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@@ -0,0 +1,79 @@
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+package connection
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+
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+import (
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+ "errors"
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+ "fmt"
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+ "github.com/samber/lo"
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+ "math"
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+)
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+
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+type Connection[T Cursor] struct {
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+ Edges []T `json:"edges"`
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+ PageInfo *PageInfo `json:"page_info"`
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+}
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+
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+func (c *Connection[T]) Reverse() {
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+ c.Edges = lo.Reverse[T](c.Edges)
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+}
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+
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+func (c *Connection[T]) Grain(after, before *string) error {
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+ if after != nil && before != nil {
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+ return errors.New("illegal arguments: only one of `after` or `before` can be used at a time")
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+ }
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+
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+ if len(c.Edges) == 0 {
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+ c.PageInfo = new(PageInfo)
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+ return nil
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+ }
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+
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+ edges := lo.FlatMap[T, string](c.Edges, func(item T, _ int) []string {
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+ return []string{item.Cursor()}
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+ })
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+
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+ c.PageInfo = &PageInfo{
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+ StartCursor: lo.ToPtr(edges[0]),
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+ EndCursor: lo.ToPtr(edges[(len(edges) - 1)]),
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+ }
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+
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+ if after != nil {
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+ if idx := lo.IndexOf(edges, *after); idx != -1 {
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+ c.Edges = lo.Slice[T](c.Edges, idx+1, math.MaxUint32)
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+ }
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+ }
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+
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+ if before != nil {
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+ if idx := lo.IndexOf(edges, *before); idx != -1 {
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+ c.Edges = lo.Subset[T](c.Edges, -idx, math.MaxUint32)
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+ }
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+ }
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+
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+ return nil
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+}
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+
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+func (c *Connection[T]) Slice(first, last *int) error {
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+ if first != nil && last != nil {
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+ return fmt.Errorf("illegal agruments: only one of `first` or `last` can be used at a time")
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+ }
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+
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+ if first != nil {
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+ c.Edges = lo.Slice[T](c.Edges, 0, *first)
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+ }
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+
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+ if last != nil {
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+ c.Edges = lo.Subset[T](c.Edges, -*last, math.MaxUint32)
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+ }
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+
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+ if len(c.Edges) < 1 {
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+ c.PageInfo.HasPreviousPage = c.PageInfo.StartCursor != nil
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+ c.PageInfo.HasNextPage = c.PageInfo.EndCursor != nil
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+ c.PageInfo.StartCursor = nil
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+ c.PageInfo.EndCursor = nil
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+ } else {
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+ c.PageInfo.HasPreviousPage = !(*c.PageInfo.StartCursor == c.Edges[0].Cursor())
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+ c.PageInfo.HasNextPage = !(*c.PageInfo.EndCursor == c.Edges[len(c.Edges)-1].Cursor())
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+ c.PageInfo.StartCursor = lo.ToPtr(c.Edges[0].Cursor())
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+ c.PageInfo.EndCursor = lo.ToPtr(c.Edges[len(c.Edges)-1].Cursor())
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+ }
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+
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+ return nil
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+}
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