/*
 *    The contents of this file are subject to the Initial
 *    Developer's Public License Version 1.0 (the "License");
 *    you may not use this file except in compliance with the
 *    License. You may obtain a copy of the License at
 *    https://github.com/FirebirdSQL/NETProvider/raw/master/license.txt.
 *
 *    Software distributed under the License is distributed on
 *    an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, either
 *    express or implied. See the License for the specific
 *    language governing rights and limitations under the License.
 *
 *    All Rights Reserved.
 */

//$Authors = Jiri Cincura (jiri@cincura.net)

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.Common;
using System.Linq;
using FirebirdSql.Data.FirebirdClient;
using FirebirdSql.Data.Services;
using Microsoft.EntityFrameworkCore.Metadata;
using Microsoft.EntityFrameworkCore.Migrations;
using Microsoft.EntityFrameworkCore.Scaffolding;
using Microsoft.EntityFrameworkCore.Scaffolding.Metadata;
using Microsoft.Extensions.Logging;

namespace FirebirdSql.EntityFrameworkCore.Firebird.Scaffolding.Internal;

public class FbDatabaseModelFactory : DatabaseModelFactory
{
	public int MajorVersionNumber { get; private set; }

	public override DatabaseModel Create(string connectionString, DatabaseModelFactoryOptions options)
	{
		using (var connection = new FbConnection(connectionString))
		{
			return Create(connection, options);
		}
	}

	public override DatabaseModel Create(DbConnection connection, DatabaseModelFactoryOptions options)
	{
		var databaseModel = new DatabaseModel();

		var connectionStartedOpen = connection.State == ConnectionState.Open;
		if (!connectionStartedOpen)
		{
			connection.Open();
		}

		var serverVersion = FbServerProperties.ParseServerVersion(connection.ServerVersion);
		MajorVersionNumber = serverVersion.Major;

		try
		{
			databaseModel.DatabaseName = connection.Database;
			databaseModel.DefaultSchema = GetDefaultSchema(connection);

			var schemaList = new List<string>();
			var tableList = options.Tables.ToList();
			var tableFilter = GenerateTableFilter(tableList, schemaList);

			var tables = GetTables(connection, tableFilter);
			foreach (var table in tables)
			{
				table.Database = databaseModel;
				if (tableFilter.Invoke(table))
				{
					databaseModel.Tables.Add(table);
				}
			}

			return databaseModel;
		}
		finally
		{
			if (!connectionStartedOpen)
			{
				connection.Close();
			}
		}
	}

	private static string GetDefaultSchema(DbConnection connection)
	{
		return null;
	}

	private static Func<DatabaseTable, bool> GenerateTableFilter(IReadOnlyList<string> tables, IReadOnlyList<string> schemas)
	{
		return tables.Any() ? x => tables.Contains(x.Name) : _ => true;
	}

	private const string GetTablesQuery =
		@"SELECT
                trim(r.RDB$RELATION_NAME),
                r.RDB$DESCRIPTION,
                r.RDB$RELATION_TYPE
              FROM
               RDB$RELATIONS r
             WHERE
              r.RDB$SYSTEM_FLAG is distinct from 1
             ORDER BY
              r.RDB$RELATION_NAME";

	private IEnumerable<DatabaseTable> GetTables(DbConnection connection, Func<DatabaseTable, bool> filter)
	{
		using (var command = connection.CreateCommand())
		{
			var tables = new List<DatabaseTable>();
			command.CommandText = GetTablesQuery;
			using (var reader = command.ExecuteReader())
			{
				while (reader.Read())
				{
					var name = reader.GetString(0);
					var comment = reader.GetString(1);
					var type = reader.GetInt32(2);

					var table = type == 0
						? new DatabaseTable()
						: new DatabaseView();

					table.Schema = null;
					table.Name = name;
					table.Comment = string.IsNullOrEmpty(comment) ? null : comment;

					tables.Add(table);
				}
			}

			GetColumns(connection, tables, filter);
			GetPrimaryKeys(connection, tables);
			GetIndexes(connection, tables, filter);
			GetConstraints(connection, tables);

			return tables;
		}
	}

	private const string GetColumnsQuery =
		@"SELECT
               trim(RF.RDB$FIELD_NAME) as COLUMN_NAME,
               COALESCE(RF.RDB$DEFAULT_SOURCE, F.RDB$DEFAULT_SOURCE) as COLUMN_DEFAULT,
               COALESCE(COALESCE(RF.RDB$NULL_FLAG, F.RDB$NULL_FLAG), 0) as NOT_NULL,
               CASE Coalesce(F.RDB$FIELD_TYPE, 0)
                WHEN 7 THEN
                 CASE F.RDB$FIELD_SUB_TYPE
                  WHEN 0 THEN 'SMALLINT'
			      WHEN 1 THEN 'NUMERIC(' || (F.RDB$FIELD_PRECISION) || ',' || ABS(F.RDB$FIELD_SCALE) || ')'
			      WHEN 2 THEN 'DECIMAL(' || (F.RDB$FIELD_PRECISION) || ',' || ABS(F.RDB$FIELD_SCALE) || ')'
				  ELSE '?'
                 END
                WHEN 8 THEN
                 CASE F.RDB$FIELD_SUB_TYPE
                  WHEN 0 THEN 'INTEGER'
			      WHEN 1 THEN 'NUMERIC(' || (F.RDB$FIELD_PRECISION) || ',' || ABS(F.RDB$FIELD_SCALE) || ')'
			      WHEN 2 THEN 'DECIMAL(' || (F.RDB$FIELD_PRECISION) || ',' || ABS(F.RDB$FIELD_SCALE) || ')'
				  ELSE '?'
                 END
				WHEN 9 THEN 'QUAD'
				WHEN 10 THEN 'FLOAT'
				WHEN 12 THEN 'DATE'
				WHEN 13 THEN 'TIME'
				WHEN 14 THEN 'CHAR(' || (TRUNC(F.RDB$FIELD_LENGTH / CH.RDB$BYTES_PER_CHARACTER)) || ')'
				WHEN 16 THEN
				 CASE F.RDB$FIELD_SUB_TYPE
				  WHEN 0 THEN 'BIGINT'
			      WHEN 1 THEN 'NUMERIC(' || (F.RDB$FIELD_PRECISION) || ',' || ABS(F.RDB$FIELD_SCALE) || ')'
			      WHEN 2 THEN 'DECIMAL(' || (F.RDB$FIELD_PRECISION) || ',' || ABS(F.RDB$FIELD_SCALE) || ')'
				  ELSE '?'
				 END
				WHEN 23 THEN 'BOOLEAN'
				WHEN 27 THEN 'DOUBLE PRECISION'
				WHEN 35 THEN 'TIMESTAMP'
				WHEN 37 THEN 'VARCHAR(' || (TRUNC(F.RDB$FIELD_LENGTH / CH.RDB$BYTES_PER_CHARACTER)) || ')'
				WHEN 40 THEN 'CSTRING' || (TRUNC(F.RDB$FIELD_LENGTH / CH.RDB$BYTES_PER_CHARACTER)) || ')'
				WHEN 45 THEN 'BLOB_ID'
				WHEN 261 THEN 'BLOB SUB_TYPE ' ||
				  CASE F.RDB$FIELD_SUB_TYPE
					WHEN 0 THEN 'BINARY'
					WHEN 1 THEN 'TEXT'
					ELSE F.RDB$FIELD_SUB_TYPE
				  END
				ELSE 'RDB$FIELD_TYPE: ' || F.RDB$FIELD_TYPE || '?'
			   END as STORE_TYPE,
               F.rdb$description as COLUMN_COMMENT,
               COALESCE({1}, 0)   as AUTO_GENERATED,
               ch.RDB$CHARACTER_SET_NAME as CHARACTER_SET_NAME
              FROM
               RDB$RELATION_FIELDS RF
               JOIN  RDB$FIELDS F ON(F.RDB$FIELD_NAME = RF.RDB$FIELD_SOURCE)
               LEFT OUTER JOIN  RDB$CHARACTER_SETS CH ON(CH.RDB$CHARACTER_SET_ID = F.RDB$CHARACTER_SET_ID)
              WHERE
               trim(RF.RDB$RELATION_NAME) = '" + "{0}" + @"'
               AND COALESCE(RF.RDB$SYSTEM_FLAG, 0) = 0
             ORDER BY
              RF.RDB$FIELD_POSITION;";

	private void GetColumns(DbConnection connection, IReadOnlyList<DatabaseTable> tables, Func<DatabaseTable, bool> tableFilter)
	{
		var identityType = MajorVersionNumber < 3 ? "null" : "rf.RDB$IDENTITY_TYPE";

		foreach (var table in tables)
		{
			using (var command = connection.CreateCommand())
			{
				command.CommandText = string.Format(GetColumnsQuery, table.Name, identityType);
				using (var reader = command.ExecuteReader())
				{
					while (reader.Read())
					{
						var name = reader["COLUMN_NAME"].ToString();
						var defaultValue = reader["COLUMN_DEFAULT"].ToString();
						var nullable = !Convert.ToBoolean(reader["NOT_NULL"]);
						var autoGenerated = Convert.ToBoolean(reader["AUTO_GENERATED"]);
						var storeType = reader["STORE_TYPE"].ToString();
						var charset = reader["CHARACTER_SET_NAME"].ToString();
						var comment = reader["COLUMN_COMMENT"].ToString();


						var valueGenerated = ValueGenerated.Never;

						if (autoGenerated)
						{
							valueGenerated = ValueGenerated.OnAdd;
						}

						var column = new DatabaseColumn
						{
							Table = table,
							Name = name,
							StoreType = storeType,
							IsNullable = nullable,
							DefaultValueSql = CreateDefaultValueString(defaultValue),
							ValueGenerated = valueGenerated,
							Comment = string.IsNullOrEmpty(comment) ? null : comment,
						};

						table.Columns.Add(column);
					}
				}
			}
		}
	}

	private string CreateDefaultValueString(string defaultValue)
	{
		if (defaultValue == null)
		{
			return null;
		}
		if (defaultValue.StartsWith("default "))
		{
			return defaultValue.Remove(0, 8);
		}
		else
		{
			return null;
		}

	}

	private const string GetPrimaryQuery =
	@"SELECT
           trim(i.rdb$index_name) as INDEX_NAME,
           trim(sg.rdb$field_name) as FIELD_NAME
          FROM
           RDB$INDICES i
           LEFT JOIN rdb$index_segments sg on i.rdb$index_name = sg.rdb$index_name
           LEFT JOIN rdb$relation_constraints rc on rc.rdb$index_name = I.rdb$index_name
          WHERE
           rc.rdb$constraint_type = 'PRIMARY KEY'
           AND trim(i.rdb$relation_name) = '{0}'
          ORDER BY sg.RDB$FIELD_POSITION;";

	private void GetPrimaryKeys(DbConnection connection, IReadOnlyList<DatabaseTable> tables)
	{
		foreach (var x in tables)
		{
			using (var command = connection.CreateCommand())
			{
				command.CommandText = string.Format(GetPrimaryQuery, x.Name);

				using (var reader = command.ExecuteReader())
				{
					DatabasePrimaryKey index = null;
					while (reader.Read())
					{
						if (index == null)
						{
							index = new DatabasePrimaryKey
							{
								Table = x,
								Name = reader.GetString(0).Trim()
							};
						}
						index.Columns.Add(x.Columns.Single(y => y.Name == reader.GetString(1).Trim()));
						x.PrimaryKey = index;
					}
				}
			}
		}
	}

	private const string GetIndexesQuery =
		@"SELECT
               trim(I.rdb$index_name) as INDEX_NAME,
               COALESCE(I.rdb$unique_flag, 0) as IS_UNIQUE,
               Coalesce(I.rdb$index_type, 0) as IS_DESC,
               list(trim(sg.RDB$FIELD_NAME)) as COLUMNS
              FROM
               RDB$INDICES i
               LEFT JOIN rdb$index_segments sg on i.rdb$index_name = sg.rdb$index_name
               LEFT JOIN rdb$relation_constraints rc on rc.rdb$index_name = I.rdb$index_name and rc.rdb$constraint_type = null
              WHERE
               trim(i.rdb$relation_name) = '{0}'
              GROUP BY
               INDEX_NAME, IS_UNIQUE, IS_DESC ;";

	/// <remarks>
	/// Primary keys are handled as in <see cref="GetConstraints"/>, not here
	/// </remarks>
	private void GetIndexes(DbConnection connection, IReadOnlyList<DatabaseTable> tables, Func<DatabaseTable, bool> tableFilter)
	{
		foreach (var table in tables)
		{
			using (var command = connection.CreateCommand())
			{
				command.CommandText = string.Format(GetIndexesQuery, table.Name);

				using (var reader = command.ExecuteReader())
				{
					while (reader.Read())
					{
						var index = new DatabaseIndex
						{
							Table = table,
							Name = reader.GetString(0).Trim(),
							IsUnique = reader.GetBoolean(1),
						};

						foreach (var column in reader.GetString(3).Split(','))
						{
							index.Columns.Add(table.Columns.Single(y => y.Name == column.Trim()));
						}

						if (reader.GetBoolean(2))
						{
							var isDescending = new bool[index.Columns.Count];
							isDescending.AsSpan().Fill(true);
							index.IsDescending = isDescending;
						}

						table.Indexes.Add(index);
					}
				}
			}
		}
	}

	private const string GetConstraintsQuery =
		@"SELECT
               trim(drs.rdb$constraint_name) as CONSTRAINT_NAME,
               trim(drs.RDB$RELATION_NAME) as TABLE_NAME,
               trim(mrc.rdb$relation_name) AS REFERENCED_TABLE_NAME,
               (select list(trim(di.rdb$field_name)||'|'||trim(mi.rdb$field_name))
                from
                 rdb$index_segments di
                 join rdb$index_segments mi on mi.RDB$FIELD_POSITION=di.RDB$FIELD_POSITION and mi.rdb$index_name = mrc.rdb$index_name
                where
                 di.rdb$index_name = drs.rdb$index_name) as PAIRED_COLUMNS,
               trim(rc.RDB$DELETE_RULE) as DELETE_RULE
              FROM
               rdb$relation_constraints drs
               left JOIN rdb$ref_constraints rc ON drs.rdb$constraint_name = rc.rdb$constraint_name
               left JOIN rdb$relation_constraints mrc ON rc.rdb$const_name_uq = mrc.rdb$constraint_name
              WHERE
               drs.rdb$constraint_type = 'FOREIGN KEY'
               AND trim(drs.RDB$RELATION_NAME) = '{0}' ";

	private void GetConstraints(DbConnection connection, IReadOnlyList<DatabaseTable> tables)
	{
		foreach (var table in tables)
		{
			using (var command = connection.CreateCommand())
			{
				command.CommandText = string.Format(GetConstraintsQuery, table.Name);
				using (var reader = command.ExecuteReader())
				{
					while (reader.Read())
					{
						var referencedTableName = reader.GetString(2);
						var referencedTable = tables.First(t => t.Name == referencedTableName);
						var fkInfo = new DatabaseForeignKey { Name = reader.GetString(0), OnDelete = ConvertToReferentialAction(reader.GetString(4)), Table = table, PrincipalTable = referencedTable };
						foreach (var pair in reader.GetString(3).Split(','))
						{
							fkInfo.Columns.Add(table.Columns.Single(y =>
								string.Equals(y.Name, pair.Split('|')[0], StringComparison.OrdinalIgnoreCase)));
							fkInfo.PrincipalColumns.Add(fkInfo.PrincipalTable.Columns.Single(y =>
								string.Equals(y.Name, pair.Split('|')[1], StringComparison.OrdinalIgnoreCase)));
						}

						table.ForeignKeys.Add(fkInfo);
					}
				}
			}
		}
	}

	private static ReferentialAction? ConvertToReferentialAction(string onDeleteAction)
	{
		return onDeleteAction.ToUpperInvariant() switch
		{
			"RESTRICT" => ReferentialAction.Restrict,
			"CASCADE" => ReferentialAction.Cascade,
			"SET NULL" => ReferentialAction.SetNull,
			"NO ACTION" => ReferentialAction.NoAction,
			_ => null,
		};
	}
}
