Snel/src/sequencer.cpp

/*
 * child.cpp
 *
 *  Created on: Feb 11, 2019
 *      Author: hoo2
 */

#include "sequencer.h"

namespace snel {


   //! A type-safe memcpy
   template <typename T>
   void memcpy (T* to, const T* from, size_t n) {
      for (size_t i=0 ; i<n ; ++i)
         *to++ = *from++;
   }

   /*!
    * Split a string to tokens and store them in a container, using a delimiter
    * character.
    * \note
    *    Requires: container with push_back functionality
    * @param str
    * @param cont
    * @param delim
    */
   template <typename T, typename Container>
   void split(const std::basic_string<T>& str, Container& cont, T delim) {
      std::basic_stringstream<T> ss(str);
      std::basic_string<T> token;
      while (std::getline(ss, token, delim)) {
          cont.push_back(token);
      }
   }

   /*
    * ========== ArgList ==========
    */
   ArgList::~ArgList() {
      for (vtype p : args_) {
         if (p != nullptr)
            delete[] p;
      }
   }
   ArgList& ArgList::push_back(const std::basic_string<type>& item) {
      vtype it = new type[item.length()+1];

      // get data
      memcpy (it, item.c_str(), item.length());
      it[item.length()] = 0;

      // update the argument vector
      args_.back() = it;
      args_.push_back(nullptr);
      return *this;
   }

   /*
    * ========== Child ==========
    */
   Child::~Child () {
      for (int i=0 ; i<3 ; ++i)
         restore_std_if(i);
   }

   void Child::redirect_std_if(std::string fn, fd_t std_fd) {
      if (fn != "") {
         if ((files[std_fd] = openat(AT_FDCWD, fn.c_str(), O_RDWR | O_CREAT, 0640)) == -1)
            throw Error ("Child: Can not open file");
         if ((sstd[std_fd] = dup (std_fd)) == -1)  // save STDxxx
            throw Error ("Child: Can not create file descriptor");
         if ((dup2(files[std_fd], std_fd)) == -1)  // use input as STDIN_
            throw Error ("Child: Can not redirect file descriptor");
      }
   }
   void Child::restore_std_if(fd_t std_fd) {
      if (sstd[std_fd] != -1) {
         dup2(sstd[std_fd], std_fd);
         close (sstd[std_fd]);
         sstd[std_fd]  = -1;
      }
      if (files[std_fd] != -1) {
         close (files[std_fd]);
         files[std_fd] = -1;
      }

   }
   Child& Child::make_arguments () {
      bool in{false}, out{false}, err{false};

      for (auto& t: command) {
         if (t == "" || t== " ") continue; // skip crap

         if (t == "&&")       logic = LogicOp::AND;
         else if (t == "||")  logic = LogicOp::OR;
         // one pass redirection parsing
         else if (!t.compare(0, 1, "<"))  filenames[STDIN_]  = t.substr(1);
         else if (!t.compare(0, 1, ">"))  filenames[STDOUT_] = t.substr(1);
         else if (!t.compare(0, 2, "1>")) filenames[STDOUT_] = t.substr(2);
         else if (!t.compare(0, 2, "2>")) filenames[STDERR_] = t.substr(2);
         // two pass redirection parsing (if redirection came in 2 arguments)
         else if (t == "<")               in  = true;
         else if (t == "1>" || t == ">")  out = true;
         else if (t == "2>")              err = true;
         else if (in) {
            filenames[STDIN_] = t;  in = false;
         }
         else if (out) {
            filenames[STDOUT_] = t; out = false;
         }
         else if (err) {
            filenames[STDERR_] = t; err = false;
         }
         else
            arguments.push_back(t);
      }
      return *this;
   }

   bool Child::execute() {
      bool stop = {false};

      redirect_std_if (filenames[STDIN_],  STDIN_);
      redirect_std_if (filenames[STDOUT_], STDOUT_);
      redirect_std_if (filenames[STDERR_], STDERR_);
      pid_t pid = fork();
      if (pid < 0) {
         throw Error("Child::execute(): Can not create child process");
      }
      else if (pid == 0) { // child

         execvp(arguments.front(), arguments.data());
         // error if we got here
         std::cout << "Can not invoke: " << arguments.front() << std::endl;
         throw Error("Child::execute(): Can not run child process");
      }
      else {   // parent
         int exit_status;
         waitpid(pid, &exit_status, 0);  // wait child process to finish
         restore_std_if (STDIN_);
         restore_std_if (STDOUT_);
         restore_std_if (STDERR_);

         switch (logic) {
            case LogicOp::AND:
               if (exit_status)  stop = true;
               break;
            case LogicOp::OR:
               if (!exit_status) stop = true;
               break;
            default: break;
         }
      }

      return stop;
   }

   /*
    * ======== Sequencer ===========
    */
   Sequencer& Sequencer::parse (const std::string& input) {
      std::vector<std::string> commands;
      std::vector<std::string> tokens;
      Child::command_t command;

      split (input, commands, ';'); // split all commands
      for (auto& s : commands) {
         command.clear();      //clear child tokens
         tokens.clear();            // make a new token vector for command
         split (s, tokens, ' ');

         seq_.emplace_back(std::vector<Child>{});  // make a new child for command
         // check tokens inside command
         for (auto& t: tokens) {
            if (is_pipe(t)) {

            }

            command.push_back(t);    // get current token
            if (is_seperator(t)) {
               // construct a child with what we have so far and clear command
               seq_.back().emplace_back(command);
               command.clear();
            }
         }
         seq_.back().emplace_back(command);   // construct the child with tokens
      }

      return *this;
   }

   Sequencer& Sequencer::execute() {
      for (auto& batch : seq_)
         for (auto& command: batch)
            if (command.make_arguments().execute())
               break;
      seq_.clear();
      return *this;
   }

}