#ifndef SIMPLE_WEB_SERVER_UTILITY_HPP
#define SIMPLE_WEB_SERVER_UTILITY_HPP

#include "status_code.hpp"
#include <iostream>
#include <memory>
#include <string>
#include <unordered_map>

namespace SimpleWeb {
#ifndef CASE_INSENSITIVE_EQUAL_AND_HASH
#define CASE_INSENSITIVE_EQUAL_AND_HASH
  inline bool case_insensitive_equal(const std::string &str1, const std::string &str2) {
    return str1.size() == str2.size() &&
           std::equal(str1.begin(), str1.end(), str2.begin(), [](char a, char b) {
             return tolower(a) == tolower(b);
           });
  }
  class CaseInsensitiveEqual {
  public:
    bool operator()(const std::string &str1, const std::string &str2) const {
      return case_insensitive_equal(str1, str2);
    }
  };
  // Based on https://stackoverflow.com/questions/2590677/how-do-i-combine-hash-values-in-c0x/2595226#2595226
  class CaseInsensitiveHash {
  public:
    size_t operator()(const std::string &str) const {
      size_t h = 0;
      std::hash<int> hash;
      for(auto c : str)
        h ^= hash(tolower(c)) + 0x9e3779b9 + (h << 6) + (h >> 2);
      return h;
    }
  };
#endif

  typedef std::unordered_multimap<std::string, std::string, CaseInsensitiveHash, CaseInsensitiveEqual> CaseInsensitiveMultimap;

  /// Percent encoding and decoding
  class Percent {
  public:
    /// Returns percent-encoded string
    static std::string encode(const std::string &value) {
      static auto hex_chars = "0123456789ABCDEF";

      std::string result;
      result.reserve(value.size()); // Minimum size of result

      for(auto &chr : value) {
        if(chr == ' ')
          result += '+';
        else if(chr == '!' || chr == '#' || chr == '$' || (chr >= '&' && chr <= ',') || (chr >= '/' && chr <= ';') || chr == '=' || chr == '?' || chr == '@' || chr == '[' || chr == ']')
          result += std::string("%") + hex_chars[chr >> 4] + hex_chars[chr & 15];
        else
          result += chr;
      }

      return result;
    }

    /// Returns percent-decoded string
    static std::string decode(const std::string &value) {
      std::string result;
      result.reserve(value.size() / 3 + (value.size() % 3)); // Minimum size of result

      for(size_t i = 0; i < value.size(); ++i) {
        auto &chr = value[i];
        if(chr == '%' && i + 2 < value.size()) {
          auto hex = value.substr(i + 1, 2);
          auto decoded_chr = static_cast<char>(std::strtol(hex.c_str(), nullptr, 16));
          result += decoded_chr;
          i += 2;
        }
        else if(chr == '+')
          result += ' ';
        else
          result += chr;
      }

      return result;
    }
  };

  /// Query string creation and parsing
  class QueryString {
  public:
    /// Returns query string created from given field names and values
    static std::string create(const CaseInsensitiveMultimap &fields) {
      std::string result;

      bool first = true;
      for(auto &field : fields) {
        result += (!first ? "&" : "") + field.first + '=' + Percent::encode(field.second);
        first = false;
      }

      return result;
    }

    /// Returns query keys with percent-decoded values.
    static CaseInsensitiveMultimap parse(const std::string &query_string) {
      CaseInsensitiveMultimap result;

      if(query_string.empty())
        return result;

      size_t name_pos = 0;
      size_t name_end_pos = -1;
      size_t value_pos = -1;
      for(size_t c = 0; c < query_string.size(); ++c) {
        if(query_string[c] == '&') {
          auto name = query_string.substr(name_pos, (name_end_pos == std::string::npos ? c : name_end_pos) - name_pos);
          if(!name.empty()) {
            auto value = value_pos == std::string::npos ? std::string() : query_string.substr(value_pos, c - value_pos);
            result.emplace(std::move(name), Percent::decode(value));
          }
          name_pos = c + 1;
          name_end_pos = -1;
          value_pos = -1;
        }
        else if(query_string[c] == '=') {
          name_end_pos = c;
          value_pos = c + 1;
        }
      }
      if(name_pos < query_string.size()) {
        auto name = query_string.substr(name_pos, name_end_pos - name_pos);
        if(!name.empty()) {
          auto value = value_pos >= query_string.size() ? std::string() : query_string.substr(value_pos);
          result.emplace(std::move(name), Percent::decode(value));
        }
      }

      return result;
    }
  };


  class RequestMessage {
  public:
    /// Parse request line and header fields
    static bool parse(std::istream &stream, std::string &method, std::string &path, std::string &query_string, std::string &version, CaseInsensitiveMultimap &header) {
      header.clear();
      std::string line;
      getline(stream, line);
      size_t method_end;
      if((method_end = line.find(' ')) != std::string::npos) {
        method = line.substr(0, method_end);

        size_t query_start = std::string::npos;
        size_t path_and_query_string_end = std::string::npos;
        for(size_t i = method_end + 1; i < line.size(); ++i) {
          if(line[i] == '?' && (i + 1) < line.size())
            query_start = i + 1;
          else if(line[i] == ' ') {
            path_and_query_string_end = i;
            break;
          }
        }
        if(path_and_query_string_end != std::string::npos) {
          if(query_start != std::string::npos) {
            path = line.substr(method_end + 1, query_start - method_end - 2);
            query_string = line.substr(query_start, path_and_query_string_end - query_start);
          }
          else
            path = line.substr(method_end + 1, path_and_query_string_end - method_end - 1);

          size_t protocol_end;
          if((protocol_end = line.find('/', path_and_query_string_end + 1)) != std::string::npos) {
            if(line.compare(path_and_query_string_end + 1, protocol_end - path_and_query_string_end - 1, "HTTP") != 0)
              return false;
            version = line.substr(protocol_end + 1, line.size() - protocol_end - 2);
          }
          else
            return false;

          getline(stream, line);
          size_t param_end;
          while((param_end = line.find(':')) != std::string::npos) {
            size_t value_start = param_end + 1;
            if(value_start < line.size()) {
              if(line[value_start] == ' ')
                value_start++;
              if(value_start < line.size())
                header.emplace(line.substr(0, param_end), line.substr(value_start, line.size() - value_start - 1));
            }

            getline(stream, line);
          }
        }
        else
          return false;
      }
      else
        return false;
      return true;
    }
  };

  class ResponseMessage {
  public:
    /// Parse status line and header fields
    static bool parse(std::istream &stream, std::string &version, std::string &status_code, CaseInsensitiveMultimap &header) {
      header.clear();
      std::string line;
      getline(stream, line);
      size_t version_end = line.find(' ');
      if(version_end != std::string::npos) {
        if(5 < line.size())
          version = line.substr(5, version_end - 5);
        else
          return false;
        if((version_end + 1) < line.size())
          status_code = line.substr(version_end + 1, line.size() - (version_end + 1) - 1);
        else
          return false;

        getline(stream, line);
        size_t param_end;
        while((param_end = line.find(':')) != std::string::npos) {
          size_t value_start = param_end + 1;
          if((value_start) < line.size()) {
            if(line[value_start] == ' ')
              value_start++;
            if(value_start < line.size())
              header.insert(std::make_pair(line.substr(0, param_end), line.substr(value_start, line.size() - value_start - 1)));
          }

          getline(stream, line);
        }
      }
      else
        return false;
      return true;
    }
  };
}

#ifdef PTHREAD_RWLOCK_INITIALIZER
namespace SimpleWeb {
  /// Read-preferring R/W lock.
  /// Uses pthread_rwlock.
  class SharedMutex {
    pthread_rwlock_t rwlock;

  public:
    class SharedLock {
      friend class SharedMutex;
      pthread_rwlock_t &rwlock;

      SharedLock(pthread_rwlock_t &rwlock) : rwlock(rwlock) {
        pthread_rwlock_rdlock(&rwlock);
      }

    public:
      ~SharedLock() {
        pthread_rwlock_unlock(&rwlock);
      }
    };

    class UniqueLock {
      friend class SharedMutex;
      pthread_rwlock_t &rwlock;

      UniqueLock(pthread_rwlock_t &rwlock) : rwlock(rwlock) {
        pthread_rwlock_wrlock(&rwlock);
      }

    public:
      ~UniqueLock() {
        pthread_rwlock_unlock(&rwlock);
      }
    };

  public:
    SharedMutex() {

      pthread_rwlock_init(&rwlock, nullptr);
    }

    ~SharedMutex() {
      pthread_rwlock_destroy(&rwlock);
    }

    std::unique_ptr<SharedLock> shared_lock() {
      return std::unique_ptr<SharedLock>(new SharedLock(rwlock));
    }

    std::unique_ptr<UniqueLock> unique_lock() {
      return std::unique_ptr<UniqueLock>(new UniqueLock(rwlock));
    }
  };
} // namespace SimpleWeb
#else
#include <condition_variable>
#include <mutex>
namespace SimpleWeb {
  /// Read-preferring R/W lock.
  /// Based on https://en.wikipedia.org/wiki/Readers%E2%80%93writer_lock#Using_a_condition_variable_and_a_mutex pseudocode.
  /// TODO: Someone that uses Windows should implement Windows specific R/W locks here.
  class SharedMutex {
    std::mutex m;
    std::condition_variable c;
    int r = 0;
    bool w = false;

  public:
    class SharedLock {
      friend class SharedMutex;
      std::condition_variable &c;
      int &r;
      std::unique_lock<std::mutex> lock;

      SharedLock(std::mutex &m, std::condition_variable &c, int &r, bool &w) : c(c), r(r), lock(m) {
        while(w)
          c.wait(lock);
        ++r;
        lock.unlock();
      }

    public:
      ~SharedLock() {
        lock.lock();
        --r;
        if(r == 0)
          c.notify_all();
        lock.unlock();
      }
    };

    class UniqueLock {
      friend class SharedMutex;
      std::condition_variable &c;
      bool &w;
      std::unique_lock<std::mutex> lock;

      UniqueLock(std::mutex &m, std::condition_variable &c, int &r, bool &w) : c(c), w(w), lock(m) {
        while(w || r > 0)
          c.wait(lock);
        w = true;
        lock.unlock();
      }

    public:
      ~UniqueLock() {
        lock.lock();
        w = false;
        c.notify_all();
        lock.unlock();
      }
    };

  public:
    std::unique_ptr<SharedLock> shared_lock() {
      return std::unique_ptr<SharedLock>(new SharedLock(m, c, r, w));
    }

    std::unique_ptr<UniqueLock> unique_lock() {
      return std::unique_ptr<UniqueLock>(new UniqueLock(m, c, r, w));
    }
  };
} // namespace SimpleWeb
#endif

#endif // SIMPLE_WEB_SERVER_UTILITY_HPP