#include "weblog.h"

#include "libreichwein/file.h"
#include "libreichwein/mime.h"
#include "libreichwein/stringhelper.h"
#include "libreichwein/url.h"

#include <fcgiapp.h>

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

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

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

namespace {

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

 // Used to return errors by generating response page and HTTP status code
 void HttpStatus(std::string status, std::string message, FCGX_Request& request)
 {
  FCGX_FPrintF(request.out, "Status: %s Error\r\n", status.c_str());
  FCGX_PutS("Content-Type: text/plain\r\n\r\n", request.out);

  FCGX_FPrintF(request.out, "%s %s", status.c_str(), message.c_str());
 }

 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.string()) != "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)};

  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, size_t page)
 {
  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 index0{std::min(number_of_articles_on_front_page * (page), result.size())};
  size_t index1{std::min(number_of_articles_on_front_page * (page + 1), result.size())};
  // sort backwards
  std::partial_sort(result.begin(), result.begin() + index1, result.end(), [](const ArticleInfo& a0, const ArticleInfo& a1){ return a0.path.string() > a1.path.string();});
  
  return {result.begin() + index0, result.begin() + index1};
 }

 std::string plainTextFromPTree(const pt::ptree& tree)
 {
  std::string result;

  for (auto child: tree) {
   if (child.first == "<xmltext>")
    result += child.second.data();
   else
    result += plainTextFromPTree(child.second);
  }

  return result;
 }

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

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

  return plainTextFromPTree(tree);
 }

 std::string verbatimText(std::string text)
 {
  boost::algorithm::replace_all(text, "<", "&lt;");
  boost::algorithm::replace_all(text, ">", "&gt;");

  return "<pre>"s + text + "</pre>";
 }

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

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

  auto metaData{getMetaData(path)};
  auto it {metaData.find("Content-Type")};

  // convert html to plaintext, if tagged as such
  // default: text/html
  if (it == metaData.end() || it->second == "text/html")
   article = plainTextFromHTML(article);

  size_t pos{1000};

  std::smatch match;
  if (std::regex_search(article, match, re)) {
   pos = std::min(pos, static_cast<size_t>(match.position() + match.length()));
  }
  
  return article.substr(0, pos);
 }

 std::string get_rel_target(FCGX_Request& request)
 {
  std::string result{FCGX_GetParam("PATH_INFO", request.envp)};
  auto pos{result.find('?')};
  if (pos != result.npos)
   result = result.substr(0, pos);
  return result;
 }

 std::string plugin_path(FCGX_Request& request)
 {
  std::string target{FCGX_GetParam("DOCUMENT_URI", request.envp)};
  while (target.size() > 1 && target.back() == '/') {
   target = target.substr(0, target.size() - 1);
  }
  
  std::string rel_target{get_rel_target(request)};
  while (rel_target.size() > 1 && rel_target.back() == '/') {
   rel_target = rel_target.substr(0, rel_target.size() - 1);
  }
  
  if (target.ends_with(rel_target)) {
   return target.substr(0, target.size() - rel_target.size());
  }
  return "/";
 }

 class HtmlPage
 {
  Config& m_config;
  std::string mContents;
  std::string mHeader;
  const std::string mFooter;
  
 public:
  HtmlPage(FCGX_Request& request, Config& config,
           std::string s = ""s):
   m_config{config},
   mContents{s},
   mHeader("<!DOCTYPE html><html><head>"
           "<meta charset=\"utf-8\"/>"
           "<meta name=\"viewport\" content=\"width=device-width, initial-scale=1\">"
           "<title>" + m_config.getName() + "</title>"
           "<meta name=\"keywords\" content=\"" + m_config.getKeywords() + "\"/>"
           "<link rel=\"shortcut icon\" href=\"" + (fs::path{plugin_path(request)} / "favicon.ico").generic_string() + "\" type=\"image/x-icon\"/>"
           "<link rel=\"stylesheet\" type=\"text/css\" href=\"" + (fs::path{plugin_path(request)} / "blog.css").generic_string() + "\"/>"
           "</head><body><div class=\"page\">"),
   mFooter("<br/><br/><br/><div class=\"impressum\"><a href=\""s +
           (fs::path{plugin_path(request)} / "impressum.html").generic_string() +
           "\">Impressum, Datenschutzerklärung</a></div></div></body></html>")
  {
  }

  HtmlPage& operator+=(const std::string& s)
  {
   mContents += s;
   return *this;
  }

  operator std::string() const
  {
   return mHeader + mContents + mFooter;
  }
 };

 void generateIndexPage(fs::path& path,
                        FCGX_Request& request,
                        Config& config,
                        size_t page)
 {
  try {
   if (page > std::numeric_limits<int>::max())
    throw std::runtime_error("Bad page index: "s + std::to_string(page));

   HtmlPage htmlPage{request, config, "<h1>"s + config.getName() + "</h1>"s};

   fs::path link{ plugin_path(request) };
   
   auto list{getArticleList(path, page)};
   if (list.empty())
    htmlPage += "(no articles found.)";
   else {
    for (const auto& article: list) {
     std::string linkstart{"<a href=\"" + (link / article.path.filename()).string() + "/\">"};
     std::string linkend{"</a>"};
     htmlPage += "<h2>"s + linkstart + article.subject + linkend + "</h2>"s;
     htmlPage += "<div class=\"date\">" + article.date + "</div>"s;
     
     auto sv{shortVersion(article.path)};
     if (sv.size()) {
      htmlPage += sv + " "s + linkstart + "more..." + linkend;
     }
    }
    htmlPage += "<br/><br/><br/>";
    if (page > 0)
     htmlPage += "<a href=\"?page="s + std::to_string(page - 1) + "\">&lt;&lt;newer</a> "s;
    htmlPage += "page "s + std::to_string(page + 1);
    if (list.size() == number_of_articles_on_front_page)
     htmlPage += " <a href=\"?page="s + std::to_string(page + 1) + "\">older&gt;&gt;</a>"s;
    htmlPage += "<br/>";
   }
   FCGX_PutS("Content-Type: text/html\r\n", request.out);
   FCGX_FPrintF(request.out, "Cache-Control: no-store\r\n\r\n");
   std::string data{htmlPage};
   FCGX_PutStr(data.c_str(), data.size(), request.out);
  } catch (const std::exception& ex) {
   HttpStatus("500", "Reading Index page: "s + ex.what(), request);
  }
 }

 void generateArticlePage(fs::path& path, FCGX_Request& request, Config& config)
 {
  try {
   auto metaData{getMetaData(path)};

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

   size_t pos {data.find("\n\n")};
   if (pos == data.npos)
    throw std::runtime_error("Error parsing article");
   
   data = data.substr(pos + 2);

   auto it {metaData.find("Content-Type")};
   if (it != metaData.end() && it->second == "text/plain")
    data = verbatimText(data);

   HtmlPage htmlPage{request, config, "<h1>"s + metaData.at("Subject") + "</h1>"
     "<div class=\"date\">" + metaData.at("Date") + "</div>"
     "<br/><br/>"s + data + "<br/>&squ;"};

   std::string result {htmlPage};
   FCGX_PutS("Content-Type: text/html\r\n\r\n", request.out);
   FCGX_PutStr(result.c_str(), result.size(), request.out);
  } catch (const std::exception& ex) {
   return HttpStatus("500", "Reading Article: "s + ex.what(), request);
  }
 }

 void generateStaticFile(fs::path& path, FCGX_Request& request)
 {
  try {
   FCGX_FPrintF(request.out, "Content-Type: %s\r\n\r\n", mime_type(path.string()).c_str());
   std::string data{File::getFile(path)};
   FCGX_PutStr(data.c_str(), data.size(), request.out);
  } catch (const std::exception& ex) {
   HttpStatus("500", "Reading Article file: "s + ex.what(), request);
  }
 }

 std::unordered_map<std::string, std::string> SplitQueryString(std::string& s)
 {
  std::unordered_map<std::string, std::string> result;

  size_t qpos = s.find('?');
  if (qpos != s.npos) {
   auto list {split(s.substr(qpos + 1), "&")};
   for (auto i: list) {
    size_t apos = i.find('=');
    if (apos != i.npos) {
     result[Reichwein::URL::urlDecode(i.substr(0, apos))] = Reichwein::URL::urlDecode(i.substr(apos + 1));
    }
   }
  }

  s = s.substr(0, qpos);
  
  return result;
 }

 void usage()
 {
  std::cout << "usage: weblog [-c <config-path>]" << std::endl;
 }

 fs::path getConfigPath(int argc, char* argv[])
 {
  if (argc == 2 && argv[1] == "-h"s) {
   usage();
   exit(0);
  }
  if (argc == 3 && argv[1] == "-c"s)
   return argv[2];
  return {};
 }

} // anonymous namespace

Weblog::Weblog(int argc, char* argv[]): m_config{getConfigPath(argc, argv).empty() ? Config{} : Config{getConfigPath(argc, argv)}}
{
}

Weblog::~Weblog()
{
}

namespace {

void generate_page(FCGX_Request& request, Config& config)
{
 try {
  // Make sure we can handle the method
  std::string method {FCGX_GetParam("REQUEST_METHOD", request.envp)};
  if (method != "GET" && method != "HEAD")
   return HttpStatus("400", "Unknown HTTP method", request);

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

  std::unordered_map<std::string, std::string> query { SplitQueryString(rel_target) };

  // Build the path to the requested file
  std::string path_translated{config.getDataPath()};
  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{path_translated} / rel_target};
  if (target.size() && target.back() != '/' && fs::is_directory(path) && !boost::algorithm::contains(target, "?")) {
   std::string location{target + "/"s};
   FCGX_FPrintF(request.out, "Location: %s\r\n", location.c_str());
   return HttpStatus("301", "Correcting directory path", request);
  }
  
  size_t page {0};
  auto it {query.find("page")};
  if (it != query.end()) {
   try {
    page = stoul(it->second);
   } catch(...) {
    // ignore: keep default 0
   }
  }

  if (is_index_page(rel_target)) {
   return generateIndexPage(path, request, config, page);
  }

  if (is_article_page(rel_target, path)) {
   return generateArticlePage(path, request, config);
  }

  if (is_index_file(rel_target, path) || is_article_file(rel_target, path)) {
   return generateStaticFile(path, request);
  }

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

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

} // namespace

int Weblog::run()
{
 int result = FCGX_Init();
 if (result != 0) { // error on init
  std::cerr << "Error: FCGX_Init()" << std::endl;
  return 1;
 }
 
 result = FCGX_IsCGI();
 if (result) {
  std::cerr << "Error: No FCGI environment available" << std::endl;
  return 1;
 }
  
 FCGX_Request request;
 result = FCGX_InitRequest(&request, 0, 0);
 if (result != 0) {
  std::cerr << "Error: FCGX_InitRequest()" << std::endl;
  return 1;
 } 
   
 while (FCGX_Accept_r(&request) >= 0) {
  try {
   generate_page(request, m_config);
  } catch (const std::exception& ex) {
   FCGX_PutS("Status: 500 Internal Server Error\r\n", request.out);
   FCGX_PutS("Content-Type: text/plain\r\n\r\n", request.out);
   FCGX_FPrintF(request.out, "Error: %s\r\n", ex.what());
  }
 }
 return 0;
}