#include "roster.h"
#include <QSet>

namespace Roster {
ParsedNames parse(const QString &text)
{
    ParsedNames result;
    QSet<QString> seen;
    const QStringList lines = text.split(QLatin1Char('\n'));
    int lineNumber = 0;
    for (const QString &line : lines) {
        ++lineNumber;
        const QString name = line.trimmed();
        if (name.isEmpty()) continue;
        if (seen.contains(name)) {
            result.error = QStringLiteral("第 %1 行与前面的条目重复：%2。"
                "同名学生请加上学号后再应用名单。").arg(lineNumber).arg(name);
            return result;
        }
        if (name.size() > 100) {
            result.error = QStringLiteral("第 %1 行超过 100 个字符，请检查是否粘贴了整段文字。")
                               .arg(lineNumber);
            return result;
        }
        seen.insert(name);
        result.names.append(name);
    }
    if (result.names.isEmpty())
        result.error = QStringLiteral("名单为空，请每行输入一位学生。");
    else if (result.names.size() > 5000)
        result.error = QStringLiteral("名单超过 5000 人，请分批操作。");
    return result;
}

void Session::setNames(const QStringList &names)
{
    m_names = names;
    resetDraw();
}

void Session::resetDraw() { m_pool = m_names; }

QStringList Session::draw(int count, QRandomGenerator &random)
{
    QStringList selected;
    if (count <= 0 || count > m_pool.size()) return selected;
    for (int i = 0; i < count; ++i) {
        const int index = random.bounded(static_cast<int>(m_pool.size()));
        // 从候选池中移除已抽到的人，本轮后续抽签就不会重复。
        selected.append(m_pool.takeAt(index));
    }
    return selected;
}

QList<QStringList> Session::groups(int value, bool valueIsGroupCount,
                                   QRandomGenerator &random) const
{
    QList<QStringList> result;
    const int n = static_cast<int>(m_names.size());
    if (n == 0 || value <= 0 || (valueIsGroupCount && value > n)) return result;
    const int count = valueIsGroupCount ? value : (n + value - 1) / value;
    QStringList shuffled = m_names;
    // Fisher–Yates 洗牌。每次从尚未固定的位置中均匀选取一个。
    for (int i = n - 1; i > 0; --i)
        qSwap(shuffled[i], shuffled[random.bounded(i + 1)]);
    for (int i = 0; i < count; ++i) result.append(QStringList());
    // 轮流放入各组，保证每人出现一次，各组人数最多相差 1。
    for (int i = 0; i < n; ++i) result[i % count].append(shuffled.at(i));
    return result;
}
}