commands: implement prompt completion

This patch implements :prompt completion.
The completion mechanism only provides completions when there is at least
one argument specified (prompt text).
The mechanism is based on other commands' completions and works as follows:

   1. Attempts to look up a command by the name specified in args[1].

   2.a On success it uses command.Complete.

   2.b Otherwise, if total arguments count is lesser or equals than 2
       (i.e. no command arguments specified), it attempts to complete
       the command's name.

Additional effort is made to preserve prompt text, which often contains
spaces and formatting.

Signed-off-by: Sergey Smirnykh <sergey.smirnykh@siborgium.xyz>
Acked-by: Robin Jarry <robin@jarry.cc>

1 files changed, 7 insertions, 0 deletions

diff --git a/commands/commands.go b/commands/commands.go
index 2753686f..1aa8e1af 100644
--- a/commands/commands.go
+++ b/commands/commands.go
@@ -37,6 +37,13 @@ func (cmds *Commands) Names() []string {
 	return names
 }
 
+func (cmds *Commands) ByName(name string) Command {
+	if cmd, ok := cmds.dict()[name]; ok {
+		return cmd
+	}
+	return nil
+}
+
 func (cmds *Commands) Register(cmd Command) {
 	// TODO enforce unique aliases, until then, duplicate each
 	if len(cmd.Aliases()) < 1 {