org.apache.juneau.svl.vars.SwitchVar Maven / Gradle / Ivy

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package org.apache.juneau.svl.vars;

import static org.apache.juneau.common.internal.ArgUtils.*;
import static org.apache.juneau.common.internal.StringUtils.*;

import java.util.regex.*;

import org.apache.juneau.svl.*;

/**
 * A basic switch/case logic variable resolver.
 *
 * 
 * The format for this var is one of the following:
 * 

 * 	"$SW{stringArg, pattern:thenValue[, pattern:thenValue...]}"
 * 	
...
 * 
 *
 * 
 * The pattern can be any string optionally containing '*' or '?' representing any or one character
 * respectively.
 *
 * 
Example:
 * 
 * 	// Create a variable resolver that resolves system properties and $SW vars.
 * 	VarResolver varResolver = VarResolver.create().vars(SwitchVar.class, SystemPropertiesVar.class).build();
 *
 * 	// Use it!
 * 	System.out.println(varResolver.resolve("We are running on $SW{$P{os.name},*win*:Windows,*:Something else}!"));
 * 
 *
 * 
 * Since this is a {@link MultipartVar}, any variables contained in the result will be recursively resolved.
 * 
Likewise, if the arguments contain any variables, those will be resolved before they are passed to this var.
 *
 * 
See Also:

 * 	Simple Variable Language
 * 
 */
public class SwitchVar extends MultipartVar {

	/** The name of this variable. */
	public static final String NAME = "SW";

	/**
	 * Constructor.
	 */
	public SwitchVar() {
		super(NAME);
	}

	@Override /* MultipartVar */
	public String resolve(VarResolverSession session, String[] args) {
		assertArg(args.length >= 2, "Invalid number of arguments passed to $SW var.  Must have 2 or more arguments.");

		String stringArg = args[0];
		for (int i = 1; i < args.length; i++) {
			String pattern = args[i];

			String[] parts = split(pattern, ':', 2);
			assertArg(parts.length >= 2, "Invalid arguments passed to $SW var.  Each case statement must contains 'pattern:value'.");

			Pattern p = Pattern.compile(parts[0].replace("*", ".*").replace("?", "."));
			if (p.matcher(stringArg).matches())
				return parts[1];
		}

		// Nothing matched and no else clause.
		return "";
	}
}