// Package notices 承载系统通知(广播 + 定向)的数据访问层:合并查询、已读水位、
// 事务内插入(供其他领域事件钩子复用)、后台管理(nodectl)增删改查。
package notices

import (
	"context"
	"database/sql"
	"time"
)

// Notice 是对外(API/nodectl)的通知视图。json tag 是 API 契约,勿改。
type Notice struct {
	ID          int64     `json:"id"`
	Type        string    `json:"type"`
	UserID      *int64    `json:"-"`
	TitleZH     string    `json:"title_zh"`
	TitleEN     string    `json:"title_en"`
	BodyZH      string    `json:"body_zh,omitempty"`
	BodyEN      string    `json:"body_en,omitempty"`
	Link        string    `json:"link,omitempty"`
	PublishedAt time.Time `json:"published_at"`
	Unread      bool      `json:"unread"`
}

// AdminRow 是 nodectl list 消费的后台视图:不含正文,多一个 status 摘要字段。
type AdminRow struct {
	ID          int64
	Type        string
	TitleZH     string
	PublishedAt time.Time
	Status      string // active|revoked|expired
}

type Store struct{ db *sql.DB }

func NewStore(db *sql.DB) *Store { return &Store{db: db} }

// ListForUser 返回广播(user_id IS NULL)∪ 定向(user_id=uid)的未撤回、未过期通知,
// 按 published_at 倒序,并根据 users.notices_read_at 水位计算每条 Unread 与 unreadCount。
// 水位为 NULL 时按零值时间处理,即全部未读。
func (s *Store) ListForUser(ctx context.Context, uid int64, now time.Time, limit int) ([]Notice, int, error) {
	var readAt sql.NullTime
	if err := s.db.QueryRowContext(ctx, `SELECT notices_read_at FROM users WHERE id=?`, uid).Scan(&readAt); err != nil {
		return nil, 0, err
	}
	watermark := time.Time{}
	if readAt.Valid {
		watermark = readAt.Time
	}

	rows, err := s.db.QueryContext(ctx, `
		SELECT id, type, user_id, title_zh, title_en, COALESCE(body_zh,''), COALESCE(body_en,''),
		       COALESCE(link,''), published_at
		FROM notices
		WHERE (user_id IS NULL OR user_id = ?)
		  AND revoked_at IS NULL
		  AND (expires_at IS NULL OR expires_at > ?)
		ORDER BY published_at DESC
		LIMIT ?
	`, uid, now, limit)
	if err != nil {
		return nil, 0, err
	}
	defer rows.Close()

	var items []Notice
	unreadCount := 0
	for rows.Next() {
		var n Notice
		var userID sql.NullInt64
		if err := rows.Scan(&n.ID, &n.Type, &userID, &n.TitleZH, &n.TitleEN, &n.BodyZH, &n.BodyEN, &n.Link, &n.PublishedAt); err != nil {
			return nil, 0, err
		}
		if userID.Valid {
			id := userID.Int64
			n.UserID = &id
		}
		n.Unread = n.PublishedAt.After(watermark)
		if n.Unread {
			unreadCount++
		}
		items = append(items, n)
	}
	if err := rows.Err(); err != nil {
		return nil, 0, err
	}
	return items, unreadCount, nil
}

// MarkRead 把用户的通知已读水位推进到 at。
func (s *Store) MarkRead(ctx context.Context, uid int64, at time.Time) error {
	_, err := s.db.ExecContext(ctx, `UPDATE users SET notices_read_at=? WHERE id=?`, at, uid)
	return err
}

// InsertNoticeTx 在调用方已开的事务内插入一条定向通知(不自开/自提交事务),
// 供其他领域的事件钩子(如奖励发放)在同一事务里原子写入。
func (s *Store) InsertNoticeTx(ctx context.Context, tx *sql.Tx, userID int64, typ, titleZH, titleEN, bodyZH, bodyEN, link string, now time.Time) error {
	_, err := tx.ExecContext(ctx, `
		INSERT INTO notices (type, user_id, title_zh, title_en, body_zh, body_en, link, published_at)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?)
	`, typ, userID, titleZH, titleEN, nullIfEmpty(bodyZH), nullIfEmpty(bodyEN), nullIfEmpty(link), now)
	return err
}

// InsertBroadcast 插入一条全员广播通知(user_id=NULL),自管连接,返回新 id。供
// nodectl / 发版流程使用。expiresAt 可为 nil(永不过期)。
func (s *Store) InsertBroadcast(ctx context.Context, typ, titleZH, titleEN, bodyZH, bodyEN, link string, publishedAt time.Time, expiresAt *time.Time) (int64, error) {
	res, err := s.db.ExecContext(ctx, `
		INSERT INTO notices (type, user_id, title_zh, title_en, body_zh, body_en, link, published_at, expires_at)
		VALUES (?, NULL, ?, ?, ?, ?, ?, ?, ?)
	`, typ, titleZH, titleEN, nullIfEmpty(bodyZH), nullIfEmpty(bodyEN), nullIfEmpty(link), publishedAt, nullTime(expiresAt))
	if err != nil {
		return 0, err
	}
	return res.LastInsertId()
}

// Revoke 撤回一条通知(置 revoked_at)。目标不存在或已撤回时返回 sql.ErrNoRows。
func (s *Store) Revoke(ctx context.Context, id int64, at time.Time) error {
	res, err := s.db.ExecContext(ctx, `UPDATE notices SET revoked_at=? WHERE id=? AND revoked_at IS NULL`, at, id)
	if err != nil {
		return err
	}
	n, err := res.RowsAffected()
	if err != nil {
		return err
	}
	if n == 0 {
		return sql.ErrNoRows
	}
	return nil
}

// ListAdmin 供 nodectl list 使用:全字段倒序;includeInactive=false 时只保留
// 未撤回、未过期(与 ListForUser 相同判据)的记录。
func (s *Store) ListAdmin(ctx context.Context, includeInactive bool, limit int) ([]AdminRow, error) {
	now := time.Now().UTC()
	query := `
		SELECT id, type, title_zh, published_at, revoked_at, expires_at
		FROM notices
	`
	args := []any{}
	if !includeInactive {
		query += ` WHERE revoked_at IS NULL AND (expires_at IS NULL OR expires_at > ?)`
		args = append(args, now)
	}
	query += ` ORDER BY published_at DESC LIMIT ?`
	args = append(args, limit)

	rows, err := s.db.QueryContext(ctx, query, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var out []AdminRow
	for rows.Next() {
		var r AdminRow
		var revokedAt, expiresAt sql.NullTime
		if err := rows.Scan(&r.ID, &r.Type, &r.TitleZH, &r.PublishedAt, &revokedAt, &expiresAt); err != nil {
			return nil, err
		}
		switch {
		case revokedAt.Valid:
			r.Status = "revoked"
		case expiresAt.Valid && !expiresAt.Time.After(now):
			r.Status = "expired"
		default:
			r.Status = "active"
		}
		out = append(out, r)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	return out, nil
}

// MarkEmailSent 标记该通知的邮件兜底已发送(幂等:只在未发送过时置位)。
func (s *Store) MarkEmailSent(ctx context.Context, id int64, at time.Time) error {
	_, err := s.db.ExecContext(ctx, `UPDATE notices SET email_sent_at=? WHERE id=? AND email_sent_at IS NULL`, at, id)
	return err
}

// ListActiveUserEmails 返回所有 active 用户的邮箱,供邮件兜底批量发送。
func (s *Store) ListActiveUserEmails(ctx context.Context) ([]string, error) {
	rows, err := s.db.QueryContext(ctx, `SELECT email FROM users WHERE status='active'`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var out []string
	for rows.Next() {
		var email string
		if err := rows.Scan(&email); err != nil {
			return nil, err
		}
		out = append(out, email)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	return out, nil
}

func nullIfEmpty(s string) any {
	if s == "" {
		return nil
	}
	return s
}

func nullTime(t *time.Time) any {
	if t == nil {
		return nil
	}
	return *t
}