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//! JIT compilation.

use crate::tunables::Tunables;
use crate::{Artifact, DeserializeError};
use std::path::Path;
use std::sync::atomic::{AtomicUsize, Ordering::SeqCst};
use std::sync::Arc;
use wasmer_compiler::{CompileError, Target};
use wasmer_types::FunctionType;
use wasmer_vm::{VMSharedSignatureIndex, VMTrampoline};

/// A unimplemented Wasmer `Engine`.
///
/// This trait is used by implementors to implement custom engines
/// such as: JIT or Native.
///
/// The product that an `Engine` produces and consumes is the [`Artifact`].
pub trait Engine {
    /// Gets the target
    fn target(&self) -> &Target;

    /// Register a signature
    fn register_signature(&self, func_type: &FunctionType) -> VMSharedSignatureIndex;

    /// Lookup a signature
    fn lookup_signature(&self, sig: VMSharedSignatureIndex) -> Option<FunctionType>;

    /// Retrieves a trampoline given a signature
    fn function_call_trampoline(&self, sig: VMSharedSignatureIndex) -> Option<VMTrampoline>;

    /// Validates a WebAssembly module
    fn validate(&self, binary: &[u8]) -> Result<(), CompileError>;

    /// Compile a WebAssembly binary
    fn compile(
        &self,
        binary: &[u8],
        tunables: &dyn Tunables,
    ) -> Result<Arc<dyn Artifact>, CompileError>;

    /// Deserializes a WebAssembly module
    ///
    /// # Safety
    ///
    /// The serialized content must represent a serialized WebAssembly module.
    unsafe fn deserialize(&self, bytes: &[u8]) -> Result<Arc<dyn Artifact>, DeserializeError>;

    /// Deserializes a WebAssembly module from a path
    ///
    /// # Safety
    ///
    /// The file's content must represent a serialized WebAssembly module.
    unsafe fn deserialize_from_file(
        &self,
        file_ref: &Path,
    ) -> Result<Arc<dyn Artifact>, DeserializeError> {
        let bytes = std::fs::read(file_ref)?;
        self.deserialize(&bytes)
    }

    /// A unique identifier for this object.
    ///
    /// This exists to allow us to compare two Engines for equality. Otherwise,
    /// comparing two trait objects unsafely relies on implementation details
    /// of trait representation.
    fn id(&self) -> &EngineId;

    /// Clone the engine
    fn cloned(&self) -> Arc<dyn Engine + Send + Sync>;
}

#[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
#[repr(transparent)]
/// A unique identifier for an Engine.
pub struct EngineId {
    id: usize,
}

impl EngineId {
    /// Format this identifier as a string.
    pub fn id(&self) -> String {
        format!("{}", &self.id)
    }
}

impl Clone for EngineId {
    fn clone(&self) -> Self {
        Self::default()
    }
}

impl Default for EngineId {
    fn default() -> Self {
        static NEXT_ID: AtomicUsize = AtomicUsize::new(0);
        Self {
            id: NEXT_ID.fetch_add(1, SeqCst),
        }
    }
}