package mysql

import (
	"context"
	"database/sql"
	"errors"
	"math"

	"git.yuntuo.hk/k2safe/orbit/internal/jsonwire"
	core "git.yuntuo.hk/k2safe/orbit/model"
	"git.yuntuo.hk/k2safe/orbit/platform/events"
)

// appendResultEvent 必须在来源任务更新和事件写入之后、原事务提交之前调用。
// 流行一直锁到提交；后来的事务无法提交更大序号并越过尚未提交的较小序号。
// 不访问订阅或交付行：慢消费者不能反向阻塞任务的结果持久化。
func appendResultEvent(ctx context.Context, tx *sql.Tx, ns, eventID, taskID core.ID, revision uint64, eventType string) error {
	var snapshot events.TaskResult
	var raw []byte
	snapshot.SchemaVersion = 1
	err := tx.QueryRowContext(ctx, `SELECT id,queue_id,state,revision,result,effect_uncertain,current_attempt_id FROM pulse_tasks WHERE namespace_id=? AND id=?`, ns, taskID).Scan(&snapshot.TaskID, &snapshot.QueueID, &snapshot.State, &snapshot.Revision, &raw, &snapshot.EffectUncertain, &snapshot.CurrentAttemptID)
	if err != nil {
		return err
	}
	if snapshot.Revision != revision || eventType != "task."+map[string]string{"SUCCEEDED": "succeeded", "FAILED": "failed", "CANCELLED": "cancelled", "NEEDS_REVIEW": "needs_review"}[snapshot.State] {
		return errors.New("task result event does not match persisted task state")
	}
	snapshot.Result = raw
	body, err := jsonwire.Marshal(snapshot)
	if err != nil {
		return err
	}
	head, _, err := lockEventStream(ctx, tx, ns)
	if err != nil {
		return err
	}
	if head == math.MaxUint64 {
		return errors.New("event sequence exhausted")
	}
	if _, err = tx.ExecContext(ctx, `INSERT INTO orbit_result_events(namespace_id,id,sequence,queue_id,snapshot) VALUES (?,?,?,?,?)`, ns, eventID, head+1, snapshot.QueueID, string(body)); err != nil {
		return err
	}
	_, err = tx.ExecContext(ctx, `UPDATE orbit_event_streams SET last_sequence=?,updated_at=UTC_TIMESTAMP(6) WHERE namespace_id=?`, head+1, ns)
	return err
}
func lockEventStream(ctx context.Context, tx *sql.Tx, ns core.ID) (head, retained uint64, err error) {
	if _, err = tx.ExecContext(ctx, `INSERT INTO orbit_event_streams(namespace_id) VALUES (?) ON DUPLICATE KEY UPDATE namespace_id=orbit_event_streams.namespace_id`, ns); err != nil {
		return
	}
	err = tx.QueryRowContext(ctx, `SELECT last_sequence,retained_from_sequence FROM orbit_event_streams WHERE namespace_id=? FOR UPDATE`, ns).Scan(&head, &retained)
	return
}