deck: Implement next()

I make sure to remove empty playlists from the deck and throw an error
if there are no playable tracks on the deck.

Signed-off-by: Anna Schumaker <schumaker.anna@gmail.com>

design/deck.txt

@@ -47,6 +47,8 @@ Deck: (lib/deck.cpp)
 		If the playlist is empty after calling next(), remove it from
 		the deck.
 
+		If there are no playable IDs, throw -1.
+
 	void deck :: reset();
 		This function only exists if CONFIG_DEBUG is enabled.  Erase
 		all the playlist information and reset the deck list.

include/deck.h

@@ -13,6 +13,7 @@ namespace deck
 	void remove(unsigned int);
 	Playlist *get(unsigned int);
 	void move(unsigned int, unsigned int);
+	unsigned int next();
 
 #ifdef CONFIG_DEBUG
 	void print_info();

lib/deck.cpp

@@ -48,6 +48,23 @@ void deck :: move(unsigned int old_pos, unsigned int new_pos)
 	playlist_deck.splice(it_new, playlist_deck, it_old);
 }
 
+unsigned int deck :: next()
+{
+	unsigned int id = 0;
+	std::list<Playlist>::iterator it;
+
+	for (it = playlist_deck.begin(); it != playlist_deck.end(); it++) {
+		if (it->get_flags() & PL_ENABLED) {
+			id = it->next();
+			if (it->size() == 0)
+				playlist_deck.erase(it);
+			return id;
+		}
+	}
+
+	throw -1;
+}
+
 #ifdef CONFIG_DEBUG
 void deck :: print_info()
 {

tests/deck/deck.cpp

@@ -68,11 +68,35 @@ void test_3()
 	print("\n");
 }
 
+/* Test the next() function for playlists */
+void test_4()
+{
+	print("Test 4:\n");
+
+	deck :: get(0)->unset_flag(PL_ENABLED);
+	deck :: get(1)->unset_flag(PL_ENABLED);
+	deck :: get(4)->unset_flag(PL_ENABLED);
+
+	for (unsigned int i = 0; i < 37; i++) {
+		try {
+			print("Playing id: %u\n", deck :: next());
+			if (i == 11 || i == 25)
+				deck :: print_info();
+		} catch (int error) {
+			print("No playable tracks!\n");
+			break;
+		}
+	}
+
+	deck :: print_info();
+}
+
 int main(int argc, char **argv)
 {
 	test_0();
 	test_1();
 	test_2();
 	test_3();
+	test_4();
 	return 0;
 }

tests/deck/deck.good

@@ -55,3 +55,61 @@ deck[2] = Playlist { size = 12, flags = 1 }
 deck[3] = Playlist { size = 14, flags = 1 }
 deck[4] = Playlist { size = 15, flags = 1 }
 deck[5] = Playlist { size = 10, flags = 1 }
+
+deck[0] = Playlist { size = 16, flags = 1 }
+deck[1] = Playlist { size = 19, flags = 1 }
+deck[2] = Playlist { size = 12, flags = 1 }
+deck[3] = Playlist { size = 14, flags = 1 }
+deck[4] = Playlist { size = 15, flags = 1 }
+deck[5] = Playlist { size = 10, flags = 1 }
+
+Test 4:
+Playing id: 0
+Playing id: 1
+Playing id: 2
+Playing id: 3
+Playing id: 4
+Playing id: 5
+Playing id: 6
+Playing id: 7
+Playing id: 8
+Playing id: 9
+Playing id: 10
+Playing id: 11
+deck[0] = Playlist { size = 16, flags = 0 }
+deck[1] = Playlist { size = 19, flags = 0 }
+deck[2] = Playlist { size = 14, flags = 1 }
+deck[3] = Playlist { size = 15, flags = 0 }
+deck[4] = Playlist { size = 10, flags = 1 }
+Playing id: 0
+Playing id: 1
+Playing id: 2
+Playing id: 3
+Playing id: 4
+Playing id: 5
+Playing id: 6
+Playing id: 7
+Playing id: 8
+Playing id: 9
+Playing id: 10
+Playing id: 11
+Playing id: 12
+Playing id: 13
+deck[0] = Playlist { size = 16, flags = 0 }
+deck[1] = Playlist { size = 19, flags = 0 }
+deck[2] = Playlist { size = 15, flags = 0 }
+deck[3] = Playlist { size = 10, flags = 1 }
+Playing id: 0
+Playing id: 1
+Playing id: 2
+Playing id: 3
+Playing id: 4
+Playing id: 5
+Playing id: 6
+Playing id: 7
+Playing id: 8
+Playing id: 9
+No playable tracks!
+deck[0] = Playlist { size = 16, flags = 0 }
+deck[1] = Playlist { size = 19, flags = 0 }
+deck[2] = Playlist { size = 15, flags = 0 }