using Soul2.Tools.General;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Soul2.Tools.sql {

    /// <summary>
    /// SQL语句简单生成器
    /// </summary>
    public class SqlBuilder {
        private class WhereItem {
            public string Key { get; set; }
            public string Value { get; set; }

            public WhereItem(string key, string value) {
                Key = key;
                Value = value;
            }
        }

        private List<WhereItem> _where;
        private List<string> _select;
        private string _tbName;
        private List<string> _isNullList;
        private string _lastJoin;

        public SqlBuilder(string tbName) {
            _tbName = tbName;
            _where = new List<WhereItem>();
            _select = new List<string>();
            _isNullList = new List<string>();
        }

        public SqlBuilder Where(string whichCol, string whatValue) {
            _where.Add(new WhereItem(whichCol, whatValue));
            return this;
        }

        public SqlBuilder Select(string select) {
            _select.Add(select);
            return this;
        }

        public SqlBuilder IsNull(string col) {
            _isNullList.Add($"{col} is null");
            return this;
        }

        public SqlBuilder IsNotNull(string col) {
            _isNullList.Add($"{col} is not null");
            return this;
        }

        public SqlBuilder Last(string lastSql) {
            _lastJoin = lastSql;
            return this;
        }

        public string Build() {
            var select = "*";
            if (_select.Count > 0) {
                select = string.Join(", ", _select);
            }
            var sql = $"select {select} from {_tbName}";
            if (_where.Count > 0) {
                var whereBuilder = new StringBuilder();
                foreach (var item in _where) {
                    if (_where.IndexOf(item) != 0) {
                        whereBuilder.Append(" and ");
                    }
                    whereBuilder.Append($"{item.Key} = @{item.Key}");
                }
                sql += $" where {whereBuilder}";
            }
            if (_isNullList.Count > 0) {
                foreach (var item in _isNullList) {
                    sql += $" {item}";
                }
            }
            sql += _lastJoin;
            return sql;
        }
    }
}