using System;
using System.Collections.Generic;
using System.Data;
using System.Data.Odbc;
using System.Linq;
using System.Threading.Tasks;
using DataConnection.Interfaces;

namespace DataConnection.EF.SchemaProviders;

/// <summary>
/// Provider di schema per database ODBC generici
/// Utilizza le funzioni ODBC standard per ottenere metadati del database
/// </summary>
public class OdbcSchemaProvider : IDatabaseSchemaProvider
{
    public async Task<IDictionary<string, IEnumerable<DbColumnInfo>>> GetDatabaseSchemaAsync(string connectionString)
    {
        var result = new Dictionary<string, IEnumerable<DbColumnInfo>>();

        try
        {
            using var connection = new OdbcConnection(connectionString);
            await connection.OpenAsync();

            Console.WriteLine($"ODBC Schema Provider - Connesso a: {connection.Database}");
            Console.WriteLine($"Driver: {connection.Driver}");
            Console.WriteLine($"Server Version: {connection.ServerVersion}");

            // Ottieni le tabelle dal database usando GetSchema
            var tablesSchema = connection.GetSchema("Tables");

            // Filtra solo le tabelle utente (esclude views, system tables, ecc.)
            var userTables = tablesSchema.AsEnumerable()
                .Where(row =>
                {
                    var tableType = row["TABLE_TYPE"].ToString();
                    return tableType == "TABLE" || tableType == "BASE TABLE";
                })
                .Select(row => new
                {
                    Schema = row.IsNull("TABLE_SCHEM") ? null : row["TABLE_SCHEM"].ToString(),
                    TableName = row["TABLE_NAME"].ToString() ?? string.Empty,
                    FullName = GetFullTableName(row)
                })
                .Where(t => !string.IsNullOrEmpty(t.TableName))
                .ToList();

            Console.WriteLine($"Trovate {userTables.Count} tabelle utente");

            // Per ogni tabella, ottieni le colonne
            foreach (var table in userTables)
            {
                try
                {
                    var columns = await GetTableColumnsAsync(connection, table.Schema, table.TableName);
                    
                    if (columns.Any())
                    {
                        result[table.FullName] = columns;
                        Console.WriteLine($"Tabella {table.FullName}: {columns.Count()} colonne");
                    }
                }
                catch (Exception ex)
                {
                    Console.WriteLine($"Errore nel leggere le colonne della tabella {table.FullName}: {ex.Message}");
                }
            }

            if (result.Count == 0)
            {
                Console.WriteLine("ATTENZIONE: Nessuna tabella trovata o nessuna colonna leggibile");
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Errore in OdbcSchemaProvider.GetDatabaseSchemaAsync: {ex.Message}");
            throw;
        }

        return result;
    }

    private static string GetFullTableName(DataRow tableRow)
    {
        var schema = tableRow.IsNull("TABLE_SCHEM") ? null : tableRow["TABLE_SCHEM"].ToString();
        var tableName = tableRow["TABLE_NAME"].ToString() ?? string.Empty;

        if (!string.IsNullOrEmpty(schema) && schema != "dbo")
            return $"{schema}.{tableName}";
        
        return tableName;
    }

    private async Task<List<DbColumnInfo>> GetTableColumnsAsync(OdbcConnection connection, string? schemaName, string tableName)
    {
        var columns = new List<DbColumnInfo>();

        try
        {
            // Usa GetSchema per ottenere le colonne
            // Alcuni driver ODBC supportano restrizioni per schema e table name
            string?[] restrictions = new string?[4];
            restrictions[0] = null; // Catalog
            restrictions[1] = schemaName; // Schema
            restrictions[2] = tableName; // Table name
            restrictions[3] = null; // Column name

            DataTable columnsSchema;
            
            try
            {
                columnsSchema = connection.GetSchema("Columns", restrictions);
            }
            catch
            {
                // Alcuni driver non supportano le restrizioni, proviamo senza
                columnsSchema = connection.GetSchema("Columns");
                
                // Filtra manualmente per table name
                columnsSchema = columnsSchema.AsEnumerable()
                    .Where(row => row["TABLE_NAME"].ToString() == tableName)
                    .CopyToDataTable();
            }

            // Ottieni le primary keys per questa tabella
            var primaryKeys = GetPrimaryKeys(connection, schemaName, tableName);

            // Ottieni le foreign keys per questa tabella
            var foreignKeys = GetForeignKeys(connection, schemaName, tableName);

            foreach (DataRow columnRow in columnsSchema.Rows)
            {
                var columnName = columnRow["COLUMN_NAME"].ToString() ?? string.Empty;
                
                if (string.IsNullOrEmpty(columnName))
                    continue;

                var dataType = columnRow["TYPE_NAME"].ToString() ?? "unknown";
                var isNullable = ParseNullable(columnRow["IS_NULLABLE"]);
                
                // Formatta il tipo di dati con dimensioni se disponibili
                var formattedDataType = FormatDataType(dataType, columnRow);

                var columnInfo = new DbColumnInfo
                {
                    Name = columnName,
                    DataType = formattedDataType,
                    IsNullable = isNullable,
                    IsPrimaryKey = primaryKeys.Contains(columnName),
                    IsForeignKey = foreignKeys.ContainsKey(columnName),
                    ReferencedTable = foreignKeys.ContainsKey(columnName) ? foreignKeys[columnName].ReferencedTable : null,
                    ReferencedColumn = foreignKeys.ContainsKey(columnName) ? foreignKeys[columnName].ReferencedColumn : null
                };

                columns.Add(columnInfo);
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Errore nel recuperare le colonne per {tableName}: {ex.Message}");
        }

        return columns;
    }

    private HashSet<string> GetPrimaryKeys(OdbcConnection connection, string? schemaName, string tableName)
    {
        var primaryKeys = new HashSet<string>(StringComparer.OrdinalIgnoreCase);

        try
        {
            string?[] restrictions = new string?[4];
            restrictions[0] = null; // Catalog
            restrictions[1] = schemaName; // Schema
            restrictions[2] = tableName; // Table name
            restrictions[3] = null; // Column name

            var pkSchema = connection.GetSchema("PrimaryKeys", restrictions);
            
            foreach (DataRow row in pkSchema.Rows)
            {
                var columnName = row["COLUMN_NAME"].ToString();
                if (!string.IsNullOrEmpty(columnName))
                    primaryKeys.Add(columnName);
            }
        }
        catch (Exception ex)
        {
            // Alcuni driver ODBC non supportano PrimaryKeys schema collection
            Console.WriteLine($"GetSchema PrimaryKeys non supportato: {ex.Message}");
        }

        return primaryKeys;
    }

    private Dictionary<string, (string ReferencedTable, string ReferencedColumn)> GetForeignKeys(OdbcConnection connection, string? schemaName, string tableName)
    {
        var foreignKeys = new Dictionary<string, (string, string)>(StringComparer.OrdinalIgnoreCase);

        try
        {
            string?[] restrictions = new string?[4];
            restrictions[0] = null; // Catalog
            restrictions[1] = schemaName; // Schema
            restrictions[2] = tableName; // Table name
            restrictions[3] = null; // Column name

            var fkSchema = connection.GetSchema("ForeignKeys", restrictions);

            foreach (DataRow row in fkSchema.Rows)
            {
                var columnName = row["FKCOLUMN_NAME"].ToString();
                var referencedTable = row["PKTABLE_NAME"].ToString();
                var referencedColumn = row["PKCOLUMN_NAME"].ToString();

                if (!string.IsNullOrEmpty(columnName) && !string.IsNullOrEmpty(referencedTable) && !string.IsNullOrEmpty(referencedColumn))
                {
                    foreignKeys[columnName] = (referencedTable, referencedColumn);
                }
            }
        }
        catch (Exception ex)
        {
            // Alcuni driver ODBC non supportano ForeignKeys schema collection
            Console.WriteLine($"GetSchema ForeignKeys non supportato: {ex.Message}");
        }

        return foreignKeys;
    }

    private bool ParseNullable(object? isNullableValue)
    {
        if (isNullableValue == null || isNullableValue == DBNull.Value)
            return true;

        var strValue = isNullableValue.ToString()?.ToUpperInvariant();
        
        return strValue switch
        {
            "YES" => true,
            "NO" => false,
            "1" => true,
            "0" => false,
            _ => true // Default a nullable se non riusciamo a determinarlo
        };
    }

    private string FormatDataType(string dataType, DataRow columnRow)
    {
        try
        {
            // Prova ad ottenere lunghezza/precisione/scala
            var columnSize = columnRow.IsNull("COLUMN_SIZE") ? 0 : Convert.ToInt32(columnRow["COLUMN_SIZE"]);
            var decimalDigits = columnRow.IsNull("DECIMAL_DIGITS") ? 0 : Convert.ToInt32(columnRow["DECIMAL_DIGITS"]);

            var upperDataType = dataType.ToUpperInvariant();

            // Tipi numerici con precisione e scala
            if (upperDataType.Contains("DECIMAL") || upperDataType.Contains("NUMERIC"))
            {
                if (columnSize > 0 && decimalDigits >= 0)
                    return $"{dataType}({columnSize},{decimalDigits})";
            }
            // Tipi stringa con lunghezza
            else if (upperDataType.Contains("CHAR") || upperDataType.Contains("VARCHAR") || 
                     upperDataType.Contains("TEXT") || upperDataType.Contains("STRING"))
            {
                if (columnSize > 0 && columnSize < 8000)
                    return $"{dataType}({columnSize})";
                else if (columnSize >= 8000)
                    return $"{dataType}(MAX)";
            }
            // Tipi floating point
            else if (upperDataType.Contains("FLOAT") || upperDataType.Contains("DOUBLE") || upperDataType.Contains("REAL"))
            {
                if (columnSize > 0)
                    return $"{dataType}({columnSize})";
            }

            return dataType;
        }
        catch
        {
            return dataType;
        }
    }

    public async Task<IEnumerable<string>> GetAvailableDatabasesAsync(string connectionString)
    {
        var databases = new List<string>();

        try
        {
            using var connection = new OdbcConnection(connectionString);
            await connection.OpenAsync();

            // Tenta di ottenere i database disponibili usando GetSchema
            try
            {
                var catalogsSchema = connection.GetSchema("Catalogs");
                
                foreach (DataRow row in catalogsSchema.Rows)
                {
                    var catalogName = row["CATALOG_NAME"]?.ToString();
                    if (!string.IsNullOrEmpty(catalogName))
                        databases.Add(catalogName);
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine($"GetSchema Catalogs non supportato: {ex.Message}");
                
                // Fallback: alcuni driver potrebbero usare "Databases" invece di "Catalogs"
                try
                {
                    var dbSchema = connection.GetSchema("Databases");
                    foreach (DataRow row in dbSchema.Rows)
                    {
                        var dbName = row[0]?.ToString(); // Prima colonna dovrebbe essere il nome
                        if (!string.IsNullOrEmpty(dbName))
                            databases.Add(dbName);
                    }
                }
                catch
                {
                    // Se nemmeno questo funziona, restituisci il database corrente
                    if (!string.IsNullOrEmpty(connection.Database))
                        databases.Add(connection.Database);
                }
            }
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Errore in GetAvailableDatabasesAsync: {ex.Message}");
        }

        return databases;
    }

    public async Task<IEnumerable<string>> GetTableNamesAsync(string connectionString)
    {
        var tableNames = new List<string>();

        try
        {
            using var connection = new OdbcConnection(connectionString);
            await connection.OpenAsync();

            var tablesSchema = connection.GetSchema("Tables");

            tableNames = tablesSchema.AsEnumerable()
                .Where(row =>
                {
                    var tableType = row["TABLE_TYPE"].ToString();
                    return tableType == "TABLE" || tableType == "BASE TABLE";
                })
                .Select(row => GetFullTableName(row))
                .Where(name => !string.IsNullOrEmpty(name))
                .ToList();
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Errore in GetTableNamesAsync: {ex.Message}");
        }

        return tableNames;
    }

    public async Task<IEnumerable<DbColumnInfo>> GetTableSchemaAsync(string connectionString, string tableName)
    {
        try
        {
            using var connection = new OdbcConnection(connectionString);
            await connection.OpenAsync();

            // Separa schema e nome tabella se presente il punto
            string? schemaName = null;
            string actualTableName = tableName;

            if (tableName.Contains('.'))
            {
                var parts = tableName.Split('.');
                schemaName = parts[0];
                actualTableName = parts[1];
            }

            return await GetTableColumnsAsync(connection, schemaName, actualTableName);
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Errore in GetTableSchemaAsync per {tableName}: {ex.Message}");
            return Enumerable.Empty<DbColumnInfo>();
        }
    }
}