using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Threading.Tasks;
using Sozsoft.SqlQueryManager.Application.Contracts;
using Sozsoft.SqlQueryManager.Domain.Services;
using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using Volo.Abp.Application.Services;
using Volo.Abp.MultiTenancy;
using System.Text.RegularExpressions;

namespace Sozsoft.SqlQueryManager.Application;

/// <summary>
/// Executes T-SQL against configured data sources and exposes database metadata.
/// Does not persist SQL objects (queries, procedures, views, functions) to its own tables.
/// </summary>
[Authorize("App.SqlQueryManager")]
public class SqlObjectManagerAppService : ApplicationService, ISqlObjectManagerAppService
{
    private const string QueryExecutedSuccessfullyMessage = "Query executed successfully.";
    private const string QueryExecutedAndDeployedMessage = "Query executed and deployed successfully";

    private const string SqlIdentifierPattern = @"(?:\[[^\]]+\]|\""[^\""\r\n]+\""|[A-Za-z_][A-Za-z0-9_@$#]*)";
    private const string MultiPartSqlIdentifierPattern = SqlIdentifierPattern + @"(?:\s*\.\s*" + SqlIdentifierPattern + @"){0,2}";

    private static readonly Regex SqlObjectDefinitionRegex = new(
        @"^\s*(?:(?:--[^\r\n]*|/\*[\s\S]*?\*/)\s*)*(?<verb>CREATE|ALTER)\s+(?:OR\s+ALTER\s+)?(?<type>VIEW|PROC(?:EDURE)?|FUNCTION)\s+(?<name>" + MultiPartSqlIdentifierPattern + @")",
        RegexOptions.IgnoreCase | RegexOptions.Multiline | RegexOptions.Compiled);

    private static readonly Regex SqlObjectDropRegex = new(
        @"^\s*(?:(?:--[^\r\n]*|/\*[\s\S]*?\*/)\s*)*DROP\s+(?<type>VIEW|PROC(?:EDURE)?|FUNCTION)\s+(?:IF\s+EXISTS\s+)?(?<names>" + MultiPartSqlIdentifierPattern + @"(?:\s*,\s*" + MultiPartSqlIdentifierPattern + @")*)",
        RegexOptions.IgnoreCase | RegexOptions.Multiline | RegexOptions.Compiled);

    private static readonly Regex SqlObjectHeaderCanonicalizeRegex = new(
        @"^(?<prefix>\s*(?:(?:--[^\r\n]*\r?\n|/\*[\s\S]*?\*/)\s*)*)(?<verb>CREATE|ALTER)\s+(?<after>(?:OR\s+ALTER\s+)?(?:VIEW|PROC(?:EDURE)?|FUNCTION)\b)",
        RegexOptions.IgnoreCase | RegexOptions.Multiline | RegexOptions.Compiled);

    private readonly ISqlExecutorService _sqlExecutorService;
    private readonly ISqlTemplateProvider _templateProvider;
    private readonly ICurrentTenant _currentTenant;
    private readonly IHttpContextAccessor _httpContextAccessor;
    private readonly IHostEnvironment _hostEnvironment;
    private readonly ILogger<SqlObjectManagerAppService> _logger;

    public SqlObjectManagerAppService(
        ISqlExecutorService sqlExecutorService,
        ISqlTemplateProvider templateProvider,
        ICurrentTenant currentTenant,
        IHttpContextAccessor httpContextAccessor,
        IHostEnvironment hostEnvironment,
        ILogger<SqlObjectManagerAppService> logger)
    {
        _sqlExecutorService = sqlExecutorService;
        _templateProvider = templateProvider;
        _currentTenant = currentTenant;
        _httpContextAccessor = httpContextAccessor;
        _hostEnvironment = hostEnvironment;
        _logger = logger;
    }

    private string GetTenantFromHeader()
    {
        return _httpContextAccessor.HttpContext?
            .Request?
            .Headers["__tenant"]
            .FirstOrDefault();
    }

    private void ValidateTenantAccess()
    {
        var headerTenant = GetTenantFromHeader();
        var currentTenantName = _currentTenant.Name;

        if (_currentTenant.IsAvailable)
        {
            if (headerTenant != currentTenantName)
            {
                throw new Volo.Abp.UserFriendlyException($"Tenant mismatch. Header tenant '{headerTenant}' does not match current tenant '{currentTenantName}'.");
            }
        }
    }

    public async Task<SqlObjectExplorerDto> GetAllObjectsAsync(string dataSourceCode)
    {
        ValidateTenantAccess();
        var result = new SqlObjectExplorerDto();

        result.Tables = await GetTablesAsync(dataSourceCode);
        result.Views = await GetNativeObjectsAsync(dataSourceCode, "V");
        result.StoredProcedures = await GetNativeObjectsAsync(dataSourceCode, "P");
        result.Functions = await GetNativeObjectsAsync(dataSourceCode, "FN", "IF", "TF");

        result.Templates = _templateProvider.GetAvailableQueryTemplates()
            .Select(t => new SqlTemplateDto
            {
                Type = t.Type,
                Name = t.Name,
                Description = t.Description,
                Template = _templateProvider.GetQueryTemplate(t.Type)
            })
            .ToList();

        return result;
    }

    private async Task<List<SqlNativeObjectDto>> GetNativeObjectsAsync(string dataSourceCode, params string[] objectTypes)
    {
        var typeList = string.Join(",", objectTypes.Select(t => $"'{t}'"));
        var query = $@"
            SELECT 
                SCHEMA_NAME(o.schema_id) AS SchemaName,
                o.name AS ObjectName
            FROM 
                sys.objects o
            WHERE 
                o.type IN ({typeList})
                AND o.is_ms_shipped = 0
            ORDER BY 
                SCHEMA_NAME(o.schema_id), o.name";

        var result = await _sqlExecutorService.ExecuteQueryAsync(query, dataSourceCode);

        var objects = new List<SqlNativeObjectDto>();
        if (result.Success && result.Data != null)
        {
            foreach (var row in result.Data)
            {
                var dict = row as IDictionary<string, object>;
                if (dict != null)
                {
                    objects.Add(new SqlNativeObjectDto
                    {
                        SchemaName = dict["SchemaName"]?.ToString() ?? "dbo",
                        ObjectName = dict["ObjectName"]?.ToString() ?? ""
                    });
                }
            }
        }

        return objects;
    }

    private async Task<List<DatabaseTableDto>> GetTablesAsync(string dataSourceCode)
    {
        var query = @"
            SELECT 
                SCHEMA_NAME(t.schema_id) AS SchemaName,
                t.name AS TableName
            FROM 
                sys.tables t
            WHERE 
                t.is_ms_shipped = 0
            ORDER BY 
                SCHEMA_NAME(t.schema_id), t.name";

        var result = await _sqlExecutorService.ExecuteQueryAsync(query, dataSourceCode);

        var tables = new List<DatabaseTableDto>();
        if (result.Success && result.Data != null)
        {
            foreach (var row in result.Data)
            {
                var dict = row as IDictionary<string, object>;
                if (dict != null)
                {
                    tables.Add(new DatabaseTableDto
                    {
                        SchemaName = dict["SchemaName"]?.ToString() ?? "dbo",
                        TableName = dict["TableName"]?.ToString() ?? ""
                    });
                }
            }
        }

        return tables;
    }

    public async Task<SqlQueryExecutionResultDto> ExecuteQueryAsync(ExecuteSqlQueryDto input)
    {
        ValidateTenantAccess();
        var isDeployed = false;

        // Split on GO batch separators (SQL Server SSMS convention — not valid T-SQL)
        var batches = Regex.Split(input.QueryText ?? string.Empty, @"^\s*GO\s*$", RegexOptions.Multiline | RegexOptions.IgnoreCase)
            .Select(b => b.Trim())
            .Where(b => !string.IsNullOrWhiteSpace(b))
            .ToList();

        if (batches.Count <= 1)
        {
            // Single batch — original path
            var result = await _sqlExecutorService.ExecuteQueryAsync(
                input.QueryText,
                input.DataSourceCode,
                input.Parameters);

            if (result.Success)
            {
                isDeployed = TrySyncSqlObjectScriptFile(input.QueryText);
            }

            return MapExecutionResult(result, isDeployed);
        }

        // Multiple batches — execute sequentially, return last meaningful result
        SqlExecutionResult lastResult = null;
        foreach (var batch in batches)
        {
            lastResult = await _sqlExecutorService.ExecuteQueryAsync(
                batch,
                input.DataSourceCode,
                input.Parameters);

            if (!lastResult.Success)
                return MapExecutionResult(lastResult);

            isDeployed |= TrySyncSqlObjectScriptFile(batch);
        }

        return MapExecutionResult(lastResult!, isDeployed);
    }

    public async Task<string> GetNativeObjectDefinitionAsync(string dataSourceCode, string schemaName, string objectName)
    {
        ValidateTenantAccess();
        var query = @"
            SELECT OBJECT_DEFINITION(OBJECT_ID(@ObjectName)) AS Definition";

        var fullObjectName = $"[{schemaName}].[{objectName}]";
        var result = await _sqlExecutorService.ExecuteQueryAsync(
            query.Replace("@ObjectName", $"'{fullObjectName}'"),
            dataSourceCode);

        if (result.Success && result.Data != null)
        {
            var dataList = result.Data.ToList();
            if (dataList.Count > 0)
            {
                var row = dataList[0] as IDictionary<string, object>;
                if (row != null && row.ContainsKey("Definition"))
                {
                    var definition = row["Definition"]?.ToString() ?? string.Empty;
                    // Always open object script as CREATE OR ALTER in editor.
                    definition = Regex.Replace(
                        definition,
                        @"^\s*(?:CREATE|ALTER)\s+(?:OR\s+ALTER\s+)?",
                        "CREATE OR ALTER ",
                        RegexOptions.IgnoreCase);
                    return definition;
                }
            }
        }

        return string.Empty;
    }

    public async Task<List<DatabaseColumnDto>> GetTableColumnsAsync(string dataSourceCode, string schemaName, string tableName)
    {
        ValidateTenantAccess();
        var query = $@"
            SELECT 
                c.name AS ColumnName,
                TYPE_NAME(c.user_type_id) AS DataType,
                c.is_nullable AS IsNullable,
                c.max_length AS MaxLength
            FROM 
                sys.columns c
                INNER JOIN sys.tables t ON c.object_id = t.object_id
                INNER JOIN sys.schemas s ON t.schema_id = s.schema_id
            WHERE 
                s.name = '{schemaName}'
                AND t.name = '{tableName}'
            ORDER BY 
                c.column_id";

        var result = await _sqlExecutorService.ExecuteQueryAsync(query, dataSourceCode);

        var columns = new List<DatabaseColumnDto>();
        if (result.Success && result.Data != null)
        {
            foreach (var row in result.Data)
            {
                var dict = row as IDictionary<string, object>;
                if (dict != null)
                {
                    columns.Add(new DatabaseColumnDto
                    {
                        ColumnName = dict["ColumnName"]?.ToString() ?? "",
                        DataType = dict["DataType"]?.ToString() ?? "",
                        IsNullable = dict["IsNullable"] is bool b && b,
                        MaxLength = dict["MaxLength"] != null ? int.Parse(dict["MaxLength"].ToString()) : null
                    });
                }
            }
        }

        return columns;
    }

    private SqlQueryExecutionResultDto MapExecutionResult(SqlExecutionResult result, bool isDeployed = false)
    {
        return new SqlQueryExecutionResultDto
        {
            Success = result.Success,
            Message = result.Success
                ? (isDeployed ? QueryExecutedAndDeployedMessage : QueryExecutedSuccessfullyMessage)
                : result.Message,
            Data = result.Data,
            RowsAffected = result.RowsAffected,
            ExecutionTimeMs = result.ExecutionTimeMs,
            Metadata = result.Metadata
        };
    }

    public Task SaveTableScriptAsync(SaveTableScriptDto input)
    {
        // Security: reject any path traversal attempts
        if (string.IsNullOrWhiteSpace(input?.FileName) ||
            input.FileName.Contains('/') ||
            input.FileName.Contains('\\') ||
            input.FileName.Contains(".."))
        {
            throw new Volo.Abp.UserFriendlyException("Invalid file name.");
        }

        try
        {
            var outputPath = ResolveSqlDataOutputPath();
            Directory.CreateDirectory(outputPath);

            var safeFileName = string.Concat(input.FileName.Trim().Split(Path.GetInvalidFileNameChars()));
            var filePath = Path.Combine(outputPath, $"{safeFileName}.sql");
            File.WriteAllText(filePath, input.SqlScript);

            _logger.LogInformation("SQL seed file saved: {FilePath}", filePath);
        }
        catch (Exception ex)
        {
            // File save failure does not block the deploy
            _logger.LogError(ex, "Failed to save SQL seed file: {Message}", ex.Message);
        }

        return Task.CompletedTask;
    }

    private bool TrySyncSqlObjectScriptFile(string sqlScript)
    {
        if (string.IsNullOrWhiteSpace(sqlScript))
            return false;

        if (TrySaveSqlObjectScript(sqlScript))
            return true;

        return TryDeleteSqlObjectScripts(sqlScript);
    }

    private bool TrySaveSqlObjectScript(string sqlScript)
    {
        var match = SqlObjectDefinitionRegex.Match(sqlScript);
        if (!match.Success)
            return false;

        var objectType = NormalizeObjectType(match.Groups["type"].Value);
        var (schemaName, objectName) = ParseSchemaAndObjectName(match.Groups["name"].Value);

        if (string.IsNullOrWhiteSpace(objectName))
            return false;

        var fileName = BuildSqlObjectScriptFileName(objectType, schemaName, objectName);
        var canonicalScript = CanonicalizeSqlObjectScriptForSeed(sqlScript);
        SaveSqlDataFile(fileName, canonicalScript);
        return true;
    }

    private bool TryDeleteSqlObjectScripts(string sqlScript)
    {
        var match = SqlObjectDropRegex.Match(sqlScript);
        if (!match.Success)
            return false;

        var objectType = NormalizeObjectType(match.Groups["type"].Value);
        var rawNames = match.Groups["names"].Value
            .Split(',')
            .Select(x => x.Trim())
            .Where(x => !string.IsNullOrWhiteSpace(x))
            .Distinct(StringComparer.OrdinalIgnoreCase)
            .ToList();

        foreach (var rawName in rawNames)
        {
            var (schemaName, objectName) = ParseSchemaAndObjectName(rawName);
            if (string.IsNullOrWhiteSpace(objectName))
                continue;

            var fileName = BuildSqlObjectScriptFileName(objectType, schemaName, objectName);
            DeleteSqlDataFile(fileName);
        }

        return rawNames.Count > 0;
    }

    private void SaveSqlDataFile(string fileName, string content)
    {
        try
        {
            var outputPath = ResolveSqlDataOutputPath();
            Directory.CreateDirectory(outputPath);

            var safeFileName = string.Concat(fileName.Split(Path.GetInvalidFileNameChars()));
            if (string.IsNullOrWhiteSpace(safeFileName))
                return;

            var filePath = Path.Combine(outputPath, $"{safeFileName}.sql");
            File.WriteAllText(filePath, content ?? string.Empty);
            _logger.LogInformation("SQL object script saved: {FilePath}", filePath);
        }
        catch (Exception ex)
        {
            // File save failure does not block query execution
            _logger.LogError(ex, "Failed to save SQL object script: {Message}", ex.Message);
        }
    }

    private void DeleteSqlDataFile(string fileName)
    {
        try
        {
            var outputPath = ResolveSqlDataOutputPath();
            if (!Directory.Exists(outputPath))
                return;

            var safeFileName = string.Concat(fileName.Split(Path.GetInvalidFileNameChars()));
            if (string.IsNullOrWhiteSpace(safeFileName))
                return;

            var filePath = Path.Combine(outputPath, $"{safeFileName}.sql");
            if (!File.Exists(filePath))
                return;

            File.Delete(filePath);
            _logger.LogInformation("SQL object script deleted: {FilePath}", filePath);
        }
        catch (Exception ex)
        {
            // File delete failure does not block query execution
            _logger.LogError(ex, "Failed to delete SQL object script: {Message}", ex.Message);
        }
    }

    private static string BuildSqlObjectScriptFileName(string objectType, string schemaName, string objectName)
    {
        return objectName;
    }

    private static string CanonicalizeSqlObjectScriptForSeed(string sqlScript)
    {
        if (string.IsNullOrWhiteSpace(sqlScript))
            return string.Empty;

        var canonical = SqlObjectHeaderCanonicalizeRegex.Replace(sqlScript, match =>
        {
            var prefix = match.Groups["prefix"].Value;
            var after = match.Groups["after"].Value;
            after = Regex.Replace(after, @"^OR\s+ALTER\s+", string.Empty, RegexOptions.IgnoreCase);
            return $"{prefix}CREATE OR ALTER {after}";
        }, 1);

        return canonical;
    }

    private static string NormalizeObjectType(string rawType)
    {
        if (string.Equals(rawType, "PROC", StringComparison.OrdinalIgnoreCase) ||
            string.Equals(rawType, "PROCEDURE", StringComparison.OrdinalIgnoreCase))
        {
            return "procedure";
        }

        if (string.Equals(rawType, "FUNCTION", StringComparison.OrdinalIgnoreCase))
        {
            return "function";
        }

        return "view";
    }

    private static (string SchemaName, string ObjectName) ParseSchemaAndObjectName(string fullName)
    {
        var parts = SplitSqlMultipartIdentifier(fullName)
            .Select(UnquoteSqlIdentifier)
            .Where(p => !string.IsNullOrWhiteSpace(p))
            .ToList();

        if (parts.Count == 0)
            return ("dbo", string.Empty);

        if (parts.Count == 1)
            return ("dbo", parts[0]);

        return (parts[^2], parts[^1]);
    }

    private static List<string> SplitSqlMultipartIdentifier(string value)
    {
        var parts = new List<string>();
        if (string.IsNullOrWhiteSpace(value))
            return parts;

        var buffer = new System.Text.StringBuilder();
        var inBracket = false;
        var inDoubleQuote = false;

        foreach (var ch in value)
        {
            if (ch == '[' && !inDoubleQuote)
            {
                inBracket = true;
                buffer.Append(ch);
                continue;
            }

            if (ch == ']' && inBracket)
            {
                inBracket = false;
                buffer.Append(ch);
                continue;
            }

            if (ch == '"' && !inBracket)
            {
                inDoubleQuote = !inDoubleQuote;
                buffer.Append(ch);
                continue;
            }

            if (ch == '.' && !inBracket && !inDoubleQuote)
            {
                var token = buffer.ToString().Trim();
                if (!string.IsNullOrWhiteSpace(token))
                    parts.Add(token);

                buffer.Clear();
                continue;
            }

            buffer.Append(ch);
        }

        var lastToken = buffer.ToString().Trim();
        if (!string.IsNullOrWhiteSpace(lastToken))
            parts.Add(lastToken);

        return parts;
    }

    private static string UnquoteSqlIdentifier(string value)
    {
        if (string.IsNullOrWhiteSpace(value))
            return string.Empty;

        value = value.Trim();
        if (value.Length >= 2 && value[0] == '[' && value[^1] == ']')
            return value.Substring(1, value.Length - 2);

        if (value.Length >= 2 && value[0] == '"' && value[^1] == '"')
            return value.Substring(1, value.Length - 2);

        return value;
    }

    [HttpPost("api/app/sql-object-manager/delete-sql-data-files")]
    public Task DeleteSqlDataFilesAsync(DeleteSqlDataFilesDto input)
    {
        if (input?.FileNames == null || input.FileNames.Count == 0)
            return Task.CompletedTask;

        try
        {
            var outputPath = ResolveSqlDataOutputPath();
            if (!Directory.Exists(outputPath))
                return Task.CompletedTask;

            foreach (var rawName in input.FileNames.Distinct())
            {
                if (string.IsNullOrWhiteSpace(rawName))
                    continue;

                // Security: reject any path traversal attempts
                if (rawName.Contains('/') || rawName.Contains('\\') || rawName.Contains(".."))
                    continue;

                var safeFileName = string.Concat(rawName.Trim().Split(Path.GetInvalidFileNameChars()));
                if (string.IsNullOrWhiteSpace(safeFileName))
                    continue;

                var filePath = Path.Combine(outputPath, $"{safeFileName}.sql");
                if (!File.Exists(filePath))
                    continue;

                File.Delete(filePath);
                _logger.LogInformation("SQL seed file deleted: {FilePath}", filePath);
            }
        }
        catch (Exception ex)
        {
            // File delete failure does not block drop operation
            _logger.LogError(ex, "Failed to delete SQL seed file(s): {Message}", ex.Message);
        }

        return Task.CompletedTask;
    }

    private string ResolveSqlDataOutputPath()
    {
        const string dbMigratorName = "Sozsoft.Platform.DbMigrator";
        var dir = new DirectoryInfo(_hostEnvironment.ContentRootPath);

        while (dir != null)
        {
            var candidate = Path.Combine(dir.FullName, "src", dbMigratorName, "Seeds");
            if (Directory.Exists(candidate))
                return Path.Combine(candidate, "SqlData");

            candidate = Path.Combine(dir.FullName, dbMigratorName, "Seeds");
            if (Directory.Exists(candidate))
                return Path.Combine(candidate, "SqlData");

            dir = dir.Parent;
        }

        return Path.Combine(_hostEnvironment.ContentRootPath, "Seeds", "SqlData");
    }
}