using Microsoft.EntityFrameworkCore;
using Volo.Abp.Application.Services;
using Volo.Abp.Domain.Repositories;
using Volo.Abp.Application.Dtos;
using System.Text;
using Volo.Abp.Domain.Entities;
using Kurs.Platform.Entities;
using Kurs.Platform.DeveloperKit;
using System;
using System.Threading.Tasks;
using System.Collections.Generic;
using System.Linq;
using Kurs.Platform.Domain.DeveloperKit;

namespace Platform.Api.Application;

public class CrudMigrationAppService : CrudAppService<
    CrudMigration,
    CrudMigrationDto,
    Guid,
    PagedAndSortedResultRequestDto,
    CreateUpdateCrudMigrationDto>, ICrudMigrationAppService
{
    private readonly IRepository<CrudMigration, Guid> _migrationRepository;
    private readonly IRepository<CustomEntity, Guid> _entityRepository;
    private readonly IRepository<CustomEntity, Guid> _fieldRepository;
    private readonly IApiMigrationRepository _customSqlExecutor;

    public CrudMigrationAppService(
        IRepository<CrudMigration, Guid> migrationRepository,
        IRepository<CustomEntity, Guid> entityRepository,
        IRepository<CustomEntity, Guid> fieldRepository,
        IApiMigrationRepository customSqlExecutor
        ) : base(migrationRepository)
    {
        _migrationRepository = migrationRepository;
        _entityRepository = entityRepository;
        _fieldRepository = fieldRepository;
        _customSqlExecutor = customSqlExecutor;
    }

    public virtual async Task<CrudMigrationDto> ApplyMigrationAsync(Guid id)
    {
        var migration = await _migrationRepository.GetAsync(id);

        try
        {
            await _customSqlExecutor.ExecuteSqlAsync(migration.SqlScript);

            migration.Status = "applied";
            migration.AppliedAt = DateTime.UtcNow;
            migration.ErrorMessage = null;

            await _migrationRepository.UpdateAsync(migration, autoSave: true);

            var entity = await _entityRepository.GetAsync(migration.EntityId);
            entity.MigrationStatus = "applied";
            await _entityRepository.UpdateAsync(entity, autoSave: true);

            return ObjectMapper.Map<CrudMigration, CrudMigrationDto>(migration);
        }
        catch (Exception ex)
        {
            migration.Status = "failed";
            migration.ErrorMessage = ex.Message;
            await _migrationRepository.UpdateAsync(migration, autoSave: true);

            var entity = await _entityRepository.GetAsync(migration.EntityId);
            entity.MigrationStatus = "failed";
            await _entityRepository.UpdateAsync(entity, autoSave: true);

            throw;
        }
    }


    public virtual async Task<List<CrudMigrationDto>> GetPendingMigrationsAsync()
    {
        var queryable = await _migrationRepository.GetQueryableAsync();
        var pending = await queryable
            .Where(m => m.Status == "pending")
            .OrderBy(m => m.CreationTime)
            .ToListAsync();

        return ObjectMapper.Map<List<CrudMigration>, List<CrudMigrationDto>>(pending);
    }


    public virtual async Task<CrudMigrationDto> GenerateMigrationAsync(Guid entityId)
    {
        var queryable = await _entityRepository.GetQueryableAsync();
        var entity = await queryable
            .Include(x => x.Fields)
            .FirstOrDefaultAsync(x => x.Id == entityId);

        if (entity == null)
            throw new EntityNotFoundException($"CustomEntity with id {entityId} not found");

        // Check if there are any previously applied migrations for this entity
        var migrationQueryable = await _migrationRepository.GetQueryableAsync();
        var lastAppliedMigration = await migrationQueryable
            .Where(m => m.EntityId == entityId && m.Status == "applied")
            .OrderByDescending(m => m.CreationTime)
            .FirstOrDefaultAsync();

        // Use "Update" if migrations were applied before, otherwise "Create"
        var operationType = lastAppliedMigration != null ? "Update" : "Create";
        var fileName = $"{DateTime.UtcNow:yyyyMMddHHmmss}_{operationType}{entity.Name}Table.sql";

        var sqlScript = lastAppliedMigration != null 
            ? GenerateAlterTableScript(entity, lastAppliedMigration)
            : GenerateCreateTableScript(entity);

        var migration = new CrudMigration
        {
            EntityId = entityId,
            EntityName = entity.Name,
            FileName = fileName,
            SqlScript = sqlScript,
            Status = "pending"
        };

        migration = await _migrationRepository.InsertAsync(migration, autoSave: true);

        entity.MigrationId = migration.Id;
        entity.MigrationStatus = "pending";
        await _entityRepository.UpdateAsync(entity, autoSave: true);

        return ObjectMapper.Map<CrudMigration, CrudMigrationDto>(migration);
    }

    private string GenerateCreateTableScript(CustomEntity entity)
    {
        if (entity.Fields == null || !entity.Fields.Any())
            throw new InvalidOperationException($"Entity '{entity.Name}' does not have any fields defined.");

        var sb = new StringBuilder();

        sb.AppendLine($@"/*
  # Create {entity.DisplayName} table

  1. New Table
    - [{entity.TableName}]");

        foreach (var field in entity.Fields)
        {
            sb.AppendLine($"      - [{field.Name}] ({field.Type}{(field.IsRequired ? ", required" : "")})");
        }

        sb.AppendLine("*/");

        sb.AppendLine($"\nIF OBJECT_ID(N'{entity.TableName}', N'U') IS NULL");
        sb.AppendLine($"CREATE TABLE [{entity.TableName}] (");
        sb.AppendLine("  [Id] UNIQUEIDENTIFIER PRIMARY KEY DEFAULT NEWID(),");

        foreach (var field in entity.Fields)
        {
            var sqlType = GetSqlType(field.Type, field.MaxLength);
            sb.Append($"  [{field.Name}] {sqlType}");

            if (field.IsRequired)
                sb.Append(" NOT NULL");

            if (!string.IsNullOrWhiteSpace(field.DefaultValue))
                sb.Append($" DEFAULT {FormatDefaultValue(field.Type, field.DefaultValue)}");

            sb.AppendLine(",");
        }

        // Add TenantId if entity is multi-tenant
        if (entity.IsMultiTenant)
        {
            sb.AppendLine("  [TenantId] UNIQUEIDENTIFIER NULL,");
        }

        // Add Full Audited Entity fields (includes both audit and soft delete)
        if (entity.IsFullAuditedEntity)
        {
            sb.AppendLine("  [CreationTime] DATETIME2 DEFAULT SYSUTCDATETIME() NOT NULL,");
            sb.AppendLine("  [CreatorId] UNIQUEIDENTIFIER NULL,");
            sb.AppendLine("  [LastModificationTime] DATETIME2 NULL,");
            sb.AppendLine("  [LastModifierId] UNIQUEIDENTIFIER NULL,");
            sb.AppendLine("  [IsDeleted] BIT DEFAULT 0 NOT NULL,");
            sb.AppendLine("  [DeleterId] UNIQUEIDENTIFIER NULL,");
            sb.AppendLine("  [DeletionTime] DATETIME2 NULL,");
        }

        // Remove last comma
        var script = sb.ToString().TrimEnd(',', '\r', '\n');
        script += "\n);\n";

        return script;
    }

    private string GenerateAlterTableScript(CustomEntity entity, CrudMigration lastAppliedMigration)
    {
        if (entity.Fields == null || !entity.Fields.Any())
            throw new InvalidOperationException($"Entity '{entity.Name}' does not have any fields defined.");

        // Parse the last applied migration's SQL to understand what fields existed
        var existingFieldNames = ExtractFieldNamesFromCreateScript(lastAppliedMigration.SqlScript);
        
        var sb = new StringBuilder();

        sb.AppendLine($@"/*
  # Update {entity.DisplayName} table

  1. Alter Table
    - [{entity.TableName}]
    - Adding new fields or modifying existing ones");

        sb.AppendLine("*/\n");

        // Find new fields that need to be added
        var newFields = entity.Fields.Where(f => !existingFieldNames.Contains(f.Name)).ToList();

        if (newFields.Any())
        {
            foreach (var field in newFields)
            {
                var sqlType = GetSqlType(field.Type, field.MaxLength);
                sb.Append($"IF NOT EXISTS (SELECT * FROM sys.columns WHERE object_id = OBJECT_ID(N'[{entity.TableName}]') AND name = '{field.Name}')\n");
                sb.Append($"BEGIN\n");
                sb.Append($"  ALTER TABLE [{entity.TableName}] ADD [{field.Name}] {sqlType}");

                if (field.IsRequired)
                    sb.Append(" NOT NULL");
                else
                    sb.Append(" NULL");

                if (!string.IsNullOrWhiteSpace(field.DefaultValue))
                    sb.Append($" DEFAULT {FormatDefaultValue(field.Type, field.DefaultValue)}");

                sb.AppendLine(";");
                sb.AppendLine($"END\n");
            }
        }
        else
        {
            sb.AppendLine("-- No new fields to add");
        }

        return sb.ToString();
    }

    private HashSet<string> ExtractFieldNamesFromCreateScript(string sqlScript)
    {
        var fieldNames = new HashSet<string>(StringComparer.OrdinalIgnoreCase);
        
        // Simple parsing - extract field names between [ and ]
        var lines = sqlScript.Split('\n');
        foreach (var line in lines)
        {
            var trimmedLine = line.Trim();
            if (trimmedLine.StartsWith("[") && trimmedLine.Contains("]"))
            {
                var fieldName = trimmedLine.Substring(1, trimmedLine.IndexOf("]") - 1);
                if (fieldName != "Id" && 
                    fieldName != "TenantId" &&
                    fieldName != "CreationTime" && 
                    fieldName != "CreatorId" && 
                    fieldName != "LastModificationTime" && 
                    fieldName != "LastModifierId" &&
                    fieldName != "IsDeleted" &&
                    fieldName != "DeleterId" &&
                    fieldName != "DeletionTime")
                {
                    fieldNames.Add(fieldName);
                }
            }
        }
        
        return fieldNames;
    }

    private string GetSqlType(string fieldType, int? maxLength)
    {
        return fieldType.ToLower() switch
        {
            "string" => maxLength.HasValue ? $"NVARCHAR({maxLength.Value})" : "NVARCHAR(MAX)",
            "number" => "INT",
            "decimal" => "DECIMAL(18, 2)",
            "boolean" => "BIT",
            "date" => "DATETIME2",
            "guid" => "UNIQUEIDENTIFIER",
            _ => "NVARCHAR(MAX)"
        };
    }

    private string FormatDefaultValue(string fieldType, string defaultValue)
    {
        return fieldType.ToLower() switch
        {
            "string" => $"N'{defaultValue}'",
            "date" => $"'{defaultValue}'", // ISO format beklenir
            "guid" => $"'{defaultValue}'",
            "boolean" => (defaultValue.ToLower() == "true" || defaultValue == "1") ? "1" : "0",
            _ => defaultValue
        };
    }
}