#include "weblog.h"

#include <boost/algorithm/string/predicate.hpp>
#include <boost/property_tree/ptree.hpp>
#include <boost/property_tree/xml_parser.hpp>

#include <algorithm>
#include <filesystem>
#include <fstream>
#include <iostream>
#include <string>

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

namespace {

 const size_t number_of_articles_on_front_page {10};
 const std::string article_filename{"article.data"};

 // Return a reasonable mime type based on the extension of a file.
 std::string mime_type(fs::path path)
 {
  using boost::algorithm::iequals;
  auto const ext = [&path]
  {
   size_t pos = path.string().rfind(".");
   if (pos == std::string::npos)
    return std::string{};
   return path.string().substr(pos);
  }();
  if(iequals(ext, ".htm"))  return "text/html"; // TODO: unordered_map
  if(iequals(ext, ".html")) return "text/html";
  if(iequals(ext, ".php"))  return "text/html";
  if(iequals(ext, ".css"))  return "text/css";
  if(iequals(ext, ".txt"))  return "text/plain";
  if(iequals(ext, ".js"))   return "application/javascript";
  if(iequals(ext, ".json")) return "application/json";
  if(iequals(ext, ".xml"))  return "application/xml";
  if(iequals(ext, ".swf"))  return "application/x-shockwave-flash";
  if(iequals(ext, ".flv"))  return "video/x-flv";
  if(iequals(ext, ".png"))  return "image/png";
  if(iequals(ext, ".jpe"))  return "image/jpeg";
  if(iequals(ext, ".jpeg")) return "image/jpeg";
  if(iequals(ext, ".jpg"))  return "image/jpeg";
  if(iequals(ext, ".gif"))  return "image/gif";
  if(iequals(ext, ".bmp"))  return "image/bmp";
  if(iequals(ext, ".ico"))  return "image/vnd.microsoft.icon";
  if(iequals(ext, ".tiff")) return "image/tiff";
  if(iequals(ext, ".tif"))  return "image/tiff";
  if(iequals(ext, ".svg"))  return "image/svg+xml";
  if(iequals(ext, ".svgz")) return "image/svg+xml";
  return "application/text";
 }

 // Used to return errors by generating response page and HTTP status code
 std::string HttpStatus(std::string status, std::string message, std::function<plugin_interface_setter_type>& SetResponseHeader)
 {
  SetResponseHeader("status", status);
  SetResponseHeader("content_type", "text/html");
  return status + " " + message;
 }

 std::string getFile(const fs::path& filename)
 {
  std::ifstream file(filename.string(), std::ios::in | std::ios::binary | std::ios::ate);

  if (file.is_open()) {
   std::ifstream::pos_type fileSize = file.tellg();
   file.seekg(0, std::ios::beg);

   std::string bytes(fileSize, ' ');
   file.read(reinterpret_cast<char*>(bytes.data()), fileSize);

   return bytes;

  } else {
   throw std::runtime_error("Opening "s + filename.string() + " for reading");
  }
 }

 bool is_index_page(std::string& rel_target)
 {
  return (rel_target.size() == 0 || rel_target == "/");
 }

 bool is_index_file(std::string& rel_target, fs::path& path)
 {
  // must be top-level file, recognized as mime_type()
  return rel_target.find("/") == rel_target.npos && mime_type(path) != "application/text";
 }

 bool is_article_page(std::string& rel_target, fs::path& path)
 {
  return (rel_target.size() >= 2 && rel_target.back() == '/' && fs::is_directory(path));
 }

 bool is_article_file(std::string& rel_target, fs::path& path)
 {
  return (fs::is_regular_file(path) && path.filename().string() != article_filename);
 }

 struct ArticleInfo
 {
  fs::path path;
  std::string subject;
  std::string date;
 };

 // get article metadata from header lines
 std::unordered_map<std::string, std::string> getMetaData(fs::path path)
 {
  if (path.string().size() > 0 && path.string().back() == '/') {
   std::string s {path.string()};
   path = s.substr(0, s.size() - 1);
  }
  std::unordered_map<std::string, std::string> result;

  std::string pathname{path.filename().string()};
  // ISO date
  std::string date{pathname.substr(0, 4) + "-"s + pathname.substr(4, 2) + "-"s + pathname.substr(6, 2)};
  std::string time{pathname.substr(9, 2) + ":"s + pathname.substr(11, 2)};
  if (time != "00:00")
   date += " " + time;

  result["Date"] = date;

  fs::path filepath {path / article_filename};

  std::ifstream file(filepath.string(), std::ios::in);

  if (file.is_open()) {
   std::string line;
   while (!file.eof()) {
    std::getline(file, line);
    if (line.empty()) // found header end
     break;
    size_t pos {line.find(": ")};
    if (pos == line.npos) {
     std::cerr << "Warning: Found bad header line in " << filepath << ": " << line << std::endl;
     continue;
    }
    result[line.substr(0, pos)] = line.substr(pos + 2);
   }
   return result;

  } else {
   throw std::runtime_error("Opening "s + filepath.string() + " for reading");
  }
 }

 std::vector<ArticleInfo> getArticleList(fs::path& path)
 {
  std::vector<ArticleInfo> result;

  for (auto& year_entry: fs::directory_iterator(path)) {
   std::string year_entry_filename{year_entry.path().filename().string()};
   if (fs::is_directory(year_entry)) {
    for (auto& entry: fs::directory_iterator(year_entry.path())) {
     auto metaData{getMetaData(entry.path())};
     result.emplace_back(ArticleInfo{entry.path(), metaData.at("Subject"), metaData.at("Date")});
    }
   }
  }

  size_t size{std::min(number_of_articles_on_front_page, result.size())};
  // sort backwards
  std::partial_sort(result.begin(), result.begin() + size, result.end(), [](const ArticleInfo& a0, const ArticleInfo& a1){ return a0.date > a1.date;});
  
  return {result.begin(), result.begin() + size};
 }

 // returns plain text of string (xml elements removed)
 std::string plainText(const std::string& text)
 {
  pt::ptree tree;

  std::istringstream ss{text};
  //pt::read_xml(ss, tree, pt::xml_parser::no_comments | pt::xml_parser::trim_whitespace);

  //std::cout << "DEBUG: " << tree.get<std::string>("file") << std::endl;

  return text;
 }

 // returns teaser of article in plain text
 std::string shortVersion(const fs::path& path)
 {
  std::string article {getFile(path / article_filename)};
  size_t pos0 {article.find("\n\n")};
  if (pos0 == article.npos)
   return "";

  article = "<file>" + article.substr(pos0 + 2) + "</file>";

  article = plainText(article);

  size_t pos1 {article.find(".")};
  
  size_t num {std::min(static_cast<size_t>(1000), pos1) + 1};

  return article.substr(0, num);
 }

 std::string generateIndexPage(fs::path& path,
                               std::function<std::string(const std::string& key)>& GetRequestParam,
                               std::function<plugin_interface_setter_type>& SetResponseHeader)
 {
  try {
   std::string result{"<!DOCTYPE html><html><head><meta charset=\"utf-8\"/></head><body><h1>"s + GetRequestParam("WEBLOG_NAME") + "</h1>"s};
   
   fs::path link{ GetRequestParam("rel_target")};
   
   auto list{getArticleList(path)};
   for (const auto& article: list) {
    std::string linkstart{"<a href=\"" + (link / article.path.filename()).string() + "/\">"};
    std::string linkend{"</a>"};
    result += "<h2>"s + linkstart + article.subject + linkend + "</h2>"s + article.date + "<br/>"s;
    
    auto sv{shortVersion(article.path)};
    if (sv.size()) {
     result += sv + " "s + linkstart + "more..." + linkend;
    }
   }
   result += "<br/><br/><br/>";
   result += "<a href=\"impressum.html\">Impressum</a>";
   result += "</body></html>";
   return result;
  } catch (const std::exception& ex) {
   return HttpStatus("500", "Reading Index page: "s + ex.what(), SetResponseHeader);
  }
 }

 std::string generateArticlePage(fs::path& path,
                                 std::function<plugin_interface_setter_type>& SetResponseHeader)
 {
  try {
   auto metaData{getMetaData(path)};

   std::string data { getFile(path / article_filename)};

   size_t pos {data.find("\n\n")};
   if (pos == data.npos)
    throw std::runtime_error("Error parsing article");
   
   std::string result { "<!DOCTYPE html><html><head><meta charset=\"utf-8\"/></head><body><h1>"s + metaData.at("Subject") + "</h1>"s + metaData.at("Date") + "<br/><br/>"s + data.substr(pos + 2) + "</body></html>"s};

   return result;
  } catch (const std::exception& ex) {
   return HttpStatus("500", "Reading Article: "s + ex.what(), SetResponseHeader);
  }
 }

 std::string generateStaticFile(fs::path& path, std::function<plugin_interface_setter_type>& SetResponseHeader)
 {
  try {
   SetResponseHeader("content_type", mime_type(path));
   return getFile(path);
  } catch (const std::exception& ex) {
   return HttpStatus("500", "Reading Article file: "s + ex.what(), SetResponseHeader);
  }
 }

} // anonymous namespace

std::string weblog_plugin::name()
{
 return "weblog";
}

weblog_plugin::weblog_plugin()
{
 //std::cout << "Plugin constructor" << std::endl;
}

weblog_plugin::~weblog_plugin()
{
 //std::cout << "Plugin destructor" << std::endl;
}

std::string weblog_plugin::generate_page(
  std::function<std::string(const std::string& key)>& GetServerParam,
  std::function<std::string(const std::string& key)>& GetRequestParam, // request including body (POST...)
  std::function<void(const std::string& key, const std::string& value)>& SetResponseHeader // to be added to result string
)
{
 try {
  // Make sure we can handle the method
  std::string method {GetRequestParam("method")};
  if (method != "GET" && method != "HEAD")
   return HttpStatus("400", "Unknown HTTP method", SetResponseHeader);

  // Request path must not contain "..".
  std::string rel_target{GetRequestParam("rel_target")};
  std::string target{GetRequestParam("target")};
  if (rel_target.find("..") != std::string::npos) {
   return HttpStatus("400", "Illegal request: "s + target, SetResponseHeader);
  }

  // Build the path to the requested file
  std::string doc_root{GetRequestParam("doc_root")};
  if (rel_target.size() >= 4 && std::all_of(rel_target.begin(), rel_target.begin() + 4, isdigit)) {
   rel_target = rel_target.substr(0, 4) + "/" + rel_target;
  }
  fs::path path {fs::path{doc_root} / rel_target};
  if (target.size() && target.back() != '/' && fs::is_directory(path)) {
   std::string location{GetRequestParam("location") + "/"s};
   SetResponseHeader("location", location);
   return HttpStatus("301", "Correcting directory path", SetResponseHeader);
  }
  
  SetResponseHeader("content_type", "text/html");
  
  if (is_index_page(rel_target))
   return generateIndexPage(path, GetRequestParam, SetResponseHeader);

  if (is_article_page(rel_target, path))
   return generateArticlePage(path, SetResponseHeader);

  if (is_index_file(rel_target, path) || is_article_file(rel_target, path))
   return generateStaticFile(path, SetResponseHeader);

  return HttpStatus("404", "Bad path specification: "s + rel_target, SetResponseHeader);

 } catch (const std::exception& ex) {
  return HttpStatus("500", "Unknown Error: "s + ex.what(), SetResponseHeader);
 }
}