using System;
using System.Collections.Generic;

namespace JM.LinqFaster
{
    public static partial class LinqFaster
    {
        // --------------------------  Arrays --------------------------------------------

        /// <summary>
        /// Returns the last element of a sequence.
        /// </summary>        
        /// <param name="source">An sequence to return the last element of.</param>
        /// <returns>The value at the last position in the source sequence.</returns>
        public static T LastF<T>(this T[] source)
        {
            if (source == null)
            {
                throw Error.ArgumentNull("source");
            }
            if (source.Length == 0)
            {
                throw Error.NoElements();
            }
            return source[source.Length - 1];
        }

        /// <summary>
        /// Returns the last element of a sequence that satisfies a specified condition.
        /// </summary>        
        /// <param name="source">A sequence to return an element from.</param>
        /// <param name="predicate">A function to test each element for a condition.</param>
        /// <returns></returns>       
        public static T LastF<T>(this T[] source, Predicate<T> predicate)
        {
            if (source == null)
            {
                throw Error.ArgumentNull("source");
            }

            if (predicate == null)
            {
                throw Error.ArgumentNull("predicate");
            }

            var lastIndex = Array.FindLastIndex(source, predicate);

            if (lastIndex == -1)
                throw Error.NoMatch();
            else
                return source[lastIndex];
        }

        /// <summary>
        /// Returns the last element of a sequence, or a default value if the sequence contains no elements.
        /// </summary>        
        /// <param name="source">An sequence to return the last element of.</param>
        /// <returns>default value if the source sequence is empty; otherwise, 
        /// the last element in the sequence</returns>
        public static T LastOrDefaultF<T>(this T[] source)
        {
            if (source == null)
            {
                throw Error.ArgumentNull("source");
            }
            if (source.Length == 0)
            {
                return default(T);
            }
            return source[source.Length - 1];
        }

        /// <summary>
        /// Returns the last element of a sequence that satisfies a condition or a default value if no such element is found.
        /// </summary>        
        /// <param name="source">A sequence to return the last element of.</param>
        /// <param name="predicate">A function to test each element for a condition.</param>
        /// <returns>default value if the sequence is empty or if no elements pass the test 
        /// in the predicate function; otherwise, the last element that passes the test in the 
        /// predicate function.</returns>
        public static T LastOrDefaultF<T>(this T[] source, Predicate<T> predicate)
        {
            if (source == null)
            {
                throw Error.ArgumentNull("source");
            }

            if (predicate == null)
            {
                throw Error.ArgumentNull("predicate");
            }

            var lastIndex = Array.FindLastIndex(source, predicate);

            if (lastIndex == -1)
                return default(T);
            else
                return source[lastIndex];
        }

        // --------------------------  Lists --------------------------------------------

        /// <summary>
        /// Returns the last element of a sequence.
        /// </summary>        
        /// <param name="source">An sequence to return the last element of.</param>
        /// <returns>The value at the last position in the source sequence.</returns>
        public static T LastF<T>(this List<T> source)
        {
            if (source == null)
            {
                throw Error.ArgumentNull("source");
            }
            if (source.Count == 0)
            {
                throw Error.NoElements();
            }
            return source[source.Count - 1];
        }

        /// <summary>
        /// Returns the last element of a sequence that satisfies a specified condition.
        /// </summary>        
        /// <param name="source">A sequence to return an element from.</param>
        /// <param name="predicate">A function to test each element for a condition.</param>
        /// <returns></returns>
        public static T LastF<T>(this List<T> source, Predicate<T> predicate)
        {
            if (source == null)
            {
                throw Error.ArgumentNull("source");
            }

            if (predicate == null)
            {
                throw Error.ArgumentNull("predicate");
            }

            var lastIndex = source.FindLastIndex(predicate);

            if (lastIndex == -1)
                throw Error.NoMatch();
            else
                return source[lastIndex];
        }

        /// <summary>
        /// Returns the last element of a sequence, or a default value if the sequence contains no elements.
        /// </summary>        
        /// <param name="source">An sequence to return the last element of.</param>
        /// <returns>default value if the source sequence is empty; otherwise, 
        /// the last element in the sequence</returns>        
        public static T LastOrDefaultF<T>(this List<T> source)
        {
            if (source == null)
            {
                throw Error.ArgumentNull("source");
            }
            if (source.Count == 0)
            {
                return default(T);
            }
            return source[source.Count - 1];
        }

        /// <summary>
        /// Returns the last element of a sequence that satisfies a condition or a default value if no such element is found.
        /// </summary>        
        /// <param name="source">A sequence to return the last element of.</param>
        /// <param name="predicate">A function to test each element for a condition.</param>
        /// <returns>default value if the sequence is empty or if no elements pass the test 
        /// in the predicate function; otherwise, the last element that passes the test in the 
        /// predicate function.</returns>
        public static T LastOrDefaultF<T>(this List<T> source, Predicate<T> predicate)
        {
            if (source == null)
            {
                throw Error.ArgumentNull("source");
            }

            if (predicate == null)
            {
                throw Error.ArgumentNull("predicate");
            }

            var lastIndex = source.FindLastIndex(predicate);

            if (lastIndex == -1)
                return default(T);
            else
                return source[lastIndex];
        }
    }
}