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use crate::sys::tunables::BaseTunables;
use loupe::MemoryUsage;
use std::any::Any;
use std::fmt;
use std::sync::{Arc, RwLock};
#[cfg(all(feature = "compiler", feature = "engine"))]
use wasmer_compiler::CompilerConfig;
use wasmer_engine::{is_wasm_pc, Engine, Tunables};
use wasmer_vm::{init_traps, TrapHandler, TrapHandlerFn};

/// The store represents all global state that can be manipulated by
/// WebAssembly programs. It consists of the runtime representation
/// of all instances of functions, tables, memories, and globals that
/// have been allocated during the lifetime of the abstract machine.
///
/// The `Store` holds the engine (that is —amongst many things— used to compile
/// the Wasm bytes into a valid module artifact), in addition to the
/// [`Tunables`] (that are used to create the memories, tables and globals).
///
/// Spec: <https://webassembly.github.io/spec/core/exec/runtime.html#store>
#[derive(Clone, MemoryUsage)]
pub struct Store {
    engine: Arc<dyn Engine + Send + Sync>,
    tunables: Arc<dyn Tunables + Send + Sync>,
    #[loupe(skip)]
    trap_handler: Arc<RwLock<Option<Box<TrapHandlerFn>>>>,
}

impl Store {
    /// Creates a new `Store` with a specific [`Engine`].
    pub fn new<E>(engine: &E) -> Self
    where
        E: Engine + ?Sized,
    {
        Self::new_with_tunables(engine, BaseTunables::for_target(engine.target()))
    }

    /// Set the trap handler in this store.
    pub fn set_trap_handler(&self, handler: Option<Box<TrapHandlerFn>>) {
        let mut m = self.trap_handler.write().unwrap();
        *m = handler;
    }

    /// Creates a new `Store` with a specific [`Engine`] and [`Tunables`].
    pub fn new_with_tunables<E>(engine: &E, tunables: impl Tunables + Send + Sync + 'static) -> Self
    where
        E: Engine + ?Sized,
    {
        // Make sure the signal handlers are installed.
        // This is required for handling traps.
        if engine.use_signals() {
            init_traps(is_wasm_pc);
        }
        Self {
            engine: engine.cloned(),
            tunables: Arc::new(tunables),
            trap_handler: Arc::new(RwLock::new(None)),
        }
    }

    /// Returns the [`Tunables`].
    pub fn tunables(&self) -> &dyn Tunables {
        self.tunables.as_ref()
    }

    /// Returns the [`Engine`].
    pub fn engine(&self) -> &Arc<dyn Engine + Send + Sync> {
        &self.engine
    }

    /// Checks whether two stores are identical. A store is considered
    /// equal to another store if both have the same engine. The
    /// tunables are excluded from the logic.
    pub fn same(a: &Self, b: &Self) -> bool {
        a.engine.id() == b.engine.id()
    }
}

impl PartialEq for Store {
    fn eq(&self, other: &Self) -> bool {
        Self::same(self, other)
    }
}

unsafe impl TrapHandler for Store {
    #[inline]
    fn as_any(&self) -> &dyn Any {
        self
    }

    fn custom_trap_handler(&self, call: &dyn Fn(&TrapHandlerFn) -> bool) -> bool {
        if let Some(handler) = *&self.trap_handler.read().unwrap().as_ref() {
            call(handler)
        } else {
            false
        }
    }
}

// This is required to be able to set the trap_handler in the
// Store.
unsafe impl Send for Store {}
unsafe impl Sync for Store {}

// We only implement default if we have assigned a default compiler and engine
#[cfg(all(feature = "default-compiler", feature = "default-engine"))]
impl Default for Store {
    fn default() -> Self {
        // We store them on a function that returns to make
        // sure this function doesn't emit a compile error even if
        // more than one compiler is enabled.
        #[allow(unreachable_code)]
        fn get_config() -> impl CompilerConfig + 'static {
            cfg_if::cfg_if! {
                if #[cfg(feature = "default-cranelift")] {
                    wasmer_compiler_cranelift::Cranelift::default()
                } else if #[cfg(feature = "default-llvm")] {
                    wasmer_compiler_llvm::LLVM::default()
                } else if #[cfg(feature = "default-singlepass")] {
                    wasmer_compiler_singlepass::Singlepass::default()
                } else {
                    compile_error!("No default compiler chosen")
                }
            }
        }

        #[allow(unreachable_code, unused_mut)]
        fn get_engine(mut config: impl CompilerConfig + 'static) -> impl Engine + Send + Sync {
            cfg_if::cfg_if! {
                if #[cfg(feature = "default-universal")] {
                    wasmer_engine_universal::Universal::new(config)
                        .engine()
                } else if #[cfg(feature = "default-dylib")] {
                    wasmer_engine_dylib::Dylib::new(config)
                        .engine()
                } else {
                    compile_error!("No default engine chosen")
                }
            }
        }

        let config = get_config();
        let engine = get_engine(config);
        let tunables = BaseTunables::for_target(engine.target());
        Self::new_with_tunables(&engine, tunables)
    }
}

impl fmt::Debug for Store {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        f.debug_struct("Store").finish()
    }
}

/// A trait represinting any object that lives in the `Store`.
pub trait StoreObject {
    /// Return true if the object `Store` is the same as the provided `Store`.
    fn comes_from_same_store(&self, store: &Store) -> bool;
}