[analyze] Add environment variable support to text inputs

The values will only be replaced if the input begins with a dollar sign,
and allows for multiple expansions like "${A} and ${B}". The requirement
for the first character to be a dollar sign prevents any issues with a
dollar sign embedded in a key itself.

pkg/analyzer/tui/form.go

@@ -25,14 +25,18 @@ func NewFormPage(c *common.Common, keyType string) FormPage {
 	switch strings.ToLower(keyType) {
 	case "twilio":
 		inputs = []textinputs.InputConfig{{
-			Label:    "SID",
-			Key:      "sid",
-			Required: true,
+			Label:       "SID",
+			Key:         "sid",
+			Required:    true,
+			AllowEnv:    true,
+			Placeholder: "$TWILIO_SID",
 		}, {
 			Label:       "Token",
 			Key:         "key",
 			Required:    true,
 			RedactInput: true,
+			AllowEnv:    true,
+			Placeholder: "$TWILIO_TOKEN",
 		}}
 	case "shopify":
 		inputs = []textinputs.InputConfig{{
@@ -40,25 +44,33 @@ func NewFormPage(c *common.Common, keyType string) FormPage {
 			Key:         "key",
 			Required:    true,
 			RedactInput: true,
+			AllowEnv:    true,
+			Placeholder: "$SHOPIFY_TOKEN",
 		}, {
-			Label:    "Shopify URL",
-			Key:      "url",
-			Required: true,
+			Label:       "Shopify URL",
+			Key:         "url",
+			Required:    true,
+			AllowEnv:    true,
+			Placeholder: "$SHOPIFY_URL",
 		}}
 	default:
+		kt := strings.ToUpper(keyType)
 		inputs = []textinputs.InputConfig{{
 			Label:       "Secret",
 			Key:         "key",
 			Required:    true,
 			RedactInput: true,
+			AllowEnv:    true,
+			Placeholder: fmt.Sprintf("$%s_TOKEN", kt),
 		}}
 	}
 
 	// Always append a log file option.
 	inputs = append(inputs, textinputs.InputConfig{
-		Label: "Log file",
-		Help:  "Log HTTP requests that analysis performs to this file",
-		Key:   "log_file",
+		Label:    "Log file",
+		Help:     "Log HTTP requests that analysis performs to this file",
+		Key:      "log_file",
+		AllowEnv: true,
 	})
 
 	form := textinputs.New(inputs).

pkg/tui/components/textinputs/textinputs.go

@@ -4,6 +4,7 @@ package textinputs
 
 import (
 	"fmt"
+	"os"
 	"strings"
 
 	"github.com/charmbracelet/bubbles/textinput"
@@ -47,6 +48,7 @@ type InputConfig struct {
 	Required    bool
 	Placeholder string
 	RedactInput bool
+	AllowEnv    bool
 }
 
 type Input struct {
@@ -64,6 +66,9 @@ func (m Model) GetInputs() map[string]Input {
 			isDefault = true
 			value = input.Placeholder
 		}
+		if m.configs[i].AllowEnv && strings.HasPrefix(value, "$") {
+			value = os.ExpandEnv(value)
+		}
 		inputs[m.configs[i].Key] = Input{Value: value, IsDefault: isDefault}
 	}
 
@@ -191,15 +196,10 @@ func (m Model) View() string {
 			b.WriteString(m.GetLabel(m.configs[i]))
 		}
 
+		// Make a copy of the input so we don't update the display.
 		input := m.inputs[i]
-		if val := input.Value(); len(val) > 4 && m.configs[i].RedactInput {
-			if len(val) > 10 {
-				// start***end
-				input.SetValue(val[:4] + strings.Repeat("*", len(val)-8) + val[len(val)-4:])
-			} else {
-				// start***
-				input.SetValue(val[:4] + strings.Repeat("*", len(val)-4))
-			}
+		if redacted, ok := redactFilter(input.Value(), m.configs[i]); ok {
+			input.SetValue(redacted)
 		}
 		b.WriteString(input.View())
 		b.WriteRune('\n')
@@ -221,6 +221,21 @@ func (m Model) View() string {
 	return b.String()
 }
 
+func redactFilter(input string, config InputConfig) (string, bool) {
+	if !config.RedactInput || len(input) <= 4 {
+		return input, false
+	}
+	if config.AllowEnv && strings.HasPrefix(input, "$") {
+		return input, false
+	}
+	if len(input) <= 10 {
+		// start***
+		return input[:4] + strings.Repeat("*", len(input)-4), true
+	}
+	// start***end
+	return input[:4] + strings.Repeat("*", len(input)-8) + input[len(input)-4:], true
+}
+
 func (m Model) GetLabel(c InputConfig) string {
 	var label strings.Builder