using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Localization;
using Sozsoft.Platform.Data.Seeds;
using Sozsoft.Platform.Enums;
using Sozsoft.Platform.Localization;
using Volo.Abp;
using Volo.Abp.Domain.Services;

namespace Sozsoft.Mcp.Services;

/// <summary>
/// Yeni tabloyu SQL Query Manager'daki tablo tasarimcisiyla ayni sozlesmeyle kurar: script
/// tasarimcinin <c>generateCreateTableSql</c> ciktisiyla ayni bicimdedir ve tasarimcinin deploy
/// sonrasi yazdigi yerlere (<c>sql/object/{Tablo}.sql</c> ve PostgreSQL esi <c>postgres/object/{Tablo}.sql</c>) yazilir; boylece tablo
/// tasarimcida acilip duzenlenebilir ve veritabani sifirlandiginda seed ile geri gelir.
/// <para>
/// Yalnizca olusturma yapar. Var olan tabloya dokunulmaz — kolon ekleme/degistirme tasarimcinin
/// isidir ve sema degisikligi kurallarina (kayipsiz ekleme, degistirme/dusurme yok) tabidir.
/// Kolon tipi ve varsayilan deger serbest metin degil, beyaz listeden gecer; istemci SQL yazamaz.
/// </para>
/// </summary>
public interface IMcpTableCreator
{
    Task<McpCreatedTable> CreateAsync(McpTableDefinition definition);
}

public class McpTableCreator(
    IMcpQueryExecutor queryExecutor,
    IConfiguration configuration,
    IStringLocalizer<PlatformResource> localizer) : DomainService, IMcpTableCreator
{
    private const string SchemaName = "dbo";
    private const int DefaultTextLength = 100;
    private const int MaxTextLength = 4000;

    private static readonly Regex SafeIdentifierRegex = new(
        @"^[A-Za-z_][A-Za-z0-9_]{0,127}$",
        RegexOptions.Compiled | RegexOptions.CultureInvariant);

    /// <summary>
    /// Varsayilan deger olarak kabul edilenler: sayi, metin sabiti ve tasarimcinin kendi
    /// sablonlarinda kullandigi fonksiyonlar. Baska bir ifade script'e hic girmez.
    /// </summary>
    /// <summary>
    /// Istemcinin SQL bicimiyle yazdigi tip: <c>nvarchar(50)</c>, <c>nvarchar (MAX)</c>,
    /// <c>decimal(18, 4)</c>. Boyut tipten ayrilir; tip adi yine beyaz listeden gecer.
    /// </summary>
    private static readonly Regex SizedTypeRegex = new(
        @"^(?<name>[A-Za-z0-9]+)\s*\(\s*(?<size>[^)]*?)\s*\)$",
        RegexOptions.Compiled | RegexOptions.CultureInvariant);

    /// <summary>Tasarimci decimal'i her zaman bu kesinlikle yazar (<c>ToColumnLine</c>).</summary>
    private const string DecimalSize = "18,4";

    private static readonly Regex SafeDefaultRegex = new(
        @"^(?:-?\d{1,18}(?:\.\d{1,18})?|N?'(?:[^']|'')*'|NEWID\(\)|GETDATE\(\)|GETUTCDATE\(\)|SYSUTCDATETIME\(\))$",
        RegexOptions.Compiled | RegexOptions.IgnoreCase | RegexOptions.CultureInvariant);

    /// <summary>Tasarimcinin tip listesi (<c>DATA_TYPES</c>) ile aynidir.</summary>
    private static readonly string[] SupportedTypes =
    [
        "nvarchar", "nvarchar(MAX)", "int", "bigint", "decimal", "float", "bit",
        "datetime", "datetime2", "date", "uniqueidentifier", "money"
    ];

    // Sablon kolonlari tasarimcinin FULL_AUDIT_COLUMNS / TENANT_COLUMN tanimlariyla aynidir.
    private static readonly McpTableColumn IdColumn = new("Id", "uniqueidentifier", null, false, "NEWID()");

    private static readonly McpTableColumn TenantColumn = new("TenantId", "uniqueidentifier", null, true, null);

    private static readonly McpTableColumn[] AuditColumns =
    [
        new("CreationTime", "datetime2", null, false, "GETUTCDATE()"),
        new("CreatorId", "uniqueidentifier", null, true, null),
        new("LastModificationTime", "datetime2", null, true, null),
        new("LastModifierId", "uniqueidentifier", null, true, null),
        new("IsDeleted", "bit", null, false, "0"),
        new("DeletionTime", "datetime2", null, true, null),
        new("DeleterId", "uniqueidentifier", null, true, null)
    ];

    public async Task<McpCreatedTable> CreateAsync(McpTableDefinition definition)
    {
        Check.NotNull(definition, nameof(definition));

        var tableName = (definition.TableName ?? string.Empty).Trim();
        EnsureSafeIdentifier(tableName);

        var columns = BuildColumns(definition);

        var context = await queryExecutor.ResolveDataSourceAsync();
        var isPostgreSql = context.DataSourceType == DataSourceTypeEnum.Postgresql;

        var existing = await context.Repository.ExecuteScalarAsync<object?>(
            isPostgreSql ? "SELECT to_regclass(@name)::text" : "SELECT OBJECT_ID(@name, 'U')",
            context.ConnectionString,
            new Dictionary<string, object> { ["name"] = isPostgreSql ? $"public.\"{tableName}\"" : $"{SchemaName}.{tableName}" });

        if (existing is not null and not DBNull)
        {
            throw new UserFriendlyException(localizer[McpErrorCodes.TableAlreadyExists, tableName]);
        }

        // Dosya biçimi tasarımcınınkiyle aynı T-SQL'dir; PostgreSQL eşi ondan üretilir ve PG veri
        // kaynağında çalıştırılan da o eştir.
        var script = BuildScript(tableName, columns);
        if (!PostgreSqlTableScript.TryConvert(script, out var postgreSqlScript))
        {
            throw new InvalidOperationException($"PostgreSQL script could not be generated for {tableName}.");
        }

        // GO yalnizca SSMS ayiricidir; tek batch oldugu icin calistirirken atilir, dosyada kalir.
        await context.Repository.ExecuteAsync(
            isPostgreSql ? postgreSqlScript : string.Join('\n', script.Split('\n').Where(line => line.Trim() != "GO")),
            context.ConnectionString);

        var (seedFilePath, _) = PostgreSqlTableScript.WriteSeedFiles(configuration, tableName, script);

        return new McpCreatedTable(tableName, script, seedFilePath);
    }

    private List<McpTableColumn> BuildColumns(McpTableDefinition definition)
    {
        if (definition.Columns.Count == 0)
        {
            throw new UserFriendlyException(localizer[McpErrorCodes.TableColumnsRequired]);
        }

        var userColumns = definition.Columns.Select(NormalizeColumn).ToList();

        var columns = new List<McpTableColumn> { IdColumn };
        if (definition.MultiTenant)
        {
            columns.Add(TenantColumn);
        }

        columns.AddRange(userColumns);

        if (definition.FullAudited)
        {
            columns.AddRange(AuditColumns);
        }

        var duplicate = columns
            .GroupBy(column => column.Name, StringComparer.OrdinalIgnoreCase)
            .FirstOrDefault(group => group.Count() > 1);

        if (duplicate is not null)
        {
            throw new UserFriendlyException(localizer[McpErrorCodes.DuplicateColumn, duplicate.Key]);
        }

        return columns;
    }

    private McpTableColumn NormalizeColumn(McpTableColumn column)
    {
        var name = (column.Name ?? string.Empty).Trim();
        EnsureSafeIdentifier(name);

        var (type, sizedLength) = ResolveType(column.Type);

        int? maxLength = null;
        if (type == "nvarchar")
        {
            maxLength = column.MaxLength ?? sizedLength ?? DefaultTextLength;
            if (maxLength is < 1 or > MaxTextLength)
            {
                throw new UserFriendlyException(localizer[McpErrorCodes.InvalidColumnLength, name, MaxTextLength]);
            }
        }

        var defaultValue = string.IsNullOrWhiteSpace(column.DefaultValue) ? null : column.DefaultValue.Trim();
        if (defaultValue is not null && !SafeDefaultRegex.IsMatch(defaultValue))
        {
            throw new UserFriendlyException(localizer[McpErrorCodes.InvalidDefaultValue, name, defaultValue]);
        }

        return new McpTableColumn(name, type, maxLength, column.IsNullable, defaultValue);
    }

    /// <summary>
    /// Tipi beyaz listedeki adina indirger. <c>nvarchar(N)</c> uzunlugu dondurur,
    /// <c>nvarchar(MAX)</c> kendi tipidir; decimal yalnizca tasarimcinin kesinligiyle kabul edilir —
    /// baska bir kesinligi 18,4'e cevirmek sessizce veri kaybi riski tasirdi.
    /// </summary>
    private (string Type, int? MaxLength) ResolveType(string? rawType)
    {
        var trimmed = rawType?.Trim() ?? string.Empty;
        var name = trimmed;
        string? size = null;

        var sized = SizedTypeRegex.Match(trimmed);
        if (sized.Success)
        {
            name = sized.Groups["name"].Value;
            size = Regex.Replace(sized.Groups["size"].Value, @"\s+", string.Empty);
        }

        int? maxLength = null;
        if (size is not null)
        {
            if (name.Equals("nvarchar", StringComparison.OrdinalIgnoreCase) && size.Equals("max", StringComparison.OrdinalIgnoreCase))
            {
                name = "nvarchar(MAX)";
            }
            else if (name.Equals("nvarchar", StringComparison.OrdinalIgnoreCase) && int.TryParse(size, out var length))
            {
                maxLength = length;
            }
            else if (!(name.Equals("decimal", StringComparison.OrdinalIgnoreCase) && size == DecimalSize))
            {
                name = trimmed;
            }
        }

        var type = SupportedTypes.FirstOrDefault(candidate =>
            string.Equals(candidate, name, StringComparison.OrdinalIgnoreCase))
            ?? throw new UserFriendlyException(
                localizer[McpErrorCodes.UnsupportedColumnType, trimmed, string.Join(", ", SupportedTypes)]);

        return (type, maxLength);
    }

    private static string BuildScript(string tableName, List<McpTableColumn> columns)
    {
        var fullTableName = $"[{SchemaName}].[{tableName}]";

        var lines = new List<string>
        {
            $"IF OBJECT_ID(N'{fullTableName}', 'U') IS NULL",
            "BEGIN",
            $"    CREATE TABLE {fullTableName}",
            "    ("
        };

        lines.AddRange(columns.Select(column => ToColumnLine(column) + ","));
        lines.Add($"        CONSTRAINT [PK_{tableName}] PRIMARY KEY NONCLUSTERED");
        lines.Add("    (");
        lines.Add("        [Id] ASC");
        lines.Add("    )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, OPTIMIZE_FOR_SEQUENTIAL_KEY = OFF) ON [PRIMARY]");
        lines.Add("    ) ON [PRIMARY]");
        lines.Add("END");
        lines.Add("GO");

        return string.Join('\n', lines);
    }

    private static string ToColumnLine(McpTableColumn column)
    {
        var type = column.Type switch
        {
            "nvarchar" => $"nvarchar({column.MaxLength})",
            "decimal" => "decimal(18, 4)",
            _ => column.Type
        };

        var nullPart = column.IsNullable ? "NULL" : "NOT NULL";
        var defaultPart = column.DefaultValue is null ? string.Empty : $" DEFAULT {column.DefaultValue}";

        return $"        [{column.Name}] {type} {nullPart}{defaultPart}";
    }

    private void EnsureSafeIdentifier(string identifier)
    {
        if (!SafeIdentifierRegex.IsMatch(identifier))
        {
            throw new UserFriendlyException(localizer[McpErrorCodes.InvalidIdentifier, identifier]);
        }
    }
}

/// <param name="FullAudited">Tam audit kolonlari (olusturma/degistirme/silme izi) eklensin mi.</param>
/// <param name="MultiTenant"><c>TenantId</c> kolonu eklensin mi.</param>
public sealed record McpTableDefinition(
    string TableName,
    IReadOnlyList<McpTableColumn> Columns,
    bool FullAudited,
    bool MultiTenant);

/// <param name="MaxLength">Yalnizca <c>nvarchar</c> icin; bos ise tasarimcinin varsayilani (100).</param>
public sealed record McpTableColumn(
    string Name,
    string Type,
    int? MaxLength,
    bool IsNullable,
    string? DefaultValue);

/// <param name="SeedFilePath">Seed kokune gore goreli yol.</param>
public sealed record McpCreatedTable(string TableName, string Script, string SeedFilePath);