feat: month calendar

README.md

@@ -4,6 +4,15 @@
 
 bubbles is a collection of TUI elements for [Bubble Tea](https://github.com/charmbracelet/bubbletea) applications.
 
+## Calendar
+
+![Calendar monthly journal demo](assets/calendar-month-journal.gif)
+
+`calendar` enables the rendering and management of monthly calendars.
+While defaults are configured for the US, things such as the start of the week, days of the week, and more are configurable.
+
+* [Example code, monthly journal](examples/calendar/month-journal/main.go)
+
 ## Radio
 
 ![Simple radio button demo](assets/radio-simple.gif)

assets/calendar-month-journal.tape

@@ -0,0 +1,22 @@
+Set Shell zsh
+Set Height 650
+Sleep 1s
+Type "./demo"
+Enter
+Sleep 3s
+Right 1
+Sleep 2s
+Down 1
+Sleep 800ms
+Down 1
+Sleep 1500ms
+Down 1
+Sleep 800ms
+Down 1
+Sleep 800ms
+Down 1
+Sleep 800ms
+Down 1
+Sleep 2s
+Right 1
+Sleep 3s

calendar/keymap.go

@@ -0,0 +1,23 @@
+package calendar
+
+import (
+	"github.com/charmbracelet/bubbles/key"
+)
+
+// KeyMap contains relevant keys for tab navigation.
+type KeyMap struct {
+	Left  key.Binding
+	Right key.Binding
+	Up    key.Binding
+	Down  key.Binding
+}
+
+// DefaultKeyMap contains default key mappings for calendar navigation.
+func DefaultKeyMap() KeyMap {
+	return KeyMap{
+		Left:  key.NewBinding(key.WithKeys("left"), key.WithHelp("left", "←")),
+		Right: key.NewBinding(key.WithKeys("right"), key.WithHelp("right", "→")),
+		Up:    key.NewBinding(key.WithKeys("up"), key.WithHelp("up", "↑")),
+		Down:  key.NewBinding(key.WithKeys("down"), key.WithHelp("down", "↓")),
+	}
+}

calendar/month.go

@@ -0,0 +1,325 @@
+package calendar
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/charmbracelet/bubbles/key"
+	tea "github.com/charmbracelet/bubbletea"
+	gloss "github.com/charmbracelet/lipgloss"
+)
+
+// DayContentMsg enables updates for the content of a single day.
+type DayContentMsg struct {
+	// The day to update
+	Date time.Time
+
+	// The day model
+	Content tea.Model
+}
+
+// ActiveDateMsg notifies to other models which date is set as the active date.
+type ActiveDateMsg struct {
+	// The day to update
+	Date time.Time
+}
+
+// MonthModel represents a full calendar month.
+type MonthModel struct {
+	// keyMap is key bindings for calendar navigation
+	keyMap KeyMap
+
+	// year of the month represented
+	year int
+	// month to represent
+	month time.Month
+
+	// startOfWeek is the day that represents the beginning of the week
+	startOfWeek time.Weekday
+
+	// days contains user-provided information about each day
+	days map[int]tea.Model
+
+	activeDay int
+
+	// Styles
+	styles MonthStyles
+}
+
+// NewMonth creates a new MonthModel.
+func NewMonth(year int, month time.Month) MonthModel {
+	m := MonthModel{
+		keyMap: DefaultKeyMap(),
+
+		year:  year,
+		month: month,
+
+		startOfWeek: time.Sunday,
+
+		days:      make(map[int]tea.Model),
+		activeDay: 0,
+
+		styles: DefaultMonthStyles(),
+	}
+
+	return m
+}
+
+// StartOfWeek sets the first day of the week.
+func (m MonthModel) StartOfWeek(weekday time.Weekday) MonthModel {
+	m.startOfWeek = weekday
+
+	// Re-shuffle the days-of-the-week labels to match this change
+	dow := m.styles.DaysOfWeek[int(m.startOfWeek):]
+	dow = append(dow, m.styles.DaysOfWeek[:int(m.startOfWeek)]...)
+	m.styles.DaysOfWeek = dow
+
+	return m
+}
+
+// Styles enables custom styling.
+func (m MonthModel) Styles(styles MonthStyles) MonthModel {
+	m.styles = styles
+	return m
+}
+
+// Init the MonthModel.
+func (m MonthModel) Init() tea.Cmd { return nil }
+
+// Update the MonthModel.
+func (m MonthModel) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
+	var cmds []tea.Cmd
+	switch msg := msg.(type) {
+	case tea.KeyMsg:
+		oldActiveDay := m.activeDay
+		daysInMonth := DaysInMonth(m.year, m.month)
+		switch {
+		case key.Matches(msg, m.keyMap.Left):
+			i := m.activeDay - 1
+			if i <= 0 {
+				i = daysInMonth
+			}
+			m.activeDay = i
+		case key.Matches(msg, m.keyMap.Right):
+			i := m.activeDay + 1
+			if i > daysInMonth {
+				i = 1
+			}
+			m.activeDay = i
+		case key.Matches(msg, m.keyMap.Up):
+			i := m.activeDay - 7
+			if i < 0 {
+				i = m.activeDay + 28
+				if i > daysInMonth {
+					i = i - 7
+				}
+			}
+			m.activeDay = i
+		case key.Matches(msg, m.keyMap.Down):
+			i := m.activeDay + 7
+			if i > daysInMonth {
+				i = m.activeDay - 28
+				if m.activeDay < 28 {
+					i = i + 7
+				}
+			}
+			m.activeDay = i
+		}
+
+		if oldActiveDay != m.activeDay {
+			cmds = append(cmds, func() tea.Msg {
+				return ActiveDateMsg{
+					Date: time.Date(m.year, m.month, m.activeDay, 0, 0, 0, 0, time.UTC),
+				}
+			})
+		}
+	case DayContentMsg:
+		if msg.Date.Year() != m.year {
+			break
+		}
+		if msg.Date.Month() != m.month {
+			break
+		}
+		// Translate from 1-indexed date to 0-indexed array
+		i := msg.Date.Day() - 1
+		m.days[i] = msg.Content
+	default:
+		for i, d := range m.days {
+			n, cmd := d.Update(msg)
+			m.days[i] = n
+			if cmd != nil {
+				cmds = append(cmds, cmd)
+			}
+		}
+	}
+
+	return m, tea.Batch(cmds...)
+}
+
+// View renders the Model.
+func (m MonthModel) View() string {
+	return gloss.JoinVertical(
+		gloss.Top,
+		m.ViewDaysOfWeek(),
+		m.ViewWeeks(),
+	)
+}
+
+// ViewDaysOfWeek renders the days-of-the-week header.
+func (m MonthModel) ViewDaysOfWeek() string {
+	var days []string
+	for i, wd := range m.styles.DaysOfWeek {
+		style := m.styles.MiddleDaysOfWeekStyle
+		if i == 0 {
+			style = m.styles.LeftDaysOfWeekStyle
+		} else if i == len(m.styles.DaysOfWeek)-1 {
+			style = m.styles.RightDaysOfWeekStyle
+		}
+		days = append(days, style.Render(wd))
+	}
+
+	return gloss.JoinHorizontal(gloss.Top, days...)
+}
+
+// ViewWeeks renders the calendar main block.
+func (m MonthModel) ViewWeeks() string {
+	daysInMonth := DaysInMonth(m.year, m.month)
+	firstWeekdayOfMonth := FirstWeekdayOfMonth(m.year, m.month)
+	weeksInMonth := CalendarRowsInMonth(m.year, m.month, m.startOfWeek)
+
+	var weeks [][]string
+	var week []string
+	for i := 0; i < daysInMonth; i++ {
+		wd := time.Weekday((i + int(firstWeekdayOfMonth)) % 7)
+		// If it is the start of the week, but is not the first day of the month,
+		// add week to calendar, reset week slice, and begin new week
+		if wd == m.startOfWeek && i != 0 {
+			weeks = append(weeks, week)
+			week = nil
+		}
+
+		// Render day number and day body into one block of text
+		body := m.styles.DateStyles.BodyStyle.Render("")
+		if dayBodyModel, ok := m.days[i]; ok {
+			body = m.styles.DateStyles.BodyStyle.Render(dayBodyModel.View())
+		}
+
+		lastWeek := len(weeks) == (weeksInMonth - 1)
+		day := m.ViewDay(wd, i+1, body, lastWeek)
+
+		// Add bordered day to week
+		week = append(week, day)
+
+	}
+
+	// Pad end of month
+	for i := len(week); i < 7; i++ {
+		wd := time.Weekday((int(m.startOfWeek) + i) % 7)
+		day := m.ViewDay(wd, 0, "", true)
+		week = append(week, day)
+	}
+	weeks = append(weeks, week)
+
+	// Pad start of month
+	firstWeek := weeks[0]
+	for i := (7 - len(firstWeek) - 1); i >= 0; i-- {
+		wd := time.Weekday((int(m.startOfWeek) + i) % 7)
+		firstWeek = append([]string{m.ViewDay(wd, 0, "", false)}, firstWeek...)
+	}
+	weeks[0] = firstWeek
+
+	// Combine each week into a horiztonal string
+	var rows []string
+	for _, week := range weeks {
+		rows = append(
+			rows,
+			gloss.JoinHorizontal(gloss.Top, week...),
+		)
+	}
+
+	// Combine individual week rows together into a vertical month
+	return gloss.JoinVertical(gloss.Top, rows...)
+}
+
+// ViewDay renders a single day.
+//
+// If zero is passed in for the day, an empty date block will be rendered.
+func (m MonthModel) ViewDay(weekday time.Weekday, day int, body string, lastRow bool) string {
+	num := m.styles.DateStyles.NumberStyle.Render("")
+	if day > 0 {
+		style := m.styles.DateStyles.NumberStyle
+		if day == m.activeDay {
+			style = m.styles.DateStyles.ActiveNumberStyle
+		}
+		num = style.Render(fmt.Sprintf("%d", day))
+	}
+
+	dateBlock := gloss.JoinVertical(
+		gloss.Top,
+		num,
+		body,
+	)
+
+	// Figure out if the border style is left, middle, right
+	// or bottom-left, bottom-middle, or bottom-right
+	var style gloss.Style
+	endOfWeek := time.Weekday((int(m.startOfWeek) + 6) % 7)
+	switch weekday {
+	case m.startOfWeek:
+		style = m.styles.MiddleLeftDayStyle
+		if lastRow {
+			style = m.styles.BottomLeftDayStyle
+		}
+	case endOfWeek:
+		style = m.styles.MiddleRightDayStyle
+		if lastRow {
+			style = m.styles.BottomRightDayStyle
+		}
+	default:
+		style = m.styles.MiddleDayStyle
+		if lastRow {
+			style = m.styles.BottomDayStyle
+		}
+	}
+
+	// Put border around day content and return
+	return style.Render(dateBlock)
+}
+
+// Title generates a title for the calendar that may be used during rendering.
+func (m MonthModel) Title(includeYear bool) string {
+	d := time.Date(m.year, m.month, 1, 0, 0, 0, 0, time.UTC)
+
+	if includeYear {
+		return d.Format("January 2006")
+	}
+	return d.Format("January")
+}
+
+// DaysInMonth calculates the number of days in a given month and year.
+func DaysInMonth(year int, month time.Month) int {
+	return time.Date(year, month+1, 0, 0, 0, 0, 0, time.UTC).Day()
+}
+
+// FirstWeekdayOfMonth calculates the weekday of the first day of the month.
+func FirstWeekdayOfMonth(year int, month time.Month) time.Weekday {
+	d := time.Date(year, month, 1, 0, 0, 0, 0, time.UTC)
+	return d.Weekday()
+}
+
+// CalendarRowsInMonth calculates the number of calendar rows for a month.
+func CalendarRowsInMonth(year int, month time.Month, startOfWeek time.Weekday) int {
+	dim := DaysInMonth(year, month)
+
+	n := 1
+	fdom := FirstWeekdayOfMonth(year, month)
+	for i := 1; i <= dim; i++ {
+		wd := time.Weekday(((i - 1) + int(fdom)) % 7)
+
+		if wd == startOfWeek && i != 1 {
+			n++
+		}
+	}
+
+	return n
+}