replacer api, unit tests, and benchmarks (#354)

* added abstracted replacer api, and both char and regex based implementations

* added test dependencies for jmh and junit

* added unit tests and benchmarks for the replacer implementations

* updated replacers to accept specific closure types, added test to verify malformed placeholder handling

* updated jmh to 1.23, updated junit to 5.6.2

src/test/java/me/clip/placeholderapi/Values.java

@@ -0,0 +1,188 @@
+package me.clip.placeholderapi;
+
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
+import me.clip.placeholderapi.expansion.PlaceholderExpansion;
+import me.clip.placeholderapi.replacer.CharsReplacer;
+import me.clip.placeholderapi.replacer.RegexReplacer;
+import me.clip.placeholderapi.replacer.Replacer;
+import org.bukkit.ChatColor;
+import org.bukkit.OfflinePlayer;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.Set;
+import java.util.function.Function;
+
+public interface Values
+{
+
+	String SMALL_TEXT = "My name is %player_name%";
+	String LARGE_TEXT = "My name is %player_name% and my location is (%player_x%, %player_y%, %player_z%), this placeholder is invalid %server_name%";
+
+	ImmutableMap<String, PlaceholderHook> PLACEHOLDERS = ImmutableMap.<String, PlaceholderHook>builder()
+			.put("player", new MockPlayerPlaceholderHook())
+			.build();
+
+
+	Replacer CHARS_REPLACER = new CharsReplacer(Replacer.Closure.PERCENT);
+	Replacer REGEX_REPLACER = new RegexReplacer(Replacer.Closure.PERCENT);
+	Replacer TESTS_REPLACER = new Replacer()
+	{
+		private final Set<Character> COLOR_CODES = ImmutableSet.of('0', '1', '2', '3', '4', '5', '6', '7', '8', '9',
+																		  'a', 'b', 'c', 'd', 'e', 'f', 'k', 'l', 'm', 'o', 'r', 'x');
+
+		private final boolean colorize = true;
+		private final PlaceholderReplacer.Closure closure = PlaceholderReplacer.Closure.PERCENT;
+
+		@Override
+		public @NotNull String apply(final @NotNull String text, final @Nullable OfflinePlayer player, final @NotNull Function<String, @Nullable PlaceholderHook> lookup)
+		{
+			char[]        chars   = text.toCharArray();
+			StringBuilder builder = new StringBuilder(chars.length);
+
+			// This won't cause memory leaks. It's inside a method. And we want to use setLength instead of
+			// creating a new string builder to use the maximum capacity and avoid initializing new objects.
+			StringBuilder   identifier = new StringBuilder(50);
+			PlaceholderHook handler    = null;
+
+			// Stages:
+			//   Stage -1: Look for the color code in the next character.
+			//   Stage 0: No closures detected, or the detected identifier is invalid. We're going forward while appending the characters normally.
+			//   Stage 1: The closure has been detected, looking for the placeholder identifier...
+			//   Stage 2: Detected the identifier and the parameter. Translating the placeholder...
+			int stage = 0;
+
+			for (char ch : chars)
+			{
+				if (stage == -1 && COLOR_CODES.contains(ch))
+				{
+					builder.append(ChatColor.COLOR_CHAR).append(ch);
+					stage = 0;
+					continue;
+				}
+
+				// Check if the placeholder starts or ends.
+				if (ch == closure.start || ch == closure.end)
+				{
+					// If the placeholder ends.
+					if (stage == 2)
+					{
+						String parameter  = identifier.toString();
+						String translated = handler.onRequest(player, parameter);
+
+						if (translated == null)
+						{
+							String name = handler.isExpansion() ? ((PlaceholderExpansion) handler).getIdentifier() : "";
+							builder.append(closure.start).append(name).append('_').append(parameter).append(closure.end);
+						}
+						else
+						{
+							builder.append(translated);
+						}
+
+						identifier.setLength(0);
+						stage = 0;
+						continue;
+					}
+					else if (stage == 1)
+					{ // If it just started | Double closures | If it's still hasn't detected the indentifier, reset.
+						builder.append(closure.start).append(identifier);
+					}
+
+					identifier.setLength(0);
+					stage = 1;
+					continue;
+				}
+
+				// Placeholder identifier started.
+				if (stage == 1)
+				{
+					// Compare the current character with the idenfitier's.
+					// We reached the end of our identifier.
+					if (ch == '_')
+					{
+						handler = lookup.apply(identifier.toString());
+						if (handler == null)
+						{
+							builder.append(closure.start).append(identifier).append('_');
+							stage = 0;
+						}
+						else
+						{
+							identifier.setLength(0);
+							stage = 2;
+						}
+						continue;
+					}
+
+					// Keep building the identifier name.
+					identifier.append(ch);
+					continue;
+				}
+
+				// Building the placeholder parameter.
+				if (stage == 2)
+				{
+					identifier.append(ch);
+					continue;
+				}
+
+				// Nothing placeholder related was found.
+				if (colorize && ch == '&')
+				{
+					stage = -1;
+					continue;
+				}
+				builder.append(ch);
+			}
+
+			if (identifier != null)
+			{
+				if (stage > 0)
+				{
+					builder.append(closure.end);
+				}
+				builder.append(identifier);
+			}
+			return builder.toString();
+		}
+	};
+
+
+	final class MockPlayerPlaceholderHook extends PlaceholderHook
+	{
+
+		public static final String PLAYER_X    = String.valueOf(10);
+		public static final String PLAYER_Y    = String.valueOf(20);
+		public static final String PLAYER_Z    = String.valueOf(30);
+		public static final String PLAYER_NAME = "Sxtanna";
+
+
+		@Override
+		public String onRequest(final OfflinePlayer player, final String params)
+		{
+			final String[] parts = params.split("_");
+			if (parts.length == 0)
+			{
+				return null;
+			}
+
+			switch (parts[0])
+			{
+				case "name":
+					return PLAYER_NAME;
+				case "x":
+					return PLAYER_X;
+				case "y":
+					return PLAYER_Y;
+				case "z":
+					return PLAYER_Z;
+			}
+
+			return null;
+		}
+
+	}
+
+}