package store

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

// Invite — приглашение на сервер (AGENT.md 7.9).
type Invite struct {
	Code      string
	GuildID   uint64
	ChannelID *uint64
	CreatorID *uint64
	MaxUses   int
	Uses      int
	MaxAgeSec int
	ExpiresAt *time.Time
	CreatedAt time.Time
}

// CreateInviteParams — параметры приглашения.
type CreateInviteParams struct {
	Code      string
	GuildID   uint64
	ChannelID *uint64
	CreatorID uint64
	MaxUses   int
	MaxAgeSec int
}

const inviteColumns = `code, guild_id, channel_id, creator_id, max_uses, uses,
	max_age_sec, expires_at, created_at`

// CreateInvite сохраняет приглашение с кодом, лимитом использований и сроком.
func (s *Store) CreateInvite(ctx context.Context, params CreateInviteParams) (*Invite, error) {
	var expiresAt any
	if params.MaxAgeSec > 0 {
		expiresAt = s.Timestamp(time.Now().UTC().Add(time.Duration(params.MaxAgeSec) * time.Second))
	}
	_, err := s.writer.ExecContext(ctx, `
		INSERT INTO invites (code, guild_id, channel_id, creator_id, max_uses, uses, max_age_sec, expires_at, created_at)
		VALUES (?, ?, ?, ?, ?, 0, ?, ?, ?)`,
		params.Code, int64(params.GuildID), nullableID(params.ChannelID), int64(params.CreatorID),
		params.MaxUses, params.MaxAgeSec, expiresAt, s.Now())
	if err != nil {
		return nil, mapError(err)
	}
	return s.GetInvite(ctx, params.Code)
}

func (s *Store) GetInvite(ctx context.Context, code string) (*Invite, error) {
	row := s.reader.QueryRowContext(ctx, `SELECT `+inviteColumns+` FROM invites WHERE code = ?`, code)
	return scanInvite(row)
}

// ListGuildInvites возвращает приглашения сервера (для панели управления).
func (s *Store) ListGuildInvites(ctx context.Context, guildID uint64, limit int) ([]Invite, error) {
	if limit <= 0 || limit > 200 {
		limit = 50
	}
	rows, err := s.reader.QueryContext(ctx, `
		SELECT `+inviteColumns+` FROM invites WHERE guild_id = ? ORDER BY created_at DESC LIMIT ?`,
		int64(guildID), limit)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	invites := make([]Invite, 0, limit)
	for rows.Next() {
		invite, err := scanInvite(rows)
		if err != nil {
			return nil, err
		}
		invites = append(invites, *invite)
	}
	return invites, rows.Err()
}

// UseInvite атомарно увеличивает счётчик использований, проверяя лимит и срок.
// Возвращает ErrNotFound, если приглашение исчерпано или истекло (AGENT.md 7.9).
func (s *Store) UseInvite(ctx context.Context, code string) (*Invite, error) {
	result, err := s.writer.ExecContext(ctx, `
		UPDATE invites SET uses = uses + 1
		WHERE code = ?
		  AND (max_uses = 0 OR uses < max_uses)
		  AND (expires_at IS NULL OR expires_at > ?)`, code, s.Now())
	if err != nil {
		return nil, err
	}
	if affected, err := result.RowsAffected(); err == nil && affected == 0 {
		return nil, ErrNotFound
	}
	return s.GetInvite(ctx, code)
}

func (s *Store) DeleteInvite(ctx context.Context, code string) error {
	result, err := s.writer.ExecContext(ctx, `DELETE FROM invites WHERE code = ?`, code)
	if err != nil {
		return err
	}
	if affected, err := result.RowsAffected(); err == nil && affected == 0 {
		return ErrNotFound
	}
	return nil
}

// ListPublicGuilds возвращает публичные серверы для каталога (AGENT.md 7.20).
func (s *Store) ListPublicGuilds(ctx context.Context, limit int) ([]Guild, error) {
	if limit <= 0 || limit > 100 {
		limit = 50
	}
	rows, err := s.reader.QueryContext(ctx, `
		SELECT `+guildColumns+` FROM guilds
		WHERE is_discoverable = 1 ORDER BY id LIMIT ?`, limit)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	guilds := make([]Guild, 0, limit)
	for rows.Next() {
		guild, err := scanGuild(rows)
		if err != nil {
			return nil, err
		}
		guilds = append(guilds, *guild)
	}
	return guilds, rows.Err()
}

func scanInvite(scanner interface{ Scan(...any) error }) (*Invite, error) {
	var (
		invite    Invite
		channelID sql.NullInt64
		creatorID sql.NullInt64
		expiresAt sql.NullString
		createdAt string
	)
	err := scanner.Scan(&invite.Code, &invite.GuildID, &channelID, &creatorID, &invite.MaxUses,
		&invite.Uses, &invite.MaxAgeSec, &expiresAt, &createdAt)
	if err != nil {
		return nil, mapError(err)
	}
	invite.ChannelID = optionalID(channelID)
	invite.CreatorID = optionalID(creatorID)
	if expiresAt.Valid {
		value := parseTimestamp(expiresAt.String)
		invite.ExpiresAt = &value
	}
	invite.CreatedAt = parseTimestamp(createdAt)
	return &invite, nil
}