using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using UnityEngine;

namespace Unity.VisualScripting
{
    public static class SearchUtility
    {
        private static bool Compare(char a, char b)
        {
            return char.ToLowerInvariant(a) == char.ToLowerInvariant(b);
        }

        private static bool Match(string query, string haystack, bool strictOnly, float strictWeight, float looseWeight, out float score, bool[] indices)
        {
            score = 0;
            var isStreaking = false;
            var haystackIndex = 0;
            var matchedAny = false;

            for (var queryIndex = 0; queryIndex < query.Length; queryIndex++)
            {
                var queryCharacter = query[queryIndex];

                if (StringUtility.IsWordDelimiter(queryCharacter))
                {
                    continue;
                }

                var matched = false;

                for (; haystackIndex < haystack.Length; haystackIndex++)
                {
                    var haystackCharacter = haystack[haystackIndex];

                    if (StringUtility.IsWordDelimiter(haystackCharacter))
                    {
                        isStreaking = false;
                        continue;
                    }

                    var matchesLoose = Compare(queryCharacter, haystackCharacter);
                    var matchesStrict = matchesLoose && (isStreaking || StringUtility.IsWordBeginning(haystack, haystackIndex));

                    var matches = strictOnly ? matchesStrict : matchesLoose;

                    if (matches)
                    {
                        score += matchesStrict ? strictWeight : looseWeight;
                        matched = true;

                        if (indices != null)
                        {
                            indices[haystackIndex] = true;
                        }

                        isStreaking = true;
                        haystackIndex++;
                        break;
                    }
                    else
                    {
                        isStreaking = false;
                    }
                }

                if (matched)
                {
                    matchedAny = true;
                }
                else
                {
                    return false;
                }
            }

            if (!matchedAny)
            {
                return false;
            }

            score /= query.Length;
            return true;
        }

        private static float? Score(string query, string haystack, bool strictOnly, float strictWeight, float looseWeight)
        {
            if (Match(query, haystack, strictOnly, strictWeight, looseWeight, out var score, null))
            {
                return score;
            }
            else
            {
                return null;
            }
        }

        private static bool[] Indices(string query, string haystack, bool strictOnly)
        {
            bool[] indices = new bool[haystack.Length];

            if (Match(query, haystack, strictOnly, 0, 0, out var score, indices))
            {
                return indices;
            }
            else
            {
                return null;
            }
        }

        public static float Relevance(string query, string haystack)
        {
            // Configurable score weights
            var strictWeight = 1;
            var looseWeight = 0.25f;
            var shortnessWeight = 1;

            // Calculate the strict score first, then the loose score if the former fails
            var score = Score(query, haystack, true, strictWeight, looseWeight) ?? Score(query, haystack, false, strictWeight, looseWeight);

            if (score == null)
            {
                // If loose matching fails as well, return a failure
                return -1;
            }

            // Calculate the shortness factor
            var shortness = (float)query.Length / haystack.Length;

            // Sum and normalize scores
            var scoreWeight = Mathf.Max(strictWeight, looseWeight);
            var maxWeight = scoreWeight + shortnessWeight;
            var totalWeight = (score.Value * scoreWeight) + (shortness * shortnessWeight);
            return totalWeight / maxWeight;
        }

        static float Relevance(string query, string haystack, string formerHaystack)
        {
            // Configurable score weights
            var strictWeight = 1;
            var looseWeight = 0.25f;
            var shortnessWeight = 1;

            // Calculate the strict score first, then the loose score if the former fails
            var score = ComputeScore(query, haystack, strictWeight, looseWeight);
            score = Math.Max(score, ComputeScore(query, formerHaystack, strictWeight, looseWeight));

            if (score == -1)
            {
                // If loose matching fails as well, return a failure
                return -1;
            }

            // Calculate the shortness factor
            var shortness = (float)query.Length / haystack.Length;

            // Sum and normalize scores
            var scoreWeight = Mathf.Max(strictWeight, looseWeight);
            var maxWeight = scoreWeight + shortnessWeight;
            var totalWeight = (score * scoreWeight) + (shortness * shortnessWeight);
            return totalWeight / maxWeight;
        }

        static float ComputeScore(string query, string haystack, float strictWeight, float looseWeight)
        {
            var score = Score(query, haystack, true, strictWeight, looseWeight) ?? Score(query, haystack, false, strictWeight, looseWeight);
            return score ?? -1;
        }

        public static bool Matches(string query, string haystack)
        {
            return Matches(Relevance(query, haystack));
        }

        public static bool Matches(float relevance)
        {
            return relevance > 0;
        }

        public static bool Matches(ISearchResult result)
        {
            return Matches(result.relevance);
        }

        public static string HighlightQuery(string haystack, string query, string openTag = "<b>", string closeTag = "</b>")
        {
            if (string.IsNullOrEmpty(query))
            {
                return haystack;
            }

            bool[] matchingIndices = Indices(query, haystack, true) ?? Indices(query, haystack, false);

            if (matchingIndices == null)
            {
                return haystack;
            }

            var sb = new StringBuilder();

            var isHighlighted = false;
            var wasHighlighted = false;

            for (var i = 0; i < haystack.Length; i++)
            {
                var character = haystack[i];
                isHighlighted = matchingIndices[i];

                if (!wasHighlighted && isHighlighted)
                {
                    sb.Append(openTag);
                }
                else if (wasHighlighted && !isHighlighted)
                {
                    sb.Append(closeTag);
                }

                sb.Append(character);

                wasHighlighted = isHighlighted;
            }

            if (isHighlighted)
            {
                sb.Append(closeTag);
            }

            return sb.ToString();
        }

        public static IEnumerable<SearchResult<TResult>> OrderableSearchFilter<THaystack, TResult>(this IEnumerable<THaystack> enumeration,
            Func<THaystack, TResult> getResult,
            string query,
            Func<THaystack, string> getHaystack)
        {
            return enumeration.Select(item => new SearchResult<TResult>(getResult(item), Relevance(query, getHaystack(item))))
                .Where(result => Matches(result.relevance));
        }

        public static IEnumerable<SearchResult<T>> OrderableSearchFilter<T>(this IEnumerable<T> enumeration,
            string query,
            Func<T, string> haystack)
        {
            return OrderableSearchFilter(enumeration, r => r, query, haystack);
        }

        public static IEnumerable<SearchResult<TResult>> OrderableSearchFilter<THaystack, TResult>(this IEnumerable<THaystack> enumeration,
            Func<THaystack, TResult> getResult,
            string query,
            Func<THaystack, string> getHaystack,
            Func<THaystack, string> getFormerHaystack)
        {
            return enumeration.Select(item => new SearchResult<TResult>(getResult(item), Relevance(query, getHaystack(item), getFormerHaystack(item))))
                .Where(result => Matches(result.relevance));
        }

        public static IEnumerable<SearchResult<T>> OrderableSearchFilter<T>(this IEnumerable<T> enumeration,
            string query,
            Func<T, string> haystack,
            Func<T, string> formerHaystack)
        {
            return OrderableSearchFilter(enumeration, r => r, query, haystack, formerHaystack);
        }

        public static IEnumerable<T> OrderByRelevance<T>(this IEnumerable<SearchResult<T>> results)
        {
            return results.OrderByDescending(osr => osr.relevance).Select(osr => osr.result);
        }

        public static IEnumerable<object> OrderByRelevance(this IEnumerable<ISearchResult> results)
        {
            return results.OrderByDescending(osr => osr.relevance).Select(osr => osr.result);
        }

        public static IEnumerable<T> UnorderedSearchFilter<T>(this IEnumerable<T> enumeration, string query, Func<T, string> haystack)
        {
            return enumeration.Where(item => Matches(query, haystack(item)));
        }

        public static IEnumerable<T> OrderedSearchFilter<T>(this IEnumerable<T> enumeration, string query, Func<T, string> haystack)
        {
            return enumeration.OrderableSearchFilter(r => r, query, haystack).OrderByRelevance();
        }
    }
}