////////////////////////////////////////////////////////////////////////////////
//
// Copyright 2013 - 2021, Tomas Babej, Paul Beckingham, Federico Hernandez.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
//
// https://www.opensource.org/licenses/mit-license.php
//
////////////////////////////////////////////////////////////////////////////////

#include <cmake.h>
// cmake.h include header must come first

#include <Color.h>
#include <Context.h>
#include <DOM.h>
#include <Eval.h>
#include <Task.h>
#include <format.h>
#include <shared.h>
#include <time.h>

#include <map>

////////////////////////////////////////////////////////////////////////////////
// Supported operators, borrowed from C++, particularly the precedence.
// Note: table is sorted by length of operator string, so searches match
//       longest first.
static struct {
  std::string op;
  int precedence;
  char type;           // b=binary, u=unary, c=circumfix
  char associativity;  // l=left, r=right, _=?
} operators[] = {
    // Operator   Precedence  Type  Associativity
    {"^", 16, 'b', 'r'},  // Exponent

    {"!", 15, 'u', 'r'},      // Unary not
    {"_neg_", 15, 'u', 'r'},  // Unary minus
    {"_pos_", 15, 'u', 'r'},  // Unary plus

    {"_hastag_", 14, 'b', 'l'},  // +tag  [Pseudo-op]
    {"_notag_", 14, 'b', 'l'},   // -tag  [Pseudo-op]

    {"*", 13, 'b', 'l'},  // Multiplication
    {"/", 13, 'b', 'l'},  // Division
    {"%", 13, 'b', 'l'},  // Modulus

    {"+", 12, 'b', 'l'},  // Addition
    {"-", 12, 'b', 'l'},  // Subtraction

    {"<=", 10, 'b', 'l'},  // Less than or equal
    {">=", 10, 'b', 'l'},  // Greater than or equal
    {">", 10, 'b', 'l'},   // Greater than
    {"<", 10, 'b', 'l'},   // Less than

    {"=", 9, 'b', 'l'},    // Equal (partial)
    {"==", 9, 'b', 'l'},   // Equal (exact)
    {"!=", 9, 'b', 'l'},   // Inequal (partial)
    {"!==", 9, 'b', 'l'},  // Inequal (exact)

    {"~", 8, 'b', 'l'},   // Regex match
    {"!~", 8, 'b', 'l'},  // Regex non-match

    {"and", 5, 'b', 'l'},  // Conjunction
    {"or", 4, 'b', 'l'},   // Disjunction
    {"xor", 3, 'b', 'l'},  // Disjunction

    {"(", 0, 'c', '_'},  // Precedence start
    {")", 0, 'c', '_'},  // Precedence end
};

#define NUM_OPERATORS (sizeof(operators) / sizeof(operators[0]))

////////////////////////////////////////////////////////////////////////////////
// Built-in support for some named constants.
static bool namedConstants(const std::string& name, Variant& value) {
  if (name == "true")
    value = Variant(true);
  else if (name == "false")
    value = Variant(false);
  else if (name == "pi")
    value = Variant(3.14159165);
  else
    return false;

  return true;
}

////////////////////////////////////////////////////////////////////////////////
// Support for evaluating DOM references (add with `e.AddSource(domSource)`)
bool domSource(const std::string& identifier, Variant& value) {
  if (getDOM(identifier, Context::getContext().currentTask, value)) {
    value.source(identifier);
    return true;
  }

  return false;
}

////////////////////////////////////////////////////////////////////////////////
Eval::Eval() { addSource(namedConstants); }

////////////////////////////////////////////////////////////////////////////////
void Eval::addSource(bool (*source)(const std::string&, Variant&)) { _sources.push_back(source); }

////////////////////////////////////////////////////////////////////////////////
void Eval::evaluateInfixExpression(const std::string& e, Variant& v) const {
  // Reduce e to a vector of tokens.
  Lexer l(e);
  std::vector<std::pair<std::string, Lexer::Type>> tokens;
  std::string token;
  Lexer::Type type;
  while (l.token(token, type)) tokens.emplace_back(token, type);

  // Parse for syntax checking and operator replacement.
  if (_debug) Context::getContext().debug("FILTER Infix        " + dump(tokens));
  infixParse(tokens);
  if (_debug) Context::getContext().debug("FILTER Infix parsed " + dump(tokens));

  // Convert infix --> postfix.
  infixToPostfix(tokens);
  if (_debug) Context::getContext().debug("FILTER Postfix      " + dump(tokens));

  // Call the postfix evaluator.
  evaluatePostfixStack(tokens, v);
}

////////////////////////////////////////////////////////////////////////////////
void Eval::evaluatePostfixExpression(const std::string& e, Variant& v) const {
  // Reduce e to a vector of tokens.
  Lexer l(e);
  std::vector<std::pair<std::string, Lexer::Type>> tokens;
  std::string token;
  Lexer::Type type;
  while (l.token(token, type)) tokens.emplace_back(token, type);

  if (_debug) Context::getContext().debug("FILTER Postfix      " + dump(tokens));

  // Call the postfix evaluator.
  evaluatePostfixStack(tokens, v);
}

////////////////////////////////////////////////////////////////////////////////
void Eval::compileExpression(const std::vector<std::pair<std::string, Lexer::Type>>& precompiled) {
  _compiled = precompiled;

  // Parse for syntax checking and operator replacement.
  if (_debug) Context::getContext().debug("FILTER Infix        " + dump(_compiled));
  infixParse(_compiled);
  if (_debug) Context::getContext().debug("FILTER Infix parsed " + dump(_compiled));

  // Convert infix --> postfix.
  infixToPostfix(_compiled);
  if (_debug) Context::getContext().debug("FILTER Postfix      " + dump(_compiled));
}

////////////////////////////////////////////////////////////////////////////////
void Eval::evaluateCompiledExpression(Variant& v) {
  // Call the postfix evaluator.
  evaluatePostfixStack(_compiled, v);
}

////////////////////////////////////////////////////////////////////////////////
void Eval::debug(bool value) { _debug = value; }

////////////////////////////////////////////////////////////////////////////////
// Static.
std::vector<std::string> Eval::getOperators() {
  std::vector<std::string> all;
  all.reserve(NUM_OPERATORS);
  for (const auto& opr : operators) all.push_back(opr.op);

  return all;
}

////////////////////////////////////////////////////////////////////////////////
// Static.
std::vector<std::string> Eval::getBinaryOperators() {
  std::vector<std::string> all;
  for (const auto& opr : operators)
    if (opr.type == 'b') all.push_back(opr.op);

  return all;
}

////////////////////////////////////////////////////////////////////////////////
void Eval::evaluatePostfixStack(const std::vector<std::pair<std::string, Lexer::Type>>& tokens,
                                Variant& result) const {
  if (tokens.size() == 0) throw std::string("No expression to evaluate.");

  // This is stack used by the postfix evaluator.
  std::vector<Variant> values;
  values.reserve(tokens.size());

  for (const auto& token : tokens) {
    // Unary operators.
    if (token.second == Lexer::Type::op && token.first == "!") {
      if (values.size() < 1) throw std::string("The expression could not be evaluated.");

      Variant right = values.back();
      values.pop_back();
      Variant result = !right;
      values.push_back(result);
      if (_debug)
        Context::getContext().debug(format("Eval {1} ↓'{2}' → ↑'{3}'", token.first,
                                           (std::string)right, (std::string)result));
    } else if (token.second == Lexer::Type::op && token.first == "_neg_") {
      if (values.size() < 1) throw std::string("The expression could not be evaluated.");

      Variant right = values.back();
      values.pop_back();

      Variant result(0);
      result -= right;
      values.push_back(result);

      if (_debug)
        Context::getContext().debug(format("Eval {1} ↓'{2}' → ↑'{3}'", token.first,
                                           (std::string)right, (std::string)result));
    } else if (token.second == Lexer::Type::op && token.first == "_pos_") {
      // The _pos_ operator is a NOP.
      if (_debug)
        Context::getContext().debug(format("[{1}] eval op {2} NOP", values.size(), token.first));
    }

    // Binary operators.
    else if (token.second == Lexer::Type::op) {
      if (values.size() < 2) throw std::string("The expression could not be evaluated.");

      Variant right = values.back();
      values.pop_back();

      Variant left = values.back();
      values.pop_back();

      auto contextTask = Context::getContext().currentTask;

      // Ordering these by anticipation frequency of use is a good idea.
      Variant result;
      if (token.first == "and")
        result = left && right;
      else if (token.first == "or")
        result = left || right;
      else if (token.first == "&&")
        result = left && right;
      else if (token.first == "||")
        result = left || right;
      else if (token.first == "<")
        result = left < right;
      else if (token.first == "<=")
        result = left <= right;
      else if (token.first == ">")
        result = left > right;
      else if (token.first == ">=")
        result = left >= right;
      else if (token.first == "==")
        result = left.operator==(right);
      else if (token.first == "!==")
        result = left.operator!=(right);
      else if (token.first == "=")
        result = left.operator_partial(right);
      else if (token.first == "!=")
        result = left.operator_nopartial(right);
      else if (token.first == "+")
        result = left + right;
      else if (token.first == "-")
        result = left - right;
      else if (token.first == "*")
        result = left * right;
      else if (token.first == "/")
        result = left / right;
      else if (token.first == "^")
        result = left ^ right;
      else if (token.first == "%")
        result = left % right;
      else if (token.first == "xor")
        result = left.operator_xor(right);
      else if (contextTask) {
        if (token.first == "~")
          result = left.operator_match(right, *contextTask);
        else if (token.first == "!~")
          result = left.operator_nomatch(right, *contextTask);
        else if (token.first == "_hastag_")
          result = left.operator_hastag(right, *contextTask);
        else if (token.first == "_notag_")
          result = left.operator_notag(right, *contextTask);
        else
          throw format("Unsupported operator '{1}'.", token.first);
      } else
        throw format("Unsupported operator '{1}'.", token.first);

      values.push_back(result);

      if (_debug)
        Context::getContext().debug(format("Eval ↓'{1}' {2} ↓'{3}' → ↑'{4}'", (std::string)left,
                                           token.first, (std::string)right, (std::string)result));
    }

    // Literals and identifiers.
    else {
      Variant v(token.first);
      switch (token.second) {
        case Lexer::Type::number:
          if (Lexer::isAllDigits(token.first)) {
            v.cast(Variant::type_integer);
            if (_debug)
              Context::getContext().debug(format("Eval literal number ↑'{1}'", (std::string)v));
          } else {
            v.cast(Variant::type_real);
            if (_debug)
              Context::getContext().debug(format("Eval literal decimal ↑'{1}'", (std::string)v));
          }
          break;

        case Lexer::Type::op:
          throw std::string("Operator expected.");
          break;

        case Lexer::Type::dom:
        case Lexer::Type::identifier: {
          bool found = false;
          for (const auto& source : _sources) {
            if (source(token.first, v)) {
              if (_debug)
                Context::getContext().debug(
                    format("Eval identifier source '{1}' → ↑'{2}'", token.first, (std::string)v));
              found = true;
              break;
            }
          }

          // An identifier that fails lookup is a string.
          if (!found) {
            v.cast(Variant::type_string);
            if (_debug)
              Context::getContext().debug(
                  format("Eval identifier source failed '{1}'", token.first));
          }
        } break;

        case Lexer::Type::date:
          v.cast(Variant::type_date);
          if (_debug)
            Context::getContext().debug(format("Eval literal date ↑'{1}'", (std::string)v));
          break;

        case Lexer::Type::duration:
          v.cast(Variant::type_duration);
          if (_debug)
            Context::getContext().debug(format("Eval literal duration ↑'{1}'", (std::string)v));
          break;

        // Nothing to do.
        case Lexer::Type::string:
        default:
          if (_debug)
            Context::getContext().debug(format("Eval literal string ↑'{1}'", (std::string)v));
          break;
      }

      values.push_back(v);
    }
  }

  // If there is more than one variant left on the stack, then the original
  // expression was not valid.
  if (values.size() != 1) throw std::string("The value is not an expression.");

  result = values[0];
}

////////////////////////////////////////////////////////////////////////////////
//
// Grammar:
//   Logical     --> Regex {( "and" | "or" | "xor" ) Regex}
//   Regex       --> Equality {( "~" | "!~" ) Equality}
//   Equality    --> Comparative {( "==" | "=" | "!=" ) Comparative}
//   Comparative --> Arithmetic {( "<=" | "<" | ">=" | ">" ) Arithmetic}
//   Arithmetic  --> Geometric {( "+" | "-" ) Geometric}
//   Geometric   --> Tag {( "*" | "/" | "%" ) Tag}
//   Tag         --> Unary {( "_hastag_" | "_notag_" ) Unary}
//   Unary       --> [( "-" | "+" | "!" )] Exponent
//   Exponent    --> Primitive ["^" Primitive]
//   Primitive   --> "(" Logical ")" | Variant
//
void Eval::infixParse(std::vector<std::pair<std::string, Lexer::Type>>& infix) const {
  unsigned int i = 0;
  parseLogical(infix, i);
}

////////////////////////////////////////////////////////////////////////////////
// Logical     --> Regex {( "and" | "or" | "xor" ) Regex}
bool Eval::parseLogical(std::vector<std::pair<std::string, Lexer::Type>>& infix,
                        unsigned int& i) const {
  if (i < infix.size() && parseRegex(infix, i)) {
    while (i < infix.size() && infix[i].second == Lexer::Type::op &&
           (infix[i].first == "and" || infix[i].first == "or" || infix[i].first == "xor")) {
      ++i;
      if (!parseRegex(infix, i)) return false;
    }

    return true;
  }

  return false;
}

////////////////////////////////////////////////////////////////////////////////
// Regex       --> Equality {( "~" | "!~" ) Equality}
bool Eval::parseRegex(std::vector<std::pair<std::string, Lexer::Type>>& infix,
                      unsigned int& i) const {
  if (i < infix.size() && parseEquality(infix, i)) {
    while (i < infix.size() && infix[i].second == Lexer::Type::op &&
           (infix[i].first == "~" || infix[i].first == "!~")) {
      ++i;
      if (!parseEquality(infix, i)) return false;
    }

    return true;
  }

  return false;
}

////////////////////////////////////////////////////////////////////////////////
// Equality    --> Comparative {( "==" | "=" | "!==" | "!=" ) Comparative}
bool Eval::parseEquality(std::vector<std::pair<std::string, Lexer::Type>>& infix,
                         unsigned int& i) const {
  if (i < infix.size() && parseComparative(infix, i)) {
    while (i < infix.size() && infix[i].second == Lexer::Type::op &&
           (infix[i].first == "==" || infix[i].first == "=" || infix[i].first == "!==" ||
            infix[i].first == "!=")) {
      ++i;
      if (!parseComparative(infix, i)) return false;
    }

    return true;
  }

  return false;
}

////////////////////////////////////////////////////////////////////////////////
// Comparative --> Arithmetic {( "<=" | "<" | ">=" | ">" ) Arithmetic}
bool Eval::parseComparative(std::vector<std::pair<std::string, Lexer::Type>>& infix,
                            unsigned int& i) const {
  if (i < infix.size() && parseArithmetic(infix, i)) {
    while (i < infix.size() && infix[i].second == Lexer::Type::op &&
           (infix[i].first == "<=" || infix[i].first == "<" || infix[i].first == ">=" ||
            infix[i].first == ">")) {
      ++i;
      if (!parseArithmetic(infix, i)) return false;
    }

    return true;
  }

  return false;
}

////////////////////////////////////////////////////////////////////////////////
// Arithmetic  --> Geometric {( "+" | "-" ) Geometric}
bool Eval::parseArithmetic(std::vector<std::pair<std::string, Lexer::Type>>& infix,
                           unsigned int& i) const {
  if (i < infix.size() && parseGeometric(infix, i)) {
    while (i < infix.size() && infix[i].second == Lexer::Type::op &&
           (infix[i].first == "+" || infix[i].first == "-")) {
      ++i;
      if (!parseGeometric(infix, i)) return false;
    }

    return true;
  }

  return false;
}

////////////////////////////////////////////////////////////////////////////////
// Geometric   --> Tag {( "*" | "/" | "%" ) Tag}
bool Eval::parseGeometric(std::vector<std::pair<std::string, Lexer::Type>>& infix,
                          unsigned int& i) const {
  if (i < infix.size() && parseTag(infix, i)) {
    while (i < infix.size() && infix[i].second == Lexer::Type::op &&
           (infix[i].first == "*" || infix[i].first == "/" || infix[i].first == "%")) {
      ++i;
      if (!parseTag(infix, i)) return false;
    }

    return true;
  }

  return false;
}

////////////////////////////////////////////////////////////////////////////////
// Tag         --> Unary {( "_hastag_" | "_notag_" ) Unary}
bool Eval::parseTag(std::vector<std::pair<std::string, Lexer::Type>>& infix,
                    unsigned int& i) const {
  if (i < infix.size() && parseUnary(infix, i)) {
    while (i < infix.size() && infix[i].second == Lexer::Type::op &&
           (infix[i].first == "_hastag_" || infix[i].first == "_notag_")) {
      ++i;
      if (!parseUnary(infix, i)) return false;
    }

    return true;
  }

  return false;
}

////////////////////////////////////////////////////////////////////////////////
// Unary       --> [( "-" | "+" | "!" )] Exponent
bool Eval::parseUnary(std::vector<std::pair<std::string, Lexer::Type>>& infix,
                      unsigned int& i) const {
  if (i < infix.size()) {
    if (infix[i].first == "-") {
      infix[i].first = "_neg_";
      ++i;
    } else if (infix[i].first == "+") {
      infix[i].first = "_pos_";
      ++i;
    } else if (infix[i].first == "!") {
      ++i;
    }
  }

  return parseExponent(infix, i);
}

////////////////////////////////////////////////////////////////////////////////
// Exponent    --> Primitive ["^" Primitive]
bool Eval::parseExponent(std::vector<std::pair<std::string, Lexer::Type>>& infix,
                         unsigned int& i) const {
  if (i < infix.size() && parsePrimitive(infix, i)) {
    while (i < infix.size() && infix[i].second == Lexer::Type::op && infix[i].first == "^") {
      ++i;
      if (!parsePrimitive(infix, i)) return false;
    }

    return true;
  }

  return false;
}

////////////////////////////////////////////////////////////////////////////////
// Primitive   --> "(" Logical ")" | Variant
bool Eval::parsePrimitive(std::vector<std::pair<std::string, Lexer::Type>>& infix,
                          unsigned int& i) const {
  if (i < infix.size()) {
    if (infix[i].first == "(") {
      ++i;
      if (i < infix.size() && parseLogical(infix, i)) {
        if (i < infix.size() && infix[i].first == ")") {
          ++i;
          return true;
        }
      }
    } else {
      bool found = false;
      for (const auto& source : _sources) {
        Variant v;
        if (source(infix[i].first, v)) {
          found = true;
          break;
        }
      }

      if (found) {
        ++i;
        return true;
      } else if (infix[i].second != Lexer::Type::op) {
        ++i;
        return true;
      }
    }
  }

  return false;
}

////////////////////////////////////////////////////////////////////////////////
// Dijkstra Shunting Algorithm.
// https://en.wikipedia.org/wiki/Shunting-yard_algorithm
//
//   While there are tokens to be read:
//     Read a token.
//     If the token is an operator, o1, then:
//       while there is an operator token, o2, at the top of the stack, and
//             either o1 is left-associative and its precedence is less than or
//             equal to that of o2,
//             or o1 is right-associative and its precedence is less than that
//             of o2,
//         pop o2 off the stack, onto the output queue;
//       push o1 onto the stack.
//     If the token is a left parenthesis, then push it onto the stack.
//     If the token is a right parenthesis:
//       Until the token at the top of the stack is a left parenthesis, pop
//       operators off the stack onto the output queue.
//       Pop the left parenthesis from the stack, but not onto the output queue.
//       If the token at the top of the stack is a function token, pop it onto
//       the output queue.
//       If the stack runs out without finding a left parenthesis, then there
//       are mismatched parentheses.
//     If the token is a number, then add it to the output queue.
//
//   When there are no more tokens to read:
//     While there are still operator tokens in the stack:
//       If the operator token on the top of the stack is a parenthesis, then
//       there are mismatched parentheses.
//       Pop the operator onto the output queue.
//   Exit.
//
void Eval::infixToPostfix(std::vector<std::pair<std::string, Lexer::Type>>& infix) const {
  // Short circuit.
  if (infix.size() == 1) return;

  // Result.
  std::vector<std::pair<std::string, Lexer::Type>> postfix;

  // Shunting yard.
  std::vector<std::pair<std::string, Lexer::Type>> op_stack;

  // Operator characteristics.
  char type;
  unsigned int precedence;
  char associativity;

  for (auto& token : infix) {
    if (token.second == Lexer::Type::op && token.first == "(") {
      op_stack.push_back(token);
    } else if (token.second == Lexer::Type::op && token.first == ")") {
      while (op_stack.size() && op_stack.back().first != "(") {
        postfix.push_back(op_stack.back());
        op_stack.pop_back();
      }

      if (op_stack.size())
        op_stack.pop_back();
      else
        throw std::string("Mismatched parentheses in expression");
    } else if (token.second == Lexer::Type::op &&
               identifyOperator(token.first, type, precedence, associativity)) {
      char type2;
      unsigned int precedence2;
      char associativity2;
      while (op_stack.size() > 0 &&
             identifyOperator(op_stack.back().first, type2, precedence2, associativity2) &&
             ((associativity == 'l' && precedence <= precedence2) ||
              (associativity == 'r' && precedence < precedence2))) {
        postfix.push_back(op_stack.back());
        op_stack.pop_back();
      }

      op_stack.push_back(token);
    } else {
      postfix.push_back(token);
    }
  }

  while (op_stack.size()) {
    if (op_stack.back().first == "(" || op_stack.back().first == ")")
      throw std::string("Mismatched parentheses in expression");

    postfix.push_back(op_stack.back());
    op_stack.pop_back();
  }

  infix = postfix;
}

////////////////////////////////////////////////////////////////////////////////
bool Eval::identifyOperator(const std::string& op, char& type, unsigned int& precedence,
                            char& associativity) const {
  for (const auto& opr : operators) {
    if (opr.op == op) {
      type = opr.type;
      precedence = opr.precedence;
      associativity = opr.associativity;
      return true;
    }
  }

  return false;
}

////////////////////////////////////////////////////////////////////////////////
std::string Eval::dump(std::vector<std::pair<std::string, Lexer::Type>>& tokens) const {
  // Set up a color mapping.
  std::map<Lexer::Type, Color> color_map;
  color_map[Lexer::Type::op] = Color("gray14 on gray6");
  color_map[Lexer::Type::number] = Color("rgb530 on gray6");
  color_map[Lexer::Type::hex] = Color("rgb303 on gray6");
  color_map[Lexer::Type::string] = Color("rgb550 on gray6");
  color_map[Lexer::Type::dom] = Color("rgb045 on gray6");
  color_map[Lexer::Type::identifier] = Color("rgb035 on gray6");
  color_map[Lexer::Type::date] = Color("rgb150 on gray6");
  color_map[Lexer::Type::duration] = Color("rgb531 on gray6");

  std::string output;
  for (auto i = tokens.begin(); i != tokens.end(); ++i) {
    if (i != tokens.begin()) output += ' ';

    Color c;
    if (color_map[i->second].nontrivial())
      c = color_map[i->second];
    else
      c = Color("rgb000 on gray6");

    output += c.colorize(i->first);
  }

  return output;
}

////////////////////////////////////////////////////////////////////////////////