Move gid and page pkg

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

pkg/page/cursor.go

@@ -0,0 +1,112 @@
+// 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
+
+import (
+	"fmt"
+
+	"github.com/jackc/pgx/v5"
+)
+
+type (
+	Cursor struct {
+		Size     int
+		Key      *CursorKey
+		Position Position
+	}
+
+	Position int8
+)
+
+const (
+	DefaultCursorSize = 25
+
+	Tail Position = iota
+	Head
+)
+
+func (p Position) ToDirection() string {
+	switch p {
+	case Tail:
+		return "ASC"
+	case Head:
+		return "DESC"
+	default:
+		panic(fmt.Errorf("unknown direction: %d", p))
+	}
+}
+
+func NewCursor(size int, from *CursorKey, pos Position) *Cursor {
+	if size == 0 {
+		size = DefaultCursorSize
+	}
+
+	return &Cursor{
+		Size:     size,
+		Key:      from,
+		Position: pos,
+	}
+}
+
+func (c *Cursor) SQLFragment() string {
+	return `
+  CASE
+    WHEN @cursor_order = 'DESC' AND @cursor_from_id::TEXT IS NOT NULL THEN (
+      (created_at <= @cursor_from_ts) AND NOT (created_at = @cursor_from_ts AND id > @cursor_from_id)
+    )
+    WHEN @cursor_order = 'ASC' AND @cursor_from_id::TEXT IS NOT NULL THEN (
+      (created_at >= @cursor_from_ts) AND NOT (created_at = @cursor_from_ts AND id < @cursor_from_id)
+    )
+    ELSE TRUE
+  END
+ORDER BY
+  CASE
+    WHEN @cursor_order = 'ASC' THEN created_at
+  END ASC,
+  CASE
+    WHEN @cursor_order = 'ASC' THEN id
+  END ASC,
+  CASE
+    WHEN @cursor_order = 'DESC' THEN created_at
+  END DESC,
+  CASE
+    WHEN @cursor_order = 'DESC' THEN id
+  END DESC
+LIMIT @cursor_limit
+`
+}
+
+func (c *Cursor) SQLArguments() pgx.NamedArgs {
+	var size = c.Size
+	if c.Key == nil {
+		size += 1
+	} else {
+		size += 2
+	}
+
+	arguments := pgx.NamedArgs{
+		"cursor_order":   c.Position.ToDirection(),
+		"cursor_limit":   size,
+		"cursor_from_id": nil,
+		"cursor_from_ts": nil,
+	}
+
+	if c.Key != nil {
+		arguments["cursor_from_id"] = c.Key.ID()
+		arguments["cursor_from_ts"] = c.Key.Timestamp()
+	}
+
+	return arguments
+}