//===-- macro-parser.cpp - definitions for godumpspec macro parser --------===//
//
// Copyright 2018 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//
//===----------------------------------------------------------------------===//
//
// Definitions for MacroParser class
//
//===----------------------------------------------------------------------===//

#include "macro-parser.h"

#include <iostream>
#include <vector>
#include <algorithm>

int MacroParser::visitMacroLine(const std::string &line, unsigned lno)
{
  // Chop off the initial "#define "
  if (std::strncmp(line.c_str(), "#define ", 8) != 0) {
    llvm::errs() << "malformed macro input at line "
                 << lno << ": " << line << "\n";
    return 1;
  }
  std::string mac(line.substr(8));
  auto spos = mac.find(' ');
  if (spos == std::string::npos) {
    llvm::errs() << "malformed macro input at line "
                 << lno << ": " << line << "\n";
    return 1;
  }

  // Divide into macro name and macro body
  MacroDef d;
  d.name = mac.substr(0, spos);
  d.body = mac.substr(spos+1);

  // Don't try to process functions.
  auto ppos = d.name.find('(');
  if (ppos != std::string::npos)
    return 0;

  // A collision here typically indicates that we have
  // a clash between a macro and an enum literal.
  auto it = macros_.find(d);
  if (it != macros_.end()) {
    assert(it->enumDef);
    return 0;
  }

  // Add entry to macro table for later post-processing
  d.enumDef = false;
  macros_.insert(d);

  return 0;
}

void MacroParser::addEnumLiteralPseudoMacro(const std::string &name,
                                            const std::string &value)
{
  MacroDef d;
  d.name = name;
  d.body = value;
  d.enumDef = true;
  assert(macros_.find(d) == macros_.end());
  macros_.insert(d);
}

// This method parses the body of the specified macro so as to decide
// whether it can be represented as a Go constant. This means
// decomposing it into tokens and then insuring that the expression it
// represents is suitable for Go. Macros are allowed to refer to other
// macros, as we discover references to other macros as part of the
// process we visit them as well. If a macro body looks OK, we fill in
// the "expanded" data member with its canonicalized representation.

void MacroParser::visitMacro(MacroDef *m)
{
  switch(m->mstate) {
    case VisitInProgress:
      // Cycles not allowed.
      m->mstate = VisitedWithError;
      return;
    case VisitedOK:
    case VisitedEmpty:
    case VisitedWithError:
      // already processed
      return;
    case Unvisited:
      m->mstate = VisitInProgress;
      break;
    default:
      assert(false);
  }

  MacroTokenizer t(m->body);
  std::string str;
  llvm::raw_string_ostream os(str);

  bool eof = false;
  bool error = false;
  bool saw_operand = false;
  bool expect_operand = false;

  while(!error && !eof) {
    std::pair<MacTokenTyp, std::string> tv = t.getToken();
      switch(tv.first) {
        case TOK_ERROR:
          error = true;
          break;
        case TOK_END_OF_STRING:
          eof = true;
          break;
        case TOK_IDENTIFIER: {
          if (saw_operand) {
            error = true;
            break;
          }
          MacroDef *m2 = lookup(tv.second);
          if (m2 == nullptr) {
            // Not a macro -- bail here
            error = true;
            break;
          }
          visitMacro(m2);
          if (m2->mstate == VisitedWithError) {
            error = true;
            break;
          }
          if (m2->mstate == VisitedEmpty) {
            // Nothing to emit here
          } else {
            assert(m2->mstate == VisitedOK);
            os << "_" << m2->name;
            saw_operand = true;
            expect_operand = false;
          }
          break;
        }
        case TOK_NUMERIC_CONSTANT:
          os << tv.second;
          saw_operand = true;
          expect_operand = false;
          break;
        case TOK_SPACE:
          os << tv.second;
          break;
        case TOK_ADDSUB:
          saw_operand = false;
          os << tv.second;
          break;
        case TOK_UNOP:
          if (saw_operand) {
            error = true;
            break;
          }
          expect_operand = true;
          os << tv.second;
          break;
        case TOK_BINOP:
          if (!saw_operand) {
            error = true;
            break;
          }
          saw_operand = false;
          expect_operand = true;
          os << tv.second;
          break;
        case TOK_OPEN_PAREN:
          saw_operand = false;
          expect_operand = false;
          os << tv.second;
          break;
        case TOK_CLOSE_PAREN:
          if (expect_operand) {
            error = true;
            break;
          }
          saw_operand = true;
          os << tv.second;
          break;
        case TOK_STRING_CONSTANT:
          if (saw_operand) {
            error = true;
            break;
          }
          saw_operand = true;
          expect_operand = false;
          os << tv.second;
          break;
        default:
          error = true;
          break;
      }
  }

  if (error || expect_operand) {
    m->mstate = VisitedWithError;
    return;
  }
  m->expanded = os.str();
  auto notEmpty = m->expanded.find_first_not_of(" \t");
  if (notEmpty == std::string::npos) {
    m->mstate = VisitedEmpty;
  } else {
    m->mstate = VisitedOK;
  }
}

void MacroParser::postProcessMacros()
{
  for (auto it = macros_.begin(); it != macros_.end(); it++)
    visitMacro(const_cast<MacroDef*>(&(*it)));
}

void MacroParser::emitMacros(llvm::raw_ostream &os,
                             const std::unordered_set<std::string> &emittedTypes)
{
  // Collect all emittable macros
  std::vector<MacroDef *> defs;
  for (auto it = macros_.begin(); it != macros_.end(); it++) {
    MacroDef *def = const_cast<MacroDef*>(&(*it));

    // Weed out macros that had problems in parsing.
    if (def->mstate != VisitedOK)
      continue;

    // Types take precedence over macros
    if (emittedTypes.find(def->name) != emittedTypes.end())
      continue;

    defs.push_back(def);
  }

  // Sort by name for nicer output
  std::sort(defs.begin(), defs.end(),
            [](MacroDef *d1, MacroDef *d2) {
              return d1->name.compare(d2->name) < 0;
            });

  // Output a Go equivalent.
  for (auto it = defs.begin(); it != defs.end(); it++) {
    MacroDef *d = (*it);
    os << "const _" << d->name << " = " << d->expanded << "\n";
  }
}