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package com.termux.shared.shell;

import java.util.List;
import java.util.LinkedList;

/**
 * Utility class which can tokenize a String into a list of String arguments,
 * with behavior similar to parsing command line arguments to a program.
 * Quoted Strings are treated as single arguments, and escaped characters
 * are translated so that the tokenized arguments have the same meaning.
 * Since all methods are static, the class is declared abstract to prevent
 * instantiation.
 * @version $Id$
 */
public abstract class ArgumentTokenizer {

    private static final int NO_TOKEN_STATE = 0;

    private static final int NORMAL_TOKEN_STATE = 1;

    private static final int SINGLE_QUOTE_STATE = 2;

    private static final int DOUBLE_QUOTE_STATE = 3;

    /**
     * Tokenizes the given String into String tokens
     * @param arguments A String containing one or more command-line style arguments to be tokenized.
     * @return A list of parsed and properly escaped arguments.
     */
    public static List<String> tokenize(String arguments) {
        return tokenize(arguments, false);
    }

    /**
     * Tokenizes the given String into String tokens.
     * @param arguments A String containing one or more command-line style arguments to be tokenized.
     * @param stringify whether or not to include escape special characters
     * @return A list of parsed and properly escaped arguments.
     */
    public static List<String> tokenize(String arguments, boolean stringify) {
        LinkedList<String> argList = new LinkedList<String>();
        StringBuilder currArg = new StringBuilder();
        boolean escaped = false;
        // start in the NO_TOKEN_STATE
        int state = NO_TOKEN_STATE;
        int len = arguments.length();
        // Loop over each character in the string
        for (int i = 0; i < len; i++) {
            char c = arguments.charAt(i);
            if (escaped) {
                // Escaped state: just append the next character to the current arg.
                escaped = false;
                currArg.append(c);
            } else {
                switch(state) {
                    case SINGLE_QUOTE_STATE:
                        if (c == '\'') {
                            // Seen the close quote; continue this arg until whitespace is seen
                            state = NORMAL_TOKEN_STATE;
                        } else {
                            currArg.append(c);
                        }
                        break;
                    case DOUBLE_QUOTE_STATE:
                        if (c == '"') {
                            // Seen the close quote; continue this arg until whitespace is seen
                            state = NORMAL_TOKEN_STATE;
                        } else if (c == '\\') {
                            // Look ahead, and only escape quotes or backslashes
                            i++;
                            char next = arguments.charAt(i);
                            if (next == '"' || next == '\\') {
                                currArg.append(next);
                            } else {
                                currArg.append(c);
                                currArg.append(next);
                            }
                        } else {
                            currArg.append(c);
                        }
                        break;
                    //          case NORMAL_TOKEN_STATE:
                    //            if (Character.isWhitespace(c)) {
                    //              // Whitespace ends the token; start a new one
                    //              argList.add(currArg.toString());
                    //              currArg = new StringBuffer();
                    //              state = NO_TOKEN_STATE;
                    //            }
                    //            else if (c == '\\') {
                    //              // Backslash in a normal token: escape the next character
                    //              escaped = true;
                    //            }
                    //            else if (c == '\'') {
                    //              state = SINGLE_QUOTE_STATE;
                    //            }
                    //            else if (c == '"') {
                    //              state = DOUBLE_QUOTE_STATE;
                    //            }
                    //            else {
                    //              currArg.append(c);
                    //            }
                    //            break;
                    case NO_TOKEN_STATE:
                    case NORMAL_TOKEN_STATE:
                        switch(c) {
                            case '\\':
                                escaped = true;
                                state = NORMAL_TOKEN_STATE;
                                break;
                            case '\'':
                                state = SINGLE_QUOTE_STATE;
                                break;
                            case '"':
                                state = DOUBLE_QUOTE_STATE;
                                break;
                            default:
                                if (!Character.isWhitespace(c)) {
                                    currArg.append(c);
                                    state = NORMAL_TOKEN_STATE;
                                } else if (state == NORMAL_TOKEN_STATE) {
                                    // Whitespace ends the token; start a new one
                                    argList.add(currArg.toString());
                                    currArg = new StringBuilder();
                                    state = NO_TOKEN_STATE;
                                }
                        }
                        break;
                    default:
                        throw new IllegalStateException("ArgumentTokenizer state " + state + " is invalid!");
                }
            }
        }
        // If we're still escaped, put in the backslash
        if (escaped) {
            currArg.append('\\');
            argList.add(currArg.toString());
        } else // Close the last argument if we haven't yet
        if (state != NO_TOKEN_STATE) {
            argList.add(currArg.toString());
        }
        // Format each argument if we've been told to stringify them
        if (stringify) {
            for (int i = 0; i < argList.size(); i++) {
                argList.set(i, "\"" + _escapeQuotesAndBackslashes(argList.get(i)) + "\"");
            }
        }
        return argList;
    }

    /**
     * Inserts backslashes before any occurrences of a backslash or
     * quote in the given string.  Also converts any special characters
     * appropriately.
     */
    protected static String _escapeQuotesAndBackslashes(String s) {
        final StringBuilder buf = new StringBuilder(s);
        // Walk backwards, looking for quotes or backslashes.
        //  If we see any, insert an extra backslash into the buffer at
        //  the same index.  (By walking backwards, the index into the buffer
        //  will remain correct as we change the buffer.)
        for (int i = s.length() - 1; i >= 0; i--) {
            char c = s.charAt(i);
            if ((c == '\\') || (c == '"')) {
                buf.insert(i, '\\');
            } else // Replace any special characters with escaped versions
            if (c == '\n') {
                buf.deleteCharAt(i);
                buf.insert(i, "\\n");
            } else if (c == '\t') {
                buf.deleteCharAt(i);
                buf.insert(i, "\\t");
            } else if (c == '\r') {
                buf.deleteCharAt(i);
                buf.insert(i, "\\r");
            } else if (c == '\b') {
                buf.deleteCharAt(i);
                buf.insert(i, "\\b");
            } else if (c == '\f') {
                buf.deleteCharAt(i);
                buf.insert(i, "\\f");
            }
        }
        return buf.toString();
    }
}
