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>
/// Veritabaninda calistirilmaz: tabloyu, wizard deploy'unun ekranini kurdugu gibi kullanicinin
/// calistirdigi DB Migrate kurar (<c>SqlDataSeeder</c>).
/// </para>
/// <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<McpOutcome<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>
    /// 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";

    /// <summary>
    /// Varsayilan deger olarak kabul edilenler: sayi, metin sabiti ve tasarimcinin kendi
    /// sablonlarinda kullandigi fonksiyonlar. Baska bir ifade script'e hic girmez.
    /// </summary>
    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.
    /// <summary>Tasarimcinin FK silme davranislari; anahtar istemcinin yazdigi, deger SQL karsiligidir.</summary>
    private static readonly Dictionary<string, string> ReferentialActions = new(StringComparer.OrdinalIgnoreCase)
    {
        ["NoAction"] = "NO ACTION",
        ["Cascade"] = "CASCADE",
        ["SetNull"] = "SET NULL",
    };

    private const string DefaultReferentialAction = "NoAction";

    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<McpOutcome<McpCreatedTable>> CreateAsync(McpTableDefinition definition)
    {
        Check.NotNull(definition, nameof(definition));

        var tableName = (definition.TableName ?? string.Empty).Trim();
        if (CheckIdentifier(tableName) is { } invalidName)
        {
            return invalidName;
        }

        if (!BuildColumns(definition).TryGetValue(out var columns, out var problem) ||
            !BuildIndexes(tableName, definition.Indexes, columns).TryGetValue(out var indexes, out problem) ||
            !BuildForeignKeys(definition.ForeignKeys, columns).TryGetValue(out var foreignKeys, out problem))
        {
            return problem;
        }

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

        async Task<bool> TableExistsAsync(string name)
        {
            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.\"{name}\"" : $"{SchemaName}.{name}" });

            return existing is not null and not DBNull;
        }

        // Henuz migrate edilmemis bir create_table da tabloyu sahiplenmis sayilir; ikinci cagri onun
        // scriptinin ustune yazmaz.
        if (await TableExistsAsync(tableName) || PostgreSqlTableScript.ReadSeedColumns(configuration, tableName).Count > 0)
        {
            return Problem(McpErrorCodes.TableAlreadyExists, tableName);
        }

        foreach (var foreignKey in foreignKeys)
        {
            if (await CheckReferenceInstalledFirstAsync(tableName, foreignKey, TableExistsAsync) is { } notInstalled)
            {
                return notInstalled;
            }
        }

        // Dosya biçimi tasarımcınınkiyle aynı T-SQL'dir; PostgreSQL eşi ondan üretilir.
        var script = BuildScript(tableName, columns, indexes, foreignKeys);
        if (!PostgreSqlTableScript.TryConvert(script, out _))
        {
            throw new InvalidOperationException($"PostgreSQL script could not be generated for {tableName}.");
        }

        // Tablo veritabaninda kurulmaz: wizard deploy'u gibi yalnizca seed yazilir, kurulum kullanicinin
        // calistirdigi DB Migrate'tedir (SqlDataSeeder).
        var (seedFilePath, _) = PostgreSqlTableScript.WriteSeedFiles(configuration, tableName, script);

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

    private McpOutcome<List<McpTableColumn>> BuildColumns(McpTableDefinition definition)
    {
        if (definition.Columns.Count == 0)
        {
            return Problem(McpErrorCodes.TableColumnsRequired);
        }

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

        foreach (var column in definition.Columns)
        {
            if (!NormalizeColumn(column).TryGetValue(out var normalized, out var problem))
            {
                return problem;
            }

            columns.Add(normalized);
        }

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

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

        return duplicate is null ? columns : Problem(McpErrorCodes.DuplicateColumn, duplicate.Key);
    }

    /// <summary>Index ve unique kolonlari tablonun kolonlari arasinda olmalidir; ad tasarimcinin kalibindadir.</summary>
    private McpOutcome<List<McpTableIndex>> BuildIndexes(string tableName, IReadOnlyList<McpTableIndex> indexes, List<McpTableColumn> columns)
    {
        var result = new List<McpTableIndex>();
        foreach (var index in indexes)
        {
            var indexColumns = new List<string>();
            foreach (var column in index.Columns)
            {
                if (!ResolveColumn(column, columns).TryGetValue(out var resolved, out var problem))
                {
                    return problem;
                }

                if (!indexColumns.Contains(resolved))
                    indexColumns.Add(resolved);
            }

            var name = $"{(index.Unique ? "UQ" : "IX")}_{tableName}_{string.Join("_", indexColumns)}";

            // Kolonsuz ya da ayni kolonlarla tekrar eden index uretilecek bir sey tasimaz.
            if (indexColumns.Count > 0 && !result.Exists(existing => string.Equals(existing.Name, name, StringComparison.OrdinalIgnoreCase)))
                result.Add(new McpTableIndex(indexColumns, index.Unique, name));
        }

        return result;
    }

    private McpOutcome<List<McpTableForeignKey>> BuildForeignKeys(IReadOnlyList<McpTableForeignKey> foreignKeys, List<McpTableColumn> columns)
    {
        var result = new List<McpTableForeignKey>();
        foreach (var foreignKey in foreignKeys)
        {
            if (!ResolveColumn(foreignKey.Column, columns).TryGetValue(out var column, out var problem))
            {
                return problem;
            }

            var referencedTable = (foreignKey.ReferencedTable ?? string.Empty).Trim();
            var referencedColumn = string.IsNullOrWhiteSpace(foreignKey.ReferencedColumn) ? IdColumn.Name : foreignKey.ReferencedColumn.Trim();
            if ((CheckIdentifier(referencedTable) ?? CheckIdentifier(referencedColumn)) is { } invalid)
            {
                return invalid;
            }

            // Tanimadigi davranis (Restrict gibi) SQL Server'in varsayilanina, NO ACTION'a duser.
            var action = ReferentialActions.Keys.FirstOrDefault(key => string.Equals(key, foreignKey.OnDelete?.Trim(), StringComparison.OrdinalIgnoreCase))
                ?? DefaultReferentialAction;

            // Bir kolonun tek FK'si olur; ayni kolon icin tekrar eden tanimin ilki gecerlidir.
            if (!result.Exists(existing => string.Equals(existing.Column, column, StringComparison.OrdinalIgnoreCase)))
                result.Add(new McpTableForeignKey(column, referencedTable, referencedColumn, action));
        }

        return result;
    }

    /// <summary>
    /// Seed scriptleri DB Migrate'te dosya adi sirasiyla calisir (<c>SqlDataSeeder</c>). FK'nin
    /// gosterdigi tablo bir seed scriptiyle kuruluyorsa o dosya bu tablonunkinden once gelmelidir;
    /// scripti yoksa (EF ile kurulan platform tablosu) veritabaninda bulunmalidir. Aksi halde
    /// sifirdan kurulumda migrate FK satirinda duserdi.
    /// </summary>
    private async Task<McpProblem?> CheckReferenceInstalledFirstAsync(string tableName, McpTableForeignKey foreignKey, Func<string, Task<bool>> tableExistsAsync)
    {
        var hasScript = PostgreSqlTableScript.ReadSeedColumns(configuration, foreignKey.ReferencedTable).Count > 0;
        var installed = hasScript
            ? Comparer<string>.Default.Compare($"{foreignKey.ReferencedTable}.sql", $"{tableName}.sql") < 0
            : await tableExistsAsync(foreignKey.ReferencedTable);

        return installed
            ? null
            : Problem(McpErrorCodes.ForeignKeyTableNotInstalledFirst, foreignKey.Column, foreignKey.ReferencedTable, tableName);
    }

    private McpOutcome<string> ResolveColumn(string? name, List<McpTableColumn> columns)
    {
        var match = columns.FirstOrDefault(column => string.Equals(column.Name, name?.Trim(), StringComparison.OrdinalIgnoreCase));

        return match is null ? Problem(McpErrorCodes.TableColumnNotFound, name ?? string.Empty) : match.Name;
    }

    private McpOutcome<McpTableColumn> NormalizeColumn(McpTableColumn column)
    {
        var name = (column.Name ?? string.Empty).Trim();
        if (CheckIdentifier(name) is { } invalidName)
        {
            return invalidName;
        }

        if (!ResolveType(column.Type).TryGetValue(out var resolved, out var problem))
        {
            return problem;
        }

        int? maxLength = null;
        if (resolved.Type == "nvarchar")
        {
            maxLength = column.MaxLength ?? resolved.MaxLength ?? DefaultTextLength;
            if (maxLength is < 1 or > MaxTextLength)
            {
                return Problem(McpErrorCodes.InvalidColumnLength, name, MaxTextLength);
            }
        }

        var defaultValue = string.IsNullOrWhiteSpace(column.DefaultValue) ? null : column.DefaultValue.Trim();
        if (defaultValue is not null && !SafeDefaultRegex.IsMatch(defaultValue))
        {
            return Problem(McpErrorCodes.InvalidDefaultValue, name, defaultValue);
        }

        return new McpTableColumn(name, resolved.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 McpOutcome<ResolvedType> 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));

        return type is null
            ? Problem(McpErrorCodes.UnsupportedColumnType, trimmed, string.Join(", ", SupportedTypes))
            : new ResolvedType(type, maxLength);
    }

    private sealed record ResolvedType(string Type, int? MaxLength);

    private static string BuildScript(string tableName, List<McpTableColumn> columns, List<McpTableIndex> indexes, List<McpTableForeignKey> foreignKeys)
    {
        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");

        // Tasarimcinin unique/index/FK deyimleri; her biri varlik kontroluyle yazilir ki migrate
        // scripti yeniden calistirdiginda dusmesin.
        foreach (var index in indexes)
        {
            var columnList = string.Join(", ", index.Columns.Select(column => $"[{column}] ASC"));
            lines.Add(string.Empty);
            if (index.Unique)
            {
                lines.Add($"IF OBJECT_ID(N'[{SchemaName}].[{index.Name}]', 'UQ') IS NULL");
                lines.Add("BEGIN");
                lines.Add($"    ALTER TABLE {fullTableName} ADD CONSTRAINT [{index.Name}] UNIQUE NONCLUSTERED ({columnList});");
            }
            else
            {
                lines.Add($"IF INDEXPROPERTY(OBJECT_ID(N'{fullTableName}'), '{index.Name}', 'IndexID') IS NULL");
                lines.Add("BEGIN");
                lines.Add($"    CREATE INDEX [{index.Name}] ON {fullTableName} ({columnList});");
            }

            lines.Add("END");
            lines.Add("GO");
        }

        foreach (var foreignKey in foreignKeys)
        {
            var name = $"FK_{tableName}_{foreignKey.Column}";
            lines.Add(string.Empty);
            lines.Add($"IF OBJECT_ID(N'[{SchemaName}].[{name}]', 'F') IS NULL");
            lines.Add("BEGIN");
            lines.Add($"    ALTER TABLE {fullTableName} ADD CONSTRAINT [{name}] FOREIGN KEY ([{foreignKey.Column}]) " +
                      $"REFERENCES [{SchemaName}].[{foreignKey.ReferencedTable}] ([{foreignKey.ReferencedColumn}]) " +
                      $"ON DELETE {ReferentialActions[foreignKey.OnDelete!]} ON UPDATE NO ACTION;");
            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 McpProblem? CheckIdentifier(string identifier)
        => SafeIdentifierRegex.IsMatch(identifier) ? null : Problem(McpErrorCodes.InvalidIdentifier, identifier);

    private McpProblem Problem(string name, params object[] arguments)
        => McpProblem.From(localizer, name, arguments);
}

/// <param name="FullAudited">Tam audit kolonlari (olusturma/degistirme/silme izi) eklensin mi.</param>
/// <param name="MultiTenant"><c>TenantId</c> kolonu eklensin mi.</param>
/// <param name="Indexes">Index ve unique kisitlari; ad sunucuda uretilir (<c>IX_/UQ_{Tablo}_{Kolonlar}</c>).</param>
/// <param name="ForeignKeys">FK'ler; ad <c>FK_{Tablo}_{Kolon}</c>.</param>
public sealed record McpTableDefinition(
    string TableName,
    IReadOnlyList<McpTableColumn> Columns,
    bool FullAudited,
    bool MultiTenant,
    IReadOnlyList<McpTableIndex> Indexes,
    IReadOnlyList<McpTableForeignKey> ForeignKeys);

public sealed record McpTableIndex(IReadOnlyList<string> Columns, bool Unique, string? Name = null);

/// <param name="ReferencedColumn">Bos ise <c>Id</c>.</param>
/// <param name="OnDelete"><c>NoAction</c> (varsayilan), <c>Cascade</c> ya da <c>SetNull</c>.</param>
public sealed record McpTableForeignKey(string Column, string ReferencedTable, string? ReferencedColumn, string? OnDelete);

/// <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);