use crate::{domain::Domain, string::StringHandle};

/// A task is a logical unit of work performed by a particular thread. See the [Task API]

/// documentation for more information.

///

/// [Task API]:

///     https://www.intel.com/content/www/us/en/develop/documentation/vtune-help/top/api-support/instrumentation-and-tracing-technology-apis/instrumentation-tracing-technology-api-reference/task-api.html

///

/// ```

/// # use ittapi::{Domain, StringHandle, Task};

/// let _env_path = scoped_env::ScopedEnv::set("INTEL_LIBITTNOTIFY64", "<some path>");

/// let domain = Domain::new("domain");

/// let name = StringHandle::new("task");

/// // Measure a task using a pre-initialized string handle (most efficient).

/// {

///     let task = Task::begin(&domain, name);

///     let _ = 2 + 2;

///     task.end(); // Task ended here.

///     let _ = 3 + 3;

/// }

/// // Measure a task using a string reference (most convenient).

/// {

///     let _task = Task::begin(&domain, "task");

///     let _ = 2 + 2;

///     // Task ended here, when dropped.

/// }

/// ```

pub struct Task<'a>(&'a Domain);

impl<'a> Task<'a> {

    /// Start a task on the current thread.

    pub fn begin(domain: &'a Domain, name: impl Into<StringHandle>) -> Self {

        if let Some(create_fn) = unsafe { ittapi_sys::__itt_task_begin_ptr__3_0 } {

            // Currently the `taskid` and `parentid` parameters are unimplemented (TODO).

            unsafe { create_fn(domain.as_ptr(), ITT_NULL, ITT_NULL, name.into().as_ptr()) };

        }

        Self(domain)

    }

    /// Finish the task.

    #[allow(clippy::unused_self)]

    pub fn end(self) {

        // Do nothing; the `Drop` implementation does the work. See discussion at

        // https://stackoverflow.com/questions/53254645.

    }

}

impl<'a> Drop for Task<'a> {

    fn drop(&mut self) {

        // If `ittnotify` has not been initialized, this function may not be wired up.

        if let Some(end_fn) = unsafe { ittapi_sys::__itt_task_end_ptr__3_0 } {

            unsafe { end_fn(self.0.as_ptr()) }

        }

    }

}

/// Using the `__itt_null` symbol results in errors so we redefine it here.

const ITT_NULL: ittapi_sys::__itt_id = ittapi_sys::__itt_id {

    d1: 0,

    d2: 0,

    d3: 0,

};

#[cfg(test)]

mod tests {

    use super::*;

    #[test]

    fn sanity() {

        let domain = Domain::new("domain");

        let name = StringHandle::new("task");

        let _task = Task::begin(&domain, name);

    }

}