# Copyright 2013 The Chromium Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.


import threading


class TestCollection:
    """A threadsafe collection of tests.

    Args:
      tests: List of tests to put in the collection.
    """

    def __init__(self, tests=None):
        if not tests:
            tests = []
        self._lock = threading.Lock()
        self._tests = []
        self._tests_in_progress = 0
        # Used to signal that an item is available or all items have been handled.
        self._item_available_or_all_done = threading.Event()
        for t in tests:
            self.add(t)

    def _pop(self):
        """Pop a test from the collection.

        Waits until a test is available or all tests have been handled.

        Returns:
          A test or None if all tests have been handled.
        """
        while True:
            # Wait for a test to be available or all tests to have been handled.
            self._item_available_or_all_done.wait()
            with self._lock:
                # Check which of the two conditions triggered the signal.
                if self._tests_in_progress == 0:
                    return None
                try:
                    return self._tests.pop(0)
                except IndexError:
                    # Another thread beat us to the available test, wait again.
                    self._item_available_or_all_done.clear()

    def add(self, test):
        """Add a test to the collection.

        Args:
          test: A test to add.
        """
        with self._lock:
            self._tests.append(test)
            self._item_available_or_all_done.set()
            self._tests_in_progress += 1

    def test_completed(self):
        """Indicate that a test has been fully handled."""
        with self._lock:
            self._tests_in_progress -= 1
            if self._tests_in_progress == 0:
                # All tests have been handled, signal all waiting threads.
                self._item_available_or_all_done.set()

    def __iter__(self):
        """Iterate through tests in the collection until all have been handled."""
        while True:
            r = self._pop()
            if r is None:
                break
            yield r

    def __len__(self):
        """Return the number of tests currently in the collection."""
        return len(self._tests)

    def test_names(self):
        """Return a list of the names of the tests currently in the collection."""
        with self._lock:
            return list(t.test for t in self._tests)