6cc - Markdown Foldblock Extension

6cc.cpp

#include <bits/stdc++.h>

using namespace std;

int now;
string s;

vector<int> sta;

bool match(string t) {
  if (now + t.size() > s.size())
    return false;
  if (s.substr(now, t.size()) != t)
    return false;
  now += t.size();
  return true;
}

bool matchg() {
  int old = now;
  while (now < min(old + 4, (int)s.size()) && s[now] == ' ')
    now++;
  if (now - old < 4 && match(">"))
    return match(" "), true;
  return now = old, false;
}

int matchl() {
  int old = now;
  while (now < min(old + 4, (int)s.size()) && s[now] == ' ')
    now++;
  if (now - old < 4) {
    bool matched = 0;
    if (match("+ ") || match("- ") || match("* "))
      matched = 1;
    if (!matched) {
      bool digit = 0;
      while (now < s.size() && isdigit(s[now]))
        digit = 1, now++;
      if (digit && match(". "))
        matched = 1;
    }
    if (matched) {
      for (int i = 0; i <= 3; i++)
        match(" ");
      return now - old;
    }
  }
  return now = old, 0;
}

void matchcb(int &codemode) {
  int old = now;
  while (now < min(old + 4, (int)s.size()) && s[now] == ' ')
    now++;
  if (now - old < 4) {
    if ((codemode == 0 || codemode == 1) && match("```"))
      return void(codemode = codemode ^ 1);
    if ((codemode == 0 || codemode == 2) && match("~~~"))
      return void(codemode = codemode ^ 2);
  }
  now = old;
}

void printsta() {
  for (int x : sta) {
    if (x == -1)
      printf("> ");
    else if (x != -2)
      printf("%s", string(x, ' ').c_str());
  }
}

void popblank() {
  while (!s.empty() && isblank(s.back()))
    s.pop_back();
  reverse(s.begin(), s.end());
  while (!s.empty() && isblank(s.back()))
    s.pop_back();
  reverse(s.begin(), s.end());
}

void foundblock(int type) {
  printsta();
  printf("<details open%s>",
         type == -2 ? "" : " class=\"detail-fold-default-closed\"");
  s = s.substr(now);
  popblank();
  if (s.empty())
    puts("");
  else
    printf("<summary>%s</summary>\n", s.c_str());
  sta.push_back(-2);
  printsta(), puts("");
}

string text;

void printhelp(const char *name) {
  printf("6cc the extended commonmark compiler, built on %s.\n"
         "Usage: %s <inputfile> <outputfile>\n",
         __DATE__, name);
  exit(1);
}

int main(int argc, char **argv) {
  if (argc != 3)
    printhelp(argv[0]);
  freopen(argv[1], "r", stdin);
  freopen(argv[2], "w", stdout);
  bool ended = 0;
  int codemode = 0;
  while (!cin.eof() || !ended) {
    if (cin.eof())
      ended = 1, s = "";
    else
      getline(cin, s);
    text += s + "\n";
    now = 0;

    if (codemode) {
      for (int t = 0; t < sta.size(); t++) {
        int x = sta[t];
        if (x < 0)
          assert(matchg());
        else
          assert(match(string(x, ' ')));
      }
      printsta();
      printf("%s\n", s.substr(now).c_str());
      matchcb(codemode);
      continue;
    }

    int t = 0;
    bool flag = 0;
    for (; t < sta.size(); t++) {
      int x = sta[t];
      if (x < 0) {
        if (matchg()) {
          flag = 1;
          continue;
        }
        break;
      } else {
        assert(x);
        if (match(string(x, ' '))) {
          flag = 0;
          continue;
        }
        break;
      }
    }

    for (int p = now; p < s.size(); p++)
      if (s[p] != ' ')
        goto PS;
    for (; t < sta.size(); ++t)
      if (sta[t] < 0)
        goto PS;
    printsta(), puts("");
    continue;
  PS:

    int type = -1;
    if (flag) {
      if (match("[+]"))
        type = -2;
      else if (match("[-]"))
        type = -3;
      if (type != -1)
        t--;
    }
    while (sta.size() > t) {
      int x = sta.back();
      sta.pop_back();
      if (x == -2) {
        printsta();
        puts("</details>");
      }
    }
    if (type == -1)
      while (matchg()) {
        if (match("[+]"))
          type = -2;
        else if (match("[-]"))
          type = -3;
        if (type != -1)
          break;
        sta.push_back(-1);
      }
    if (type != -1) {
      match(" ");
      foundblock(type);
      continue;
    }
    printsta();
    printf("%s\n", s.substr(now).c_str());
    int x = matchl();
    if (x)
      sta.push_back(x);
    matchcb(codemode);
  }
  printf("<!--\n%s-->", text.c_str());
  return 0;
}