Blind pass at paginator

pager/pager.go

@@ -0,0 +1,119 @@
+// package pager provides a Tea package for calulating pagination and rendering
+// pagination info. Note that this package does not render actual pages: it's
+// purely for handling keystrokes related to pagination, and rendering
+// pagination status.
+package pager
+
+import (
+	"fmt"
+
+	"github.com/charmbracelet/tea"
+)
+
+// PagerType specifies the way we render pagination
+type PagerType int
+
+// Pagination rendering options
+const (
+	Dots PagerType = iota
+	Arabic
+)
+
+// Model is the Tea model for this user interface
+type Model struct {
+	Page         int
+	PerPage      int
+	TotalPages   int
+	ActiveDot    string
+	InactiveDot  string
+	ArabicFormat string
+	RTL          bool
+}
+
+// SetTotalPages is a helper method for calculatng the total number of pages
+// from a given number of items. It's use is optional. Note that it both
+// returns the number of total pages and alters the model.
+func (m *Model) SetTotalPages(items int) int {
+	if items == 0 {
+		return 0
+	}
+	n := items / m.PerPage
+	if items%m.PerPage > 0 {
+		n += 1
+	}
+	m.TotalPages = n
+	return n
+}
+
+// NewModel creates a new model with defaults
+func NewModel() Model {
+	return Model{
+		Page:         0,
+		PerPage:      1,
+		TotalPages:   1,
+		ActiveDot:    "•",
+		InactiveDot:  "○",
+		ArabicFormat: "%d/%d",
+		RTL:          false,
+	}
+}
+
+// Update is the Tea update function which binds keystrokes to pagination
+func Update(msg tea.Msg, model tea.Model) (tea.Model, tea.Cmd) {
+	m, ok := model.(Model)
+	if !ok {
+		return tea.ModelAssertionErr, nil
+	}
+	switch msg := msg.(type) {
+	case tea.KeyMsg:
+		switch msg.String() {
+		case "left":
+			if m.Page > 0 {
+				m.Page--
+			}
+		case "right":
+			if m.Page < m.TotalPages-1 {
+				m.Page++
+			}
+		}
+	}
+	return m, nil
+}
+
+// View renders the pagination to a string
+func View(model tea.Model) string {
+	m, ok := model.(Model)
+	if !ok {
+		return ""
+	}
+	return dotsView(m)
+}
+
+func dotsView(m Model) string {
+	var s string
+	if m.RTL {
+		for i := m.TotalPages; i > 0; i-- {
+			if i == m.Page {
+				s += m.ActiveDot
+				continue
+			}
+			s += m.InactiveDot
+		}
+		return s
+	}
+	for i := 0; i < m.TotalPages; i++ {
+		if i == m.Page {
+			s += m.ActiveDot
+			continue
+		}
+		s += m.InactiveDot
+	}
+	return s
+}
+
+func arabicView(m Model) string {
+	if m.RTL {
+		return fmt.Sprintf(m.ArabicFormat, m.TotalPages, m.Page+1)
+	}
+	return fmt.Sprintf(m.ArabicFormat, m.Page+1, m.TotalPages)
+}