using DevLab.JmesPath.Functions;
using DevLab.JmesPath.Utils;
using Newtonsoft.Json.Linq;
using System.Text.RegularExpressions;

namespace afd_2._0.webapi.example.JMESPathCustomFunctions
{
    /// <summary>
    /// This class provides JMESPath Custom Function ageAtReferenceDate, for a YYY-MM-DD formattted date string.
    /// </summary>
    public class AgeAtReferenceDateFunction : JmesPathFunction
    {
        /// <summary>
        /// JMESPath custom function Name
        /// </summary>
        const string cFunctionName = "ageAtReferenceDate";

        /// <summary>
        /// JMESPath custom function number of arguments
        /// </summary>
        const int cNumberOfArguments = 2;

        /// <summary>
        /// regex to validate the subjectDateString argument
        /// </summary>
        const string cDateRegex = @"^(?<years>[0-9]+)[-](?<months>[0-9]+)[-](?<days>[0-9]+)$";

        /// <summary>
        /// Define Custom Function
        /// </summary>
        public AgeAtReferenceDateFunction()
            : base(cFunctionName, cNumberOfArguments)
        {
        }

        /// <summary>
        /// Validate this custom function arguments
        /// </summary>
        /// <param name="arguments"></param>
        /// <exception cref="Exception"></exception>
        public override void Validate(params JmesPathFunctionArgument[] arguments)
        {
            base.Validate(arguments);
            if (arguments.Length != cNumberOfArguments)
            {
                throw new Exception($"Error: invalid-arity, JmesPath Custom Function '{nameof(AgeAtReferenceDateFunction)}' expects {cNumberOfArguments} argument(s), but gets {arguments.Length} arguments.");
            }

            var subjectDateString = arguments[0];
            var dateRegex = new Regex(cDateRegex);
            if (arguments[0].Token.GetTokenType() != "string")
            {
                throw new Exception($"Error: invalid-value, JmesPath Custom Function '{nameof(AgeAtReferenceDateFunction)}' expects the subjectDate to be a string.");
            }
            var referenceDateString = arguments[1];
            if (arguments[1].Token.GetTokenType() != "string")
            {
                throw new Exception($"Error: invalid-value, JmesPath Custom Function '{nameof(AgeAtReferenceDateFunction)}' expects the referenceDate to be a string.");
            }

            var subjectDateValue = subjectDateString.Token.Value<string>() ?? string.Empty;
                        var referenceDateValue = referenceDateString.Token.Value<string>() ?? string.Empty;
            if (!dateRegex.Match(subjectDateValue).Success)
            {
                throw new Exception($"Error: invalid-value, JmesPath Custom Function '{nameof(AgeAtReferenceDateFunction)}' expects the subjectDate '{subjectDateValue}' to be formatted as 'yyyy-dd-mm'.");
            };
            if (!dateRegex.Match(referenceDateValue).Success)
            {
                throw new Exception($"Error: invalid-value, JmesPath Custom Function '{nameof(AgeAtReferenceDateFunction)}' expects the referenceDate '{referenceDateValue}' to be formatted as 'yyyy-dd-mm'.");
            };
            if (!DateOnly.TryParse(subjectDateValue, out var subjectDate))
            {
                throw new Exception($"Error: invalid-value, JmesPath Custom Function '{nameof(AgeAtReferenceDateFunction)}' found an invalid subjectDate '{subjectDateValue}'.");
            }
            if (!DateOnly.TryParse(referenceDateValue, out var referenceDate))
            {
                throw new Exception($"Error: invalid-value, JmesPath Custom Function '{nameof(AgeAtReferenceDateFunction)}' found an invalid referenceDate '{referenceDateValue}'.");
            }
            if (referenceDate < subjectDate)
            {
                throw new Exception($"Error: invalid-values, JmesPath Custom Function '{nameof(AgeAtReferenceDateFunction)}' referenceDate must be >= subjectdate '{referenceDateValue}'.");
            }
        }

        /// <summary>
        /// Calculate subject age in years at reference date.
        /// </summary>
        /// <param name="arguments">
        ///     arguments[0] subjectDate in "YYYY-MM-DD" format.
        ///     arguments[1] referenceDate in "YYYY-MM-DD" format.
        /// </param>
        /// <returns>Subject age in full years at reference date.</returns>
        /// <exception cref="Exception"></exception>
        public override JToken Execute(params JmesPathFunctionArgument[] arguments)
        {
            var regex = new Regex(cDateRegex);

            // Determine subject date parts
            var subjectDateString = arguments[0].Token.Value<string>() ?? string.Empty;
            var subjectMatch = regex.Match(subjectDateString);
            var subjectYears = int.Parse(subjectMatch.Groups["years"].Value);
            var subjectMonths = int.Parse(subjectMatch.Groups["months"].Value);
            var subjectDays = int.Parse(subjectMatch.Groups["days"].Value);

            // Determine reference date parts
            var referenceDateString = arguments[1].Token.Value<string>() ?? string.Empty;
            var referenceMatch = regex.Match(referenceDateString);
            var referenceYears = int.Parse(referenceMatch.Groups["years"].Value);
            var referenceMonths = int.Parse(referenceMatch.Groups["months"].Value);
            var referenceDays = int.Parse(referenceMatch.Groups["days"].Value);

            // Calculate subject date and reference date values
            var subjectDateValue = 100 * (100 * subjectYears + subjectMonths) + subjectDays;
            var referenceDateValue = 100 * (100 * referenceYears + referenceMonths) + referenceDays;

            // Calculate subject date in years at reference date.
            var ageInYears = (referenceDateValue - subjectDateValue) / 10000;

            return new JValue(ageInYears);
        }
    }
}