Add a ShellManager which handles executing shell commands

ShellManager provides shell commands with environement variable
to retrieve some internal values in the shell parameters.

src/command_manager.cc

@@ -3,11 +3,9 @@
 #include "utils.hh"
 #include "assert.hh"
 #include "context.hh"
+#include "shell_manager.hh"
 
 #include <algorithm>
-#include <cstring>
-#include <sys/types.h>
-#include <sys/wait.h>
 
 namespace Kakoune
 {
@@ -101,29 +99,7 @@ static void shell_eval(std::vector<String>& params,
                        const String& cmdline,
                        const Context& context)
 {
-    int write_pipe[2];
-    int read_pipe[2];
-
-    pipe(write_pipe);
-    pipe(read_pipe);
-
-    if (pid_t pid = fork())
-    {
-        close(write_pipe[0]);
-        close(read_pipe[1]);
-        close(write_pipe[1]);
-
-        String output;
-        char buffer[1024];
-        while (size_t size = read(read_pipe[0], buffer, 1024))
-        {
-            if (size == -1)
-                break;
-            output += String(buffer, buffer+size);
-        }
-        close(read_pipe[0]);
-        waitpid(pid, NULL, 0);
-
+        String output = ShellManager::instance().eval(cmdline, context);
         TokenList tokens = split(output);
 
         for (auto it = tokens.begin(); it != tokens.end(); ++it)
@@ -132,19 +108,6 @@ static void shell_eval(std::vector<String>& params,
                                            it->second - it->first));
         }
 }
-    else
-    {
-        close(write_pipe[1]);
-        close(read_pipe[0]);
-
-        dup2(read_pipe[1], 1);
-        dup2(write_pipe[0], 0);
-
-        if (context.has_buffer())
-            setenv("kak_bufname", context.buffer().name().c_str(), 1);
-        execlp("sh", "sh", "-c", cmdline.c_str(), NULL);
-    }
-}
 
 void CommandManager::execute(const CommandParameters& params,
                              const Context& context)

src/highlighters.cc

@@ -12,6 +12,8 @@ namespace Kakoune
 
 using namespace std::placeholders;
 
+typedef boost::regex_iterator<BufferIterator> RegexIterator;
+
 void colorize_regex_range(DisplayBuffer& display_buffer,
                           const BufferIterator& range_begin,
                           const BufferIterator& range_end,

src/main.cc

@@ -1,6 +1,7 @@
 #include "window.hh"
 #include "buffer.hh"
 #include "file.hh"
+#include "shell_manager.hh"
 #include "command_manager.hh"
 #include "buffer_manager.hh"
 #include "register_manager.hh"
@@ -929,6 +930,7 @@ int main(int argc, char* argv[])
 {
     NCurses::init(prompt_func, get_key_func);
 
+    ShellManager        shell_manager;
     CommandManager      command_manager;
     BufferManager       buffer_manager;
     RegisterManager     register_manager;
@@ -939,6 +941,11 @@ int main(int argc, char* argv[])
 
     run_unit_tests();
 
+    shell_manager.register_env_var("bufname",
+                                   [](const Context& context)
+                                   { return context.buffer().name(); });
+
+
     command_manager.register_commands({ "e", "edit" }, edit<false>,
                                      CommandManager::None,
                                      PerArgumentCommandCompleter({ complete_filename }));

src/regex.hh

@@ -8,7 +8,6 @@
 namespace Kakoune
 {
 
-typedef boost::regex_iterator<BufferIterator> RegexIterator;
 typedef boost::basic_regex<Character> Regex;
 
 }

src/selectors.cc

@@ -87,6 +87,8 @@ bool skip_while_reverse(BufferIterator& it, T condition)
 
 }
 
+typedef boost::regex_iterator<BufferIterator> RegexIterator;
+
 template<bool punctuation_is_word>
 SelectionAndCaptures select_to_next_word(const Selection& selection)
 {

src/shell_manager.cc

@@ -0,0 +1,85 @@
+#include "shell_manager.hh"
+
+#include <cstring>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+namespace Kakoune
+{
+
+ShellManager::ShellManager()
+   : m_regex(LR"(\$\{kak_([a-z0-9_]+)[^}]*\}|\$kak_([a-z0-9_]+))")
+{
+}
+
+String ShellManager::eval(const String& cmdline, const Context& context)
+{
+    int write_pipe[2];
+    int read_pipe[2];
+
+    pipe(write_pipe);
+    pipe(read_pipe);
+
+    String output;
+    if (pid_t pid = fork())
+    {
+        close(write_pipe[0]);
+        close(read_pipe[1]);
+        close(write_pipe[1]);
+
+        char buffer[1024];
+        while (size_t size = read(read_pipe[0], buffer, 1024))
+        {
+            if (size == -1)
+                break;
+            output += String(buffer, buffer+size);
+        }
+        close(read_pipe[0]);
+        waitpid(pid, NULL, 0);
+    }
+    else
+    {
+        close(write_pipe[1]);
+        close(read_pipe[0]);
+
+        dup2(read_pipe[1], 1);
+        dup2(write_pipe[0], 0);
+
+        boost::regex_iterator<String::iterator> it(cmdline.begin(), cmdline.end(), m_regex);
+        boost::regex_iterator<String::iterator> end;
+
+        while (it != end)
+        {
+            auto& match = *it;
+
+            String name;
+            if (match[1].matched)
+                name = String(match[1].first, match[1].second);
+            else if (match[2].matched)
+                name = String(match[2].first, match[2].second);
+            else
+                assert(false);
+            assert(name.length() > 0);
+
+            auto env_var = m_env_vars.find(name);
+            if (env_var != m_env_vars.end())
+            {
+                String value = env_var->second(context);
+                setenv(("kak_" + name).c_str(), value.c_str(), 1);
+            }
+
+            ++it;
+        }
+
+        execlp("sh", "sh", "-c", cmdline.c_str(), NULL);
+    }
+    return output;
+}
+
+void ShellManager::register_env_var(const String& name,
+                                    EnvVarRetriever retriever)
+{
+    m_env_vars[name] = std::move(retriever);
+}
+
+}

src/shell_manager.hh

@@ -0,0 +1,32 @@
+#ifndef shell_manager_hh_INCLUDED
+#define shell_manager_hh_INCLUDED
+
+#include "utils.hh"
+#include "regex.hh"
+
+#include <unordered_map>
+
+namespace Kakoune
+{
+
+class Context;
+typedef std::function<String (const Context&)> EnvVarRetriever;
+
+class ShellManager : public Singleton<ShellManager>
+{
+public:
+    ShellManager();
+
+    String eval(const String& cmdline, const Context& context);
+
+    void register_env_var(const String& name, EnvVarRetriever retriever);
+
+private:
+    Regex                                       m_regex;
+    std::unordered_map<String, EnvVarRetriever> m_env_vars;
+};
+
+}
+
+#endif // shell_manager_hh_INCLUDED
+