package bjc.esodata;

import java.util.*;

import java.util.function.*;

/*
 * @TODO 10/11/17 Ben Culkin :StackCombinators
 * 	Implement more combinators for the stack.
 */

/**
 * A stack, with support for forth/factor style stack combinators.
 *
 * <p>
 * <h2>Stack underflow</h2>
 * <p>
 * NOTE: In general, using any operation that attempts to remove more data from
 * the stack than exists will cause a {@link StackUnderflow} to be
 * thrown. Check the size of the stack if you want to avoid this.
 * <p>
 * </p>
 *
 * @param <T>
 *        The datatype stored in the stack.
 *
 * @author Ben Culkin
 */
public abstract class Stack<T> {
	/**
	 * The exception thrown when attempting to access an element from the
	 * stack that isn't there.
	 *
	 * @author EVE
	 */
	public static class StackUnderflow extends RuntimeException {
		/* The ID of the exception */
		private static final long serialVersionUID = 1423867176204571539L;
	}

	/**
	 * Push an element onto the stack.
	 *
	 * @param elm
	 *        The element to insert.
	 */
	public abstract void push(T elm);

	/**
	 * Push multiple elements onto the stack.
	 *
	 * @param elms
	 * 	The elements to insert.
	 */
	public void pushAll(T... elms) {
		for (T elm : elms) {
			push(elm);
		}
	}

	/**
	 * Pop an element off of the stack.
	 *
	 * @return The element on top of the stack.
	 */
	public abstract T pop();

	/**
	 * Retrieve the top element of this stack without removing it from the
	 * stack.
	 *
	 * @return The top element of this stack.
	 */
	public abstract T top();

	/**
	 * Get the number of elements in the stack.
	 *
	 * @return the number of elements in the stack.
	 */
	public abstract int size();

	/**
	 * Check if the stack is empty.
	 *
	 * @return Whether or not the stack is empty.
	 */
	public boolean isEmpty() {
		return size() == 0;
	}

	/**
	 * Create a spaghetti stack branching off of this one.
	 *
	 * @return A spaghetti stack with this stack as a parent.
	 */
	public Stack<T> spaghettify() {
		return new SpaghettiStack<>(this);
	}

	/*
	 * Basic combinators
	 */

	/**
	 * Drop n items from the stack.
	 *
	 * @param n
	 *        The number of items to drop.
	 */
	public void drop(final int n) {
		for(int i = 0; i < n; i++) {
			pop();
		}
	}

	/** Drop one item from the stack. */
	public void drop() {
		drop(1);
	}

	/**
	 * Delete n items below the current one.
	 *
	 * @param n
	 *        The number of items below the top to delete.
	 */
	public void nip(final int n) {
		final T elm = pop();

		drop(n);

		push(elm);
	}

	/** Delete the second element in the stack. */
	public void nip() {
		nip(1);
	}

	/**
	 * Replicate the top n items of the stack m times.
	 *
	 * @param n
	 *        The number of items to duplicate.
	 *
	 * @param m
	 *        The number of times to duplicate items.
	 */
	public void multidup(final int n, final int m) {
		final List<T> lst = new ArrayList<>(n);

		for(int i = n; i > 0; i--) {
			lst.add(0, pop());
		}

		for(int i = 0; i <= m; i++) {
			for(final T elm : lst) {
				push(elm);
			}
		}
	}

	/**
	 * Duplicate the top n items of the stack.
	 *
	 * @param n
	 *        The number of items to duplicate.
	 */
	public void dup(final int n) {
		multidup(n, 1);
	}

	/** Duplicate the top item on the stack. */
	public void dup() {
		dup(1);
	}

	/**
	 * Replicate the n elements below the top one m times.
	 *
	 * @param n
	 *        The number of items to duplicate.
	 *
	 * @param m
	 *        The number of times to duplicate items.
	 */
	public void multiover(final int n, final int m) {
		final List<T> lst = new ArrayList<>(n);

		final T elm = pop();

		for(int i = n; i > 0; i--) {
			lst.set(i - 1, pop());
		}

		for(final T nelm : lst) {
			push(nelm);
		}
		push(elm);

		for(int i = 1; i < m; i++) {
			for(final T nelm : lst) {
				push(nelm);
			}
		}
	}

	/**
	 * Duplicate the n elements below the top one.
	 *
	 * @param n
	 *        The number of items to duplicate.
	 */
	public void over(final int n) {
		multiover(n, 2);
	}

	/** Duplicate the second item in the stack. */
	public void over() {
		over(1);
	}

	/** Duplicate the third item in the stack. */
	public void pick() {
		final T z = pop();
		final T y = pop();
		final T x = pop();

		push(x);
		push(y);
		push(z);
		push(x);
	}

	/** Swap the top two items on the stack. */
	public void swap() {
		final T y = pop();
		final T x = pop();

		push(y);
		push(x);
	}

	/** Duplicate the second item below the first item. */
	public void deepdup() {
		final T y = pop();
		final T x = pop();

		push(x);
		push(x);
		push(y);
	}

	/** Swap the second and third items in the stack. */
	public void deepswap() {
		final T z = pop();
		final T y = pop();
		final T x = pop();

		push(y);
		push(x);
		push(z);
	}

	/** Rotate the top three items on the stack */
	public void rot() {
		final T z = pop();
		final T y = pop();
		final T x = pop();

		push(y);
		push(z);
		push(x);
	}

	/** Inversely rotate the top three items on the stack */
	public void invrot() {
		final T z = pop();
		final T y = pop();
		final T x = pop();

		push(z);
		push(x);
		push(y);
	}

	/*
	 * :StackCombinators Add a general rotate/roll operator.
	 */

	/*
	 * Dataflow Combinators
	 */

	/**
	 * Hides the top n elements on the stack from an action.
	 *
	 * @param n
	 *        The number of elements to hide.
	 *
	 * @param action
	 *        The action to hide the elements from
	 */
	public void dip(final int n, final Consumer<Stack<T>> action) {
		final List<T> elms = new ArrayList<>(n);

		for(int i = n; i > 0; i--) {
			elms.set(i - 1, pop());
		}

		action.accept(this);

		for(final T elm : elms) {
			push(elm);
		}
	}

	/**
	 * Hide the top element of the stack from an action.
	 *
	 * @param action
	 *        The action to hide the top from
	 */
	public void dip(final Consumer<Stack<T>> action) {
		dip(1, action);
	}

	/**
	 * Copy the top n elements on the stack, replacing them once an action
	 * is done.
	 *
	 * @param n
	 *        The number of elements to copy.
	 *
	 * @param action
	 *        The action to execute.
	 */
	public void keep(final int n, final Consumer<Stack<T>> action) {
		/*
		 * @NOTE Is this correct?
		 */
		dup(n);
		dip(n, action);
	}

	/**
	 * Apply all the actions in a list to the top n elements of the stack.
	 *
	 * @param n
	 *        The number of elements to give to cons.
	 *
	 * @param actions
	 *        The actions to execute.
	 */
	public void multicleave(final int n, final List<Consumer<Stack<T>>> actions) {
		final List<T> elms = new ArrayList<>(n);

		for(int i = n; i > 0; i--) {
			elms.set(i - 1, pop());
		}

		for(final Consumer<Stack<T>> action : actions) {
			for(final T elm : elms) {
				push(elm);
			}

			action.accept(this);
		}
	}

	/**
	 * Apply all the actions in a list to the top element of the stack.
	 *
	 * @param actions
	 *        The actions to execute.
	 */
	public void cleave(final List<Consumer<Stack<T>>> actions) {
		multicleave(1, actions);
	}

	/**
	 * Apply every action in a list of actions to n arguments.
	 *
	 * @param n
	 *        The number of parameters each action takes.
	 *
	 * @param actions
	 *        The actions to execute.
	 */
	public void multispread(final int n, final List<Consumer<Stack<T>>> actions) {
		final List<List<T>> nelms = new ArrayList<>(actions.size());

		for(int i = actions.size(); i > 0; i--) {
			final List<T> elms = new ArrayList<>(n);

			for(int j = n; j > 0; j--) {
				elms.set(j, pop());
			}

			nelms.set(i, elms);
		}

		int i = 0;
		for(final List<T> elms : nelms) {
			for(final T elm : elms) {
				push(elm);
			}

			actions.get(i).accept(this);
			i += 1;
		}
	}

	/**
	 * Apply the actions in a list of actions to corresponding elements from
	 * the stack.
	 *
	 * @param conses
	 *        The actions to execute.
	 */
	public void spread(final List<Consumer<Stack<T>>> conses) {
		multispread(1, conses);
	}

	/**
	 * Apply an action to the first m groups of n arguments.
	 *
	 * @param n
	 *        The number of arguments cons takes.
	 *
	 * @param m
	 *        The number of time to call cons.
	 *
	 * @param action
	 *        The action to execute.
	 */
	public void multiapply(final int n, final int m, final Consumer<Stack<T>> action) {
		final List<Consumer<Stack<T>>> actions = new ArrayList<>(m);

		for(int i = 0; i < m; i++) {
			actions.add(action);
		}

		multispread(n, actions);
	}

	/**
	 * Apply an action n times to the corresponding elements in the stack.
	 *
	 * @param n
	 *        The number of times to execute cons.
	 *
	 * @param action
	 *        The action to execute.
	 */
	public void apply(final int n, final Consumer<Stack<T>> action) {
		multiapply(1, n, action);
	}

	/*
	 * Misc. functions
	 */

	/**
	 * Get an array representing this stack.
	 *
	 * @return The stack as an array.
	 */
	public abstract T[] toArray();
}