Read input regardless of whether or not it's a TTY

This commit also contains some refactors:

* Refactor away inputStatus type
* Refactor away program.inputIsTTY member
* Simplify how we setup and restore input when it's a TTY

tea.go

@@ -52,8 +52,8 @@ type Model interface {
 // function.
 type Cmd func() Msg
 
-// startupOptions contains configuration options to be run while the program
-// is initializing.
+// Options to customize the program during its initialization. These are
+// generally set with ProgramOptions.
 //
 // The options here are treated as bits.
 type startupOptions byte
@@ -62,42 +62,14 @@ func (s startupOptions) has(option startupOptions) bool {
 	return s&option != 0
 }
 
-// Available startup options.
 const (
 	withAltScreen startupOptions = 1 << iota
 	withMouseCellMotion
 	withMouseAllMotion
 	withInputTTY
+	withCustomInput
 )
 
-// inputStatus indicates the current state of the input. By default, input is
-// stdin, however we'll change this if input's not a TTY. The user can also set
-// the input.
-type inputStatus int
-
-const (
-	// Generally this will be stdin.
-	//
-	// Lint ignore note: this is the implicit default value. While it's not
-	// checked explicitly, it's presence nullifies the other possible values
-	// of this type in logical statements.
-	defaultInput inputStatus = iota // nolint:golint,deadcode,unused,varcheck
-
-	// The user explicitly set the input.
-	customInput
-
-	// We've opened a TTY for input.
-	managedInput
-)
-
-func (i inputStatus) String() string {
-	return [...]string{
-		"default input",
-		"custom input",
-		"managed input",
-	}[i]
-}
-
 // Program is a terminal user interface.
 type Program struct {
 	initialModel Model
@@ -122,8 +94,6 @@ type Program struct {
 	// is on by default.
 	CatchPanics bool
 
-	inputStatus inputStatus
-	inputIsTTY  bool
 	outputIsTTY bool
 	console     console.Console
 
@@ -311,22 +281,19 @@ func (p *Program) Start() error {
 		p.input = f
 	}
 
-	// Is input a terminal?
-	if f, ok := p.input.(*os.File); ok {
-		p.inputIsTTY = isatty.IsTerminal(f.Fd())
-	}
-
 	// If input is not a terminal, and the user hasn't set a custom input, open
 	// a TTY so we can capture input as normal. This will allow things to "just
 	// work" in cases where data was piped or redirected into this application.
-	if !p.inputIsTTY && p.inputStatus != customInput {
-		f, err := openInputTTY()
-		if err != nil {
-			return err
+	if f, ok := p.input.(*os.File); ok {
+		inputIsTTY := isatty.IsTerminal(f.Fd())
+
+		if !inputIsTTY && !p.startupOptions.has(withCustomInput) {
+			f, err := openInputTTY()
+			if err != nil {
+				return err
+			}
+			p.input = f
 		}
-		p.input = f
-		p.inputIsTTY = true
-		p.inputStatus = managedInput
 	}
 
 	// Listen for SIGINT. Note that in most cases ^C will not send an
@@ -394,7 +361,7 @@ func (p *Program) Start() error {
 	p.renderer.write(model.View())
 
 	// Subscribe to user input
-	if p.inputIsTTY {
+	if p.input != nil {
 		go func() {
 			for {
 				msg, err := readInput(p.input)