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package com.oracle.truffle.regex;

import com.oracle.truffle.api.CompilerDirectives;
import com.oracle.truffle.api.frame.VirtualFrame;
import com.oracle.truffle.regex.result.RegexResult;
import com.oracle.truffle.regex.tregex.nodes.input.InputLengthNode;
import com.oracle.truffle.regex.tregex.nodes.input.InputReadNode;

public abstract class RegexExecRootNode extends RegexBodyNode {

    private final boolean mustCheckUnicodeSurrogates;
    private @Child InputLengthNode lengthNode;
    private @Child InputReadNode charAtNode;

    public RegexExecRootNode(RegexLanguage language, RegexSource source, boolean mustCheckUnicodeSurrogates) {
        super(language, source);
        this.mustCheckUnicodeSurrogates = mustCheckUnicodeSurrogates;
    }

    @Override
    public final RegexResult execute(VirtualFrame frame) {
        Object[] args = frame.getArguments();
        assert args.length == 2;
        Object input = args[0];
        int fromIndex = (int) args[1];
        if (fromIndex < 0 || fromIndex > inputLength(input)) {
            CompilerDirectives.transferToInterpreterAndInvalidate();
            throw new IllegalArgumentException(String.format("got illegal fromIndex value: %d. fromIndex must be >= 0 and <= input length (%d)", fromIndex, inputLength(input)));
        }
        return execute(input, adjustFromIndex(fromIndex, input));
    }

    private int adjustFromIndex(int fromIndex, Object input) {
        if (mustCheckUnicodeSurrogates && fromIndex > 0 && fromIndex < inputLength(input)) {
            if (Character.isLowSurrogate((char) inputRead(input, fromIndex)) && Character.isHighSurrogate((char) inputRead(input, fromIndex - 1))) {
                return fromIndex - 1;
            }
        }
        return fromIndex;
    }

    public int inputLength(Object input) {
        if (lengthNode == null) {
            CompilerDirectives.transferToInterpreterAndInvalidate();
            lengthNode = insert(InputLengthNode.create());
        }
        return lengthNode.execute(input);
    }

    public int inputRead(Object input, int i) {
        if (charAtNode == null) {
            CompilerDirectives.transferToInterpreterAndInvalidate();
            charAtNode = insert(InputReadNode.create());
        }
        return charAtNode.execute(input, i);
    }

    protected abstract RegexResult execute(Object input, int fromIndex);
}