refactor(engine): new instantiation function

this commit adds a function to instantiate a new prompt engine
to be used within a Go application (typically a readline shell)

src/cli/print.go

@@ -2,11 +2,8 @@ package cli
 
 import (
 	"fmt"
-	"oh-my-posh/color"
-	"oh-my-posh/console"
 	"oh-my-posh/engine"
 	"oh-my-posh/platform"
-	"oh-my-posh/shell"
 
 	"github.com/spf13/cobra"
 )
@@ -46,53 +43,23 @@ var printCmd = &cobra.Command{
 			_ = cmd.Help()
 			return
 		}
-		env := &platform.Shell{
-			Version: cliVersion,
-			CmdFlags: &platform.Flags{
-				Config:        config,
-				PWD:           pwd,
-				PSWD:          pswd,
-				ErrorCode:     exitCode,
-				ExecutionTime: timing,
-				StackCount:    stackCount,
-				TerminalWidth: terminalWidth,
-				Eval:          eval,
-				Shell:         shellName,
-				ShellVersion:  shellVersion,
-			},
-		}
-		env.Init()
-		defer env.Close()
-		cfg := engine.LoadConfig(env)
-		ansi := &color.Ansi{}
-		ansi.Init(env.Shell())
-		var writer color.Writer
-		if plain {
-			ansi.InitPlain()
-			writer = &color.PlainWriter{
-				Ansi: ansi,
-			}
-		} else {
-			writerColors := cfg.MakeColors()
-			writer = &color.AnsiWriter{
-				Ansi:               ansi,
-				TerminalBackground: shell.ConsoleBackgroundColor(env, cfg.TerminalBackground),
-				AnsiColors:         writerColors,
-			}
-		}
-		consoleTitle := &console.Title{
-			Env:      env,
-			Ansi:     ansi,
-			Template: cfg.ConsoleTitleTemplate,
-		}
-		eng := &engine.Engine{
-			Config:       cfg,
-			Env:          env,
-			Writer:       writer,
-			ConsoleTitle: consoleTitle,
-			Ansi:         ansi,
-			Plain:        plain,
+
+		flags := &platform.Flags{
+			Config:        config,
+			PWD:           pwd,
+			PSWD:          pswd,
+			ErrorCode:     exitCode,
+			ExecutionTime: timing,
+			StackCount:    stackCount,
+			TerminalWidth: terminalWidth,
+			Eval:          eval,
+			Shell:         shellName,
+			ShellVersion:  shellVersion,
+			Plain:         plain,
 		}
+
+		eng := engine.New(flags)
+
 		switch args[0] {
 		case "debug":
 			fmt.Print(eng.PrintExtraPrompt(engine.Debug))

src/color/plain_writer.go

@@ -39,9 +39,6 @@ func (a *PlainWriter) Write(background, foreground, text string) {
 }
 
 func (a *PlainWriter) String() (string, int) {
+	defer a.builder.Reset()
 	return a.builder.String(), a.length
 }
-
-func (a *PlainWriter) Reset() {
-	a.builder.Reset()
-}

src/color/writer.go

@@ -13,7 +13,6 @@ const (
 type Writer interface {
 	Write(background, foreground, text string)
 	String() (string, int)
-	Reset()
 	SetColors(background, foreground string)
 	SetParentColors(background, foreground string)
 	ClearParentColors()
@@ -238,10 +237,9 @@ func (a *AnsiWriter) expandKeyword(keyword string) string {
 }
 
 func (a *AnsiWriter) String() (string, int) {
+	defer func() {
+		a.length = 0
+		a.builder.Reset()
+	}()
 	return a.builder.String(), a.length
 }
-
-func (a *AnsiWriter) Reset() {
-	a.length = 0
-	a.builder.Reset()
-}

src/engine/block.go

@@ -129,7 +129,6 @@ func (b *Block) setSegmentsText() {
 }
 
 func (b *Block) RenderSegments() (string, int) {
-	defer b.writer.Reset()
 	for _, segment := range b.Segments {
 		if !segment.Enabled && segment.Style != Accordion {
 			continue
@@ -222,7 +221,6 @@ func (b *Block) Debug() (int, []*SegmentTiming) {
 			b.setActiveSegment(segment)
 			b.renderActiveSegment()
 			segmentTiming.text, _ = b.writer.String()
-			b.writer.Reset()
 		}
 		segmentTiming.duration = time.Since(start)
 		segmentTimings = append(segmentTimings, &segmentTiming)

src/engine/config.go

@@ -5,15 +5,16 @@ import (
 	json2 "encoding/json"
 	"fmt"
 	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
 	"oh-my-posh/color"
 	"oh-my-posh/platform"
 	"oh-my-posh/properties"
 	"oh-my-posh/segments"
 	"oh-my-posh/template"
-	"os"
-	"path/filepath"
-	"strings"
-	"time"
 
 	"github.com/gookit/config/v2"
 	"github.com/gookit/config/v2/json"

src/engine/engine.go

@@ -2,13 +2,14 @@ package engine
 
 import (
 	"fmt"
+	"strings"
+	"time"
+
 	"oh-my-posh/color"
 	"oh-my-posh/console"
 	"oh-my-posh/platform"
 	"oh-my-posh/shell"
 	"oh-my-posh/template"
-	"strings"
-	"time"
 )
 
 type Engine struct {
@@ -37,7 +38,9 @@ func (e *Engine) writeANSI(text string) {
 }
 
 func (e *Engine) string() string {
-	return e.console.String()
+	text := e.console.String()
+	e.console.Reset()
+	return text
 }
 
 func (e *Engine) canWriteRPrompt(rprompt bool) bool {
@@ -130,7 +133,6 @@ func (e *Engine) shouldFill(block *Block, length int) (string, bool) {
 	}
 	e.Writer.Write("", "", block.Filler)
 	filler, lenFiller := e.Writer.String()
-	e.Writer.Reset()
 	if lenFiller == 0 {
 		return "", false
 	}
@@ -314,6 +316,7 @@ func (e *Engine) print() string {
 		prompt = e.Ansi.FormatText(prompt)
 		e.write(prompt)
 	}
+
 	return e.string()
 }
 
@@ -342,7 +345,7 @@ func (e *Engine) PrintTooltip(tip string) string {
 		Segments:  []*Segment{tooltip},
 	}
 	switch e.Env.Shell() {
-	case shell.ZSH, shell.CMD, shell.FISH:
+	case shell.ZSH, shell.CMD, shell.FISH, shell.PLAIN:
 		block.Init(e.Env, e.Writer, e.Ansi)
 		if !block.Enabled() {
 			return ""
@@ -431,7 +434,8 @@ func (e *Engine) PrintExtraPrompt(promptType ExtraPromptType) string {
 			return prompt
 		}
 		return str
-	case shell.PWSH, shell.PWSH5, shell.CMD, shell.BASH, shell.FISH, shell.NU:
+	case shell.PWSH, shell.PWSH5, shell.CMD, shell.BASH, shell.FISH, shell.NU, shell.PLAIN:
+		// Return the string and empty our buffer
 		str, _ := e.Writer.String()
 		return str
 	}

src/engine/new.go

@@ -0,0 +1,55 @@
+package engine
+
+import (
+	"oh-my-posh/color"
+	"oh-my-posh/console"
+	"oh-my-posh/platform"
+	"oh-my-posh/shell"
+)
+
+// New returns a prompt engine initialized with the
+// given configuration options, and is ready to print any
+// of the prompt components.
+func New(flags *platform.Flags) *Engine {
+	env := &platform.Shell{
+		CmdFlags: flags,
+	}
+
+	env.Init()
+	defer env.Close()
+	cfg := LoadConfig(env)
+	ansi := &color.Ansi{}
+	ansi.Init(env.Shell())
+
+	var writer color.Writer
+	if flags.Plain {
+		ansi.InitPlain()
+		writer = &color.PlainWriter{
+			Ansi: ansi,
+		}
+	} else {
+		writerColors := cfg.MakeColors()
+		writer = &color.AnsiWriter{
+			Ansi:               ansi,
+			TerminalBackground: shell.ConsoleBackgroundColor(env, cfg.TerminalBackground),
+			AnsiColors:         writerColors,
+		}
+	}
+
+	consoleTitle := &console.Title{
+		Env:      env,
+		Ansi:     ansi,
+		Template: cfg.ConsoleTitleTemplate,
+	}
+
+	eng := &Engine{
+		Config:       cfg,
+		Env:          env,
+		Writer:       writer,
+		ConsoleTitle: consoleTitle,
+		Ansi:         ansi,
+		Plain:        flags.Plain,
+	}
+
+	return eng
+}

src/platform/shell.go

@@ -62,6 +62,7 @@ type Flags struct {
 	Strict        bool
 	Debug         bool
 	Manual        bool
+	Plain         bool
 }
 
 type CommandError struct {