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
	Header         lipgloss.Style
	Title          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
	AssistantLabel 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)).
			Background(lipgloss.Color(t.Background)),

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

		Title: lipgloss.NewStyle().
			Bold(true).
			Foreground(lipgloss.Color(t.Title)),

		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)).
			Background(lipgloss.Color(t.Background)).
			Padding(0, 1),

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

		InputBox: lipgloss.NewStyle().
			Foreground(lipgloss.Color(t.Text)).
			Background(lipgloss.Color(t.Surface)).
			Border(lipgloss.NormalBorder()).
			BorderForeground(lipgloss.Color(t.Border)).
			Padding(0, 1),

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

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

		UserMessage:   messageStyle(t.Text, t.User),
		AssistantMsg:  messageStyle(t.Text, t.Assistant),
		ToolMessage:   messageStyle(t.Text, t.Tool),
		ErrorMessage:  messageStyle(t.Error, t.Error),
		SystemMessage: lipgloss.NewStyle().Foreground(lipgloss.Color(t.System)).PaddingLeft(1),
	}
}

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

func messageStyle(textColor, accentColor string) lipgloss.Style {
	return lipgloss.NewStyle().
		Foreground(lipgloss.Color(textColor)).
		Border(lipgloss.ThickBorder(), false, false, false, true).
		BorderForeground(lipgloss.Color(accentColor)).
		PaddingLeft(1)
}

func applyTextareaTheme(input *textarea.Model, t theme) {
	focused := textarea.Style{
		Base: lipgloss.NewStyle().
			Foreground(lipgloss.Color(t.Text)).
			Background(lipgloss.Color(t.Surface)),
		CursorLine: lipgloss.NewStyle().
			Background(lipgloss.Color(t.Surface)),
		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().Background(lipgloss.Color(t.Surface))

	input.FocusedStyle = focused
	input.BlurredStyle = blurred
}