using System;

using System.Collections.Generic;

using System.Linq;

using System.Text.RegularExpressions;

​

class HL7Parser

{

    private static List<string> segments;

​

    // Función para dividir el mensaje HL7

    public static void SplitHL7Message(string message)

    {

        // Dividir en segmentos basados en \r o \n

        segments = new List<string>(message.Split(new[] { "\r", "\n" }, StringSplitOptions.RemoveEmptyEntries));

    }

​

    // Función para obtener el campo basado en el accesor de campo

    public static string GetField(string accessor)

    {

        var accessor_elements = accessor.Split(['.']);

​

        var segmentId = "";

        var segmentRepetitionIndex = 0;

​

        var segmentRegex = new Regex(@"(\w+)(?:\[(\d+)\])?"); // segmentId[segmentRepetition]

        var segmentRegexMatch = segmentRegex.Match(accessor_elements[0]);

        if (segmentRegexMatch.Success)

        {

            segmentId = segmentRegexMatch.Groups[1].Value;

            segmentRepetitionIndex = segmentRegexMatch.Groups[2].Value != "" ? int.Parse(segmentRegexMatch.Groups[2].Value) - 1 : 0;

        }

​

        accessor_elements = accessor_elements.Skip(1).ToArray();

​

        var foundSegments = segments.FindAll(s => s.StartsWith(segmentId));

        if (foundSegments.Count <= segmentRepetitionIndex)

        {

            return null;

        }

​

        var segment = foundSegments[segmentRepetitionIndex];

​

        // Obtener los separadores de campos

        var headerSegment = segments[0];

        var fieldSeparator = headerSegment[3];

        var componentSeparator = headerSegment[4];

        var repetitionSeparator = headerSegment[5];

        var escapeCharacter = headerSegment[6];

        var subcomponentSeparator = headerSegment[7];

​

        // Obtener los campos del segmento

        var fields = segment.Substring(segmentId.Length + 1).Split(fieldSeparator).ToArray();

        if (segmentId == "MSH")

        {

            fields = [segmentId, $"{fieldSeparator}", $"{componentSeparator}{repetitionSeparator}{escapeCharacter}{subcomponentSeparator}", .. fields.Skip(1).ToArray()];

        }

        else

        {

            fields = [segmentId, .. fields];

        }

        if (accessor_elements.Length == 0)

        {

            return segment; // Devuelve todo el segmento si no hay un acceso específico

        }

​

        var fieldIndex = 0;

        var repetitionIndex = -1;

​

        var fieldRegex = new Regex(@"(\d+)(?:\[(\d+)\])?"); // field_index[field_repetition]

        var fieldRegexMatch = fieldRegex.Match(accessor_elements[0]);

        if (fieldRegexMatch.Success)

        {

            fieldIndex = int.Parse(fieldRegexMatch.Groups[1].Value);

            repetitionIndex = fieldRegexMatch.Groups[2].Value != "" ? int.Parse(fieldRegexMatch.Groups[2].Value) - 1 : -1;

        }

​

        if (fieldIndex >= fields.Length)

        {

            return null; // El índice especificado está fuera de los límites

        }

​

        var field = fields[fieldIndex];

​

        if (repetitionIndex >= 0)

        {

            var repetitions = field.Split(repetitionSeparator);

            if (repetitionIndex >= repetitions.Length)

            {

                return null; // El índice especificado está fuera del alcance

            }

            field = repetitions[repetitionIndex];

        }

​

        if (accessor_elements.Length == 1)

        {

            return field; // Devuelve el campo si no hay más niveles

        }

​

        // Manejar los niveles adicionales de componentes y subcomponentes

        var currentLevel = field;

​

        for (int i = 1; i < accessor_elements.Length; i++)

        {

            var currentElement = accessor_elements[i];

​

            var componentIndex = int.Parse(currentElement) - 1; // Convertir a base-0

            var components = currentLevel.Split(componentSeparator);

​

            if (componentIndex >= components.Length)

            {

                return null; // El índice especificado está fuera del alcance

            }

            currentLevel = components[componentIndex];

        }

​

        return currentLevel;

    }

​

    public static void Main(string[] args)

    {

        var message = @"MSH|^~\&|TTM||host||20230727170458+0100||SSU^U03^SSU_U03|sQELfcfwyCH2|P|2.5.1|||NE|AL||Unicode UTF-8|||LAB26^IHE~RQPO^ROCHE

EQU|TTM^ROCHE~1234-56^ROCHE|20230727170458|OP

EQU|XXX^ROCHE~5678-61^ROCHE|20240127156789|OP

SAC|||SID||PUUID|||I|HITACHI_917_R^^99ROC|CID|CPOS||||SIO^^99ROC|||||||||||OCAP^^HL70381

SPM|1|SID||“”|||||||P|||||||||||||NCFU^^HL70493|||SCT^^99ROC";

​

        SplitHL7Message(message);

​

        // Ejemplos de uso de GetField 

        Console.WriteLine(GetField("MSH"));          // MSH completo

        Console.WriteLine(GetField("MSH.1"));        // |

        Console.WriteLine(GetField("MSH.2"));        // ^~\&

        Console.WriteLine(GetField("MSH.3"));        // TTM

        Console.WriteLine(GetField("MSH.7"));        // 20230727170458+0100

        Console.WriteLine(GetField("MSH.9"));        // SSU^U03^SSU_U03

        Console.WriteLine(GetField("MSH.9.2"));      // U03

        Console.WriteLine(GetField("EQU.1"));        // TTM^ROCHE~1234-56^ROCHE

        Console.WriteLine(GetField("EQU.1[1].2"));   // ROCHE

        Console.WriteLine(GetField("EQU.1[1].1"));   // TTM

        Console.WriteLine(GetField("EQU.1[2]"));     // 1234-56^ROCHE

        Console.WriteLine(GetField("EQU.1.2"));      // ROCHE

        Console.WriteLine(GetField("SAC.9.3"));   // 99ROC 

        Console.WriteLine(GetField("EQU[2].1"));        // XXX^ROCHE~5678-61^ROCHE

    }

}

​