agentu/internal/tui/theme.go

package tui

import (
	"fmt"
	"strings"

	"github.com/charmbracelet/bubbles/textarea"
	"github.com/charmbracelet/lipgloss"
)

type ThemeMode string

const (
	ThemeLight ThemeMode = "light"
	ThemeDark  ThemeMode = "dark"
)

func ParseThemeMode(value string) (ThemeMode, error) {
	switch ThemeMode(strings.ToLower(strings.TrimSpace(value))) {
	case "", ThemeLight:
		return ThemeLight, nil
	case ThemeDark:
		return ThemeDark, nil
	default:
		return "", fmt.Errorf("unsupported theme %q; expected light or dark", value)
	}
}

type theme struct {
	Mode ThemeMode

	Background string
	Surface    string
	SurfaceAlt string
	Border     string
	Text       string
	Muted      string

	Title     string
	User      string
	Assistant string
	Tool      string
	Error     string
	System    string
}

type styles struct {
	App           lipgloss.Style
	Muted         lipgloss.Style
	Activity      lipgloss.Style
	ModelMeta     lipgloss.Style
	Footer        lipgloss.Style
	Viewport      lipgloss.Style
	InputBox      lipgloss.Style
	CommandHint   lipgloss.Style
	UserLabel     lipgloss.Style
	ToolLabel     lipgloss.Style
	ErrorLabel    lipgloss.Style
	SystemLabel   lipgloss.Style
	UserMessage   lipgloss.Style
	AssistantMsg  lipgloss.Style
	ToolMessage   lipgloss.Style
	ErrorMessage  lipgloss.Style
	SystemMessage lipgloss.Style
}

func themeForMode(mode ThemeMode) theme {
	if mode == ThemeDark {
		return darkTheme()
	}
	return lightTheme()
}

func lightTheme() theme {
	return theme{
		Mode:       ThemeLight,
		Background: "#F8FAFC",
		Surface:    "#FFFFFF",
		SurfaceAlt: "#EEF2F7",
		Border:     "#CBD5E1",
		Text:       "#111827",
		Muted:      "#64748B",
		Title:      "#0F766E",
		User:       "#2563EB",
		Assistant:  "#0F766E",
		Tool:       "#B45309",
		Error:      "#DC2626",
		System:     "#64748B",
	}
}

func darkTheme() theme {
	return theme{
		Mode:       ThemeDark,
		Background: "#111827",
		Surface:    "#1F2937",
		SurfaceAlt: "#0F172A",
		Border:     "#475569",
		Text:       "#E5E7EB",
		Muted:      "#94A3B8",
		Title:      "#5EEAD4",
		User:       "#93C5FD",
		Assistant:  "#5EEAD4",
		Tool:       "#FBBF24",
		Error:      "#FCA5A5",
		System:     "#94A3B8",
	}
}

func (t theme) styles() styles {
	return styles{
		App: lipgloss.NewStyle().
			Foreground(lipgloss.Color(t.Text)),

		Muted: lipgloss.NewStyle().
			Foreground(lipgloss.Color(t.Muted)),

		Activity: lipgloss.NewStyle().
			Bold(true).
			Foreground(lipgloss.Color(t.Background)).
			Background(lipgloss.Color(t.Title)).
			Padding(0, 1),

		ModelMeta: lipgloss.NewStyle().
			Foreground(lipgloss.Color(t.Text)).
			Background(lipgloss.Color(t.SurfaceAlt)).
			Padding(0, 1),

		Footer: lipgloss.NewStyle().
			Foreground(lipgloss.Color(t.Muted)).
			Padding(0, 1),

		Viewport: lipgloss.NewStyle().
			Foreground(lipgloss.Color(t.Text)),

		InputBox: lipgloss.NewStyle().
			Foreground(lipgloss.Color(t.Text)).
			Border(lipgloss.ThickBorder()).
			BorderForeground(lipgloss.Color(t.Border)).
			Padding(0, 2),

		CommandHint: lipgloss.NewStyle().
			Foreground(lipgloss.Color(t.Muted)).
			Background(lipgloss.Color(t.SurfaceAlt)).
			Padding(0, 1),

		UserLabel:   labelStyle(t.User),
		ToolLabel:   labelStyle(t.Tool),
		ErrorLabel:  labelStyle(t.Error),
		SystemLabel: labelStyle(t.System),

		UserMessage:   bubbleMessageStyle(t.Text, t.SurfaceAlt),
		AssistantMsg:  assistantMessageStyle(t.Text),
		ToolMessage:   messageStyle(t.Text),
		ErrorMessage:  messageStyle(t.Error),
		SystemMessage: lipgloss.NewStyle().Foreground(lipgloss.Color(t.System)).Padding(0, 1),
	}
}

func labelStyle(color string) lipgloss.Style {
	return lipgloss.NewStyle().
		Bold(true).
		Foreground(lipgloss.Color(color))
}

func messageStyle(textColor string) lipgloss.Style {
	return lipgloss.NewStyle().
		Foreground(lipgloss.Color(textColor)).
		Padding(0, 1)
}

func assistantMessageStyle(textColor string) lipgloss.Style {
	return lipgloss.NewStyle().
		Foreground(lipgloss.Color(textColor)).
		Padding(1, 2)
}

func bubbleMessageStyle(textColor, backgroundColor string) lipgloss.Style {
	return lipgloss.NewStyle().
		Foreground(lipgloss.Color(textColor)).
		Background(lipgloss.Color(backgroundColor)).
		Padding(1, 2)
}

func applyTextareaTheme(input *textarea.Model, t theme) {
	focused := textarea.Style{
		Base: lipgloss.NewStyle().
			Foreground(lipgloss.Color(t.Text)),
		CursorLine: lipgloss.NewStyle(),
		Placeholder: lipgloss.NewStyle().
			Foreground(lipgloss.Color(t.Muted)),
		Prompt: lipgloss.NewStyle().
			Foreground(lipgloss.Color(t.Muted)),
		Text: lipgloss.NewStyle().
			Foreground(lipgloss.Color(t.Text)),
		EndOfBuffer: lipgloss.NewStyle().
			Foreground(lipgloss.Color(t.Surface)),
	}
	blurred := focused
	blurred.CursorLine = lipgloss.NewStyle()

	input.FocusedStyle = focused
	input.BlurredStyle = blurred
}