using System.Collections.Generic;
using System.Text;
using System.Linq;
using AyaNova.Biz;

namespace AyaNova.PickList
{

    internal static class PickListSqlBuilder
    {
        //Maximum number of results to return at any given time
        //did a little research and may adjust this but it can be fairly girthy in this day and age
        //and many people might not want or need to autocomplete type if we provide enough leeway.
        //for example, if you're selecting a 
        const int MAXIMUM_RESULT_COUNT = 100;

        //Build the query for a picklist request
        internal static string Build(IAyaPickList pickList, List<string> templateColumnNames, string autoCompleteQuery, bool IncludeInactive)
        {


            //determine this in advance as it will be used in a loop later
            bool HasAutoCompleteQuery = !string.IsNullOrWhiteSpace(autoCompleteQuery);

            //lists to collect the clauses so to avoid comma fuckery
            List<string> lSelect = new List<string>();
            string ActiveWhereFragment = string.Empty;
            List<string> lWhere = new List<string>();
            List<string> lOrderBy = new List<string>();


            //Add rowid column as it's always required
            AyaPickListFieldDefinition rowIdColumn = pickList.ColumnDefinitions.FirstOrDefault(x => x.IsRowId == true);
            //this should only happen with a development error
            if (rowIdColumn == null)
                throw new System.ArgumentNullException($"DEV ERROR in PickListSqlBuilder.cs: picklist for {pickList.DefaultListObjectType.ToString()} has no rowId column specified in columnDefinitions list");
            lSelect.Add(rowIdColumn.SqlIdColumnName + " AS rowid");

            //add active only as default for all lists unless inactive is specified
            if (!IncludeInactive)
            {
                AyaPickListFieldDefinition activeColumn = pickList.ColumnDefinitions.FirstOrDefault(x => x.IsActiveColumn == true);
                //it's ok if there is no active column, it could happen so just roll with it
                if (activeColumn != null)
                {
                    lSelect.Add(activeColumn.SqlValueColumnName);
                    ActiveWhereFragment = activeColumn.SqlValueColumnName + " = true";
                }
            }

            foreach (string ColumnName in templateColumnNames)
            {

                AyaPickListFieldDefinition o = pickList.ColumnDefinitions.FirstOrDefault(x => x.FieldKey == ColumnName);
#if (DEBUG)                
                if (o == null)
                {
                    throw new System.ArgumentNullException($"DEV ERROR in PickListSqlBuilder.cs: field {ColumnName} specified in template was NOT found in columnDefinitions list");
                }
#endif
                if (o != null)
                {//Ignore missing fields in production

                    var valueColumnName = o.GetSqlValueColumnName();

                    // 
                    // 



                    string sWhere = string.Empty;

                    //Tags column
                    if (o.ColumnDataType == UiFieldDataType.Tags)
                    {
                        //Handle tags for each part of the sql query
                        //idea is they display as a comma separated list
                        //filter as a like comparison to each individual tag
                        //order by the array which appears to do it left to right as if it was a giant string

                        lSelect.Add($"(array_to_string({valueColumnName},',')");
                        //tags can order by without the arraytostring
                        lOrderBy.Add(valueColumnName);

                        //THIS is the best filter method for a like comparison to each individual tag:
                        //(array_to_string(awidget.tags,',') like '%zo%')
                        if (HasAutoCompleteQuery)
                            sWhere = $"(array_to_string({valueColumnName},',') like '%{autoCompleteQuery}%')";

                    }
                    else if (o.ColumnDataType == UiFieldDataType.Text || o.ColumnDataType == UiFieldDataType.EmailAddress || o.ColumnDataType == UiFieldDataType.HTTP)
                    {
                        //regular text field, no special requirements
                        lSelect.Add(valueColumnName);
                        lOrderBy.Add(valueColumnName);
                        if (HasAutoCompleteQuery)
                            sWhere = $"({valueColumnName} LIKE '%{autoCompleteQuery}%')";
                    }
                    else
                    {

                        //if any part of a select contatenation query using the || postgres concat is text then all fields are automatically converted to text
                        //so no need to make it text here as the automatic spacing character will force the whole thing to a text concat anyway 
                        //ref: https://stackoverflow.com/a/19943343/8939
                        lSelect.Add(valueColumnName);

                        //order by for now seems to be best as just order by it's value whatever it is
                        lOrderBy.Add(valueColumnName);

                        //needs to be cast to text to query on it
                        //(cast (awidget.serial as text) like '%some%')
                        if (HasAutoCompleteQuery)
                            sWhere = $"(cast ({valueColumnName} as text) LIKE '%{autoCompleteQuery}%')";
                    }


                    if (HasAutoCompleteQuery)
                        lWhere.Add(sWhere);


                }
            }

            StringBuilder sb = new StringBuilder();

            //SELECT
            sb.Append("select ");
            //select name || ' ' || serial || ' ' || array_to_string(tags,',') as display from awidget
            foreach (string s in lSelect)
            {
                sb.Append(s);
                sb.Append(",");
            }
            //clear trailing comma
            sb.Length--;

            //FROM
            sb.Append(" ");
            sb.Append(pickList.SQLFrom);


            //WHERE           
            sb.Append(" where ");
            if (!IncludeInactive)
            {
                sb.Append(ActiveWhereFragment);
                sb.Append(" and (");
            }

            foreach (string s in lWhere)
            {
                sb.Append(s);
                sb.Append(" or ");
            }
            //clear trailing or
            sb.Length -= 4;
            //enclosing parenthesis
            if (!IncludeInactive)
            {
                sb.Append(")");
            }

            //ORDER BY
            sb.Append(" order by ");
            foreach (string s in lOrderBy)
            {
                sb.Append(s);
                sb.Append(",");
            }
            //clear trailing comma
            sb.Length--;

            //LIMIT          
            sb.Append($" limit {MAXIMUM_RESULT_COUNT}");

            return sb.ToString();

        }



    }//eoc
}//ens