cli: add smart-wrap for help description

vlib/cli/help.v

@@ -1,5 +1,10 @@
 module cli
 
+import (
+	term
+	strings
+)
+
 const (
 	BASE_INDENT = 2
 	ABBREV_INDENT = 5
@@ -55,7 +60,8 @@ fn help_func(help_cmd Command) {
 
 			base_indent := ' '.repeat(BASE_INDENT)
 			description_indent := ' '.repeat(max(DESCRIPTION_INDENT-flag_name.len, 1))
-			help += '${base_indent}${flag_name}${description_indent}${flag.description}${required}\n'
+			help += '${base_indent}${flag_name}${description_indent}' +
+				pretty_description(flag.description + required) + '\n'
 		}
 		help += '\n'
 	}
@@ -65,7 +71,8 @@ fn help_func(help_cmd Command) {
 			base_indent := ' '.repeat(BASE_INDENT)
 			description_indent := ' '.repeat(max(DESCRIPTION_INDENT-command.name.len, 1))
 
-			help += '${base_indent}${command.name}${description_indent}${command.description}\n'
+			help += '${base_indent}${command.name}${description_indent}' +
+				pretty_description(command.description) + '\n'
 		}
 		help += '\n'
 	}
@@ -73,6 +80,36 @@ fn help_func(help_cmd Command) {
 	print(help)
 }
 
+// pretty_description resizes description text depending on terminal width.
+// Essentially, smart wrap-around
+fn pretty_description(s string) string {
+	width, _ := term.get_terminal_size()
+	// Don't prettify if the terminal is that small, it won't be pretty anyway.
+	if s.len + DESCRIPTION_INDENT < width || DESCRIPTION_INDENT > width {
+		return s
+	}
+	indent := ' '.repeat(DESCRIPTION_INDENT + 1)
+	chars_per_line := width - DESCRIPTION_INDENT
+	// Give us enough room, better a little bigger than smaller
+	mut acc := strings.new_builder(((s.len / chars_per_line) + 1) * (width + 1))
+
+	mut i := chars_per_line - 1
+	mut j := 0
+	for ; i < s.len ; i += chars_per_line - 1 {
+		for s.str[i] != ` ` { i-- }
+		// indent was already done the first iteration
+		if j != 0 { acc.write(indent) }
+		acc.writeln(s[j..i])
+		j = i
+	}
+	// We need this even though it should never happen
+	if j != 0 {
+		acc.write(indent)
+	}
+	acc.write(s[j..])
+	return acc.str()
+}
+
 fn max(a, b int) int {
 	return if a > b {a} else {b}
 }