#include <iostream>
#include <string>
#include <string_view>
#include <toml++/toml.hpp>
#include <fstream>
#include <cassert>
#include <cmark.h>
#include <cstdlib>
#include <inja/inja.hpp>
#include <nlohmann/json.hpp>
#include <cstring>
#include <dirent.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <vector>
#include <algorithm>

using json = nlohmann::json;
using namespace std::string_literals;

struct MainConfig {
  std::string title;
  std::string url;
  std::string author;
  int posts_per_page = 5;
};

struct FrontmatterConfig {
  std::string title;
  std::string date;
  std::string categories;
  std::string tags;
  bool draft;
  std::string body;
};

struct Config {
  MainConfig main;
  FrontmatterConfig frontmatter;
};


struct Post {
  std::string slug;
  std::string title;
  std::string date;
  std::string body_html;
};

Config
parse_config(const std::string& filepath)
{
  toml::table tbl;
  Config cfg;

  try {
    tbl = toml::parse_file(filepath);
  } catch (const toml::parse_error& err) {
    std::cerr << "parsing failed: " << err << std::endl;
    throw;
  }

  if (auto* main = tbl["main"].as_table()) {
    cfg.main.title  = (*main)["title"].value_or("untitled's blog");
    cfg.main.url    = (*main)["url"].value_or("localhost");
    cfg.main.author = (*main)["author"].value_or("linus");
    cfg.main.posts_per_page = (int)(*main)["posts_per_page"].value_or(5LL);
  }
  return cfg;
}

Config
frontmatter(const std::string& filepath)
{
  Config cfg;
  std::ifstream file(filepath);
  std::string content((std::istreambuf_iterator<char>(file)),
      std::istreambuf_iterator<char>());

  const size_t first_fence = content.find("+++");
  const size_t second_fence = (first_fence == std::string::npos)
    ? std::string::npos
    : content.find("+++", first_fence + 3);

  if (first_fence != std::string::npos && second_fence != std::string::npos) {
    std::string fm = content.substr(first_fence + 3, 
        second_fence - (first_fence+3));
    try { 
      toml::parse_result result = toml::parse(fm);
      const toml::table& tbl = result;
      cfg.frontmatter.title = tbl["title"].value_or(""s);
      cfg.frontmatter.date = tbl["date"].value_or(""s);
      cfg.frontmatter.categories = tbl["categories"].value_or(""s);
      cfg.frontmatter.tags = tbl["tags"].value_or(""s);
      cfg.frontmatter.draft = tbl["draft"].value_or(true);
    }  catch(const toml::parse_error& err) {
      std::cerr << "parsing failed: " << err << std::endl;
      throw;
    }
    cfg.frontmatter.body = content.substr(second_fence + 3);
  }
  return cfg;
}

std::string
markdown_processing(const std::string& md) {
  char *raw = cmark_markdown_to_html(md.c_str(), md.size(),0);
  std::string html(raw);
  free(raw);
  return html;
}

std::string
strip_html(const std::string& html) {
  std::string out;
  bool in_tag = false;
  for (char c : html) {
    if (c == '<') in_tag = true;
    else if (c == '>') in_tag = false;
    else if (!in_tag) out += c;
  }
  return out;
}

int main() {
  inja::Environment env;
  nlohmann::json site;
  system("rm -rf public");
  if (mkdir("public", 0755) != 0) {
    std::cerr << "cant create public" << std::endl;
    return 1;
  }
  system("cp -r static/. public/");

  Config my_config = parse_config("config.toml");
  int ppp = my_config.main.posts_per_page;
  if (ppp < 1) ppp = 5;

  site["site"]["title"] = my_config.main.title;
  site["site"]["author"] = my_config.main.author;
  site["site"]["url"]    = my_config.main.url;

  std::vector<Post> posts;
  std::string intro_html;

  DIR *dir = opendir("content");
  if (!dir) {
    std::cerr << "cant open content/" << std::endl;
    return 1;
  }

  struct dirent* ent;
  while ((ent = readdir(dir)) != nullptr) {
    if (ent->d_name[0] == '.') continue;
    const char* ext = strrchr(ent->d_name, '.');
    if (!ext || strcmp(ext, ".md") != 0) continue;

    std::string fname(ent->d_name);
    std::string slug(fname.c_str(), ext - ent->d_name);
    std::string fpath = "content/" + fname;

    Config page = frontmatter(fpath);

    if (slug == "_index") {
      intro_html = markdown_processing(page.frontmatter.body);
      continue;
    }

    if (page.frontmatter.draft) continue;

    posts.push_back({
        slug,
        page.frontmatter.title.empty() ? slug : page.frontmatter.title,
        page.frontmatter.date,
        markdown_processing(page.frontmatter.body)
        });
  }
  closedir(dir);

  std::sort(posts.begin(), posts.end(),
      [](const Post& a, const Post& b) { return a.date > b.date; });

  for (const auto& p : posts) {
    nlohmann::json data = site;
    data["title"] = p.title;
    data["date"]  = p.date;
    data["draft"] = false;
    data["body"]  = p.body_html;
    std::string html = env.render_file("templates/post.html", data);
    std::string outdir = "public/" + p.slug;
    mkdir(outdir.c_str(), 0755);
    std::ofstream out(outdir + "/index.html");
    out << html;
  }

  int total = (int)posts.size();
  int pages = total > 0 ? (total + ppp - 1) / ppp : 1;

  for (int page = 1; page <= pages; page++) {
    nlohmann::json data = site;
    data["intro"] = intro_html;
    json arr = json::array();
    int start = (page - 1) * ppp;
    int end = std::min(start + ppp, total);
    for (int i = start; i < end; i++) {
      arr.push_back({
          {"title", posts[i].title},
          {"slug", posts[i].slug},
          {"date", posts[i].date},
          {"excerpt", posts[i].body_html}
          });
    }
    data["posts"] = arr;
    data["page"] = page;
    data["total_pages"] = pages;
    data["has_prev"] = (page > 1);
    data["has_next"] = (page < pages);
    data["prev_url"] = (page == 2) ? "/" : ("/page/" + std::to_string(page - 1) + "/");
    data["next_url"] = "/page/" + std::to_string(page + 1) + "/";

    std::string outdir = (page == 1) ? "public" : ("public/page/" + std::to_string(page));
    if (page > 1) system(("mkdir -p " + outdir).c_str());
    std::string html = env.render_file("templates/index.html", data);
    std::ofstream out(outdir + "/index.html");
    out << html;
  }

  json search_idx = json::array();
  for (const auto& p : posts) {
    search_idx.push_back({
        {"title", p.title},
        {"slug", p.slug},
        {"date", p.date},
        {"text", strip_html(p.body_html)}
        });
  }
  std::ofstream sj("public/search.json");
  sj << search_idx.dump();

  nlohmann::json data = site;
  data["title"] = "Search";
  system("mkdir -p public/search");
  std::string html = env.render_file("templates/search.html", data);
  std::ofstream so("public/search/index.html");
  so << html;

  std::cout << "wrote " << posts.size() << " posts, "
    << pages << " page(s), search" << std::endl;
  return 0;
}