more refactors

internal/db/getlist.go

@@ -0,0 +1,71 @@
+package db
+
+import (
+	"context"
+	"database/sql"
+
+	"github.com/pkg/errors"
+	"github.com/uptrace/bun"
+)
+
+type listgetter[T any] struct {
+	q        *bun.SelectQuery
+	items    *[]*T
+	pageOpts *PageOpts
+	defaults *PageOpts
+}
+
+type List[T any] struct {
+	Items    []*T
+	Total    int
+	PageOpts PageOpts
+}
+
+type Filter struct {
+	Field string
+	Value any
+}
+
+func GetList[T any](tx bun.Tx, pageOpts, defaults *PageOpts) *listgetter[T] {
+	l := &listgetter[T]{
+		items:    new([]*T),
+		pageOpts: pageOpts,
+		defaults: defaults,
+	}
+	l.q = tx.NewSelect().
+		Model(l.items)
+	return l
+}
+
+func (l *listgetter[T]) Relation(name string, apply ...func(*bun.SelectQuery) *bun.SelectQuery) *listgetter[T] {
+	l.q = l.q.Relation(name, apply...)
+	return l
+}
+
+func (l *listgetter[T]) Filter(filters ...Filter) *listgetter[T] {
+	for _, filter := range filters {
+		l.q = l.q.Where("? = ?", bun.Ident(filter.Field), filter.Value)
+	}
+	return l
+}
+
+func (l *listgetter[T]) GetAll(ctx context.Context) (*List[T], error) {
+	if l.defaults == nil {
+		return nil, errors.New("default pageopts is nil")
+	}
+	total, err := l.q.Count(ctx)
+	if err != nil {
+		return nil, errors.Wrap(err, "query.Count")
+	}
+	l.q, l.pageOpts = setPageOpts(l.q, l.pageOpts, l.defaults, total)
+	err = l.q.Scan(ctx)
+	if err != nil && err != sql.ErrNoRows {
+		return nil, errors.Wrap(err, "query.Scan")
+	}
+	list := &List[T]{
+		Items:    *l.items,
+		Total:    total,
+		PageOpts: *l.pageOpts,
+	}
+	return list, nil
+}