#include "builder.h"

#include <algorithm>
#include <cstdlib>
#include <filesystem>
#include <iostream>
#include <iterator>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <string>
#include <unordered_map>
#include <unordered_set>
#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 {
 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;
 }

 // outdated according to dependency file list, non-recursively
 bool is_outdated(const fs::path& p, const std::vector<fs::path> &dependencies) {
  if (!fs::exists(p))
   return true;

  for (const auto& dep: dependencies) {
   if (!fs::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());
  }
 }

 fs::path depfile_name_from(const fs::path& p) {
  fs::path depfile{p};
  depfile.replace_extension("d");
  return depfile;
 }

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

  // 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);
 }

 // type of file can be built from dependencies
 bool is_buildable_by_extension(const fs::path& p) {
  fs::path ext{p.extension()};
  return ext.empty() || ext == ".o";
 }

 std::unordered_map<fs::path, std::vector<fs::path>> get_dependencies(const pt::ptree& ptree) {
  std::unordered_map<fs::path, std::vector<fs::path>> dependencies;
  dependencies.emplace(get_target(ptree), get_objects(ptree));
  std::vector<fs::path> sources{get_sources(ptree)};
  for (const auto& p: sources) {
   fs::path p_obj{p};
   p_obj.replace_extension("o");
   std::vector<fs::path> deps {make_depfile_from(p)};
   fs::remove(depfile_name_from(p));
   dependencies.emplace(p_obj, deps);
  }
  return dependencies;
 }

}

Builder::Builder(const pt::ptree& ptree):
 _target{get_target(ptree)},
 _objects{get_objects(ptree)},
 _sources{get_sources(ptree)},
 _dependencies{get_dependencies(ptree)}
{
}

std::vector<fs::path> Builder::dependencies_of(const fs::path& p) {
 try {
  return _dependencies.at(p);
 } catch (const std::out_of_range& ex) {
  return {}; // empty by default
 }
}

// outdated according to dependency tree, recursively
bool Builder::is_outdated(const fs::path& p) {
 if (!fs::exists(p))
  return true;

 std::vector<fs::path> deps{dependencies_of(p)};
 for (const auto& dep: deps) {
  if (!fs::exists(dep) || is_older(p, dep)) {
   return true;
  }

  if (is_outdated(dep)) {
   return true;
  }
 }

 return false;
}

// build 1 file
void Builder::build(const fs::path& p) {
 std::string command;

 if (p.extension() == ".o") {
   // compile
   fs::path cppfile{p};
   cppfile.replace_extension("cpp");
   command = fmt::format("g++ -std=c++17 -c {} -o {}", cppfile.string(), p.string());
 } else {
  // link
  command = "g++";
  std::vector<fs::path> objects{dependencies_of(p)};
  for (auto &i: objects) {
   command += fmt::format(" {}", i.string());
  }
  command += " -lfmt -lreichwein";
  command += fmt::format(" -o {}", p.string());
 }

 std::cout << command << std::endl;
 int result{system(command.c_str())};
 if (result != 0) {
  throw std::runtime_error(fmt::format("Error {}", result));
 }
}

// build list of files
// eats up input
void Builder::build(std::unordered_set<fs::path>& buildlist) {
 std::unordered_set<fs::path> activelist; // currently building
 std::unordered_set<fs::path> donelist; // build done

 if (buildlist.empty()) {
  std::cout << "Everything up to date." << std::endl;
 } else {
  std::cout << "Running commands: " << std::endl;
 }

 while (!buildlist.empty()) {
  // find file which can be built directly since its build dependencies are up to date
  // this holds for either any member of the set (e.g. at begin()), or any of its direct or indirect dependencies
  fs::path current {*buildlist.begin()};

  bool found_outdated{}; // outdated dependencies

  do {
   found_outdated = false;
   std::vector<fs::path> deps{dependencies_of(current)};
   for (auto& i: deps) {
    if (activelist.find(i) == activelist.end() && is_outdated(i)) {
     found_outdated = true;
     current = i;
     break;
    }
   }
  } while (found_outdated);

  buildlist.erase(current);

  activelist.insert(current);
  // TODO: build in background
  build(current);
  activelist.erase(current);

  donelist.insert(current);
 }
}

// build everything according to specified configuration
void Builder::build() {
 std::cout << "Target: " << _target << std::endl;

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

 // create build list by depth-first search
 std::cout << "Calculating build list..." << std::endl;
 std::unordered_set<fs::path> buildlist;
 std::stack<fs::path> container; // temporary container for search algorithm
 container.push(_target);
 while (!container.empty()) {
  fs::path current{container.top()};
  container.pop();

  std::vector<fs::path> deps{dependencies_of(current)};
  for (auto &i: deps) {
   container.push(i);
  }

  if (is_outdated(current) && is_buildable_by_extension(current)) {
   buildlist.insert(current);
  }
 }

 std::cout << "Build list:" << std::endl;
 for (auto &i: buildlist) {
  std::cout << "  " << i << std::endl;
 }

 build(buildlist);
}

void Builder::clean() {
 std::vector<fs::path> cleanlist{_objects};
 cleanlist.push_back(_target);

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