#include "godot_scene.h"

#include <absl/strings/str_split.h>

#include <fstream>
#include <sstream>
#include <variant>

namespace com::fourisland::lingo2_archipelago {

namespace {

class GodotSceneImpl : public GodotScene {
 public:
  GodotSceneImpl(std::map<std::string, GodotExtResource> ext_resources,
                 std::unique_ptr<GodotNode> root,
                 std::vector<std::unique_ptr<GodotNode>> descendents)
      : ext_resources_(std::move(ext_resources)),
        root_(std::move(root)),
        descendents_(std::move(descendents)) {}

  virtual const GodotExtResource* GetExtResource(const std::string& id) const {
    auto it = ext_resources_.find(id);
    if (it != ext_resources_.end()) {
      return &it->second;
    } else {
      return nullptr;
    }
  }

  virtual const GodotNode& GetRoot() const { return *root_; }

 private:
  std::map<std::string, GodotExtResource> ext_resources_;
  std::unique_ptr<GodotNode> root_;
  std::vector<std::unique_ptr<GodotNode>> descendents_;
};

struct Heading {
  std::string type;

  std::string id;
  std::string path;
  std::string resource_type;

  std::string name;
  std::string parent;
  GodotInstanceType instance_type;
};

Heading ParseTscnHeading(absl::string_view line) {
  std::string original_line(line);
  Heading heading;

  if (line[0] != '[') {
    std::ostringstream errormsg;
    errormsg << "Heading must start with [." << std::endl
             << "Bad heading: " << original_line;
    throw std::invalid_argument(errormsg.str());
  }

  line.remove_prefix(1);
  int divider = line.find_first_of(" ]");
  if (divider == std::string_view::npos) {
    std::ostringstream errormsg;
    errormsg << "Malformatted heading: " << line << std::endl
             << "Original line: " << original_line;
    throw std::invalid_argument(errormsg.str());
  }

  heading.type = std::string(line.substr(0, divider));
  line.remove_prefix(divider + 1);

  while (!line.empty()) {
    divider = line.find_first_of("=");
    if (divider == std::string_view::npos) {
      std::ostringstream errormsg;
      errormsg << "Malformatted heading: " << line << std::endl
               << "Original line: " << original_line;
      throw std::invalid_argument(errormsg.str());
    }

    std::string key(line.substr(0, divider));
    line.remove_prefix(divider + 1);

    if (line[0] == '"') {
      line.remove_prefix(1);
      divider = line.find_first_of("\"");

      if (divider == std::string_view::npos) {
        std::ostringstream errormsg;
        errormsg << "Malformatted heading: " << line << std::endl
                 << "Original line: " << original_line;
        throw std::invalid_argument(errormsg.str());
      }

      std::string strval(line.substr(0, divider));
      line.remove_prefix(divider + 2);

      if (key == "name") {
        heading.name = strval;
      } else if (key == "parent") {
        heading.parent = strval;
      } else if (key == "path") {
        heading.path = strval;
      } else if (key == "type") {
        heading.resource_type = strval;
      } else if (key == "id") {
        heading.id = strval;
      }
    } else if (line[0] == 'S' || line[0] == 'E') {
      GodotInstanceType rrval;
      char internal = line[0];

      line.remove_prefix(13);  // SubResource("
      divider = line.find_first_of("\"");

      if (divider == std::string_view::npos) {
        std::ostringstream errormsg;
        errormsg << "Malformatted heading: " << line << std::endl
                 << "Original line: " << original_line;
        throw std::invalid_argument(errormsg.str());
      }

      std::string refid = std::string(line.substr(0, divider));
      line.remove_prefix(divider + 3);

      GodotInstanceType instance_type;
      if (internal == 'E') {
        instance_type = GodotExtResourceRef{.id = refid};
      } else {
        // SubResource is not supported right now.
      }

      if (key == "instance") {
        heading.instance_type = instance_type;
      } else {
        // Other keys aren't supported right now.
      }
    } else {
      divider = line.find_first_of(" ]");

      if (divider == std::string_view::npos) {
        std::ostringstream errormsg;
        errormsg << "Malformatted heading: " << line << std::endl
                 << "Original line: " << original_line;
        throw std::invalid_argument(errormsg.str());
      }

      int numval = std::atoi(line.substr(0, divider).data());
      line.remove_prefix(divider + 1);

      // keyvals_[key] = numval;
    }
  }

  return heading;
}

}  // namespace

void GodotNode::AddChild(GodotNode& child) {
  children_[child.GetName()] = &child;
  child.parent_ = this;
}

std::string GodotNode::GetPath() const {
  if (parent_ == nullptr || parent_->GetName() == "") {
    return name_;
  } else {
    return parent_->GetPath() + "/" + name_;
  }
}

const GodotNode* GodotNode::GetNode(absl::string_view path) const {
  std::vector<std::string> names = absl::StrSplit(path, "/");

  auto it = children_.find(names[0]);
  if (it == children_.end()) {
    return nullptr;
  } else {
    if (names.size() == 1) {
      return it->second;
    } else {
      path.remove_prefix(names[0].size() + 1);

      return it->second->GetNode(path);
    }
  }
}

GodotNode* GodotNode::GetNode(absl::string_view path) {
  return const_cast<GodotNode*>(
      const_cast<const GodotNode*>(this)->GetNode(path));
}

std::unique_ptr<GodotScene> ReadGodotSceneFromFile(const std::string& path) {
  std::map<std::string, GodotExtResource> ext_resources;
  auto root = std::make_unique<GodotNode>("", GodotInstanceType{});
  std::vector<std::unique_ptr<GodotNode>> descendents;

  std::ifstream input(path);

  std::string line;
  bool section_started = false;
  Heading cur_heading;
  std::ostringstream cur_value;
  bool value_started = false;
  auto handle_end_of_section = [&]() {
    section_started = false;
    value_started = false;

    if (cur_heading.type == "sub_resource") {
      // sub_resources_[std::get<int>(cur_heading.GetKeyval("id"))] =
      // {cur_heading, cur_value.str(), ""};
    } else {
      // other_.emplace_back(cur_heading, cur_value.str());
    }

    cur_value = {};
  };
  while (std::getline(input, line)) {
    if (section_started && (line.empty() || line[0] == '[')) {
      handle_end_of_section();
    }
    if (!line.empty() && line[0] == '[') {
      Heading heading = ParseTscnHeading(line);
      if (heading.type == "gd_scene") {
        // file_descriptor_ = heading;
      } else if (heading.type == "ext_resource") {
        GodotExtResource ext_resource;
        ext_resource.path = heading.path;
        ext_resource.type = heading.resource_type;

        ext_resources[heading.id] = ext_resource;
      } else if (heading.type == "node") {
        if (heading.parent != "") {
          descendents.push_back(
              std::make_unique<GodotNode>(heading.name, heading.instance_type));
          GodotNode* child = descendents.back().get();

          if (heading.parent == ".") {
            root->AddChild(*child);
          } else {
            root->GetNode(heading.parent)->AddChild(*child);
          }
        }
      } else {
        cur_heading = heading;
        section_started = true;
      }
    } else if (!line.empty()) {
      if (value_started) {
        cur_value << std::endl;
      } else {
        value_started = true;
      }
      cur_value << line;
    }
  }
  if (section_started) {
    handle_end_of_section();
  }

  return std::make_unique<GodotSceneImpl>(
      std::move(ext_resources), std::move(root), std::move(descendents));
}

}  // namespace com::fourisland::lingo2_archipelago