using System;
using System.Collections.Generic;
using System.Linq;
using SyncEngine.Configuration;

namespace SyncEngine.Access
{
    /// <summary>Groups MSysIndexes rows into composite AccessIndexInfo entries.</summary>
    internal static class AccessIndexGrouper
    {
        internal sealed class MsysIndexRow
        {
            public string TableName { get; set; }
            public string IndexName { get; set; }
            public string ColumnName { get; set; }
            public int ColumnOrder { get; set; }
            public bool PrimaryKey { get; set; }
            public bool Unique { get; set; }
        }

        public static IList<AccessIndexInfo> GroupRows(IEnumerable<MsysIndexRow> rows, HashSet<string> tableSet)
        {
            var grouped = new Dictionary<string, AccessIndexInfo>(StringComparer.OrdinalIgnoreCase);
            foreach (var row in rows.OrderBy(r => r.TableName, StringComparer.OrdinalIgnoreCase)
                .ThenBy(r => r.IndexName, StringComparer.OrdinalIgnoreCase)
                .ThenBy(r => r.ColumnOrder))
            {
                if (string.IsNullOrWhiteSpace(row.TableName) ||
                    string.IsNullOrWhiteSpace(row.IndexName) ||
                    string.IsNullOrWhiteSpace(row.ColumnName) ||
                    !tableSet.Contains(row.TableName))
                {
                    continue;
                }

                if (row.IndexName.StartsWith("~", StringComparison.Ordinal))
                {
                    continue;
                }

                var key = row.TableName + "|" + row.IndexName;
                if (!grouped.TryGetValue(key, out var index))
                {
                    index = new AccessIndexInfo
                    {
                        TableName = row.TableName,
                        IndexName = row.IndexName,
                        IsPrimary = row.PrimaryKey,
                        IsUnique = row.Unique || row.PrimaryKey
                    };
                    grouped[key] = index;
                }

                index.Columns.Add(row.ColumnName);
            }

            return grouped.Values
                .Where(i => i.Columns.Count > 0)
                .ToList();
        }
    }
}