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// This file is part of Gear.

// Copyright (C) 2023-2024 Gear Technologies Inc.
// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0

// This program 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.

// This program 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 this program. If not, see <https://www.gnu.org/licenses/>.

//! `GlobalsAccessor` realizations for native and wasm runtimes.

use crate::common::{Error, GlobalNames};
use core::any::Any;
use gear_core::{memory::HostPointer, str::LimitedStr};
use gear_lazy_pages_common::{GlobalsAccessError, GlobalsAccessMod, GlobalsAccessor};
use gear_sandbox_host::sandbox::SandboxInstance;
use sp_wasm_interface_common::Value;

#[derive(Debug, Clone, Copy)]
pub(crate) enum GlobalNo {
    Gas = 0,
}

#[derive(Debug)]
pub(crate) struct GlobalsContext {
    /// Global names
    pub names: GlobalNames,
    /// Raw pointer to the globals access provider
    pub access_ptr: HostPointer,
    /// Access mod, currently two: native or WASM runtime
    pub access_mod: GlobalsAccessMod,
}

struct GlobalsAccessWasmRuntime<'a> {
    pub instance: &'a mut SandboxInstance,
}

impl GlobalsAccessor for GlobalsAccessWasmRuntime<'_> {
    fn get_i64(&mut self, name: &LimitedStr) -> Result<i64, GlobalsAccessError> {
        // SAFETY: this is safe because this method is called only from signal handler context
        unsafe {
            self.instance
                .signal_handler_get_global_val(name.as_str())
                .and_then(|value| match value {
                    Value::I64(value) => Some(value),
                    _ => None,
                })
                .ok_or(GlobalsAccessError)
        }
    }

    fn set_i64(&mut self, name: &LimitedStr, value: i64) -> Result<(), GlobalsAccessError> {
        // SAFETY: this is safe because this method is called only from signal handler context
        unsafe {
            self.instance
                .signal_handler_set_global_val(name.as_str(), Value::I64(value))
                .ok()
                .flatten()
                .ok_or(GlobalsAccessError)?
        }

        Ok(())
    }

    fn as_any_mut(&mut self) -> &mut dyn std::any::Any {
        unimplemented!("Has no use cases for this struct")
    }
}

struct GlobalsAccessNativeRuntime<'a, 'b> {
    pub inner_access_provider: &'a mut &'b mut dyn GlobalsAccessor,
}

impl GlobalsAccessor for GlobalsAccessNativeRuntime<'_, '_> {
    fn get_i64(&mut self, name: &LimitedStr) -> Result<i64, GlobalsAccessError> {
        self.inner_access_provider.get_i64(name)
    }

    fn set_i64(&mut self, name: &LimitedStr, value: i64) -> Result<(), GlobalsAccessError> {
        self.inner_access_provider.set_i64(name, value)
    }

    fn as_any_mut(&mut self) -> &mut dyn Any {
        unimplemented!("Has no use cases for this struct")
    }
}

fn apply_for_global_internal(
    mut globals_access_provider: impl GlobalsAccessor,
    name: &str,
    mut f: impl FnMut(u64) -> Result<Option<u64>, Error>,
) -> Result<u64, Error> {
    let name = LimitedStr::try_from(name).map_err(|_| Error::AccessGlobal(GlobalsAccessError))?;

    let current_value = globals_access_provider.get_i64(&name)? as u64;
    if let Some(new_value) = f(current_value)? {
        globals_access_provider.set_i64(&name, new_value as i64)?;
        Ok(new_value)
    } else {
        Ok(current_value)
    }
}

pub(crate) unsafe fn apply_for_global(
    globals_ctx: &GlobalsContext,
    global_name: &str,
    f: impl FnMut(u64) -> Result<Option<u64>, Error>,
) -> Result<u64, Error> {
    match globals_ctx.access_mod {
        GlobalsAccessMod::WasmRuntime => {
            let instance = (globals_ctx.access_ptr as *mut SandboxInstance)
                .as_mut()
                .ok_or(Error::HostInstancePointerIsInvalid)?;
            apply_for_global_internal(GlobalsAccessWasmRuntime { instance }, global_name, f)
        }
        GlobalsAccessMod::NativeRuntime => {
            let inner_access_provider = (globals_ctx.access_ptr as *mut &mut dyn GlobalsAccessor)
                .as_mut()
                .ok_or(Error::DynGlobalsAccessPointerIsInvalid)?;
            apply_for_global_internal(
                GlobalsAccessNativeRuntime {
                    inner_access_provider,
                },
                global_name,
                f,
            )
        }
    }
}