"use strict";

const fs = require("fs");
const path = require("path");
const matter = require("gray-matter");
const markdown = require("../modules/markdown.js");
const { indentForTemplate, postIndentLevel } = require("../responders.js");

const grayMatterOptions = {
  lang: "toml",
  delims: "+++"
};

function* lowercaseKeys(iterator) {
  for (let [k, v] of iterator) {
    yield [String(k).toLowerCase(), v];
  }
}

function canonicaliseMetadata(meta) {
  if (meta.data) {
    meta.data = new Map(lowercaseKeys(Object.entries(meta.data)));
  } else {
    meta.data = new Map();
  }
  return meta;
}

function getTitle(file) {
  return path.basename(file.path, path.extname(file.path));
}

function get(getURL, filename) {
  const fileMatter = matter.read(filename, grayMatterOptions);
  fileMatter.basename = getTitle(fileMatter);
  delete fileMatter.orig;
  fileMatter.body = indentForTemplate(
    markdown(fileMatter.content),
    postIndentLevel
  );
  fileMatter.url = getURL(fileMatter.basename);
  return canonicaliseMetadata(fileMatter);
}

function getFolder(folder, getURL) {
  return new Map(
    fs
      .readdirSync(folder)
      .map(f => path.resolve(folder, f))
      .map(get.bind(this, getURL))
      .map(f => [getTitle(f), f])
  );
}

function taxonomise(taxonomies, posts) {
  const taxons = new Map(Object.keys(taxonomies).map(t => [t, new Map()]));

  for (let [, post] of posts) {
    for (let [singularName, pluralName] of Object.entries(taxonomies)) {
      if (post.data.has(pluralName)) {
        for (let term of post.data.get(pluralName)) {
          const current = taxons.get(singularName).get(term);
          taxons
            .get(singularName)
            .set(term, current ? current.concat(post) : [post]);
        }
      }
    }
  }

  return taxons;
}

module.exports = function(config, getURL) {
  const posts = getFolder(config.folder, getURL);
  const taxonomies = taxonomise(config.taxonomies, posts);
  return {
    posts,
    taxonomies,
    get
  };
};