CommandManager: support per command configurable completion

src/command_manager.cc

@@ -1,20 +1,24 @@
 #include "command_manager.hh"
 
 #include "utils.hh"
+#include "assert.hh"
+
 #include <algorithm>
 
 namespace Kakoune
 {
 
-void CommandManager::register_command(const std::string& command_name, Command command)
+void CommandManager::register_command(const std::string& command_name, Command command,
+                                      const CommandCompleter& completer)
 {
-    m_commands[command_name] = command;
+    m_commands[command_name] = CommandAndCompleter { command, completer };
 }
 
-void CommandManager::register_command(const std::vector<std::string>& command_names, Command command)
+void CommandManager::register_command(const std::vector<std::string>& command_names, Command command,
+                                      const CommandCompleter& completer)
 {
     for (auto command_name : command_names)
-        register_command(command_name, command);
+        register_command(command_name, command, completer);
 }
 
 typedef std::vector<std::pair<size_t, size_t>> TokenList;
@@ -65,7 +69,7 @@ void CommandManager::execute(const std::string& command_line)
                                              it->second - it->first));
     }
 
-    command_it->second(params);
+    command_it->second.command(params);
 }
 
 Completions CommandManager::complete(const std::string& command_line, size_t cursor_pos)
@@ -96,14 +100,44 @@ Completions CommandManager::complete(const std::string& command_line, size_t cur
 
         return result;
     }
-    if (token_to_complete == 1) // filename completion
+
+    assert(not tokens.empty());
+    std::string command_name =
+        command_line.substr(tokens[0].first,
+                            tokens[0].second - tokens[0].first);
+
+    auto command_it = m_commands.find(command_name);
+    if (command_it == m_commands.end() or not command_it->second.completer)
+        return Completions();
+
+    CommandParameters params;
+    for (auto it = tokens.begin() + 1; it != tokens.end(); ++it)
     {
-        Completions result(tokens[1].first, cursor_pos);
-        std::string prefix = command_line.substr(tokens[1].first, cursor_pos);
-        result.candidates = complete_filename(prefix);
-        return result;
+        params.push_back(command_line.substr(it->first,
+                                             it->second - it->first));
     }
-    return Completions(cursor_pos, cursor_pos);
+    Completions result(tokens[token_to_complete].first, cursor_pos);
+    size_t cursor_pos_in_token = cursor_pos - tokens[token_to_complete].first;
+
+    result.candidates = command_it->second.completer(params,
+                                                     token_to_complete - 1,
+                                                     cursor_pos_in_token);
+    return result;
+}
+
+CandidateList PerArgumentCommandCompleter::operator()(const CommandParameters& params,
+                                                      size_t token_to_complete,
+                                                      size_t pos_in_token) const
+{
+    if (token_to_complete >= m_completers.size())
+        return CandidateList();
+
+    // it is possible to try to complete a new argument
+    assert(token_to_complete <= params.size());
+
+    const std::string& argument = token_to_complete < params.size() ?
+                                  params[token_to_complete] : std::string();
+    return m_completers[token_to_complete](argument, pos_in_token);
 }
 
 }

src/command_manager.hh

@@ -5,6 +5,7 @@
 #include <vector>
 #include <unordered_map>
 #include <functional>
+#include <initializer_list>
 
 #include "exception.hh"
 #include "completion.hh"
@@ -20,17 +21,53 @@ struct wrong_argument_count : runtime_error
 typedef std::vector<std::string> CommandParameters;
 typedef std::function<void (const CommandParameters&)> Command;
 
+typedef std::function<CandidateList (const CommandParameters&,
+                                     size_t, size_t)> CommandCompleter;
+
+class PerArgumentCommandCompleter
+{
+public:
+    typedef std::function<CandidateList (const std::string&, size_t)> ArgumentCompleter;
+    typedef std::vector<ArgumentCompleter> ArgumentCompleterList;
+
+    PerArgumentCommandCompleter(const ArgumentCompleterList& completers)
+        : m_completers(completers) {}
+
+    PerArgumentCommandCompleter(ArgumentCompleterList&& completers)
+        : m_completers(completers) {}
+
+    PerArgumentCommandCompleter(std::initializer_list<ArgumentCompleter> completers)
+        : m_completers(completers) {}
+
+    CandidateList operator()(const CommandParameters& params,
+                             size_t token_to_complete,
+                             size_t pos_in_token) const;
+
+private:
+    ArgumentCompleterList m_completers;
+};
+
 class CommandManager
 {
 public:
     void execute(const std::string& command_line);
     Completions complete(const std::string& command_line, size_t cursor_pos);
 
-    void register_command(const std::string& command_name, Command command);
-    void register_command(const std::vector<std::string>& command_names, Command command);
+    void register_command(const std::string& command_name,
+                          Command command,
+                          const CommandCompleter& completer = CommandCompleter());
+
+    void register_command(const std::vector<std::string>& command_names,
+                          Command command,
+                          const CommandCompleter& completer = CommandCompleter());
 
 private:
-    std::unordered_map<std::string, Command> m_commands;
+    struct CommandAndCompleter
+    {
+        Command command;
+        CommandCompleter completer;
+    };
+    std::unordered_map<std::string, CommandAndCompleter> m_commands;
 };
 
 }