))]
    pub async fn http_get_state(&mut self, aid: &AgentId, path: String) -> Result<(u16, Vec<u8>)> {
        // Get instance
        let (instance, mut store) = self
            .agent_store
            .get_agent(aid, &self.engine, &mut self.linker)
            .await?
            .ok_or_else(|| ErrorKind::MissingAgent { aid: *aid })?;

        // Prepare registers
        store
            .data_mut()
            .set_register(REGISTER_INPUT_HTTP_PATH, path.into_bytes());

        // Buffered registers
        store
            .data_mut()
            .set_register(REGISTER_EXECUTOR, self.executor.clone().unwrap_or_default());

        // Get function
        let func = instance.get_typed_func::<(), ()>(&mut store, "http_get_state")?;

        // Prepare execution
        store
            .data_mut()
            .prepare_exec(ActiveEntity::agent(*aid, false))?;

        // Call the function
        if let Err(e) = func.call_async(&mut store, ()).await {
            warn!("http_get_state failed with error: {e}");
        }
        let status = store.data().get_register(REGISTER_OUTPUT_HTTP_STATUS);
        let result = store.data().get_register(REGISTER_OUTPUT_HTTP_RESULT);

        // Finish the execution ( and commit nothing )
        let _log = store.data_mut().finish_exec(None)?;

        // Parse status
        let status = status.ok_or_else(|| ErrorKind::MissingRegisterValue("http-status"))?;
        let status_bytes = status
            .try_into()
            .map_err(|_| ErrorKind::InvalidRegisterValue {
                register: "http-status",
                expected_type: "u16",
            })?;
        let status = u16::from_be_bytes(status_bytes);

        // Check result
        let result = result.ok_or_else(|| ErrorKind::MissingRegisterValue("http-result"))?;

        Ok((status, result))
    }

    // TODO: This will directly execute the action and return a list of events
    //
    // The question is, what should be returned via the web-api ?
    /// Uses a POST request to parse and generate a [`CallAction`] object.
    ///
    /// The return type is a nested result. The outer result type should convert to a server error,
    /// as it represents errors in the runtime itself.
    /// The inner error type comes from the wasm code and contains the error status and message.
    #[cfg_attr(feature = "tracing", tracing::instrument(skip_all, fields(agent_id = %aid, %path, %writer), err))]
    pub async fn http_post_action(
        &mut self,
        aid: &AgentId,
        path: String,
        payload: Vec<u8>,
        writer: &BorderlessId, // TODO: I think the writer makes no sense here and is an artifact
    ) -> Result<std::result::Result<(Events, CallAction), (u16, String)>> {
        // Check whether agent exists
        let Some((instance, mut store)) = self
            .agent_store
            .get_agent(aid, &self.engine, &mut self.linker)
            .await?
        else {
            return Ok(Err((
                StatusCode::BAD_REQUEST.as_u16(),
                ErrorKind::MissingAgent { aid: *aid }.to_string(),
            )));
        };
        // Check whether agent is revoked
        if self.agent_revoked(aid)? {
            return Ok(Err((
                StatusCode::BAD_REQUEST.as_u16(),
                ErrorKind::RevokedAgent { aid: *aid }.to_string(),
            )));
        }

        let state = self.mutability_lock.get_lock_state(aid);
        let _guard = state.lock.lock().await;

        // NOTE: We cannot convert the payload into a call-action on-spot, as we might call a nested route.
        // To be precise - we *could* do it here, but I think it is cleaner to leave this logic up to the wasm module,
        // as otherwise we may have to duplicate the logic here (and if it changes in the macro, we have to sync this with the code of the runtime etc.).
        store
            .data_mut()
            .set_register(REGISTER_INPUT_HTTP_PATH, path.into_bytes());

        store
            .data_mut()
            .set_register(REGISTER_INPUT_HTTP_PAYLOAD, payload);

        store
            .data_mut()
            .set_register(REGISTER_WRITER, writer.into_bytes().into());

        // Buffered registers
        store
            .data_mut()
            .set_register(REGISTER_EXECUTOR, self.executor.clone().unwrap_or_default());

        // Prepare mutable execution
        store
            .data_mut()
            .prepare_exec(ActiveEntity::agent(*aid, true))?;

        // Get function
        let func = instance.get_typed_func::<(), ()>(&mut store, "http_post_action")?;

        // Call the function
        if let Err(e) = func.call_async(&mut store, ()).await {
            warn!("http_get_state failed with error: {e}");
        }
        let status = store.data().get_register(REGISTER_OUTPUT_HTTP_STATUS);
        let result = store.data().get_register(REGISTER_OUTPUT_HTTP_RESULT);
        let output = store.data().get_register(REGISTER_OUTPUT);

        // Finish the execution
        // NOTE: This will clear all the registers !
        let _log = store.data_mut().finish_exec(Some(Commit::Other))?;

        // Parse status
        let status = status.ok_or_else(|| ErrorKind::MissingRegisterValue("http-status"))?;
        let status_bytes = status
            .try_into()
            .map_err(|_| ErrorKind::InvalidRegisterValue {
                register: "http-status",
                expected_type: "u16",
            })?;
        let status = u16::from_be_bytes(status_bytes);

        // Check result
        let result = result.ok_or_else(|| ErrorKind::MissingRegisterValue("http-result"))?;

        if status == 200 {
            let events = match output {
                Some(b) => Events::from_bytes(&b)?,
                None => Events::default(),
            };
            let action = CallAction::from_bytes(&result)?;
            Ok(Ok((events, action)))
        } else {
            let error = String::from_utf8(result).map_err(|_| ErrorKind::InvalidRegisterValue {
                register: "http-result",
                expected_type: "string",
            })?;
            Ok(Err((status, error)))
        }
    }

    /// Returns the symbols of the contract
    pub async fn get_symbols(&mut self, aid: &AgentId) -> Result<Option<Symbols>> {
        let (instance, mut store) = self
            .agent_store
            .get_agent(aid, &self.engine, &mut self.linker)
            .await?
            .ok_or_else(|| ErrorKind::MissingAgent { aid: *aid })?;

        store.data_mut().prepare_exec(ActiveEntity::None)?;

        // In case the contract does not export any symbols, just return 'None'
        if let Err(e) = instance
            .get_typed_func::<(), ()>(&mut store, "get_symbols")
            .and_then(|func| func.call(&mut store, ()))
        {
            error!("get_symbols failed with error: {e}");
        }
        let output = store.data().get_register(REGISTER_OUTPUT);
        store.data_mut().finish_exec(None)?;

        let bytes = match output {
            Some(b) => b,
            None => return Ok(None),
        };
        let symbols = Symbols::from_bytes(&bytes)?;
        Ok(Some(symbols))
    }

    pub fn available_agents(&self) -> Result<Vec<AgentId>> {
        self.agent_store.available_swagents()
    }
}

// NOTE: We Mis-Use the lock here to also carry persistent state - e.g. for the websocket
#[derive(Default, Clone)]
pub struct Lock {
    lock: Arc<Mutex<()>>,
    ws_sender: Option<mpsc::Sender<Vec<u8>>>,
}

/// Global mutability lock for all SW-Agents
///
/// Since we can only allow one mutable agent execution at a given time, we need a mechanism to ensure that.
/// The `MutLock` ensures this on a per-agent basis. It holds `RwLock`s for all agents and provides threadsafe access.
///
/// The logic is similar but not identical to rusts ownership rules. While there can be only one read-write (mutable) execution,
/// there can be multiple read-only (immutable) executions even if there is an ongoing read-write execution !
/// The reason behind this is basically that read-only executions do not produce storage operations that would change the state in the database.
/// In the `VmState`, all write operations are buffered until the execution is finished. If there would be two executions in parallel,
/// we might end up commiting changes to a state, that has already changed under the hood - which is not what we want.
/// However, if there is a writer thread, the readers do not care, and also the writer does not care about the readers.
/// The readers will use the old state, until the new one is commited by the runtime.
///
/// Note: In contrast to [`borderless_runtime::rt::contract::MutLock`],
/// this version uses asynchronous locks for the agents, and a synchronous lock only for the access of the hashmap.
///
/// Additionally, this double-functions as the provider of over-arching state per agent,
/// e.g. the lock also contains the websocket sender, for agents that use websockets.
#[derive(Clone, Default)]
pub struct MutLock {
    map: Arc<SyncMutex<HashMap<AgentId, Lock>>>,
}

impl MutLock {
    /// Returns the `RwLock` for the given agent.
    ///
    /// If the agent-id is unknown, a new lock is created.
    pub fn get_lock_state(&self, aid: &AgentId) -> Lock {
        let mut map = self.map.lock();
        let lock = map.entry(*aid).or_default();
        lock.clone()
    }

    /// Inserts a new ws-sender for the agent
    ///
    /// Panics if the sender already contained a lock
    pub fn insert_ws_sender(&self, aid: &AgentId, ws_sender: mpsc::Sender<Vec<u8>>) {
        let mut map = self.map.lock();
        let lock = map.entry(*aid).or_default();
        assert!(
            lock.ws_sender.is_none(),
            "Cannot register websocket twice on the same agent"
        );
        lock.ws_sender = Some(ws_sender);
    }
}

// NOTE: We could also check, if the websocket functions are exported,
// and do a consistency check, if the module uses a websocket.
// But maybe that's overkill.
fn check_module(engine: &Engine, module: &Module) -> Result<()> {
    let functions = [
        "on_init",
        "on_shutdown",
        "process_action",
        "process_introduction",
        "process_revocation",
        "http_get_state",
        "http_post_action",
        "parse_state",
        "get_symbols",
    ];
    for func in functions {
        let exp = module
            .get_export(func)
            .ok_or_else(|| ErrorKind::MissingExport { func })?;
        if let ExternType::Func(func_type) = exp {
            if !func_type.matches(&FuncType::new(engine, [], [])) {
                return Err(ErrorKind::InvalidFuncType { func }.into());
            }
        } else {
            return Err(ErrorKind::InvalidExport { func }.into());
        }
    }
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;

    const ALL_EXPORTS: &str = r#"
(module
  ;; Declare the function `placeholder`
  (func $placeholder)

  ;; Export the functions so they can be called from outside the module
  (export "on_init" (func $placeholder))
  (export "on_shutdown" (func $placeholder))
  (export "process_action" (func $placeholder))
  (export "process_introduction" (func $placeholder))
  (export "process_revocation" (func $placeholder))
  (export "http_get_state" (func $placeholder))
  (export "http_post_action" (func $placeholder))
  (export "parse_state" (func $placeholder))
  (export "get_symbols" (func $placeholder))
)
"#;
    fn remove_line_with_pattern(original: &str, pattern: &str) -> String {
        // Create a new Vec to hold the processed lines
        let mut new_lines = Vec::new();

        for line in original.lines() {
            // Check if the line contains the pattern
            if !line.contains(pattern) {
                // Otherwise, push the original line
                new_lines.push(line);
            }
        }

        // Collect the lines back into a single string
        new_lines.join("\n")
    }

    #[test]
    fn missing_exports() {
        let mut config = Config::new();
        config.cranelift_opt_level(wasmtime::OptLevel::Speed);
        config.async_support(false);
        let engine = Engine::new(&config).unwrap();

        // These are the functions, that must not be missing
        let functions = [
            "on_init",
            "on_shutdown",
            "process_action",
            "process_introduction",
            "process_revocation",
            "http_get_state",
            "http_post_action",
            "parse_state",
            "get_symbols",
        ];
        for func in functions {
            let wat_missing = remove_line_with_pattern(ALL_EXPORTS, func);
            let module = Module::new(&engine, &wat_missing);
            assert!(module.is_ok());
            let err = check_module(&engine, &module.unwrap());
            assert!(err.is_err());
        }
        let module = Module::new(&engine, &ALL_EXPORTS);
        assert!(module.is_ok());

        let err = check_module(&engine, &module.unwrap());
        assert!(err.is_ok());
    }
}