using System;
using System.Collections.Generic;
using System.Data;
using System.Data.Common;
using System.Linq;
using System.Linq.Expressions;
using System.Threading.Tasks;
using DataConnection.Interfaces;
using Microsoft.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore.Infrastructure;
using Microsoft.EntityFrameworkCore.Metadata;
using Microsoft.Data.SqlClient;

namespace DataConnection.EF;

/// <summary>
/// Implementazione di IExistingDatabaseManager basata su Entity Framework Core
/// </summary>
public class EFCoreDatabaseManager : IDatabaseManager
{
    private readonly DbManagerOptions _options;
    private ExistingDatabaseContext _context = null!;
    
    public EFCoreDatabaseManager(DbManagerOptions options)
    {
        _options = options ?? throw new ArgumentNullException(nameof(options));
        InitializeContext();
    }
    
    private void InitializeContext()
    {
        var optionsBuilder = new DbContextOptionsBuilder<ExistingDatabaseContext>();
        _options.DbContextConfigurator(optionsBuilder);
        
        _context = new ExistingDatabaseContext(
            optionsBuilder.Options,
            _options.ModelConfigurator,
            _options.EnableAutoDiscovery,
            _options.EntityAssembly,
            _options.EntityNamespace,
            _options.NamingStrategy);
    }
    
    public async Task<bool> TestConnectionAsync()
    {
        try
        {
            return await _context.Database.CanConnectAsync();
        }
        catch
        {
            return false;
        }
    }
    
    public async Task<IEnumerable<T>> GetAsync<T>(
        Expression<Func<T, bool>>? filter = null,
        Func<IQueryable<T>, IOrderedQueryable<T>>? orderBy = null,
        string includeProperties = "",
        int? skip = null,
        int? take = null) where T : class
    {
        IQueryable<T> query = _context.Set<T>();
        
        if (filter != null)
        {
            query = query.Where(filter);
        }
        
        foreach (var includeProperty in includeProperties.Split
            (new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries))
        {
            query = query.Include(includeProperty);
        }
        
        if (orderBy != null)
        {
            query = orderBy(query);
        }
        
        if (skip.HasValue)
        {
            query = query.Skip(skip.Value);
        }
        
        if (take.HasValue)
        {
            query = query.Take(take.Value);
        }
        
        return await query.ToListAsync();
    }
    
    public async Task<T?> GetByIdAsync<T>(object id) where T : class
    {
        return await _context.Set<T>().FindAsync(id);
    }
    
    public async Task<IEnumerable<T>> ExecuteQueryAsync<T>(string sql, params object[] parameters) where T : class
    {
        return await _context.Set<T>().FromSqlRaw(sql, parameters).ToListAsync();
    }
    
    public async Task<List<Dictionary<string, object>>> ExecuteRawQueryAsync(string sql, params object[] parameters)
    {
        using var command = _context.Database.GetDbConnection().CreateCommand();
        command.CommandText = sql;
        
        // Aggiungi i parametri
        for (int i = 0; i < parameters.Length; i++)
        {
            var parameter = command.CreateParameter();
            parameter.ParameterName = $"@p{i}";
            parameter.Value = parameters[i] ?? DBNull.Value;
            command.Parameters.Add(parameter);
        }
        
        await _context.Database.OpenConnectionAsync();
        
        var results = new List<Dictionary<string, object>>();
        
        using var reader = await command.ExecuteReaderAsync();
        
        while (await reader.ReadAsync())
        {
            var row = new Dictionary<string, object>();
            
            for (int i = 0; i < reader.FieldCount; i++)
            {
                var columnName = reader.GetName(i);
                var value = reader.IsDBNull(i) ? null : reader.GetValue(i);
                row[columnName] = value ?? "";  // Usa stringa vuota invece di null
            }
            
            results.Add(row);
        }
        
        return results;
    }
    
    public async Task<int> ExecuteCommandAsync(string sql, params object[] parameters)
    {
        return await _context.Database.ExecuteSqlRawAsync(sql, parameters);
    }
      public async Task<IDictionary<string, IEnumerable<DbColumnInfo>>> GetDatabaseSchemaAsync()
    {
        try
        {
            // Assicurarsi che il contesto sia connesso
            await _context.Database.OpenConnectionAsync();
            
            // Usa la factory per ottenere il provider appropriato in base al tipo di database
            var schemaProvider = DatabaseSchemaProviderFactory.CreateProvider(_options.DatabaseType);
            
            // Usa il provider per ottenere lo schema
            var connectionString = _context.Database.GetConnectionString();
            if (connectionString == null)
                throw new InvalidOperationException("Connection string is null");
                
            var result = await schemaProvider.GetDatabaseSchemaAsync(connectionString);
            
            return result;
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Errore nel recupero dello schema del database: {ex.Message}");
            throw;
        }
    }    public async Task<IEnumerable<Dictionary<string, object>>> GetAllRecordsAsync(string tableName)
    {
        try
        {
            var records = new List<Dictionary<string, object>>();
            
            // Usa la stessa connection string utilizzata per il discovery dello schema
            var connectionString = _context.Database.GetConnectionString();
            if (connectionString == null)
                throw new InvalidOperationException("Connection string is null");
            
            // Determina il tipo di connessione in base al DatabaseType
            using var connection = CreateConnection(connectionString);
            await connection.OpenAsync();
            
            using var command = connection.CreateCommand();
            
            // Query SQL semplice per ottenere tutti i record - limitiamo a 1000 per sicurezza
            // Se il nome della tabella contiene già lo schema (es. "dbo.OCRD"), lo usiamo così com'è
            // Altrimenti aggiungiamo le parentesi quadre
            string tableReference;
            if (tableName.Contains('.'))
            {
                // Il nome contiene già lo schema, separiamo e mettiamo entrambi tra parentesi quadre
                var parts = tableName.Split('.');
                tableReference = $"[{parts[0]}].[{parts[1]}]";
            }
            else
            {
                // Solo il nome della tabella, usiamo le parentesi quadre
                tableReference = $"[{tableName}]";
            }
            
            command.CommandText = $"SELECT TOP 1000 * FROM {tableReference}";
            
            using var reader = await command.ExecuteReaderAsync();
            
            while (await reader.ReadAsync())
            {
                var record = new Dictionary<string, object>();
                
                for (int i = 0; i < reader.FieldCount; i++)
                {
                    var columnName = reader.GetName(i);
                    var value = reader.IsDBNull(i) ? null : reader.GetValue(i);
                    record[columnName] = value!;
                }
                
                records.Add(record);
            }
            
            return records;
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Errore nell'ottenere i record dalla tabella {tableName}: {ex.Message}");
            throw;
        }
    }
    
    public async Task<List<string>> GetAvailableDatabasesAsync()
    {
        try
        {
            var connectionString = _context.Database.GetConnectionString();
            if (connectionString == null)
                throw new InvalidOperationException("Connection string is null");
            
            // Crea una connessione al server (senza specificare il database)
            var serverConnectionString = GetServerConnectionString(connectionString);
            
            using var connection = CreateConnection(serverConnectionString);
            await connection.OpenAsync();
            
            using var command = connection.CreateCommand();
            
            // Query per ottenere i database disponibili (esclude quelli di sistema)
            command.CommandText = @"
                SELECT name 
                FROM sys.databases 
                WHERE state_desc = 'ONLINE' 
                AND name NOT IN ('master', 'tempdb', 'model', 'msdb', 'distribution')
                ORDER BY name";
            
            var databases = new List<string>();
            using var reader = await command.ExecuteReaderAsync();
            
            while (await reader.ReadAsync())
            {
                databases.Add(reader.GetString(0));
            }
            
            return databases;
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Errore nell'ottenere la lista dei database: {ex.Message}");
            throw;
        }
    }
    
    public async Task ChangeDatabaseAsync(string databaseName)
    {
        try
        {
            var currentConnectionString = _context.Database.GetConnectionString();
            if (currentConnectionString == null)
                throw new InvalidOperationException("Connection string is null");
            
            // Crea una nuova connection string con il database specificato
            var newConnectionString = UpdateConnectionStringDatabase(currentConnectionString, databaseName);
            
            // Ricrea il contesto con la nuova connection string
            var optionsBuilder = new DbContextOptionsBuilder<ExistingDatabaseContext>();
            
            switch (_options.DatabaseType)
            {
                case Enums.DatabaseType.SqlServer:
                    optionsBuilder.UseSqlServer(newConnectionString, options =>
                    {
                        if (_options.CommandTimeout > 0)
                            options.CommandTimeout(_options.CommandTimeout);
                    });
                    break;
                default:
                    throw new NotSupportedException($"Database type {_options.DatabaseType} is not supported");
            }
            
            // Disponi il vecchio contesto e crea quello nuovo
            _context.Dispose();
            _context = new ExistingDatabaseContext(
                optionsBuilder.Options,
                _options.ModelConfigurator,
                _options.EnableAutoDiscovery,
                _options.EntityAssembly,
                _options.EntityNamespace,
                _options.NamingStrategy);
                
            // Testa la connessione al nuovo database
            await _context.Database.OpenConnectionAsync();
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Errore nel cambio database a '{databaseName}': {ex.Message}");
            throw;
        }
    }
    
    /// <summary>
    /// Estrae la connection string del server (senza database specifico) da una connection string completa
    /// </summary>
    private string GetServerConnectionString(string connectionString)
    {
        var builder = new SqlConnectionStringBuilder(connectionString);
        builder.InitialCatalog = ""; // Rimuove il database specifico
        return builder.ConnectionString;
    }
    
    /// <summary>
    /// Aggiorna la connection string con un nuovo database
    /// </summary>
    private string UpdateConnectionStringDatabase(string connectionString, string databaseName)
    {
        var builder = new SqlConnectionStringBuilder(connectionString);
        builder.InitialCatalog = databaseName;
        return builder.ConnectionString;
    }

    /// <summary>
    /// Crea una connessione database appropriata in base al tipo di database
    /// </summary>
    private DbConnection CreateConnection(string connectionString)
    {
        switch (_options.DatabaseType)
        {
            case Enums.DatabaseType.SqlServer:
                return new SqlConnection(connectionString);
            // Aggiungi altri tipi di database quando necessario
            // case Enums.DatabaseType.MySQL:
            //     return new MySqlConnection(connectionString);
            // case Enums.DatabaseType.PostgreSQL:
            //     return new NpgsqlConnection(connectionString);
            default:
                throw new NotSupportedException($"Database type {_options.DatabaseType} is not supported for direct connections");
        }
    }
    
    public void Dispose()
    {
        _context?.Dispose();
    }

    public async Task<string?> GetPrimaryKeyFieldAsync(string tableName)
    {
        try
        {
            var connectionString = _context.Database.GetConnectionString();
            if (connectionString == null)
                throw new InvalidOperationException("Connection string is null");
            
            using var connection = CreateConnection(connectionString);
            await connection.OpenAsync();
            
            using var command = connection.CreateCommand();
            
            // Query per ottenere la Primary Key della tabella
            // Gestisce anche tabelle con schema (es. "dbo.TableName")
            string schemaName = "dbo"; // Default schema
            string tableNameOnly = tableName;
            
            if (tableName.Contains('.'))
            {
                var parts = tableName.Split('.');
                schemaName = parts[0];
                tableNameOnly = parts[1];
            }
            
            command.CommandText = @"
                SELECT COLUMN_NAME 
                FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE 
                WHERE OBJECTPROPERTY(OBJECT_ID(CONSTRAINT_SCHEMA + '.' + QUOTENAME(CONSTRAINT_NAME)), 'IsPrimaryKey') = 1 
                AND TABLE_SCHEMA = @schemaName 
                AND TABLE_NAME = @tableName
                ORDER BY ORDINAL_POSITION";
            
            // Usa parametri per evitare SQL injection
            var schemaParam = command.CreateParameter();
            schemaParam.ParameterName = "@schemaName";
            schemaParam.Value = schemaName;
            command.Parameters.Add(schemaParam);
            
            var tableParam = command.CreateParameter();
            tableParam.ParameterName = "@tableName";
            tableParam.Value = tableNameOnly;
            command.Parameters.Add(tableParam);
            
            var result = await command.ExecuteScalarAsync();
            return result?.ToString();
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Errore nel recupero della Primary Key per la tabella {tableName}: {ex.Message}");
            return null;
        }
    }
}