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use crate::Config;
use std::sync::Arc;
#[cfg(feature = "cache")]
use wasmtime_cache::CacheConfig;
use wasmtime_jit::Compiler;
use wasmtime_runtime::debug_builtins;

/// An `Engine` which is a global context for compilation and management of wasm
/// modules.
///
/// An engine can be safely shared across threads and is a cheap cloneable
/// handle to the actual engine. The engine itself will be deallocate once all
/// references to it have gone away.
///
/// Engines store global configuration preferences such as compilation settings,
/// enabled features, etc. You'll likely only need at most one of these for a
/// program.
///
/// ## Engines and `Clone`
///
/// Using `clone` on an `Engine` is a cheap operation. It will not create an
/// entirely new engine, but rather just a new reference to the existing engine.
/// In other words it's a shallow copy, not a deep copy.
///
/// ## Engines and `Default`
///
/// You can create an engine with default configuration settings using
/// `Engine::default()`. Be sure to consult the documentation of [`Config`] for
/// default settings.
#[derive(Clone)]
pub struct Engine {
    inner: Arc<EngineInner>,
}

struct EngineInner {
    config: Config,
    compiler: Compiler,
}

impl Engine {
    /// Creates a new [`Engine`] with the specified compilation and
    /// configuration settings.
    pub fn new(config: &Config) -> Engine {
        debug_builtins::ensure_exported();
        Engine {
            inner: Arc::new(EngineInner {
                config: config.clone(),
                compiler: config.build_compiler(),
            }),
        }
    }

    /// Returns the configuration settings that this engine is using.
    pub fn config(&self) -> &Config {
        &self.inner.config
    }

    pub(crate) fn compiler(&self) -> &Compiler {
        &self.inner.compiler
    }

    #[cfg(feature = "cache")]
    pub(crate) fn cache_config(&self) -> &CacheConfig {
        &self.config().cache_config
    }

    /// Returns whether the engine `a` and `b` refer to the same configuration.
    pub fn same(a: &Engine, b: &Engine) -> bool {
        Arc::ptr_eq(&a.inner, &b.inner)
    }
}

impl Default for Engine {
    fn default() -> Engine {
        Engine::new(&Config::default())
    }
}

#[cfg(test)]
mod tests {
    use crate::{Config, Engine, Module, OptLevel};
    use anyhow::Result;
    use tempfile::TempDir;

    #[test]
    fn cache_accounts_for_opt_level() -> Result<()> {
        let td = TempDir::new()?;
        let config_path = td.path().join("config.toml");
        std::fs::write(
            &config_path,
            &format!(
                "
                    [cache]
                    enabled = true
                    directory = '{}'
                ",
                td.path().join("cache").display()
            ),
        )?;
        let mut cfg = Config::new();
        cfg.cranelift_opt_level(OptLevel::None)
            .cache_config_load(&config_path)?;
        let engine = Engine::new(&cfg);
        Module::new(&engine, "(module (func))")?;
        assert_eq!(engine.config().cache_config.cache_hits(), 0);
        assert_eq!(engine.config().cache_config.cache_misses(), 1);
        Module::new(&engine, "(module (func))")?;
        assert_eq!(engine.config().cache_config.cache_hits(), 1);
        assert_eq!(engine.config().cache_config.cache_misses(), 1);

        let mut cfg = Config::new();
        cfg.cranelift_opt_level(OptLevel::Speed)
            .cache_config_load(&config_path)?;
        let engine = Engine::new(&cfg);
        Module::new(&engine, "(module (func))")?;
        assert_eq!(engine.config().cache_config.cache_hits(), 0);
        assert_eq!(engine.config().cache_config.cache_misses(), 1);
        Module::new(&engine, "(module (func))")?;
        assert_eq!(engine.config().cache_config.cache_hits(), 1);
        assert_eq!(engine.config().cache_config.cache_misses(), 1);

        let mut cfg = Config::new();
        cfg.cranelift_opt_level(OptLevel::SpeedAndSize)
            .cache_config_load(&config_path)?;
        let engine = Engine::new(&cfg);
        Module::new(&engine, "(module (func))")?;
        assert_eq!(engine.config().cache_config.cache_hits(), 0);
        assert_eq!(engine.config().cache_config.cache_misses(), 1);
        Module::new(&engine, "(module (func))")?;
        assert_eq!(engine.config().cache_config.cache_hits(), 1);
        assert_eq!(engine.config().cache_config.cache_misses(), 1);

        // FIXME(#1523) need debuginfo on aarch64 before we run this test there
        if !cfg!(target_arch = "aarch64") {
            let mut cfg = Config::new();
            cfg.debug_info(true).cache_config_load(&config_path)?;
            let engine = Engine::new(&cfg);
            Module::new(&engine, "(module (func))")?;
            assert_eq!(engine.config().cache_config.cache_hits(), 0);
            assert_eq!(engine.config().cache_config.cache_misses(), 1);
            Module::new(&engine, "(module (func))")?;
            assert_eq!(engine.config().cache_config.cache_hits(), 1);
            assert_eq!(engine.config().cache_config.cache_misses(), 1);
        }

        Ok(())
    }
}