package tasks

import (
	"context"
	"fmt"
	"time"

	"github.com/getsentry/sentry-go"
	"github.com/google/uuid"
	"github.com/rs/zerolog/log"
	"github.com/warmbly/warmbly/internal/errx"
	"github.com/warmbly/warmbly/internal/tasks/proto"
)

func (s *tasksService) HandleUserEmailTask(task *proto.ProcessTask) *errx.Error {
	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
	defer cancel()

	// STEP 1: Parse task ID
	taskID, err := uuid.Parse(task.TaskId)
	if err != nil {
		sentry.CaptureException(err)
		return errx.New(errx.BadRequest, "invalid task ID")
	}

	executionKey := "user-email:" + taskID.String()
	executionStatus := "failed"
	if s.advanced != nil {
		duplicate, xerr := s.advanced.StartTaskExecution(ctx, taskID, executionKey, map[string]interface{}{
			"task_type": "user_email",
		})
		if xerr != nil {
			return xerr
		}
		if duplicate {
			return nil
		}
		defer func() {
			_ = s.advanced.CompleteTaskExecution(ctx, taskID, executionKey, executionStatus, map[string]interface{}{
				"task_type": "user_email",
			})
		}()
	}

	// STEP 2: Load task record
	taskRecord, err := s.taskRepo.GetTask(ctx, taskID)
	if err != nil {
		sentry.CaptureException(err)
		return errx.InternalError()
	}

	if taskRecord == nil {
		// A queued Cloud Task is firing for a task row that no longer
		// exists in the DB. Treat as success so Cloud Tasks doesn't
		// retry — the only way this happens is if the row was
		// explicitly removed (e.g. account/org wipe) and we don't
		// want phantom retries piling up.
		log.Info().Str("task_id", taskID.String()).
			Msg("user_email skipped: task row missing (returning success)")
		return nil
	}

	// Soft-cancel path. The dashboard "Scheduled" view cancels a
	// queued send by flipping status to 'cancelled' (no Cloud Tasks
	// DeleteTask call — that's a paid API per cancel). When the
	// queued task fires, we see the non-pending status and return
	// success so Cloud Tasks doesn't retry. Also catches:
	//   - completed (duplicate fire / replay)
	//   - failed / dead_lettered (already terminal)
	//   - active (mid-flight by another worker)
	if taskRecord.Status != "pending" {
		log.Info().
			Str("task_id", taskID.String()).
			Str("status", taskRecord.Status).
			Msg("user_email skipped: task not in pending state")
		return nil
	}

	// STEP 3: Load email_task record (with new columns)
	emailTask, err := s.taskRepo.GetEmailTask(ctx, taskID)
	if err != nil {
		sentry.CaptureException(err)
		return errx.InternalError()
	}

	if emailTask == nil {
		return errx.ErrNotFound
	}

	// STEP 4: Load email account
	account, xerr := s.emailRepo.GetByID(ctx, taskRecord.EmailAccountID)
	if xerr != nil {
		return xerr
	}

	// Pre-execution guards. The user may have queued this send
	// hours/days/weeks ago — re-validate that:
	//   (a) the mailbox is still active (not revoked/inactive/deleted)
	//   (b) the org still has unibox/send access (sub didn't lapse)
	// If either fails we cancel the task with a clear reason instead
	// of dispatching to the worker and producing an SMTP failure
	// downstream.
	if account.Status != "active" {
		_ = s.taskRepo.RecordTaskFailure(ctx, taskID,
			"Mailbox no longer active",
			"email account status="+string(account.Status)+" at execution time")
		_ = s.taskRepo.UpdateTaskStatus(ctx, taskID, "cancelled")
		log.Info().Str("task_id", taskID.String()).Str("status", string(account.Status)).
			Msg("user_email cancelled: mailbox not active")
		return nil
	}
	// Tenancy gate: the entitlement check below is org-scoped, so a mailbox with
	// no workspace would send without it. Fail closed.
	if account.OrganizationID == nil {
		sentry.CaptureException(fmt.Errorf("email account %s reached a unibox send with no organization", account.ID))
		_ = s.taskRepo.RecordTaskFailure(ctx, taskID,
			"Mailbox has no workspace",
			"email account organization_id is NULL at execution time")
		_ = s.taskRepo.UpdateTaskStatus(ctx, taskID, "cancelled")
		log.Error().Str("task_id", taskID.String()).Str("email_account_id", account.ID.String()).
			Msg("user_email cancelled: mailbox has no organization")
		return nil
	}
	if s.featureGate != nil {
		canUse, _ := s.featureGate.CanUseUnibox(ctx, *account.OrganizationID)
		if !canUse {
			_ = s.taskRepo.RecordTaskFailure(ctx, taskID,
				"Subscription does not allow sending",
				"feature gate CanUseUnibox=false at execution time")
			_ = s.taskRepo.UpdateTaskStatus(ctx, taskID, "cancelled")
			log.Info().Str("task_id", taskID.String()).
				Msg("user_email cancelled: feature gate denied at execution time")
			return nil
		}
	}

	// STEP 5: Mark task as active (with advisory lock)
	if err := s.taskRepo.UpdateTaskStatusWithLock(ctx, taskID, "active"); err != nil {
		sentry.CaptureException(err)
		return errx.InternalError()
	}

	// STEP 6: Add signature if SignatureSync
	bodyHTML := emailTask.BodyHTML
	bodyPlain := emailTask.BodyPlain

	if account.SignatureSync {
		if bodyHTML != "" {
			bodyHTML = AddSignature(bodyHTML, account.SignatureHTML, true)
		}
		if bodyPlain != "" {
			bodyPlain = AddSignature(bodyPlain, account.SignaturePlain, false)
		}
	}

	// STEP 7: Generate Message-ID
	messageID := generateMessageID(account.Email)

	// STEP 8: Build InReplyTo string
	var inReplyTo string
	if len(emailTask.InReplyTo) > 0 {
		inReplyTo = emailTask.InReplyTo[0]
	}

	// The composer's thread is persisted on the task row; without carrying it
	// through, every dashboard reply starts a new conversation.
	var threadID string
	if emailTask.ThreadID != nil {
		threadID = *emailTask.ThreadID
	}

	// STEP 9: Build EmailMessage and send via worker
	emailMsg := EmailMessage{
		From:      account.Email,
		To:        emailTask.To,
		CC:        emailTask.CC,
		BCC:       emailTask.BCC,
		Subject:   emailTask.Subject,
		BodyHTML:  bodyHTML,
		BodyPlain: bodyPlain,
		InReplyTo: inReplyTo,
		MessageID: messageID,
		ThreadID:  threadID,
		IsWarmup:  false,
		Tracking:  nil,
	}

	if err := s.emailSender.Send(ctx, taskID, emailMsg, *account); err != nil {
		s.taskRepo.RecordTaskFailure(ctx, taskID, "Send failed", err.Error())
		if s.advanced != nil {
			_ = s.advanced.CaptureTaskDeadLetter(ctx, taskID, "user_email", map[string]interface{}{
				"account_id": account.ID.String(),
				"to":         emailTask.To,
			}, err.Error(), 1)
			_ = s.taskRepo.UpdateTaskStatus(ctx, taskID, "dead_lettered")
		}
		return nil
	}

	// STEP 10: Update task record
	taskRecord.MessageID = messageID
	taskRecord.Status = "completed"

	// STEP 11: Mark task completed (with advisory lock)
	if err := s.taskRepo.UpdateTaskStatusWithLock(ctx, taskID, "completed"); err != nil {
		sentry.CaptureException(err)
		return errx.InternalError()
	}

	// STEP 12: Publish events
	log.Info().Str("task_id", task.TaskId).Str("account_id", account.ID.String()).Msg("user email sent")

	executionStatus = "completed"
	return nil
}