using System;
using System.Text.RegularExpressions;
using SabreTools.Core.Tools;
using SabreTools.Models.Internal;

namespace SabreTools.Filter
{
    /// <summary>
    /// Represents a single filtering object
    /// </summary>
    public class FilterObject
    {
        /// <summary>
        /// Key name for the filter
        /// </summary>
        public string[] Key { get; init; }

        /// <summary>
        /// Value to match in the filter
        /// </summary>
        public string? Value { get; init; }

        /// <summary>
        /// Operation on how to match the filter
        /// </summary>
        public Operation Operation { get; init; }

        public FilterObject(string filterString)
        {
            (string? keyItem, Operation operation, string? value) = SplitFilterString(filterString);
            if (keyItem == null)
                throw new ArgumentOutOfRangeException(nameof(filterString));

            (string? itemName, string? fieldName) = FilterParser.ParseFilterId(keyItem);
            if (itemName == null || fieldName == null)
                throw new ArgumentOutOfRangeException(nameof(filterString));

            this.Key = new string[] { itemName, fieldName };
            this.Value = value;
            this.Operation = operation;
        }

        public FilterObject(string itemField, string? value, string? operation)
        {
            (string? itemName, string? fieldName) = FilterParser.ParseFilterId(itemField);
            if (itemName == null || fieldName == null)
                throw new ArgumentOutOfRangeException(nameof(value));

            this.Key = new string[] { itemName, fieldName };
            this.Value = value;
            this.Operation = GetOperation(operation);
        }

        public FilterObject(string itemField, string? value, Operation operation)
        {
            (string? itemName, string? fieldName) = FilterParser.ParseFilterId(itemField);
            if (itemName == null || fieldName == null)
                throw new ArgumentOutOfRangeException(nameof(value));

            this.Key = new string[] { itemName, fieldName };
            this.Value = value;
            this.Operation = operation;
        }

        #region Matching

        /// <summary>
        /// Determine if a DictionaryBase object matches the key and value
        /// </summary>
        public bool Matches(DictionaryBase dictionaryBase)
        {
            // TODO: Add validation of dictionary base type from this.Key[0]
            return this.Operation switch
            {
                Operation.Equals => MatchesEqual(dictionaryBase),
                Operation.NotEquals => MatchesNotEqual(dictionaryBase),
                Operation.GreaterThan => MatchesGreaterThan(dictionaryBase),
                Operation.GreaterThanOrEqual => MatchesGreaterThanOrEqual(dictionaryBase),
                Operation.LessThan => MatchesLessThan(dictionaryBase),
                Operation.LessThanOrEqual => MatchesLessThanOrEqual(dictionaryBase),
                _ => false,
            };
        }

        /// <summary>
        /// Determines if a value matches exactly
        /// </summary>
        private bool MatchesEqual(DictionaryBase dictionaryBase)
        {
            // If the key doesn't exist, we count it as null
            if (!dictionaryBase.ContainsKey(this.Key[1]))
                return this.Value == null;

            // If the value in the dictionary is null
            string? checkValue = dictionaryBase.ReadString(this.Key[1]);
            if (checkValue == null)
                return this.Value == null;

            // If we have both a potentially numeric check and value
            if (NumberHelper.IsNumeric(checkValue) && NumberHelper.IsNumeric(this.Value))
            {
                // Check Int64 values
                long? checkValueLong = NumberHelper.ConvertToInt64(checkValue);
                long? matchValueLong = NumberHelper.ConvertToInt64(checkValue);
                if (checkValueLong != null && matchValueLong != null)
                    return checkValueLong == matchValueLong;

                // Check Double values
                double? checkValueDouble = NumberHelper.ConvertToDouble(checkValue);
                double? matchValueDouble = NumberHelper.ConvertToDouble(checkValue);
                if (checkValueDouble != null && matchValueDouble != null)
                    return checkValueDouble == matchValueDouble;
            }

            // If the value might contain valid Regex
            if (this.Value != null && ContainsRegex(this.Value))
                return Regex.IsMatch(checkValue, this.Value);

            return string.Equals(checkValue, this.Value, StringComparison.OrdinalIgnoreCase);
        }

        /// <summary>
        /// Determines if a value does not match exactly
        /// </summary>
        private bool MatchesNotEqual(DictionaryBase dictionaryBase)
        {
            // If the key doesn't exist, we count it as null
            if (!dictionaryBase.ContainsKey(this.Key[1]))
                return this.Value != null;

            // If the value in the dictionary is null
            string? checkValue = dictionaryBase.ReadString(this.Key[1]);
            if (checkValue == null)
                return this.Value == null;

            // If we have both a potentially numeric check and value
            if (NumberHelper.IsNumeric(checkValue) && NumberHelper.IsNumeric(this.Value))
            {
                // Check Int64 values
                long? checkValueLong = NumberHelper.ConvertToInt64(checkValue);
                long? matchValueLong = NumberHelper.ConvertToInt64(checkValue);
                if (checkValueLong != null && matchValueLong != null)
                    return checkValueLong != matchValueLong;

                // Check Double values
                double? checkValueDouble = NumberHelper.ConvertToDouble(checkValue);
                double? matchValueDouble = NumberHelper.ConvertToDouble(checkValue);
                if (checkValueDouble != null && matchValueDouble != null)
                    return checkValueDouble != matchValueDouble;
            }

            // If the value might contain valid Regex
            if (this.Value != null && ContainsRegex(this.Value))
                return !Regex.IsMatch(checkValue, this.Value);

            return !string.Equals(checkValue, this.Value, StringComparison.OrdinalIgnoreCase);
        }

        /// <summary>
        /// Determines if a value is strictly greater than
        /// </summary>
        private bool MatchesGreaterThan(DictionaryBase dictionaryBase)
        {
            // If the key doesn't exist, we count it as null
            if (!dictionaryBase.ContainsKey(this.Key[1]))
                return false;

            // If the value in the dictionary is null
            string? checkValue = dictionaryBase.ReadString(this.Key[1]);
            if (checkValue == null)
                return false;

            // If we have both a potentially numeric check and value
            if (NumberHelper.IsNumeric(checkValue) && NumberHelper.IsNumeric(this.Value))
            {
                // Check Int64 values
                long? checkValueLong = NumberHelper.ConvertToInt64(checkValue);
                long? matchValueLong = NumberHelper.ConvertToInt64(checkValue);
                if (checkValueLong != null && matchValueLong != null)
                    return checkValueLong > matchValueLong;

                // Check Double values
                double? checkValueDouble = NumberHelper.ConvertToDouble(checkValue);
                double? matchValueDouble = NumberHelper.ConvertToDouble(checkValue);
                if (checkValueDouble != null && matchValueDouble != null)
                    return checkValueDouble > matchValueDouble;
            }

            return false;
        }

        /// <summary>
        /// Determines if a value is greater than or equal
        /// </summary>
        private bool MatchesGreaterThanOrEqual(DictionaryBase dictionaryBase)
        {
            // If the key doesn't exist, we count it as null
            if (!dictionaryBase.ContainsKey(this.Key[1]))
                return false;

            // If the value in the dictionary is null
            string? checkValue = dictionaryBase.ReadString(this.Key[1]);
            if (checkValue == null)
                return false;

            // If we have both a potentially numeric check and value
            if (NumberHelper.IsNumeric(checkValue) && NumberHelper.IsNumeric(this.Value))
            {
                // Check Int64 values
                long? checkValueLong = NumberHelper.ConvertToInt64(checkValue);
                long? matchValueLong = NumberHelper.ConvertToInt64(checkValue);
                if (checkValueLong != null && matchValueLong != null)
                    return checkValueLong >= matchValueLong;

                // Check Double values
                double? checkValueDouble = NumberHelper.ConvertToDouble(checkValue);
                double? matchValueDouble = NumberHelper.ConvertToDouble(checkValue);
                if (checkValueDouble != null && matchValueDouble != null)
                    return checkValueDouble >= matchValueDouble;
            }

            return false;
        }

        /// <summary>
        /// Determines if a value is strictly less than
        /// </summary>
        private bool MatchesLessThan(DictionaryBase dictionaryBase)
        {
            // If the key doesn't exist, we count it as null
            if (!dictionaryBase.ContainsKey(this.Key[1]))
                return false;

            // If the value in the dictionary is null
            string? checkValue = dictionaryBase.ReadString(this.Key[1]);
            if (checkValue == null)
                return false;

            // If we have both a potentially numeric check and value
            if (NumberHelper.IsNumeric(checkValue) && NumberHelper.IsNumeric(this.Value))
            {
                // Check Int64 values
                long? checkValueLong = NumberHelper.ConvertToInt64(checkValue);
                long? matchValueLong = NumberHelper.ConvertToInt64(checkValue);
                if (checkValueLong != null && matchValueLong != null)
                    return checkValueLong < matchValueLong;

                // Check Double values
                double? checkValueDouble = NumberHelper.ConvertToDouble(checkValue);
                double? matchValueDouble = NumberHelper.ConvertToDouble(checkValue);
                if (checkValueDouble != null && matchValueDouble != null)
                    return checkValueDouble < matchValueDouble;
            }

            return false;
        }

        /// <summary>
        /// Determines if a value is less than or equal
        /// </summary>
        private bool MatchesLessThanOrEqual(DictionaryBase dictionaryBase)
        {
            // If the key doesn't exist, we count it as null
            if (!dictionaryBase.ContainsKey(this.Key[1]))
                return false;

            // If the value in the dictionary is null
            string? checkValue = dictionaryBase.ReadString(this.Key[1]);
            if (checkValue == null)
                return false;

            // If we have both a potentially numeric check and value
            if (NumberHelper.IsNumeric(checkValue) && NumberHelper.IsNumeric(this.Value))
            {
                // Check Int64 values
                long? checkValueLong = NumberHelper.ConvertToInt64(checkValue);
                long? matchValueLong = NumberHelper.ConvertToInt64(checkValue);
                if (checkValueLong != null && matchValueLong != null)
                    return checkValueLong <= matchValueLong;

                // Check Double values
                double? checkValueDouble = NumberHelper.ConvertToDouble(checkValue);
                double? matchValueDouble = NumberHelper.ConvertToDouble(checkValue);
                if (checkValueDouble != null && matchValueDouble != null)
                    return checkValueDouble <= matchValueDouble;
            }

            return false;
        }

        #endregion

        #region Helpers

        /// <summary>
        /// Determine if a value may contain regex for matching
        /// </summary>
        /// <remarks>
        /// If a value contains one of the following characters:
        ///     ^ $ * ? +
        /// Then it will attempt to check if the value is regex or not.
        /// If none of those characters exist, then value will assumed
        /// not to be regex.
        /// </remarks>
        private static bool ContainsRegex(string? value)
        {
            // If the value is missing, it can't be regex
            if (value == null)
                return false;

            // If we find a special character, try parsing as regex
            if (value.Contains('^')
                || value.Contains('$')
                || value.Contains('*')
                || value.Contains('?')
                || value.Contains('+'))
            {
                try
                {
                    _ = new Regex(value);
                    return true;
                }
                catch
                {
                    return false;
                }
            }

            return false;
        }

        /// <summary>
        /// Derive an operation from the input string, if possible
        /// </summary>
        private static Operation GetOperation(string? operation)
        {
            return operation?.ToLowerInvariant() switch
            {
                "=" => Operation.Equals,
                "==" => Operation.Equals,
                ":" => Operation.Equals,
                "::" => Operation.Equals,

                "!" => Operation.NotEquals,
                "!=" => Operation.NotEquals,
                "!:" => Operation.NotEquals,

                ">" => Operation.GreaterThan,
                ">=" => Operation.GreaterThanOrEqual,

                "<" => Operation.LessThan,
                "<=" => Operation.LessThanOrEqual,

                _ => Operation.NONE,
            };
        }

        /// <summary>
        /// Derive a key, operation, and value from the input string, if possible
        /// </summary>
        private static (string?, Operation, string?) SplitFilterString(string? filterString)
        {
            if (filterString == null)
                return (null, Operation.NONE, null);

            // Split the string using regex
            var match = Regex.Match(filterString, @"^(?<itemField>[a-zA-Z.]+)(?<operation>[=!:><]{1,2})(?<value>.*)$");
            if (!match.Success)
                return (null, Operation.NONE, null);

            string itemField = match.Groups["itemField"].Value;
            Operation operation = GetOperation(match.Groups["operation"].Value);
            string value = match.Groups["value"].Value;

            return (itemField, operation, value);
        }

        #endregion
    }
}