Add selection prompt

go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/atotto/clipboard v0.1.2
 	github.com/charmbracelet/bubbletea v0.12.2
 	github.com/mattn/go-runewidth v0.0.9
+	github.com/muesli/reflow v0.2.1-0.20201126184510-3bcb929042f2
 	github.com/muesli/termenv v0.7.4
 	golang.org/x/crypto v0.0.0-20201016220609-9e8e0b390897 // indirect
 	golang.org/x/sys v0.0.0-20201020230747-6e5568b54d1a // indirect

go.sum

@@ -12,6 +12,8 @@ github.com/mattn/go-isatty v0.0.12 h1:wuysRhFDzyxgEmMf5xjvJ2M9dZoWAXNNr5LSBS7uHX
 github.com/mattn/go-isatty v0.0.12/go.mod h1:cbi8OIDigv2wuxKPP5vlRcQ1OAZbq2CE4Kysco4FUpU=
 github.com/mattn/go-runewidth v0.0.9 h1:Lm995f3rfxdpd6TSmuVCHVb/QhupuXlYr8sCI/QdE+0=
 github.com/mattn/go-runewidth v0.0.9/go.mod h1:H031xJmbD/WCDINGzjvQ9THkh0rPKHF+m2gUSrubnMI=
+github.com/muesli/reflow v0.2.1-0.20201126184510-3bcb929042f2 h1:+cpkcmASpeBn4qXz2tU+x+njyKe91NoHXqrJdhoDnZo=
+github.com/muesli/reflow v0.2.1-0.20201126184510-3bcb929042f2/go.mod h1:qT22vjVmM9MIUeLgsVYe/Ye7eZlbv9dZjL3dVhUqLX8=
 github.com/muesli/termenv v0.7.2 h1:r1raklL3uKE7rOvWgSenmEm2px+dnc33OTisZ8YR1fw=
 github.com/muesli/termenv v0.7.2/go.mod h1:ct2L5N2lmix82RaY3bMWwVu/jUFc9Ule0KGDCiKYPh8=
 github.com/muesli/termenv v0.7.4 h1:/pBqvU5CpkY53tU0vVn+xgs2ZTX63aH5nY+SSps5Xa8=

selection/choice.go

@@ -0,0 +1,60 @@
+package selection
+
+import (
+	"fmt"
+	"reflect"
+)
+
+// Choice represents a single choice. This type used as an input
+// for the selection prompt, for filtering and as a result value.
+// The index is populated by the prompt itself and is exported
+// to be accessed when filtering.
+type Choice struct {
+	Index  int
+	String string
+	Value  interface{}
+}
+
+// NewChoice creates a new choice for a given input and chooses
+// a suitable string representation. The index is left at 0 to
+// be populated by the selection prompt later on.
+func NewChoice(item interface{}) *Choice {
+	choice := &Choice{Index: 0, Value: item}
+
+	switch i := item.(type) {
+	case Choice:
+		choice.String = i.String
+		choice.Value = i.Value
+	case *Choice:
+		choice.String = i.String
+		choice.Value = i.Value
+	case string:
+		choice.String = i
+	case fmt.Stringer:
+		choice.String = i.String()
+	default:
+		choice.String = fmt.Sprintf("%+v", i)
+	}
+
+	return choice
+}
+
+// Choices converts a slice of anything to a slice of choices.
+// Choices panics if the input is not a slice.
+func Choices(sliceChoices interface{}) []*Choice {
+	switch reflect.TypeOf(sliceChoices).Kind() {
+	case reflect.Slice:
+		slice := reflect.ValueOf(sliceChoices)
+
+		choices := make([]*Choice, 0, slice.Len())
+
+		for i := 0; i < slice.Len(); i++ {
+			value := slice.Index(i).Interface()
+			choices = append(choices, NewChoice(value))
+		}
+
+		return choices
+	default:
+		panic("SliceChoices argument is not a slice")
+	}
+}

selection/keymap.go

@@ -0,0 +1,53 @@
+package selection
+
+// DefaultKeyMap is a KeyMap with sensible default key mappings
+// that can also be used as a starting point for customization.
+var DefaultKeyMap = KeyMap{
+	Down:        []string{"down"},
+	Up:          []string{"up"},
+	Select:      []string{"enter"},
+	Abort:       []string{"ctrl+c"},
+	ClearFilter: []string{"esc"},
+	ScrollDown:  []string{"pgdown", "right"},
+	ScrollUp:    []string{"pgup", "left"},
+}
+
+// KeyMap defines the keys that trigger certain actions.
+type KeyMap struct {
+	Down        []string
+	Up          []string
+	Select      []string
+	Abort       []string
+	ClearFilter []string
+	ScrollDown  []string
+	ScrollUp    []string
+}
+
+func keyMatches(key string, mapping []string) bool {
+	for _, m := range mapping {
+		if m == key {
+			return true
+		}
+	}
+
+	return false
+}
+
+// validateKeyMap returns true if the given key map contains at
+// least the bare minimum set of key bindings for the functional
+// prompt and false otherwise.
+func validateKeyMap(km KeyMap) bool {
+	if len(km.Up) == 0 {
+		return false
+	}
+
+	if len(km.Down) == 0 {
+		return false
+	}
+
+	if len(km.Select) == 0 {
+		return false
+	}
+
+	return true
+}