using EgwCoreLib.Lux.Core.RestPayload;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace EgwCoreLib.Lux.Core.MachineCalc
{
    public class Utils
    {
        #region Public Methods

        /// <summary>
        /// Calcolo delle intersezioni Macchine/Tags(Parts)
        /// </summary>
        /// <param name="machineResult"></param>
        /// <returns></returns>
        public static List<MachineTagDTO> CalculateIntersections(List<MachineCalcResultDTO> machineResult)
        {
            var results = new List<MachineTagDTO>();
            if (machineResult != null && machineResult.Count > 0)
            {
                int numParts = machineResult.FirstOrDefault()?.NumParts ?? 0;
                // Step 1: extract workable tags per machine
                var machineTags = machineResult
                    .ToDictionary(
                        m => m.Name,
                        m => m.PartList
                              .Where(p => p.CalcResult == Enums.PartVerificationResult.MACHINABLE)
                              .ToList()
                    );
                var machineNames = machineTags.Keys.ToList();

                // Step 2: generate all combinations of machines
                for (int size = 1; size <= machineNames.Count; size++)
                {
                    foreach (var combo in GetCombinations(machineNames, size))
                    {
                        var comboList = combo.ToList();

                        // Intersection of tags across all machines in this combo
                        var intersectionTags = comboList
                            .Select(name => machineTags[name].Select(p => p.Tag).ToHashSet())
                            .Aggregate((set1, set2) => { set1.IntersectWith(set2); return set1; });

                        // Compute per-machine sums of Time for these tags
                        var sums = comboList.Select(name =>
                            machineTags[name]
                                .Where(p => intersectionTags.Contains(p.Tag))
                                .Sum(p => p.Time)
                        ).ToList();

                        results.Add(new MachineTagDTO
                        {
                            TotParts = numParts,
                            Machines = comboList,
                            Tags = intersectionTags.ToList(),
                            MinTime = sums.Any() ? sums.Min() : 0,
                            MaxTime = sums.Any() ? sums.Max() : 0
                        });
                    }
                }

                // Step 3: add unique (non-intersecting) tags per machine
                foreach (var name in machineNames)
                {
                    var uniqueTags = machineTags[name]
                        .Select(p => p.Tag)
                        .Except(machineNames.Where(n => n != name)
                                            .SelectMany(n => machineTags[n].Select(p => p.Tag)))
                        .ToList();

                    if (uniqueTags.Count > 0)
                    {
                        var sum = machineTags[name]
                            .Where(p => uniqueTags.Contains(p.Tag))
                            .Sum(p => p.Time);

                        results.Add(new MachineTagDTO
                        {
                            TotParts = numParts,
                            Machines = new List<string> { name },
                            Tags = uniqueTags,
                            MinTime = sum,
                            MaxTime = sum
                        });
                    }
                }
            }
            return results;
        }

        /// <summary>
        /// Helper generazione combinazioni di items per una data length (Distinct Combinations)
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="items"></param>
        /// <param name="length"></param>
        /// <returns></returns>
        public static IEnumerable<IEnumerable<T>> GetCombinations<T>(IEnumerable<T> items, int length)
        {
            // Convert to a List to easily access elements by index.
            List<T> itemList = items.ToList();
            int n = itemList.Count;

            // Base case: length 0 returns a collection containing an empty collection
            if (length == 0)
            {
                yield return Enumerable.Empty<T>();
                yield break;
            }

            // Check if enough items are available
            if (length > n)
            {
                yield break;
            }

            // Call the internal recursive helper function
            foreach (var combination in GetCombinationsInternal(itemList, length, 0, n))
            {
                yield return combination;
            }
        }

        /// <summary>
        /// Helper generazione permutazioni di items per una data length
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="items"></param>
        /// <param name="length"></param>
        /// <returns></returns>
        public static IEnumerable<IEnumerable<T>> GetPermutations<T>(IEnumerable<T> items, int length)
        {
            if (length == 1)
                return items.Select(i => new T[] { i });

            return GetCombinations(items, length - 1)
                .SelectMany(c => items.Where(i => !c.Contains(i)),
                            (c, i) => c.Concat(new T[] { i }));
        }

        /// <summary>
        /// Helper calcolo Intersezione lista macchine
        /// </summary>
        /// <param name="machines"></param>
        /// <param name="predicate"></param>
        /// <returns></returns>
        public static IEnumerable<string> IntersectTags(List<MachineCalcResultDTO> machines, Func<PartCalcDTO, bool> predicate)
        {
            return machines
                .Select(m => m.PartList.Where(predicate).Select(p => p.Tag).ToHashSet())
                .Aggregate((set1, set2) => { set1.IntersectWith(set2); return set1; });
        }

        #endregion Public Methods

        #region Private Methods

        private static IEnumerable<IEnumerable<T>> GetCombinationsInternal<T>(
            List<T> items,
            int length,
            int startIndex,
            int n)
        {
            // Base case: combination of length 1
            if (length == 1)
            {
                // Select one item from startIndex up to the end
                for (int i = startIndex; i < n; i++)
                {
                    yield return new T[] { items[i] };
                }
                yield break;
            }

            // Recursive step
            // Iterate over elements starting from startIndex
            for (int i = startIndex; i <= n - length; i++)
            {
                T currentItem = items[i];

                // Recursively find combinations of length - 1 starting from the next index (i + 1)
                // This is the crucial step that prevents (a,b) and (b,a)
                foreach (var subCombination in GetCombinationsInternal(items, length - 1, i + 1, n))
                {
                    // Prepend the current item to the shorter combinations
                    yield return new T[] { currentItem }.Concat(subCombination);
                }
            }
        }

        #endregion Private Methods
    }
}