// Copyright (c) 2019 Pantor. All rights reserved.

#ifndef INCLUDE_INJA_RENDERER_HPP_
#define INCLUDE_INJA_RENDERER_HPP_

#include <algorithm>
#include <numeric>
#include <string>
#include <utility>
#include <vector>

#include <nlohmann/json.hpp>

#include "bytecode.hpp"
#include "template.hpp"
#include "utils.hpp"


namespace inja {

inline nonstd::string_view convert_dot_to_json_pointer(nonstd::string_view dot, std::string& out) {
  out.clear();
  do {
    nonstd::string_view part;
    std::tie(part, dot) = string_view::split(dot, '.');
    out.push_back('/');
    out.append(part.begin(), part.end());
  } while (!dot.empty());
  return nonstd::string_view(out.data(), out.size());
}

/*!
 * \brief Class for rendering a Template with data.
 */
class Renderer {
  std::vector<const json*>& get_args(const Bytecode& bc) {
    m_tmp_args.clear();

    bool has_imm = ((bc.flags & Bytecode::Flag::ValueMask) != Bytecode::Flag::ValuePop);

    // get args from stack
    unsigned int pop_args = bc.args;
    if (has_imm) {
      pop_args -= 1;
    }

    for (auto i = std::prev(m_stack.end(), pop_args); i != m_stack.end(); i++) {
      m_tmp_args.push_back(&(*i));
    }

    // get immediate arg
    if (has_imm) {
      m_tmp_args.push_back(get_imm(bc));
    }

    return m_tmp_args;
  }

  void pop_args(const Bytecode& bc) {
    unsigned int popArgs = bc.args;
    if ((bc.flags & Bytecode::Flag::ValueMask) != Bytecode::Flag::ValuePop) {
      popArgs -= 1;
    }
    for (unsigned int i = 0; i < popArgs; ++i) {
      m_stack.pop_back();
    }
  }

  const json* get_imm(const Bytecode& bc) {
    std::string ptr_buffer;
    nonstd::string_view ptr;
    switch (bc.flags & Bytecode::Flag::ValueMask) {
      case Bytecode::Flag::ValuePop:
        return nullptr;
      case Bytecode::Flag::ValueImmediate:
        return &bc.value;
      case Bytecode::Flag::ValueLookupDot:
        ptr = convert_dot_to_json_pointer(bc.str, ptr_buffer);
        break;
      case Bytecode::Flag::ValueLookupPointer:
        ptr_buffer += '/';
        ptr_buffer += bc.str;
        ptr = ptr_buffer;
        break;
    }
    try {
      return &m_data->at(json::json_pointer(ptr.data()));
    } catch (std::exception&) {
      // try to evaluate as a no-argument callback
      if (auto callback = m_callbacks.find_callback(bc.str, 0)) {
        std::vector<const json*> arguments {};
        m_tmp_val = callback(arguments);
        return &m_tmp_val;
      }
      inja_throw("render_error", "variable '" + static_cast<std::string>(bc.str) + "' not found");
      return nullptr;
    }
  }

  bool truthy(const json& var) const {
    if (var.empty()) {
      return false;
    } else if (var.is_number()) {
      return (var != 0);
    } else if (var.is_string()) {
      return !var.empty();
    }

    try {
      return var.get<bool>();
    } catch (json::type_error& e) {
      inja_throw("json_error", e.what());
      throw;
    }
  }

  void update_loop_data()  {
    LoopLevel& level = m_loop_stack.back();

    if (level.loop_type == LoopLevel::Type::Array) {
      level.data[static_cast<std::string>(level.value_name)] = level.values.at(level.index);  // *level.it;
      auto& loopData = level.data["loop"];
      loopData["index"] = level.index;
      loopData["index1"] = level.index + 1;
      loopData["is_first"] = (level.index == 0);
      loopData["is_last"] = (level.index == level.size - 1);
    } else {
      level.data[static_cast<std::string>(level.key_name)] = level.map_it->first;
      level.data[static_cast<std::string>(level.value_name)] = *level.map_it->second;
    }
  }

  const TemplateStorage& m_included_templates;
  const FunctionStorage& m_callbacks;

  std::vector<json> m_stack;


  struct LoopLevel {
    enum class Type { Map, Array };

    Type loop_type;
    nonstd::string_view key_name;    // variable name for keys
    nonstd::string_view value_name;  // variable name for values
    json data;                       // data with loop info added

    json values;                     // values to iterate over

    // loop over list
    size_t index;                    // current list index
    size_t size;                     // length of list

    // loop over map
    using KeyValue = std::pair<nonstd::string_view, json*>;
    using MapValues = std::vector<KeyValue>;
    MapValues map_values;            // values to iterate over
    MapValues::iterator map_it;      // iterator over values
  };

  std::vector<LoopLevel> m_loop_stack;
  const json* m_data;

  std::vector<const json*> m_tmp_args;
  json m_tmp_val;


 public:
  Renderer(const TemplateStorage& included_templates, const FunctionStorage& callbacks): m_included_templates(included_templates), m_callbacks(callbacks) {
    m_stack.reserve(16);
    m_tmp_args.reserve(4);
    m_loop_stack.reserve(16);
  }

  void render_to(std::ostream& os, const Template& tmpl, const json& data) {
    m_data = &data;

    for (size_t i = 0; i < tmpl.bytecodes.size(); ++i) {
      const auto& bc = tmpl.bytecodes[i];

      switch (bc.op) {
        case Bytecode::Op::Nop: {
          break;
        }
        case Bytecode::Op::PrintText: {
          os << bc.str;
          break;
        }
        case Bytecode::Op::PrintValue: {
          const json& val = *get_args(bc)[0];
          if (val.is_string()) {
            os << val.get_ref<const std::string&>();
          } else {
            os << val.dump();
          }
          pop_args(bc);
          break;
        }
        case Bytecode::Op::Push: {
          m_stack.emplace_back(*get_imm(bc));
          break;
        }
        case Bytecode::Op::Upper: {
          auto result = get_args(bc)[0]->get<std::string>();
          std::transform(result.begin(), result.end(), result.begin(), ::toupper);
          pop_args(bc);
          m_stack.emplace_back(std::move(result));
          break;
        }
        case Bytecode::Op::Lower: {
          auto result = get_args(bc)[0]->get<std::string>();
          std::transform(result.begin(), result.end(), result.begin(), ::tolower);
          pop_args(bc);
          m_stack.emplace_back(std::move(result));
          break;
        }
        case Bytecode::Op::Range: {
          int number = get_args(bc)[0]->get<int>();
          std::vector<int> result(number);
          std::iota(std::begin(result), std::end(result), 0);
          pop_args(bc);
          m_stack.emplace_back(std::move(result));
          break;
        }
        case Bytecode::Op::Length: {
          const json& val = *get_args(bc)[0];

          size_t result;
          if (val.is_string()) {
            result = val.get_ref<const std::string&>().length();
          } else {
            result = val.size();
          }

          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::Sort: {
          auto result = get_args(bc)[0]->get<std::vector<json>>();
          std::sort(result.begin(), result.end());
          pop_args(bc);
          m_stack.emplace_back(std::move(result));
          break;
        }
        case Bytecode::Op::At: {
          auto args = get_args(bc);
          auto result = args[0]->at(args[1]->get<int>());
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::First: {
          auto result = get_args(bc)[0]->front();
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::Last: {
          auto result = get_args(bc)[0]->back();
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::Round: {
          auto args = get_args(bc);
          double number = args[0]->get<double>();
          int precision = args[1]->get<int>();
          pop_args(bc);
          m_stack.emplace_back(std::round(number * std::pow(10.0, precision)) / std::pow(10.0, precision));
          break;
        }
        case Bytecode::Op::DivisibleBy: {
          auto args = get_args(bc);
          int number = args[0]->get<int>();
          int divisor = args[1]->get<int>();
          pop_args(bc);
          m_stack.emplace_back((divisor != 0) && (number % divisor == 0));
          break;
        }
        case Bytecode::Op::Odd: {
          int number = get_args(bc)[0]->get<int>();
          pop_args(bc);
          m_stack.emplace_back(number % 2 != 0);
          break;
        }
        case Bytecode::Op::Even: {
          int number = get_args(bc)[0]->get<int>();
          pop_args(bc);
          m_stack.emplace_back(number % 2 == 0);
          break;
        }
        case Bytecode::Op::Max: {
          auto args = get_args(bc);
          auto result = *std::max_element(args[0]->begin(), args[0]->end());
          pop_args(bc);
          m_stack.emplace_back(std::move(result));
          break;
        }
        case Bytecode::Op::Min: {
          auto args = get_args(bc);
          auto result = *std::min_element(args[0]->begin(), args[0]->end());
          pop_args(bc);
          m_stack.emplace_back(std::move(result));
          break;
        }
        case Bytecode::Op::Not: {
          bool result = !truthy(*get_args(bc)[0]);
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::And: {
          auto args = get_args(bc);
          bool result = truthy(*args[0]) && truthy(*args[1]);
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::Or: {
          auto args = get_args(bc);
          bool result = truthy(*args[0]) || truthy(*args[1]);
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::In: {
          auto args = get_args(bc);
          bool result = std::find(args[1]->begin(), args[1]->end(), *args[0]) !=
                        args[1]->end();
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::Equal: {
          auto args = get_args(bc);
          bool result = (*args[0] == *args[1]);
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::Greater: {
          auto args = get_args(bc);
          bool result = (*args[0] > *args[1]);
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::Less: {
          auto args = get_args(bc);
          bool result = (*args[0] < *args[1]);
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::GreaterEqual: {
          auto args = get_args(bc);
          bool result = (*args[0] >= *args[1]);
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::LessEqual: {
          auto args = get_args(bc);
          bool result = (*args[0] <= *args[1]);
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::Different: {
          auto args = get_args(bc);
          bool result = (*args[0] != *args[1]);
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::Float: {
          double result =
              std::stod(get_args(bc)[0]->get_ref<const std::string&>());
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::Int: {
          int result = std::stoi(get_args(bc)[0]->get_ref<const std::string&>());
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::Exists: {
          auto&& name = get_args(bc)[0]->get_ref<const std::string&>();
          bool result = (data.find(name) != data.end());
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::ExistsInObject: {
          auto args = get_args(bc);
          auto&& name = args[1]->get_ref<const std::string&>();
          bool result = (args[0]->find(name) != args[0]->end());
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::IsBoolean: {
          bool result = get_args(bc)[0]->is_boolean();
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::IsNumber: {
          bool result = get_args(bc)[0]->is_number();
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::IsInteger: {
          bool result = get_args(bc)[0]->is_number_integer();
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::IsFloat: {
          bool result = get_args(bc)[0]->is_number_float();
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::IsObject: {
          bool result = get_args(bc)[0]->is_object();
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::IsArray: {
          bool result = get_args(bc)[0]->is_array();
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::IsString: {
          bool result = get_args(bc)[0]->is_string();
          pop_args(bc);
          m_stack.emplace_back(result);
          break;
        }
        case Bytecode::Op::Default: {
          // default needs to be a bit "magic"; we can't evaluate the first
          // argument during the push operation, so we swap the arguments during
          // the parse phase so the second argument is pushed on the stack and
          // the first argument is in the immediate
          try {
            const json* imm = get_imm(bc);
            // if no exception was raised, replace the stack value with it
            m_stack.back() = *imm;
          } catch (std::exception&) {
            // couldn't read immediate, just leave the stack as is
          }
          break;
        }
        case Bytecode::Op::Include:
          Renderer(m_included_templates, m_callbacks).render_to(os, m_included_templates.find(get_imm(bc)->get_ref<const std::string&>())->second, *m_data);
          break;
        case Bytecode::Op::Callback: {
          auto callback = m_callbacks.find_callback(bc.str, bc.args);
          if (!callback) {
            inja_throw("render_error", "function '" + static_cast<std::string>(bc.str) + "' (" + std::to_string(static_cast<unsigned int>(bc.args)) + ") not found");
          }
          json result = callback(get_args(bc));
          pop_args(bc);
          m_stack.emplace_back(std::move(result));
          break;
        }
        case Bytecode::Op::Jump: {
          i = bc.args - 1;  // -1 due to ++i in loop
          break;
        }
        case Bytecode::Op::ConditionalJump: {
          if (!truthy(m_stack.back())) {
            i = bc.args - 1;  // -1 due to ++i in loop
          }
          m_stack.pop_back();
          break;
        }
        case Bytecode::Op::StartLoop: {
          // jump past loop body if empty
          if (m_stack.back().empty()) {
            m_stack.pop_back();
            i = bc.args;  // ++i in loop will take it past EndLoop
            break;
          }

          m_loop_stack.emplace_back();
          LoopLevel& level = m_loop_stack.back();
          level.value_name = bc.str;
          level.values = std::move(m_stack.back());
          level.data = (*m_data);
          m_stack.pop_back();

          if (bc.value.is_string()) {
            // map iterator
            if (!level.values.is_object()) {
              m_loop_stack.pop_back();
              inja_throw("render_error", "for key, value requires object");
            }
            level.loop_type = LoopLevel::Type::Map;
            level.key_name = bc.value.get_ref<const std::string&>();

            // sort by key
            for (auto it = level.values.begin(), end = level.values.end(); it != end; ++it) {
              level.map_values.emplace_back(it.key(), &it.value());
            }
            auto sort_lambda = [](const LoopLevel::KeyValue& a, const LoopLevel::KeyValue& b) { return a.first < b.first; };
            std::sort(level.map_values.begin(), level.map_values.end(), sort_lambda);
            level.map_it = level.map_values.begin();
          } else {
            if (!level.values.is_array()) {
              m_loop_stack.pop_back();
              inja_throw("render_error", "type must be array");
            }

            // list iterator
            level.loop_type = LoopLevel::Type::Array;
            level.index = 0;
            level.size = level.values.size();
          }

          // provide parent access in nested loop
          auto parent_loop_it = level.data.find("loop");
          if (parent_loop_it != level.data.end()) {
            json loop_copy = *parent_loop_it;
            (*parent_loop_it)["parent"] = std::move(loop_copy);
          }

          // set "current" data to loop data
          m_data = &level.data;
          update_loop_data();
          break;
        }
        case Bytecode::Op::EndLoop: {
          if (m_loop_stack.empty()) {
            inja_throw("render_error", "unexpected state in renderer");
          }
          LoopLevel& level = m_loop_stack.back();

          bool done;
          if (level.loop_type == LoopLevel::Type::Array) {
            level.index += 1;
            done = (level.index == level.values.size());
          } else {
            level.map_it += 1;
            done = (level.map_it == level.map_values.end());
          }

          if (done) {
            m_loop_stack.pop_back();
            // set "current" data to outer loop data or main data as appropriate
            if (!m_loop_stack.empty()) {
              m_data = &m_loop_stack.back().data;
            } else {
              m_data = &data;
            }
            break;
          }

          update_loop_data();

          // jump back to start of loop
          i = bc.args - 1;  // -1 due to ++i in loop
          break;
        }
        default: {
          inja_throw("render_error", "unknown op in renderer: " + std::to_string(static_cast<unsigned int>(bc.op)));
        }
      }
    }
  }
};

}  // namespace inja

#endif  // INCLUDE_INJA_RENDERER_HPP_