From b9f349d1d7478fb6ef0a4ea338fcfd7d47cdd6a9 Mon Sep 17 00:00:00 2001
From: Leon Mika <lmika@lmika.org>
Date: Wed, 11 Dec 2024 21:23:53 +1100
Subject: [PATCH] Added help command

---
 repl/docs.go | 31 +++++++++++++++++++++++++++++--
 repl/repl.go |  4 ++++
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/repl/docs.go b/repl/docs.go
index b3ea160..40e3485 100644
--- a/repl/docs.go
+++ b/repl/docs.go
@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"github.com/lmika/gopkgs/fp/maps"
 	"os"
+	"slices"
 	"sort"
 	"strings"
 	"text/tabwriter"
@@ -13,8 +14,15 @@ import (
 	"unicode"
 )
 
+type ArgDoc struct {
+	Name  string
+	Brief string
+}
+
 type Doc struct {
 	Brief    string
+	Usage    string
+	Args     []ArgDoc
 	Detailed string
 }
 
@@ -54,9 +62,28 @@ func (r *REPL) helpBuiltin(ctx context.Context, args ucl.CallArgs) (any, error)
 		fmt.Printf("%v\n", cmdName)
 		fmt.Printf("  %v\n", docs.Brief)
 
+		if docs.Usage != "" {
+			fmt.Println("\nUsage:")
+			fmt.Printf("  %v %v\n", cmdName, docs.Usage)
+		}
+
+		if len(docs.Args) > 0 {
+			fmt.Println("\nArguments:")
+
+			docArgs := slices.Clone(docs.Args)
+			sort.Slice(docArgs, func(i, j int) bool {
+				return strings.TrimPrefix(docs.Args[i].Name, "-") < strings.TrimPrefix(docs.Args[j].Name, "-")
+			})
+
+			tw := tabwriter.NewWriter(os.Stdout, 0, 0, 1, ' ', 0)
+			for _, arg := range docArgs {
+				fmt.Fprintf(tw, "  %v\t  %v\n", arg.Name, arg.Brief)
+			}
+			tw.Flush()
+		}
+
 		if docs.Detailed != "" {
-			fmt.Println("")
-			fmt.Println("Details:")
+			fmt.Println("\nDetails:")
 
 			lines := strings.Split(docs.Detailed, "\n")
 
diff --git a/repl/repl.go b/repl/repl.go
index 387354d..b9cf19e 100644
--- a/repl/repl.go
+++ b/repl/repl.go
@@ -23,6 +23,10 @@ func New(opts ...ucl.InstOption) *REPL {
 	}
 	r.SetCommand("help", r.helpBuiltin, Doc{
 		Brief: "displays help about a command",
+		Usage: "[command]",
+		Args: []ArgDoc{
+			{Name: "command", Brief: "command to display detailed help for"},
+		},
 		Detailed: `
 			When used without arguments, 'help' will display the list of known commands,
 			along with a brief description on what each one does.