[ADSy] - Blockchain

import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Scanner;

public class Blockchain {
    public static void main(String args[]) {
        String text = "3\n" +
                "I'm the Genesis Block\n" +
                "1\n" +
                "I'm the first block\n" +
                "2\n" +
                "I'm the second block\n" +

                "1\n" +
                "3\n" +
                "I'm the third block\n" +

                "2\n" +
                "-1328248291\n" +

                "3\n" +
                "KRAJ";
        Scanner scanner = new Scanner(text);
        //Scanner scanner = new Scanner(System.in);

        SLL<Block> list = new SLL<>();

        int numOfBlocks = scanner.nextInt();
        scanner.nextLine();

        Block rootBlock = new Block(0, scanner.nextLine(), 0);
        list.insertFirst(rootBlock);

        for (int i = 1; i < numOfBlocks; i++) {
            int index = Integer.parseInt(scanner.nextLine());
            String data = scanner.nextLine();
            list.insertLastBlock(index, data);
        }

        while (scanner.hasNextLine()) {
            String line = scanner.nextLine();
            System.out.println("read line: "+line);
            if (line.equals("KRAJ")) {
                break;
            }
            int cmd = Integer.parseInt(line);
            switch (cmd) {
                case 1:
                    int index = Integer.parseInt(scanner.nextLine());
                    String data = scanner.nextLine();
                    list.insertLastBlock(index, data);
                    break;
                case 2: //delete
                    int hash = Integer.parseInt(scanner.nextLine());
                    list.delete(hash);
                    break;
                case 3:
                    list.checkValidity();
                    break;
            }
        }

        System.out.println(list);
    }
}


class SLL<E> {
    private SLLNode<E> first;

    public SLL() {
        // Construct an empty SLL
        this.first = null;
    }

    public void deleteList() {
        first = null;
    }

    public int length() {
        int ret;
        if (first != null) {
            SLLNode<E> tmp = first;
            ret = 1;
            while (tmp.succ != null) {
                tmp = tmp.succ;
                ret++;
            }
            return ret;
        } else
            return 0;

    }

    @Override
    public String toString() {
        StringBuilder ret = new StringBuilder();
        if (first != null) {
            SLLNode<E> tmp = first;
            ret.append(tmp).append("\n->");
            while (tmp.succ != null) {
                tmp = tmp.succ;
                ret.append(tmp).append("\n->");
            }
        } else
            ret = new StringBuilder("Prazna lista!!!");
        return ret.toString();
    }

    public void insertFirst(E o) {
        SLLNode<E> ins = new SLLNode<E>(o, first);
        first = ins;
    }

    public void insertAfter(E o, SLLNode<E> node) {
        if (node != null) {
            SLLNode<E> ins = new SLLNode<E>(o, node.succ);
            node.succ = ins;
        } else {
            System.out.println("Dadenot jazol e null");
        }
    }

    public void insertBefore(E o, SLLNode<E> before) {

        if (first != null) {
            SLLNode<E> tmp = first;
            if (first == before) {
                this.insertFirst(o);
                return;
            }
            //ako first!=before
            while (tmp.succ != before)
                tmp = tmp.succ;
            if (tmp.succ == before) {
                SLLNode<E> ins = new SLLNode<E>(o, before);
                tmp.succ = ins;
            } else {
                System.out.println("Elementot ne postoi vo listata");
            }
        } else {
            System.out.println("Listata e prazna");
        }
    }

    public void insertLast(E o) {
        if (first != null) {
            SLLNode<E> tmp = first;
            while (tmp.succ != null)
                tmp = tmp.succ;
            SLLNode<E> ins = new SLLNode<E>(o, null);
            tmp.succ = ins;
        } else {
            insertFirst(o);
        }
    }

    public void insertLastBlock(int index, String data) {
        if (first != null) {
            SLLNode<Block> tmp = (SLLNode<Block>) first;
            while (tmp.succ != null)
                tmp = tmp.succ;
            Block block = new Block(index, data, tmp.element.hash);
            SLLNode<Block> ins = new SLLNode<Block>(block, null);
            tmp.succ = ins;
        }
    }

    public E deleteFirst() {
        if (first != null) {
            SLLNode<E> tmp = first;
            first = first.succ;
            return tmp.element;
        } else {
            System.out.println("Listata e prazna");
            return null;
        }
    }

    public E delete(SLLNode<E> node) {
        if (first != null) {
            SLLNode<E> tmp = first;
            if (first == node) {
                return this.deleteFirst();
            }
            while (tmp.succ != node && tmp.succ.succ != null)
                tmp = tmp.succ;
            if (tmp.succ == node) {
                tmp.succ = tmp.succ.succ;
                return node.element;
            } else {
                System.out.println("Elementot ne postoi vo listata");
                return null;
            }
        } else {
            System.out.println("Listata e prazna");
            return null;
        }

    }

    public E delete(int hash) {
        if (first != null) {
            SLLNode<Block> f = (SLLNode<Block>) first;
            SLLNode<Block> tmp = f;
            if (f.element.hash == hash) {
                System.out.print("Can't delete the rootBlock");
                return null;
            }
            while (tmp.succ.element.hash != hash && tmp.succ.succ != null) {
                tmp = tmp.succ;
            }

            if (tmp.succ.element.hash == hash) {
                tmp.succ = tmp.succ.succ;
                while(tmp.succ != null){
                    tmp.succ.element.prevHash = tmp.element.hash;
                    tmp.succ.element.hash = tmp.succ.element.hashCode();
                    tmp = tmp.succ;
                }
                return null;
            } else {
                System.out.println("Elementot ne postoi vo listata");
                return null;
            }
        } else {
            System.out.println("Listata e prazna");
            return null;
        }

    }

    public void checkValidity(){
        SLLNode<Block> tmp = (SLLNode<Block>)first;
        int prev = 0;
        while (tmp.succ != null) {
            if(tmp.element.prevHash != prev){

                System.out.println("Nevalidna");
                return;
            }
            prev = tmp.element.hash;
            tmp = tmp.succ;
        }
        System.out.println("Validna");

    }

    public SLLNode<E> getFirst() {
        return first;
    }

    public SLLNode<E> find(E o) {
        if (first != null) {
            SLLNode<E> tmp = first;
            while (tmp.element != o && tmp.succ != null)
                tmp = tmp.succ;
            if (tmp.element == o) {
                return tmp;
            } else {
                System.out.println("Elementot ne postoi vo listata");
            }
        } else {
            System.out.println("Listata e prazna");
        }
        return first;
    }

    public Iterator<E> iterator() {
        // Return an iterator that visits all elements of this list, in left-to-right order.
        return new LRIterator<E>();
    }

    // //////////Inner class ////////////

    private class LRIterator<E> implements Iterator<E> {

        private SLLNode<E> place, curr;

        private LRIterator() {
            place = (SLLNode<E>) first;
            curr = null;
        }

        public boolean hasNext() {
            return (place != null);
        }

        public E next() {
            if (place == null)
                throw new NoSuchElementException();
            E nextElem = place.element;
            curr = place;
            place = place.succ;
            return nextElem;
        }

        public void remove() {
            //Not implemented
        }
    }

    public void mirror() {
        if (first != null) {
            //m=nextsucc, p=tmp,q=next
            SLLNode<E> tmp = first;
            SLLNode<E> newsucc = null;
            SLLNode<E> next;

            while (tmp != null) {
                next = tmp.succ;
                tmp.succ = newsucc;
                newsucc = tmp;
                tmp = next;
            }
            first = newsucc;
        }

    }

    public void merge(SLL<E> in) {
        if (first != null) {
            SLLNode<E> tmp = first;
            while (tmp.succ != null)
                tmp = tmp.succ;
            tmp.succ = in.getFirst();
        } else {
            first = in.getFirst();
        }
    }
}

class Block {
    public int index;
    public String data;
    public int hash;
    public int prevHash;

    public Block(int index, String data, int prevHash) {
        this.index = index;
        this.data = data;
        this.prevHash = prevHash;
        this.hash = this.hashCode();
    }

    @Override
    public int hashCode() {
        return (Integer.valueOf(index) + data + Integer.valueOf(prevHash)).hashCode();
    }

    @Override
    public String toString() {
        return "Block{" +
                "index=" + index +
                ", data='" + data + '\'' +
                ", hash=" + hash +
                ", prevHash=" + prevHash +
                '}';
    }
}

class SLLNode<E> {
    protected E element;
    protected SLLNode<E> succ;

    public SLLNode(E elem, SLLNode<E> succ) {
        this.element = elem;
        this.succ = succ;
    }

    @Override
    public String toString() {
        return element.toString();
    }
}