using System;
using System.Collections.Generic;
using System.Data.Common;
using System.Linq;
using System.Text.Json;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Authorization;
using Microsoft.Extensions.Configuration;
using Sozsoft.Mcp.Dtos;
using Sozsoft.Mcp.Services;
using Sozsoft.Platform;
using Sozsoft.Platform.Data.Seeds;
using Sozsoft.Platform.Entities;
using Sozsoft.Platform.Enums;
using Sozsoft.Platform.ListForms.Select;
using Volo.Abp;
using Volo.Abp.Domain.Repositories;

namespace Sozsoft.Mcp;

/// <summary>
/// Salt-okunur sorgu yuzeyi. MCP kullaniciya yetki vermez, uygulamadaki yetkisini tasir:
/// <list type="bullet">
/// <item><c>query_list</c> ekranin kendi sorgusundan gecer; liste ve alan yetkileri, kiraci ve
/// sube filtreleri aynen uygulanir.</item>
/// <item>Ham SQL ve veritabani nesneleri (view/procedure/function) liste yetkilerini asar; bu
/// yuzden yalnizca uygulamada SQL Query Manager yetkisi olan kullaniciya aciktir.</item>
/// <item>Custom Endpoint'ler endpoint dispatcher'inin yetkisini ve endpoint'in kendi
/// kullanici/rol listesini ister.</item>
/// </list>
/// SQL kurallari <see cref="IMcpSqlGuard"/>, veri kaynagi cozumu ve calistirma
/// <see cref="IMcpQueryExecutor"/> icindedir.
/// </summary>
[Authorize(PlatformConsts.AppCodes.DeveloperKits.McpServers.Invoke)]
public partial class McpQueryAppService(
    IMcpServerConfigProvider serverConfigProvider,
    IMcpSqlGuard sqlGuard,
    IMcpQueryExecutor queryExecutor,
    IRepository<CustomEndpoint, Guid> customEndpointRepository,
    IListFormSelectAppService listFormSelectAppService,
    IMcpListFormAccessFilter accessFilter,
    IConfiguration configuration)
    : McpAppService(serverConfigProvider), IMcpQueryAppService
{
    private const string SqlPermission = PlatformConsts.AppCodes.SqlQueryManagers.Default;
    private const string CustomEndpointPermission = PlatformConsts.AppCodes.DeveloperKits.Get;

    public async Task<McpOutcome<McpListQueryResultDto>> QueryListAsync(McpListQueryRequestDto input)
    {
        Check.NotNull(input, nameof(input));

        if (!(await EnsureToolAllowedAsync(McpToolNames.QueryList)).TryGetValue(out var config, out var problem))
        {
            return problem;
        }

        var take = ResolveMaxRows(config, input.Take);

        var permission = await accessFilter.GetPermissionNameAsync(input.ListFormCode, AuthorizationTypeEnum.Read);
        if (permission is not null && await CheckPermissionAsync(McpToolNames.QueryList, permission) is { } denied)
        {
            return denied;
        }

        if (!ToLoadOption(nameof(input.Sort), input.Sort, McpLoadOptions.ToSort).TryGetValue(out var sort, out problem) ||
            !ToLoadOption(nameof(input.Group), input.Group, McpLoadOptions.ToGroup).TryGetValue(out var group, out problem) ||
            !ToLoadOption(nameof(input.GroupSummary), input.GroupSummary, McpLoadOptions.ToSummary).TryGetValue(out var groupSummary, out problem) ||
            !ToLoadOption(nameof(input.TotalSummary), input.TotalSummary, McpLoadOptions.ToSummary).TryGetValue(out var totalSummary, out problem))
        {
            return problem;
        }

        var result = await listFormSelectAppService.GetSelectAsync(new SelectRequestDto
        {
            ListFormCode = input.ListFormCode,
            Filter = NullIfEmpty(input.Filter),
            Sort = sort,
            Group = group,
            GroupSummary = groupSummary,
            TotalSummary = totalSummary,
            Skip = Math.Max(input.Skip, 0),
            Take = take,
            RequireTotalCount = true,
            RequireGroupCount = !string.IsNullOrWhiteSpace(input.Group)
        });

        return new McpListQueryResultDto
        {
            Data = result.Data,
            TotalCount = result.TotalCount,
            GroupCount = result.GroupCount,
            Summary = result.Summary,
            Take = take
        };
    }

    /// <summary>Bozuk girdi SQL hatasina donusmeden, hangi parametrede oldugu soylenerek reddedilir.</summary>
    private McpOutcome<string?> ToLoadOption(string parameter, string? value, Func<string?, string?> convert)
    {
        try
        {
            return convert(value);
        }
        catch (Exception ex) when (ex is JsonException or InvalidOperationException)
        {
            return Problem(McpErrorCodes.InvalidLoadOption, JsonNamingPolicy.CamelCase.ConvertName(parameter));
        }
    }

    public async Task<McpOutcome<McpQueryResultDto>> RunSelectAsync(McpSelectRequestDto input)
    {
        Check.NotNull(input, nameof(input));

        if (!(await EnsureToolAllowedAsync(McpToolNames.RunSelect)).TryGetValue(out var config, out var problem))
        {
            return problem;
        }

        var sql = (input.Sql ?? string.Empty).Trim().TrimEnd(';').Trim();
        if (sqlGuard.CheckReadOnlyStatement(sql) is { } invalid)
        {
            return invalid;
        }

        if (!sqlGuard.NormalizeParameters(input.Parameters).TryGetValue(out var parameters, out problem))
        {
            return problem;
        }

        var maxRows = ResolveMaxRows(config, input.MaxRows);
        var context = await queryExecutor.ResolveDataSourceAsync();
        var limitedSql = sqlGuard.ApplyRowLimit(sql, maxRows, context.DataSourceType);

        // Sorguyu model yazar ve tablonun kolonlarini tahmin eder (her tabloda IsDeleted yok).
        // Saglayici hatasi cevrilmezse istemciye yalnizca genel hata gider ve model sorguyu
        // duzeltemez. Arac zaten SQL yetkisi istedigi icin hata metni yeni bilgi sizdirmaz.
        try
        {
            return ToResult(await queryExecutor.ExecuteAsync(context, limitedSql, parameters, maxRows));
        }
        catch (DbException ex)
        {
            var pending = IsUnknownObjectError(ex) ? DescribePendingTables(sql) : null;
            if (pending is not null)
                return Problem(McpErrorCodes.SelectTableNotInstalled, ex.Message, pending);

            var columns = IsUnknownColumnError(ex) ? await DescribeTableColumnsAsync(context, sql) : null;
            return columns is null
                ? Problem(McpErrorCodes.SelectFailed, ex.Message)
                : Problem(McpErrorCodes.SelectFailedColumns, ex.Message, columns);
        }
    }

    private const int MaxDescribedTables = 5;

    /// <summary>SQL Server 207 ("Invalid column name"), PostgreSQL 42703 (undefined_column).</summary>
    private static bool IsUnknownColumnError(DbException ex) =>
        ex.SqlState == "42703" || ex.Message.Contains("Invalid column name", StringComparison.OrdinalIgnoreCase);

    /// <summary>SQL Server 208 ("Invalid object name"), PostgreSQL 42P01 (undefined_table).</summary>
    private static bool IsUnknownObjectError(DbException ex) =>
        ex.SqlState == "42P01" || ex.Message.Contains("Invalid object name", StringComparison.OrdinalIgnoreCase);

    /// <summary>
    /// Sorgunun andigi ve veritabaninda olmayan tablolardan seed scripti olanlar (<c>Tablo(A, B); …</c>).
    /// <c>create_table</c> tabloyu yalnizca scripte yazar, kurulum DB Migrate'tedir; model ayni talepte
    /// tabloyu sorgularsa kolon tahmini yuzunden degil kurulum beklendigi icin bos doner. Kolonlar
    /// scriptten okunur, boylece model sema araci cagirmadan ilerler. Scripti olan tablo yoksa null.
    /// </summary>
    private string? DescribePendingTables(string sql)
    {
        var described = TableReferenceRegex().Matches(sql)
            .Select(match => match.Groups["table"].Value)
            .Distinct(StringComparer.OrdinalIgnoreCase)
            .Take(MaxDescribedTables)
            .Select(table => (Table: table, Columns: PostgreSqlTableScript.ReadSeedColumns(configuration, table)))
            .Where(item => item.Columns.Count > 0)
            .Select(item => $"{item.Table}({string.Join(", ", item.Columns.Keys)})")
            .ToList();

        return described.Count == 0 ? null : string.Join("; ", described);
    }

    /// <summary>
    /// Sorgunun FROM/JOIN ile andigi tablolarin gercek kolonlari (<c>Tablo(A, B, C); …</c>). Model
    /// kolonu tahmin ettiyse dogru listeyi ayni cevapta gorur ve ayrica sema araci cagirmadan duzeltir.
    /// Kolonlar okunamazsa null doner; asil hata yine iletilir.
    /// </summary>
    private async Task<string?> DescribeTableColumnsAsync(McpDataSourceContext context, string sql)
    {
        var tables = TableReferenceRegex().Matches(sql)
            .Select(match => match.Groups["table"].Value)
            .Distinct(StringComparer.OrdinalIgnoreCase)
            .Take(MaxDescribedTables)
            .ToList();
        if (tables.Count == 0)
            return null;

        var parameters = tables.Select((table, index) => (Name: $"t{index}", Table: table))
            .ToDictionary(p => p.Name, p => (object)p.Table);

        try
        {
            var rows = await queryExecutor.ExecuteAsync(
                context,
                $"SELECT TABLE_NAME, COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME IN ({string.Join(", ", parameters.Keys.Select(name => "@" + name))}) ORDER BY TABLE_NAME, ORDINAL_POSITION",
                parameters,
                int.MaxValue);

            var described = rows.Rows
                .Select(row => (Table: ReadIgnoreCase(row, "TABLE_NAME"), Column: ReadIgnoreCase(row, "COLUMN_NAME")))
                .Where(item => item.Table is not null && item.Column is not null)
                .GroupBy(item => item.Table!, StringComparer.OrdinalIgnoreCase)
                .Select(group => $"{group.Key}({string.Join(", ", group.Select(item => item.Column))})")
                .ToList();

            return described.Count == 0 ? null : string.Join("; ", described);
        }
        catch (DbException)
        {
            return null;
        }
    }

    private static string? ReadIgnoreCase(Dictionary<string, object?> row, string key) =>
        row.FirstOrDefault(pair => string.Equals(pair.Key, key, StringComparison.OrdinalIgnoreCase)).Value?.ToString();

    /// <summary>FROM/JOIN'den sonraki ad; sema ve kose parantezi/tirnak atilir (<c>[dbo].[Tablo]</c> → <c>Tablo</c>).</summary>
    [GeneratedRegex(@"\b(?:FROM|JOIN)\s+(?:[\[""]?\w+[\]""]?\.)?[\[""]?(?<table>\w+)[\]""]?", RegexOptions.IgnoreCase | RegexOptions.CultureInvariant)]
    private static partial Regex TableReferenceRegex();

    public async Task<McpOutcome<List<McpSavedQueryDto>>> GetSavedQueriesAsync(string? search = null)
    {
        if (await EnsureToolAllowedAsync(McpToolNames.ListQueries) is { Problem: { } problem })
        {
            return problem;
        }

        var results = new List<McpSavedQueryDto>();

        if (await AuthorizationService.IsGrantedAsync(SqlPermission))
        {
            results.AddRange(await GetDatabaseObjectsAsync());
        }

        if (await AuthorizationService.IsGrantedAsync(CustomEndpointPermission))
        {
            results.AddRange(await GetCallableCustomEndpointsAsync());
        }

        if (!string.IsNullOrWhiteSpace(search))
        {
            results = [.. results.Where(item =>
                item.Name.Contains(search, StringComparison.OrdinalIgnoreCase)
                || (item.Description?.Contains(search, StringComparison.OrdinalIgnoreCase) ?? false))];
        }

        return results
            .OrderBy(item => item.Kind, StringComparer.Ordinal)
            .ThenBy(item => item.Name, StringComparer.OrdinalIgnoreCase)
            .ToList();
    }

    private async Task<List<McpSavedQueryDto>> GetDatabaseObjectsAsync()
    {
        var context = await queryExecutor.ResolveDataSourceAsync();
        var catalogSql = context.DataSourceType == DataSourceTypeEnum.Postgresql
            ? McpCatalogQueries.Postgres
            : McpCatalogQueries.SqlServer;

        // Katalog sorgusunun kendi satir siniri yoktur; nesne sayisi tavani asmaz.
        var catalog = await queryExecutor.ExecuteAsync(context, catalogSql, new Dictionary<string, object>(), int.MaxValue);

        var results = new List<McpSavedQueryDto>();

        foreach (var row in catalog.Rows)
        {
            var kind = MapCatalogKind(ReadString(row, "ObjectKind"));
            if (kind is null)
            {
                continue;
            }

            results.Add(new McpSavedQueryDto
            {
                Kind = kind,
                SchemaName = ReadString(row, "SchemaName"),
                Name = ReadString(row, "ObjectName") ?? string.Empty
            });
        }

        return results;
    }

    public async Task<McpOutcome<McpQueryResultDto>> RunSavedQueryAsync(McpSavedQueryRequestDto input)
    {
        Check.NotNull(input, nameof(input));

        if (!(await EnsureToolAllowedAsync(McpToolNames.RunQuery)).TryGetValue(out var config, out var problem))
        {
            return problem;
        }

        var isCustomEndpoint = IsKind(input.Kind, McpConsts.SavedQueryKinds.CustomEndpoint);
        if (await CheckPermissionAsync(McpToolNames.RunQuery, isCustomEndpoint ? CustomEndpointPermission : SqlPermission) is { } denied)
        {
            return denied;
        }

        if (!sqlGuard.NormalizeParameters(input.Parameters).TryGetValue(out var parameters, out problem))
        {
            return problem;
        }

        var maxRows = ResolveMaxRows(config, input.MaxRows);
        if (isCustomEndpoint)
        {
            return await RunCustomEndpointAsync(input, parameters, maxRows);
        }

        var context = await queryExecutor.ResolveDataSourceAsync();

        var schemaName = string.IsNullOrWhiteSpace(input.SchemaName)
            ? sqlGuard.DefaultSchemaName(context.DataSourceType)
            : input.SchemaName;

        if (!sqlGuard.QuoteQualifiedName(schemaName, input.Name, context.DataSourceType).TryGetValue(out var qualifiedName, out problem) ||
            !BuildSavedQuerySql(input.Kind, qualifiedName, parameters, maxRows, context.DataSourceType).TryGetValue(out var sql, out problem))
        {
            return problem;
        }

        return ToResult(await queryExecutor.ExecuteAsync(context, sql, parameters, maxRows));
    }

    private async Task<McpOutcome<McpQueryResultDto>> RunCustomEndpointAsync(
        McpSavedQueryRequestDto input,
        Dictionary<string, object> parameters,
        int maxRows)
    {
        var endpoints = await GetCallableEndpointEntitiesAsync();
        var endpoint = endpoints.Find(candidate => string.Equals(candidate.Name, input.Name, StringComparison.OrdinalIgnoreCase));
        if (endpoint is null)
        {
            return Problem(McpErrorCodes.CustomEndpointNotFound, input.Name);
        }

        // Eksik parametre Dapper tarafinda belirsiz bir hataya donusmesin diye burada yakalanir.
        var missing = endpoint.Parameters
            .Where(parameter => parameter.IsRequired && !parameters.ContainsKey(parameter.Name))
            .Select(parameter => parameter.Name)
            .ToList();

        if (missing.Count > 0)
        {
            return Problem(McpErrorCodes.MissingParameters, string.Join(", ", missing));
        }

        var context = await queryExecutor.ResolveDataSourceAsync(endpoint.DataSourceCode);

        return ToResult(await queryExecutor.ExecuteAsync(context, endpoint.Sql, parameters, maxRows));
    }

    private async Task<List<McpSavedQueryDto>> GetCallableCustomEndpointsAsync()
    {
        var endpoints = await GetCallableEndpointEntitiesAsync();

        return [.. endpoints.Select(endpoint => new McpSavedQueryDto
        {
            Kind = McpConsts.SavedQueryKinds.CustomEndpoint,
            Name = endpoint.Name,
            Description = endpoint.Description,
            ParameterNames = [.. endpoint.Parameters.Select(parameter => parameter.Name)]
        })];
    }

    /// <summary>
    /// Yalnizca okuma amacli (GET) ve istegi yapan kullaniciya acik Custom Endpoint kayitlari.
    /// Yetki sozlesmesi endpoint dispatcher'indaki ile birebir aynidir.
    /// </summary>
    private async Task<List<CustomEndpoint>> GetCallableEndpointEntitiesAsync()
    {
        var query = await customEndpointRepository.GetQueryableAsync();
        var candidates = query.Where(endpoint => endpoint.Method == "GET").ToList();

        return [.. candidates.Where(endpoint => endpoint.Permissions.Any(permission =>
            permission.ResourceType == "Global"
            || (permission.ResourceType == "User" && permission.ResourceId == CurrentUser.UserName)
            || (permission.ResourceType == "Role" && CurrentUser.Roles.Contains(permission.ResourceId))))];
    }

    private McpOutcome<string> BuildSavedQuerySql(
        string? kind,
        string qualifiedName,
        Dictionary<string, object> parameters,
        int maxRows,
        DataSourceTypeEnum dataSourceType)
    {
        var parameterList = string.Join(", ", parameters.Keys.Select(name => $"@{name}"));

        if (IsKind(kind, McpConsts.SavedQueryKinds.View))
        {
            return sqlGuard.ApplyRowLimit($"SELECT * FROM {qualifiedName}", maxRows, dataSourceType);
        }

        if (IsKind(kind, McpConsts.SavedQueryKinds.TableFunction))
        {
            return sqlGuard.ApplyRowLimit($"SELECT * FROM {qualifiedName}({parameterList})", maxRows, dataSourceType);
        }

        if (IsKind(kind, McpConsts.SavedQueryKinds.ScalarFunction))
        {
            return $"SELECT {qualifiedName}({parameterList}) AS Value";
        }

        if (IsKind(kind, McpConsts.SavedQueryKinds.Procedure))
        {
            // Prosedur cagrisina satir tavani yazilamaz; sonuc kumesi okunurken kesilir.
            return dataSourceType == DataSourceTypeEnum.Postgresql
                ? $"CALL {qualifiedName}({parameterList})"
                : $"EXEC {qualifiedName} {string.Join(", ", parameters.Keys.Select(name => $"@{name} = @{name}"))}".TrimEnd();
        }

        return Problem(McpErrorCodes.UnsupportedObjectKind, kind ?? string.Empty);
    }

    private static string? NullIfEmpty(string? value)
        => string.IsNullOrWhiteSpace(value) ? null : value;

    private static McpQueryResultDto ToResult(McpQueryRows rows) => new()
    {
        Columns = rows.Columns,
        Rows = rows.Rows,
        RowCount = rows.Rows.Count,
        Truncated = rows.Truncated,
        ExecutionTimeMs = rows.ExecutionTimeMs
    };

    private static bool IsKind(string? kind, string expected)
        => string.Equals(kind, expected, StringComparison.OrdinalIgnoreCase);

    private static string? MapCatalogKind(string? catalogKind) => catalogKind switch
    {
        McpConsts.CatalogKinds.View => McpConsts.SavedQueryKinds.View,
        McpConsts.CatalogKinds.Procedure => McpConsts.SavedQueryKinds.Procedure,
        McpConsts.CatalogKinds.TableFunction => McpConsts.SavedQueryKinds.TableFunction,
        McpConsts.CatalogKinds.ScalarFunction => McpConsts.SavedQueryKinds.ScalarFunction,
        _ => null
    };

    private static string? ReadString(Dictionary<string, object?> row, string key)
        => row.TryGetValue(key, out var value) ? value?.ToString() : null;
}