#include "xmake.h"

#include <algorithm>
#include <cstdlib>
#include <filesystem>
#include <iostream>
#include <iterator>
#include <sstream>
#include <stdexcept>
#include <string>
#include <unordered_map>
#include <vector>

#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/xml_parser.hpp>
#include <boost/process.hpp>

#include <fmt/format.h>

#include <libreichwein/file.h>
#include <libreichwein/stringhelper.h>

namespace fs = std::filesystem;
namespace bp = boost::process;
namespace pt = boost::property_tree;
using namespace std::string_literals;

namespace {
 const fs::path XMakefile{"XMakefile"};

 void usage()
 {
  std::cout << "Usage: xmake <target>" << std::endl;
 }

 fs::path get_target(const pt::ptree& ptree) {
  return ptree.get<std::string>("xmake.build.name");
 }
 
 std::vector<fs::path> get_sources(const pt::ptree& ptree) {
  std::vector<fs::path> sources;
  for (const pt::ptree::value_type &v: ptree.get_child("xmake.build")) {
   if (v.first == "source")
    sources.push_back(v.second.data());
  }
  return sources;
 }

 std::vector<fs::path> get_objects(const pt::ptree& ptree) {
  std::vector<fs::path> objects{get_sources(ptree)};
  for (auto &i: objects) {
   i.replace_extension("o");
  }
  return objects;
 }

 // both need to exist
 bool is_older(const fs::path& p, const fs::path& other) {
  auto t_p{fs::last_write_time(p)};
  auto t_other{fs::last_write_time(other)};
  return t_p < t_other;
 }

 bool is_outdated(const fs::path& p, const std::vector<fs::path> &dependencies) {
  if (!fs::exists(p))
   return true;

  for (auto& dep: dependencies) {
   if (!exists(dep) || is_older(p, dep)) {
    return true;
   }
  }

  return false;
 }

 std::vector<fs::path> deps_from_depfile(const fs::path& path) {
  std::string depfile_content{Reichwein::File::getFile(path)};
  std::vector<std::string> parts {Reichwein::Stringhelper::split(depfile_content, ":\r\n")};
  if (parts.size() >= 2) {
   std::vector<std::string> deps {Reichwein::Stringhelper::split(parts[1], " ")};
   std::vector<fs::path> result;
   std::transform(deps.cbegin(), deps.cend(), std::back_inserter(result), [](const std::string& s){ return s; });
   return result;
  } else {
   throw std::runtime_error("Bad depfile contents: "s + path.string());
  }
 }

 // return contained dependencies
 // input: cpp
 std::vector<fs::path> make_depfile_from(const fs::path& p) {
  fs::path depfile{p};
  depfile.replace_extension("d");

  // check if depfile exists and if it contains up to date info
  if (!fs::exists(depfile) || is_outdated(depfile, deps_from_depfile(depfile))) {
   // actually create depfile
   int result{system(fmt::format("g++ -MM -MF {} -c {}", depfile.string(), p.string()).c_str())};
   if (result != 0) {
    throw std::runtime_error(fmt::format("Depfile {} can't be created", depfile.string()));
   }
  }

  return deps_from_depfile(depfile);
 }

 void build(const pt::ptree& ptree) {
  fs::path target{get_target(ptree)};
  std::vector<fs::path> objects{get_objects(ptree)};
  std::vector<fs::path> sources{get_sources(ptree)};

  std::cout << "Target: " << target << std::endl;

  std::cout << "Sources: " << std::endl;
  for (auto &i: sources) {
   std::cout << "  " << i << std::endl;
  }

  std::cout << "Calculating dependencies..." << std::endl;
  std::unordered_map<fs::path, std::vector<fs::path>> dependencies;
  dependencies.emplace(target, objects);
  for (const auto& p: sources) {
   fs::path p_obj{p};
   p_obj.replace_extension("o");
   std::vector<fs::path> deps {make_depfile_from(p)};
   dependencies.emplace(p_obj, deps);
  }

  std::vector<std::string> commands;
  // compile
  for (auto &p: sources) {
   fs::path p_obj{p};
   p_obj.replace_extension("o");
   if (is_outdated(p_obj, std::vector<fs::path>{p})) {
    commands.push_back(fmt::format("g++ -std=c++17 -c {} -o {}", p.string(), p_obj.string()));
   }
  }
  // link
  std::vector<fs::path> deps{sources};
  if (is_outdated(target, deps)) {
   std::string link_command{"g++"};
   for (auto &i: objects) {
    link_command += fmt::format(" {}", i.string());
   }
   link_command += " -lfmt -lreichwein";
   link_command += fmt::format(" -o {}", target.string());
   commands.push_back(link_command);
  }

  std::cout << "Commands: " << std::endl;
  for (auto &i: commands) {
   std::cout << "  " << i << std::endl;
  }

  if (commands.size() == 0) {
   std::cout << "Everything up to date." << std::endl;
  } else {
   std::cout << "Running commands: " << std::endl;
   for (auto &i: commands) {
    std::cout << i << std::endl;
    int result{system(i.c_str())};
    if (result != 0) {
     throw std::runtime_error(fmt::format("Error {}", result));
    }
   }
  }
 }

 void clean(const pt::ptree& ptree) {
  std::vector<fs::path> cleanlist{get_objects(ptree)};
  cleanlist.push_back(get_target(ptree));

  std::vector<std::string> commands;
  for (auto &i: cleanlist) {
   commands.push_back(fmt::format("rm -f {}", i.string()));
   fs::path dep{i};
   dep.replace_extension("d");
   commands.push_back(fmt::format("rm -f {}", dep.string()));
  }

  std::cout << "Running commands: " << std::endl;
  for (auto &i: commands) {
   std::cout << i << std::endl;
   int result{system(i.c_str())};
   if (result != 0) {
    throw std::runtime_error(fmt::format("Error {}", result));
   }
  }
 }
}

int xmake(int argc, char* argv[])
{
 try {
  pt::ptree ptree;
  pt::read_xml(XMakefile, ptree, pt::xml_parser::no_comments | pt::xml_parser::trim_whitespace);

  std::string action{"default"};

  if (argc == 1) { // default action
  } else if (argc == 2) {
   action = argv[1];
  } else {
   std::cerr << "Invalid arguments." << std::endl;
   usage;
   exit(1);
  }

  if (action == "default"s || action == "build") { // build
   build(ptree);
  } else if (action == "clean") {
   clean(ptree);
  } else if (action == "install") {
   throw std::runtime_error("unimplemented");
  } else if (action == "rebuild") {
   throw std::runtime_error("unimplemented");
  } else if (action == "run") {
   throw std::runtime_error("unimplemented");
  } else {
   std::cerr << "Invalid action: " << action << std::endl;
   usage;
   exit(1);
  }

 } catch (const std::exception& ex) {
  std::cerr << "xmake: " << ex.what() << std::endl;
  return 1;
 }

 return 0;
}