package mysql

import (
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"
	"time"

	"git.yuntuo.hk/k2safe/orbit/internal/fault"
	core "git.yuntuo.hk/k2safe/orbit/model"
	"git.yuntuo.hk/k2safe/orbit/platform/auth"
	pulse "git.yuntuo.hk/k2safe/orbit/pulse/model"
	"git.yuntuo.hk/k2safe/orbit/pulse/service"
)

// CancelTask 将取消意图与开始授权串行化；已开始的尝试仍须确认结果或到期核查。
func (s *TaskStore) CancelTask(ctx context.Context, token auth.Token, id core.ID, key string, in service.CancelInput) (service.CancelResult, error) {
	var out service.CancelResult
	err := s.transaction(ctx, token, "tasks:cancel", func(tx *sql.Tx, p auth.Permissions) error {
		view, err := readTask(ctx, tx, token.NamespaceID, id, false)
		if err != nil {
			return err
		}
		if !p.AllowsQueue(view.QueueID) {
			return fault.NotFound
		}
		identity, cached, err := reserveIdentity(ctx, tx, token.NamespaceID, "task.cancel", string(id), key, "task", id, in)
		if err != nil {
			return err
		}
		if cached != nil {
			if err := json.Unmarshal(cached, &out); err != nil {
				return err
			}
			out.Deduplicated = true
			return nil
		}
		// 应用额度 → 队列 → 任务 → 尝试 → 许可；取消不获取 Worker 会话锁。
		if _, _, err := lockQueue(ctx, tx, token.NamespaceID, view.QueueID); err != nil {
			return err
		}
		task, err := readExecutionTask(ctx, tx, token.NamespaceID, id)
		if err != nil {
			return err
		}
		view = task.view
		if view.Revision != in.ExpectedRevision || view.State.Terminal() || view.CancelRequestedAt != nil {
			return fault.Conflict
		}
		var owner sql.NullString
		if err := tx.QueryRowContext(ctx, "SELECT owner_kind FROM pulse_tasks WHERE namespace_id=? AND id=?", token.NamespaceID, id).Scan(&owner); err != nil {
			return err
		}
		if owner.Valid && owner.String != "schedule" {
			return fault.Conflict
		}
		var attempt *pulse.Attempt
		if view.State == pulse.TaskLeased || view.State == pulse.TaskRunning {
			if task.current == nil {
				return errors.New("active task lacks attempt")
			}
			a, err := readAttempt(ctx, tx, token.NamespaceID, *task.current)
			if err != nil {
				return err
			}
			if a.TaskID != id || a.Epoch != task.epoch || string(a.State) != string(view.State) {
				return errors.New("task attempt identity or state mismatch")
			}
			attempt = &a
		}
		now, err := dbNow(ctx, tx)
		if err != nil {
			return err
		}
		next := view.State
		lease := task.lease
		var completed *time.Time
		if view.State == pulse.TaskWaiting || view.State == pulse.TaskLeased {
			next = pulse.TaskCancelled
			completed = &now
			lease = nil
			if view.EffectUncertain {
				next, completed = pulse.TaskNeedsReview, nil
			}
			if attempt != nil {
				if attempt.AuthorizedAt != nil {
					return errors.New("leased attempt already authorized")
				}
				result, err := tx.ExecContext(ctx, `UPDATE pulse_attempts SET state='CANCELLED',ended_at=?,error_code='CANCELLED_BEFORE_START',revision=revision+1,updated_at=? WHERE namespace_id=? AND id=? AND revision=?`, now, now, token.NamespaceID, attempt.ID, attempt.Revision)
				if err := exactlyOne(result, err); err != nil {
					return err
				}
				if err := releasePermits(ctx, tx, token.NamespaceID, attempt.ID, now); err != nil {
					return err
				}
			}
		}
		result, err := tx.ExecContext(ctx, `UPDATE pulse_tasks SET state=?,cancel_requested_at=?,lease_until=?,completed_at=?,updated_at=?,revision=revision+1 WHERE namespace_id=? AND id=? AND revision=?`, next, now, lease, completed, now, token.NamespaceID, id, in.ExpectedRevision)
		if err := exactlyOne(result, err); err != nil {
			return err
		}
		if next.Terminal() {
			if err := releaseQueueTask(ctx, tx, token.NamespaceID, view.QueueID); err != nil {
				return err
			}
		}
		out.Task, err = readTask(ctx, tx, token.NamespaceID, id, false)
		if err != nil {
			return err
		}
		event := resultEvent(next)
		if next == view.State {
			event = "task.cancel_requested"
		}
		if err := emitEvent(ctx, tx, token.NamespaceID, id, out.Task.Revision, "task", event, map[string]any{"task_id": id, "state": next, "reason": "CANCEL_REQUESTED", "effect_uncertain": view.EffectUncertain}); err != nil {
			return err
		}
		if err := appendAudit(ctx, tx, token, identity, id, "task", "task.cancel", in.Reason, map[string]any{"state": view.State, "revision": fmt.Sprint(view.Revision)}, map[string]any{"state": next, "revision": fmt.Sprint(out.Task.Revision), "cancel_requested_at": now}); err != nil {
			return err
		}
		return saveIdentity(ctx, tx, token.NamespaceID, identity, out)
	})
	return out, err
}