feat: add impure package

This adds a compatibility layer for Lip Gloss that provides a way to
continue using `AdaptiveColor` and `CompleteColor`. It's impure because
it uses global variables, is not thread-safe, and only works with the
default standard I/O streams.

Users are encouraged to use the pure API when possible.

impure/color.go

@@ -0,0 +1,81 @@
+package impure
+
+import (
+	"image/color"
+	"os"
+
+	"github.com/charmbracelet/colorprofile"
+	"github.com/charmbracelet/lipgloss/v2"
+)
+
+var (
+	// HasDarkBackground is true if the terminal has a dark background.
+	HasDarkBackground = func() bool {
+		hdb, _ := lipgloss.HasDarkBackground(os.Stdin, os.Stdout)
+		return hdb
+	}()
+
+	// Writer is the default writer that prints to stdout, automatically
+	// downsampling colors when necessary.
+	Writer = colorprofile.NewWriter(os.Stdout, os.Environ())
+)
+
+// AdaptiveColor provides color options for light and dark backgrounds. The
+// appropriate color will be returned at runtime based on the darkness of the
+// terminal background color.
+//
+// Example usage:
+//
+//	color := lipgloss.AdaptiveColor{Light: "#0000ff", Dark: "#000099"}
+type AdaptiveColor struct {
+	Light color.Color
+	Dark  color.Color
+}
+
+// RGBA returns the RGBA value of this color. This satisfies the Go Color
+// interface.
+func (c AdaptiveColor) RGBA() (uint32, uint32, uint32, uint32) {
+	if HasDarkBackground {
+		return c.Dark.RGBA()
+	}
+	return c.Light.RGBA()
+}
+
+// CompleteColor specifies exact values for truecolor, ANSI256, and ANSI color
+// profiles. Automatic color degradation will not be performed.
+type CompleteColor struct {
+	TrueColor color.Color
+	ANSI256   color.Color
+	ANSI      color.Color
+}
+
+// RGBA returns the RGBA value of this color. This satisfies the Go Color
+// interface.
+func (c CompleteColor) RGBA() (uint32, uint32, uint32, uint32) {
+	switch Writer.Profile {
+	case colorprofile.TrueColor:
+		return c.TrueColor.RGBA()
+	case colorprofile.ANSI256:
+		return c.ANSI256.RGBA()
+	case colorprofile.ANSI:
+		return c.ANSI.RGBA()
+	}
+	return lipgloss.NoColor{}.RGBA()
+}
+
+// CompleteAdaptiveColor specifies exact values for truecolor, ANSI256, and ANSI color
+// profiles, with separate options for light and dark backgrounds. Automatic
+// color degradation will not be performed.
+type CompleteAdaptiveColor struct {
+	Light CompleteColor
+	Dark  CompleteColor
+}
+
+// RGBA returns the RGBA value of this color. This satisfies the Go Color
+// interface.
+func (c CompleteAdaptiveColor) RGBA() (uint32, uint32, uint32, uint32) {
+	if HasDarkBackground {
+		return c.Dark.RGBA()
+	}
+	return c.Light.RGBA()
+}

impure/doc.go

@@ -0,0 +1,5 @@
+// Package impure is a compatibility layer for Lip Gloss that provides a way to
+// deal with the hassle of setting up a writer. It's impure because it uses
+// global variables, is not thread-safe, and only works with the default
+// standard I/O streams.
+package impure

writer.go → impure/writer.go

@@ -1,4 +1,4 @@
-package lipgloss
+package impure
 
 import (
 	"fmt"
@@ -8,10 +8,6 @@ import (
 	"github.com/charmbracelet/colorprofile"
 )
 
-// Writer is the default writer that prints to stdout, automatically
-// downsampling colors when necessary.
-var Writer = colorprofile.NewWriter(os.Stdout, os.Environ())
-
 // Println to stdout, automatically downsampling colors when necessary, ending
 // with a trailing newline.
 //