Data-Coupler/DataConnection/DB/OleDbDatabaseManager.cs

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.OleDb;
using System.Linq;
using System.Linq.Expressions;
using System.Runtime.InteropServices;
using System.Threading.Tasks;
using DataConnection.EF.SchemaProviders;
using DataConnection.Interfaces;

namespace DataConnection.DB;

/// <summary>
/// Database manager per connessioni OLE DB dirette (es. Visual FoxPro, Access, Jet)
/// Nota: i driver OLE DB come VFPOLEDB.1 sono 32-bit only — pubblicare con --runtime win-x86 se necessario
/// </summary>
public class OleDbDatabaseManager : IDatabaseManager
{
    private readonly string _connectionString;
    private readonly OleDbSchemaProvider _schemaProvider;

    public OleDbDatabaseManager(string connectionString)
    {
        if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
            throw new PlatformNotSupportedException("OLE DB è supportato solo su Windows.");

        _connectionString = connectionString ?? throw new ArgumentNullException(nameof(connectionString));
        _schemaProvider = new OleDbSchemaProvider();
    }

    public async Task<bool> TestConnectionAsync()
    {
        try
        {
            using var connection = new OleDbConnection(_connectionString);
            await Task.Run(() => connection.Open());
            return true;
        }
        catch
        {
            return false;
        }
    }

    public 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
    {
        throw new NotSupportedException("GetAsync<T> con espressioni LINQ non è supportato per OLE DB. Usare ExecuteRawQueryAsync.");
    }

    public Task<T?> GetByIdAsync<T>(object id) where T : class
    {
        throw new NotSupportedException("GetByIdAsync<T> non è supportato per OLE DB. Usare ExecuteRawQueryAsync con clausola WHERE.");
    }

    public Task<IEnumerable<T>> ExecuteQueryAsync<T>(string sql, params object[] parameters) where T : class
    {
        throw new NotSupportedException("ExecuteQueryAsync<T> non è supportato per OLE DB. Usare ExecuteRawQueryAsync.");
    }

    public async Task<List<Dictionary<string, object>>> ExecuteRawQueryAsync(string sql, string databaseName = "", params object[] parameters)
    {
        var results = new List<Dictionary<string, object>>();

        using var connection = new OleDbConnection(_connectionString);
        await Task.Run(() => connection.Open());

        // OLE DB file-based (VFP, Access) non supporta ChangeDatabaseAsync — il database è nel Data Source
        // Ignoriamo databaseName per questa tipologia di provider

        using var command = new OleDbCommand(sql, connection);

        if (parameters != null && parameters.Length > 0)
        {
            for (int i = 0; i < parameters.Length; i++)
            {
                command.Parameters.Add(new OleDbParameter($"@p{i}", parameters[i] ?? DBNull.Value));
            }
        }

        using var reader = await Task.Run(() => command.ExecuteReader());

        while (reader.Read())
        {
            var row = new Dictionary<string, object>();
            for (int i = 0; i < reader.FieldCount; i++)
            {
                var fieldName = reader.GetName(i);
                var value = reader.IsDBNull(i) ? DBNull.Value : reader.GetValue(i);
                row[fieldName] = value;
            }
            results.Add(row);
        }

        return results;
    }

    public async Task<int> ExecuteCommandAsync(string sql, params object[] parameters)
    {
        using var connection = new OleDbConnection(_connectionString);
        await Task.Run(() => connection.Open());

        using var command = new OleDbCommand(sql, connection);

        if (parameters != null && parameters.Length > 0)
        {
            for (int i = 0; i < parameters.Length; i++)
            {
                command.Parameters.Add(new OleDbParameter($"@p{i}", parameters[i] ?? DBNull.Value));
            }
        }

        return await Task.Run(() => command.ExecuteNonQuery());
    }

    public async Task<List<string>> GetAvailableDatabasesAsync()
    {
        var databases = await _schemaProvider.GetAvailableDatabasesAsync(_connectionString);
        return databases.ToList();
    }

    public async Task ChangeDatabaseAsync(string databaseName)
    {
        // I provider OLE DB file-based (VFP, Access) non supportano il cambio di database a runtime
        // Il Data Source nella connection string definisce il database
        Console.WriteLine($"[OleDb] ChangeDatabaseAsync ignorato per provider file-based (database: {databaseName})");
        await Task.CompletedTask;
    }

    public async Task<IDictionary<string, IEnumerable<DbColumnInfo>>> GetDatabaseSchemaAsync()
    {
        return await _schemaProvider.GetDatabaseSchemaAsync(_connectionString);
    }

    public async Task<IEnumerable<string>> GetTableNamesAsync()
    {
        return await _schemaProvider.GetTableNamesAsync(_connectionString);
    }

    public async Task<IEnumerable<DbColumnInfo>> GetTableSchemaAsync(string tableName)
    {
        return await _schemaProvider.GetTableSchemaAsync(_connectionString, tableName);
    }

    public async Task<IEnumerable<Dictionary<string, object>>> GetAllRecordsAsync(string tableName)
    {
        var query = $"SELECT * FROM {tableName}";
        return await ExecuteRawQueryAsync(query);
    }

    public async Task<string?> GetPrimaryKeyFieldAsync(string tableName)
    {
        try
        {
            var schema = await GetTableSchemaAsync(tableName);
            var pkColumn = schema.FirstOrDefault(c => c.IsPrimaryKey);
            return pkColumn?.Name;
        }
        catch
        {
            return null;
        }
    }

    public async Task<IEnumerable<IDictionary<string, object?>>> ExecuteQueryAsync(string query, int? maxRows = null)
    {
        var results = new List<IDictionary<string, object?>>();

        using var connection = new OleDbConnection(_connectionString);
        await Task.Run(() => connection.Open());

        var commandText = maxRows.HasValue ? WrapQueryWithLimit(query, maxRows.Value) : query;
        using var command = new OleDbCommand(commandText, connection);

        using var reader = await Task.Run(() => command.ExecuteReader());

        while (reader.Read())
        {
            var row = new Dictionary<string, object?>();
            for (int i = 0; i < reader.FieldCount; i++)
            {
                var fieldName = reader.GetName(i);
                var value = reader.IsDBNull(i) ? null : reader.GetValue(i);
                row[fieldName] = value;
            }
            results.Add(row);
        }

        return results;
    }

    public async Task<int> ExecuteNonQueryAsync(string query)
    {
        using var connection = new OleDbConnection(_connectionString);
        await Task.Run(() => connection.Open());

        using var command = new OleDbCommand(query, connection);
        return await Task.Run(() => command.ExecuteNonQuery());
    }

    public async Task<object?> ExecuteScalarAsync(string query)
    {
        using var connection = new OleDbConnection(_connectionString);
        await Task.Run(() => connection.Open());

        using var command = new OleDbCommand(query, connection);
        return await Task.Run(() => command.ExecuteScalar());
    }

    public async Task<int> InsertAsync(string tableName, IDictionary<string, object?> data)
    {
        var columns = string.Join(", ", data.Keys.Select(k => $"[{k}]"));
        var parameters = string.Join(", ", data.Keys.Select(_ => "?"));

        var query = $"INSERT INTO {tableName} ({columns}) VALUES ({parameters})";

        using var connection = new OleDbConnection(_connectionString);
        await Task.Run(() => connection.Open());

        using var command = new OleDbCommand(query, connection);

        foreach (var value in data.Values)
            command.Parameters.Add(new OleDbParameter { Value = value ?? DBNull.Value });

        return await Task.Run(() => command.ExecuteNonQuery());
    }

    public async Task<int> UpdateAsync(string tableName, IDictionary<string, object?> data, IDictionary<string, object?> whereClause)
    {
        var setClause = string.Join(", ", data.Keys.Select(k => $"[{k}] = ?"));
        var whereConditions = string.Join(" AND ", whereClause.Keys.Select(k => $"[{k}] = ?"));

        var query = $"UPDATE {tableName} SET {setClause} WHERE {whereConditions}";

        using var connection = new OleDbConnection(_connectionString);
        await Task.Run(() => connection.Open());

        using var command = new OleDbCommand(query, connection);

        foreach (var value in data.Values)
            command.Parameters.Add(new OleDbParameter { Value = value ?? DBNull.Value });

        foreach (var value in whereClause.Values)
            command.Parameters.Add(new OleDbParameter { Value = value ?? DBNull.Value });

        return await Task.Run(() => command.ExecuteNonQuery());
    }

    public async Task<int> DeleteAsync(string tableName, IDictionary<string, object?> whereClause)
    {
        var whereConditions = string.Join(" AND ", whereClause.Keys.Select(k => $"[{k}] = ?"));
        var query = $"DELETE FROM {tableName} WHERE {whereConditions}";

        using var connection = new OleDbConnection(_connectionString);
        await Task.Run(() => connection.Open());

        using var command = new OleDbCommand(query, connection);

        foreach (var value in whereClause.Values)
            command.Parameters.Add(new OleDbParameter { Value = value ?? DBNull.Value });

        return await Task.Run(() => command.ExecuteNonQuery());
    }

    public async Task<int> BulkInsertAsync(string tableName, IEnumerable<IDictionary<string, object?>> dataList)
    {
        int totalInserted = 0;

        using var connection = new OleDbConnection(_connectionString);
        await Task.Run(() => connection.Open());

        using var transaction = connection.BeginTransaction();

        try
        {
            foreach (var data in dataList)
            {
                var columns = string.Join(", ", data.Keys.Select(k => $"[{k}]"));
                var parameters = string.Join(", ", data.Keys.Select(_ => "?"));

                var query = $"INSERT INTO {tableName} ({columns}) VALUES ({parameters})";

                using var command = new OleDbCommand(query, connection, transaction);

                foreach (var value in data.Values)
                    command.Parameters.Add(new OleDbParameter { Value = value ?? DBNull.Value });

                totalInserted += await Task.Run(() => command.ExecuteNonQuery());
            }

            transaction.Commit();
        }
        catch
        {
            transaction.Rollback();
            throw;
        }

        return totalInserted;
    }

    public async Task<bool> UpsertRecordAsync(string tableName, string keyField, object? keyValue, Dictionary<string, object?> record)
    {
        try
        {
            using var connection = new OleDbConnection(_connectionString);
            await Task.Run(() => connection.Open());

            using var checkCmd = new OleDbCommand($"SELECT COUNT(*) FROM {tableName} WHERE [{keyField}] = ?", connection);
            checkCmd.Parameters.Add(new OleDbParameter { Value = keyValue ?? DBNull.Value });

            var countResult = await Task.Run(() => checkCmd.ExecuteScalar());
            bool exists = Convert.ToInt64(countResult ?? 0L) > 0;

            if (exists)
            {
                var fields = record.Keys.ToList();
                var setClauses = fields.Select(f => $"[{f}] = ?").ToList();
                var updateSql = $"UPDATE {tableName} SET {string.Join(", ", setClauses)} WHERE [{keyField}] = ?";

                using var updateCmd = new OleDbCommand(updateSql, connection);

                foreach (var f in fields)
                    updateCmd.Parameters.Add(new OleDbParameter { Value = record[f] ?? DBNull.Value });

                updateCmd.Parameters.Add(new OleDbParameter { Value = keyValue ?? DBNull.Value });

                await Task.Run(() => updateCmd.ExecuteNonQuery());
            }
            else
            {
                var fields = record.Keys.ToList();
                var fieldNames = string.Join(", ", fields.Select(f => $"[{f}]"));
                var paramPlaceholders = string.Join(", ", fields.Select(_ => "?"));
                var insertSql = $"INSERT INTO {tableName} ({fieldNames}) VALUES ({paramPlaceholders})";

                using var insertCmd = new OleDbCommand(insertSql, connection);

                foreach (var f in fields)
                    insertCmd.Parameters.Add(new OleDbParameter { Value = record[f] ?? DBNull.Value });

                await Task.Run(() => insertCmd.ExecuteNonQuery());
            }

            return true;
        }
        catch (Exception ex)
        {
            Console.WriteLine($"Errore nell'upsert OLE DB in {tableName}: {ex.Message}");
            return false;
        }
    }

    /// <summary>
    /// VFP e la maggior parte dei provider OLE DB supportano SELECT TOP N (SQL Server style)
    /// </summary>
    private static string WrapQueryWithLimit(string query, int maxRows)
    {
        var upperQuery = query.Trim().ToUpperInvariant();

        if (upperQuery.Contains("LIMIT ") || upperQuery.Contains("TOP "))
            return query;

        if (upperQuery.StartsWith("SELECT "))
            return query.Insert(7, $"TOP {maxRows} ");

        return $"{query} LIMIT {maxRows}";
    }

    public void Dispose()
    {
        // Nessuna risorsa da rilasciare
    }
}