package history

import (
	"context"
	"fmt"
)

// ListAfter 按最旧优先返回 sessionID 中严格新于 after（created_at > after）的
// 至多 limit 条消息，用于前向增量追赶：重连的客户端传入自己已见过的最新
// createdAt，只拉取错过的部分，无论有多少条（"before" 游标只能向后走，无法
// 恢复大于一页的空洞）。platform 非空时把该页进一步限制为携带该来源平台的
// 消息，与 List 完全一致。rowid 打破 created_at 的并列，使同一毫秒写入的
// 消息保持插入顺序。返回切片非 nil；limit 钳制到 [1, maxPageLimit]。
func (s *Store) ListAfter(ctx context.Context, sessionID string, after int64, limit int, platform string) ([]Message, error) {
	limit = clampLimit(limit)
	query := `SELECT ` + messageColumns + `
		FROM chat_messages WHERE session_id = ? AND created_at > ?`
	args := []any{sessionID, after}
	if platform != "" {
		query += ` AND platform = ?`
		args = append(args, platform)
	}
	query += ` ORDER BY created_at ASC, rowid ASC LIMIT ?`
	args = append(args, limit)

	rows, err := s.db.QueryContext(ctx, query, args...)
	if err != nil {
		return nil, fmt.Errorf("history: list after %s: %w", sessionID, err)
	}
	defer func() { _ = rows.Close() }()

	msgs := make([]Message, 0)
	for rows.Next() {
		m, err := scanMessage(rows)
		if err != nil {
			return nil, fmt.Errorf("history: scan list after %s: %w", sessionID, err)
		}
		msgs = append(msgs, m)
	}
	if err := rows.Err(); err != nil {
		return nil, fmt.Errorf("history: iterate list after %s: %w", sessionID, err)
	}
	return msgs, nil
}