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

namespace DataConnection.DB;

/// <summary>
/// Database manager per connessioni ODBC dirette (senza Entity Framework)
/// </summary>
public class OdbcDatabaseManager : IDatabaseManager
{
    private readonly string _connectionString;
    private readonly OdbcSchemaProvider _schemaProvider;
    private string _currentDatabase = string.Empty;

    public OdbcDatabaseManager(string connectionString)
    {
        _connectionString = connectionString ?? throw new ArgumentNullException(nameof(connectionString));
        _schemaProvider = new OdbcSchemaProvider();
    }

    public async Task<bool> TestConnectionAsync()
    {
        try
        {
            using var connection = new OdbcConnection(_connectionString);
            await connection.OpenAsync();
            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> with LINQ expressions is not supported for ODBC. Use ExecuteQueryAsync instead.");
    }

    public Task<T?> GetByIdAsync<T>(object id) where T : class
    {
        throw new NotSupportedException("GetByIdAsync<T> is not supported for ODBC. Use ExecuteQueryAsync with WHERE clause instead.");
    }

    public Task<IEnumerable<T>> ExecuteQueryAsync<T>(string sql, params object[] parameters) where T : class
    {
        throw new NotSupportedException("ExecuteQueryAsync<T> with entity type is not supported for ODBC. Use ExecuteRawQueryAsync instead.");
    }

    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 OdbcConnection(_connectionString);
        await connection.OpenAsync();

        // Cambia database se specificato
        if (!string.IsNullOrEmpty(databaseName) && databaseName != _currentDatabase)
        {
            await connection.ChangeDatabaseAsync(databaseName);
            _currentDatabase = databaseName;
        }

        using var command = new OdbcCommand(sql, connection);
        
        // Aggiungi parametri
        if (parameters != null && parameters.Length > 0)
        {
            for (int i = 0; i < parameters.Length; i++)
            {
                command.Parameters.Add(new OdbcParameter($"@p{i}", parameters[i] ?? DBNull.Value));
            }
        }

        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 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 OdbcConnection(_connectionString);
        await connection.OpenAsync();

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

        return await command.ExecuteNonQueryAsync();
    }

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

    public async Task ChangeDatabaseAsync(string databaseName)
    {
        using var connection = new OdbcConnection(_connectionString);
        await connection.OpenAsync();
        await connection.ChangeDatabaseAsync(databaseName);
        _currentDatabase = databaseName;
    }

    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}";
        var results = await ExecuteRawQueryAsync(query);
        return results;
    }

    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 OdbcConnection(_connectionString);
        await connection.OpenAsync();

        using var command = new OdbcCommand(query, connection);
        if (maxRows.HasValue)
        {
            command.CommandText = WrapQueryWithLimit(query, maxRows.Value);
        }

        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 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 OdbcConnection(_connectionString);
        await connection.OpenAsync();

        using var command = new OdbcCommand(query, connection);
        return await command.ExecuteNonQueryAsync();
    }

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

        using var command = new OdbcCommand(query, connection);
        return await command.ExecuteScalarAsync();
    }

    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((_, i) => $"?"));
        
        var query = $"INSERT INTO {tableName} ({columns}) VALUES ({parameters})";

        using var connection = new OdbcConnection(_connectionString);
        await connection.OpenAsync();

        using var command = new OdbcCommand(query, connection);
        
        foreach (var value in data.Values)
        {
            command.Parameters.Add(new OdbcParameter { Value = value ?? DBNull.Value });
        }

        return await command.ExecuteNonQueryAsync();
    }

    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 OdbcConnection(_connectionString);
        await connection.OpenAsync();

        using var command = new OdbcCommand(query, connection);
        
        // Aggiungi parametri SET
        foreach (var value in data.Values)
        {
            command.Parameters.Add(new OdbcParameter { Value = value ?? DBNull.Value });
        }
        
        // Aggiungi parametri WHERE
        foreach (var value in whereClause.Values)
        {
            command.Parameters.Add(new OdbcParameter { Value = value ?? DBNull.Value });
        }

        return await command.ExecuteNonQueryAsync();
    }

    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 OdbcConnection(_connectionString);
        await connection.OpenAsync();

        using var command = new OdbcCommand(query, connection);
        
        foreach (var value in whereClause.Values)
        {
            command.Parameters.Add(new OdbcParameter { Value = value ?? DBNull.Value });
        }

        return await command.ExecuteNonQueryAsync();
    }

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

        using var connection = new OdbcConnection(_connectionString);
        await connection.OpenAsync();

        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((_, i) => $"?"));
                
                var query = $"INSERT INTO {tableName} ({columns}) VALUES ({parameters})";

                using var command = new OdbcCommand(query, connection, transaction);
                
                foreach (var value in data.Values)
                {
                    command.Parameters.Add(new OdbcParameter { Value = value ?? DBNull.Value });
                }

                totalInserted += await command.ExecuteNonQueryAsync();
            }

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

        return totalInserted;
    }

    /// <summary>
    /// Wrappa la query con LIMIT/TOP a seconda del dialetto SQL
    /// Nota: ODBC non ha una sintassi standard, quindi usiamo TOP (SQL Server style)
    /// che è supportato dalla maggior parte dei driver
    /// </summary>
    private string WrapQueryWithLimit(string query, int maxRows)
    {
        // Verifica se la query ha già un LIMIT o TOP
        var upperQuery = query.Trim().ToUpperInvariant();
        
        if (upperQuery.Contains("LIMIT ") || upperQuery.Contains("TOP "))
        {
            return query; // Query già limitata
        }

        // Prova con SELECT TOP (SQL Server, SAP HANA)
        if (upperQuery.StartsWith("SELECT "))
        {
            return query.Insert(7, $"TOP {maxRows} ");
        }

        // Fallback: aggiungi LIMIT alla fine (MySQL, PostgreSQL style)
        return $"{query} LIMIT {maxRows}";
    }

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