/*
 * Aresh Saharkhiz
 * saharkiz@gmail.com
 * Associate Professor / Mapua Institute of Technology / Philippines
 */

using System;

// Introduction to Software Testing
// Authors: Paul Ammann & Jeff Offutt
// Chapter 2, section 2.3, page 56

internal class TestPat
{

    public static void Main(string[] argv)
    {
        const int MAX = 100;
        char[] subject = new char[MAX];
        char[] pattern = new char[MAX];
        if (argv.Length != 2)
        {
            Console.WriteLine("java TestPat String-Subject String-Pattern");
            return;
        }
        subject = argv[0].ToCharArray();
        pattern = argv[1].ToCharArray();
        TestPat testPat = new TestPat();
        int n = 0;
        if ((n = testPat.pat(subject, pattern)) == -1)
        {
            Console.WriteLine("Pattern string is not a substring of the subject string");
        }
        else
        {
            Console.WriteLine("Pattern string begins at the character " + n);
        }
    }

    public TestPat()
    {
    }

    public virtual int pat(char[] subject, char[] pattern)
    {
        // Post: if pattern is not a substring of subject, return -1
        //       else return (zero-based) index where the pattern (first)
        //       starts in subject

        const int NOTFOUND = -1;
        int iSub = 0, rtnIndex = NOTFOUND;
        bool isPat = false;
        int subjectLen = subject.Length;
        int patternLen = pattern.Length;

        while (isPat == false && iSub + patternLen - 1 < subjectLen)
        {
            if (subject[iSub] == pattern[0])
            {
                rtnIndex = iSub; // Starting at zero
                isPat = true;
                for (int iPat = 1; iPat < patternLen; iPat++)
                {
                    if (subject[iSub + iPat] != pattern[iPat])
                    {
                        rtnIndex = NOTFOUND;
                        isPat = false;
                        break; // out of for loop
                    }
                }
            }
            iSub++;
        }
        return (rtnIndex);
    }

}