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package bjc.utils.patterns;
import java.util.function.*;
import java.util.regex.*;
import bjc.data.*;
/**
* A pattern that can be matched against.
*
* @author Ben Culkin
*
* @param <InputType> The type of object being matched against.
* @param <ReturnType> The type returned by the pattern.
* @param <PredType> The state type returned by the predicate.
*/
public interface ComplexPattern<ReturnType, PredType, InputType> {
/**
* Whether or not the given input matches this pattern.
*
* @param input The object to check against this pattern.
*
* @return Whether or not this pattern is matched, as well as a state value
* that will get passed to the pattern if it did match.
*/
Pair<Boolean, PredType> matches(InputType input);
/**
* Apply this pattern, once it has matched.
*
* @param input The object to apply this pattern to.
* @param state The state from the matcher.
*
* @return The result of applying this pattern.
*/
ReturnType apply(InputType input, PredType state);
/* Pattern producing functions */
/**
* Create a pattern composed from a predicate & a function.
*
* @param <RetType> The type returned by the pattern.
* @param <PreType> The type used as intermediate state.
* @param <InpType> The type initially matched against.
*
* @param matcher The predicate that says what this pattern matches.
* @param accepter The action that happens when this pattern matches.
*
* @return A pattern composed from the passed in functions.
*/
static <RetType, PreType, InpType> ComplexPattern<RetType, PreType, InpType> from(
Function<InpType, Pair<Boolean, PreType>> matcher,
BiFunction<InpType, PreType, RetType> accepter)
{
return new FunctionalPattern<>(matcher, accepter);
}
/**
* Create a pattern which checks if an object is of a given type (or a subtype of it).
*
* @param <ClassType> The type to check if the object is an instance of.
* @param <RetType> The type returned by the action.
* @param <InpType> The type of the thing to match.
*
* @param clasz The Class instance for the type you want to check.
* @param action The action to execute if the pattern does match.
*
* @return A pattern which follows the specified condition.
*/
@SuppressWarnings("unchecked")
static <ClassType, RetType, InpType> ComplexPattern<RetType, ?, InpType> ofClass(
Class<ClassType> clasz,
Function<ClassType, RetType> action)
{
return from(
(input) -> Pair.pair(clasz.isInstance(input), null),
(input, ignored) -> action.apply((ClassType)input)
);
}
/**
* Creates a pattern which matches a given object.
*
* @param <RetType> The type returned when the pattern matches.
* @param <InpType> The type of the thing to match.
*
* @param obj The object being tested for equality.
* @param action The action to execute when the object matches.
*
* @return A pattern which tests against the equality of an object.
*/
static <RetType, InpType> ComplexPattern<RetType, ?, InpType> matchesObject(
InpType obj,
Function<InpType, RetType> action
)
{
return from(
(input) -> Pair.pair(obj.equals(input), null),
(input, ignored) -> action.apply(input)
);
}
/**
* Tests if the toString rendition of an object matches a given condition.
*
* @param <RetType> The type returned by the pattern.
* @param <InpType> The type of the thing to match.
*
* @param pattern The string to check against.
* @param action The action to check when the toString of the object matches
* the provided string. This is passed both the object, and its
* string form (in the event that you don't want to call toString
* multiple times, for whatever reason)
*
* @return A pattern which tests against the toString representation of an object.
*/
static <RetType, InpType> ComplexPattern<RetType, ?, InpType> equalsString(
String pattern,
BiFunction<InpType, String, RetType> action
)
{
Function<InpType, Pair<Boolean, String>> matcher = (input) -> {
String objString = input.toString();
return Pair.pair(pattern.equals(objString), objString);
};
return from(
matcher,
(input, objString) -> action.apply(input, objString)
);
}
/**
* Check if the toString of a given object matches a regex.
*
* @param <RetType> The type returned by the pattern.
* @param <InpType> The type of object to match against.
*
* @param regex The regex to match against.
* @param cond The predicate to use to determine if the regex matched.
* @param action The action to call when the regex matched.
*
* @return A pattern which does the regex matching.
*/
static <RetType, InpType> ComplexPattern<RetType, Matcher, InpType> matchesRegex(
String regex,
Predicate<Matcher> cond,
BiFunction<InpType, Matcher, RetType> action
)
{
java.util.regex.Pattern regexPat = java.util.regex.Pattern.compile(regex);
Function<InpType, Pair<Boolean, Matcher>> matcher = (input) -> {
String inpString = input.toString();
Matcher mat = regexPat.matcher(inpString);
if (cond.test(mat)) return Pair.pair(true, mat);
else return Pair.pair(false, null);
};
return from(
matcher,
(input, res) -> action.apply(input, res)
);
}
// @TODO Nov 21, 2020 Ben Culkin :MorePatterns
// Try and write something to iterate over Iterator in a type-safe manner
// Also, something for doing a sub-pattern match
/**
* Create a pattern which will always execute.
*
* @param <RetType> The type returned.
* @param <InpType> The type being matched against.
*
* @param action The action to execute.
*
* @return A pattern which will be executed.
*/
static <RetType, InpType> ComplexPattern<RetType, ?, InpType> otherwise(
Function<InpType, RetType> action
)
{
return from(
(input) -> Pair.pair(true, null),
(input, ignored) -> action.apply(input)
);
}
/**
* Create a pattern which checks if the string form of a given object starts
* with a specific string.
*
* @param <RetType> The type returned by the matcher.
* @param <InpType> The type being matched against.
*
* @param pattern The string to check against.
* @param action The action to execute.
*
* @return A pattern which functions as described.
*/
static <RetType, InpType> ComplexPattern<RetType, String, InpType> startsWith(
String pattern,
Function<String, RetType> action)
{
return from((input) -> {
String objString = input.toString();
if (objString.startsWith(pattern)) {
return Pair.pair(
true,
objString.substring(
pattern.length()));
} else {
return Pair.pair(false, null);
}
}, (ignored, input) -> action.apply(input));
}
}
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