TxSearchApi/BusinessLogic/SearchLogic/SearchLogic.cs

using Datamodels.DatabaseModels;
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Microsoft.Extensions.Logging;
using Repositories.Interfaces;
using Datamodels.BusinessModels;
using Datamodels.SearchModels;
using Newtonsoft.Json;
using System.Linq;
using System.Linq.Expressions;
using SearchApi.Exceptions;
using Datamodels.Enums;

namespace SearchApi.SearchLogic
{
    public class SearchLogic : ISearchLogic
    {
        private readonly ILogger<SearchLogic> _logger;
        private readonly IFwMariaSearchRepo _searchRepo;

        private List<string> _tableNames = new List<string>();
        private List<string> _joinConditions = new List<string>();
        private List<string> _fieldNames = new List<string>();
        private List<string> _whereConditions = new List<string>();
        private List<string> _sortFields = new List<string>();
        
        public SearchLogic(ILogger<SearchLogic> logger, IFwMariaSearchRepo searchRepo)
        {
            _logger = logger;
            _searchRepo = searchRepo;
        }

        public async Task<DataResult<List<Address>>> GetAllAddresses()
        {
            var result = await _searchRepo.GetAllAddresses();
            return result;
        }

        public async Task<DataResult<ResultModel>> GetFilteredData(FilterModel filter, long skip = 0, long take = -1)
        {
            var result = new DataResult<ResultModel>();
            result.Data = new ResultModel();
            result.Data.SearchModel = filter;
            var sql = await Task.Run(() => { return AssembleSqlQuery(filter); } );
            return result;
        }

        // Extract Table
        private void GetTables(FilterModel filter)
        {
            bool hasTableList = filter.TableDescriptions.Count > 0;
            _tableNames = new List<string>();
            foreach(var table in filter.TableDescriptions)
            {
                if (hasTableList && string.IsNullOrEmpty(table.TableAlias))
                {
                    throw new TableAliasMissingException($"No Alias defined for Table {table.TableName}");
                }
                _tableNames.Add($"{table.TableName} {(string.IsNullOrEmpty(table.TableAlias) ? string.Empty : table.TableAlias)}");
            }
        }

        // Extract Fieldlist
        private void GetFields(FilterModel filter)
        {
            var tables = filter.TableDescriptions;
            foreach (var table in tables)
            {
                bool hasMultipleFields = table.Fields.Count > 0;
                foreach (var field in table.Fields) {
                    if (hasMultipleFields && string.IsNullOrEmpty(field.FieldAlias))
                    {
                        throw new FieldAliasMissingException($"No Alias defined for Field {field.FieldName} in Table {table.TableName}");
                    }
                    _fieldNames.Add($"{table.TableAlias}.{field.FieldName} {field.FieldAlias}");

                }
            }
        }

        // Extract Join Path if more than one table
        private void GetTableJoinConditions(FilterModel filter)
        {

        }

        // Extract Where Conditions
        // ToDo: wenn es mehrere Values gibt, werden die generell mit OR verknüpft? Oder nehmen wir lieber AND?
        private void GetWhereConditions(string tableName, FieldModel field)
        {
            if (field.SearchDescriptions.Count > 0)
            {
                foreach (var condition in field.SearchDescriptions)
                {
                    var op = Operator(condition.SearchData.PhraseOperator);
                    if (op != "NOTHING")
                    {
                        var usedField = $"{tableName}.{field.FieldName}{op}{condition.SearchData.Values[0]}";
                        _whereConditions.Add(usedField);
                    }
                    else
                    {
                        if (condition.SearchData.PhraseOperator == PhraseOperators.Contains)
                        {
                            var usedField = $"{tableName}.{field.FieldName} like '%{condition.SearchData.Values[0]}%'";
                            _whereConditions.Add(usedField);
                        }
                        if (condition.SearchData.PhraseOperator == PhraseOperators.StartsWith)
                        {
                            var usedField = $"{tableName}.{field.FieldName} like '%{condition.SearchData.Values[0]}'";
                            _whereConditions.Add(usedField);
                        }
                        if (condition.SearchData.PhraseOperator == PhraseOperators.EndsWith)
                        {
                            var usedField = $"{tableName}.{field.FieldName} like '{condition.SearchData.Values[0]} + %'";
                            _whereConditions.Add(usedField);
                        }
                    }
                }
            }

        }

        public string Operator(PhraseOperators ops)
        {
            switch (ops)
            {
                case PhraseOperators.Equal:
                    return "=";
                case PhraseOperators.NotEqual:
                    return "!=";
                case PhraseOperators.GreaterThan:
                    return ">";
                case PhraseOperators.GreaterThanOrEqual:
                    return ">=";
                case PhraseOperators.LowerThan:
                    return "<";
                case PhraseOperators.LowerThanOrEqual:
                    return "<=";
                default:
                    return "NOTHING";
            }
        }

        // Extract Sort Items
        private void GetSortFields(FilterModel filter)
        {

        }

        // Assemble SQL Query
        private string AssembleSqlQuery(FilterModel filter)
        {
            GetTables(filter);
            GetFields(filter);
            var result = BuildSql();
            return result;
        }

        //Build SQL String itself
        private string BuildSql()
        {
            var sql = "SELECT ";
            foreach (var field in _fieldNames)
            {
                sql += field.ToUpper();
                if (_fieldNames.IndexOf(field) < _fieldNames.Count - 1) sql += ",";
            }

            sql += " FROM ";
            foreach (var table in _tableNames)
            {
                sql += table.ToUpper();
                if (_tableNames.IndexOf(table) < _tableNames.Count - 1)
                {
                    sql += ",";
                }
            }

            return sql;
        }
    }
}