Move gid and page pkg

Signed-off-by: gearnode <bryan@frimin.fr>

pkg/page/page.go

@@ -0,0 +1,115 @@
+// Copyright (c) 2025 Probo Inc <hello@getprobo.com>.
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+// AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+// OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+// PERFORMANCE OF THIS SOFTWARE.
+
+package page
+
+type (
+	Paginable interface {
+		CursorKey() CursorKey
+	}
+
+	PageInfo struct {
+		HasNext bool
+		HasPrev bool
+	}
+
+	Page[T Paginable] struct {
+		Info *PageInfo
+		Data []T
+	}
+)
+
+func (p *Page[T]) First() T {
+	if len(p.Data) == 0 {
+		var zero T
+		return zero
+	}
+
+	return p.Data[0]
+}
+
+func (p *Page[T]) Last() T {
+	if len(p.Data) == 0 {
+		var zero T
+		return zero
+	}
+
+	return p.Data[len(p.Data)-1]
+}
+
+func NewPage[T Paginable](data []T, c *Cursor) *Page[T] {
+	pi := &PageInfo{}
+
+	if len(data) == 0 {
+		return &Page[T]{
+			Info: pi,
+			Data: data,
+		}
+	}
+
+	edges := data
+	firstFromData := data[0]
+
+	switch c.Position {
+	case Head:
+		if c.Key != nil {
+			if len(edges) == c.Size+2 {
+				edges = edges[1 : len(edges)-1]
+			} else {
+				edges = edges[1:]
+			}
+		} else if c.Key == nil && len(edges) == c.Size+1 {
+			edges = edges[0 : len(edges)-1]
+		}
+
+		if c.Key != nil && *c.Key == firstFromData.CursorKey() {
+			pi.HasPrev = true
+		}
+
+		if c.Key != nil && c.Size+2 == len(data) {
+			pi.HasNext = true
+		} else if c.Key == nil && c.Size+1 == len(data) {
+			pi.HasNext = true
+		}
+	case Tail:
+		for i, j := 0, len(edges)-1; i < j; i, j = i+1, j-1 {
+			edges[i], edges[j] = edges[j], edges[i]
+		}
+
+		if c.Key != nil {
+			if len(edges) == c.Size+2 {
+				edges = edges[1 : len(edges)-1]
+			} else {
+				edges = edges[0 : len(edges)-1]
+			}
+		} else if c.Key == nil && len(edges) == c.Size+1 {
+			edges = edges[1:]
+		}
+
+		if c.Key != nil && *c.Key == firstFromData.CursorKey() {
+			pi.HasNext = true
+		}
+
+		if c.Key != nil && c.Size+2 == len(data) {
+			pi.HasPrev = true
+		} else if c.Key == nil && c.Size+1 == len(data) {
+			pi.HasPrev = true
+		}
+	}
+
+	return &Page[T]{
+		Info: pi,
+		Data: edges,
+	}
+}