function PleromaModLoader () {
  this.config = {
    "modDirectory": "/instance/pleroma-mods/",
    "mods": []
  };
  this.loadConfig();
  this.loadedMods = {};
  this.classes = {};
}
[
  function loadMods () {
    for (const mod of this.config.mods) {
      const modObject = new PleromaMod(mod);
      modObject.include();
      this.loadedMods[mod] = modObject;
    }
  },

  function loadConfig () {
    window.fetch("/instance/pleroma-mod-config.json").then((response) => {
      if (response.ok) {
        response.json().then((json) => {
          for (const key in json) {
            this.config[key] = json[key];
          }
          this.loadMods();
        }).catch((error) => {
          console.error("can't parse loader config");
          console.error(error);
        });
      }
    }).catch((error) => {
      console.warn("can't load mod loader config");
      console.warn(error);
    });
  },

  function registerClass (className, object) {
    this.classes[className] = object;
  },

  function waitUntilReady () {
    const postPanel = document.getElementsByClassName("post-status-form");
    const loginPanel = document.getElementsByClassName("login-form");
    if (postPanel.length > 0 || loginPanel.length > 0) {
      for (var modName in this.loadedMods) {
        const mod = this.loadedMods[modName];
        if (mod.instance.onReady) {
          mod.instance.onReady();
        }
      }
      this.createObserver();
    } else {
      window.setTimeout(() => { this.waitUntilReady(); }, 1000);
    }
  },

  function createObserver () {
    this.containers = {
      main: document.getElementsByClassName("main")[0],
      notifications: document.getElementsByClassName("notifications")[0]
    };

    const observerConfig = { subtree: true, childList: true };
    this.observer = new MutationObserver((mutations, observer) => {
      for (var modName in this.loadedMods) {
        const mod = this.loadedMods[modName];
        if (mod.instance.onMutation) {
          for (const mutation of mutations) {
            let filter = null;
            if (mod.instance.config.filter) {
              filter = new RegExp(mod.instance.config.filter.join("|"));
            }
            if (!filter || filter.test(mutation.target.className)) {
              mod.instance.onMutation(mutation, observer);
            }
          }
        }
      }
    });
    this.observer.observe(this.containers.main, observerConfig);
    if (this.containers.notifications) {
      this.observer.observe(this.containers.notifications, observerConfig);
    }
  }
].forEach((fn) => { PleromaModLoader.prototype[fn.name] = fn; });
[
  function registerMod (mod) {
    window.__pleromaModLoader.registerClass(mod.name, mod);
  },

  function includeModScript (src) {
    return PleromaModLoader.includeScript(window.__pleromaModLoader.config.modDirectory + src);
  },

  function includeModCss (src) {
    return PleromaModLoader.includeCss(window.__pleromaModLoader.config.modDirectory + src);
  },

  function includeScript (src) {
    return new Promise((resolve) => {
      const body = document.getElementsByTagName("body")[0];
      const script = document.createElement("script");
      script.setAttribute("src", src);
      script.setAttribute("type", "text/javascript");
      script.onload = () => { resolve(); };
      body.appendChild(script);
    });
  },

  function includeCss (src) {
    return new Promise((resolve) => {
      const head = document.getElementsByTagName("head")[0];
      const link = document.createElement("link");
      link.setAttribute("href", src);
      link.setAttribute("rel", "stylesheet");
      link.setAttribute("type", "text/css");
      link.onload = () => { resolve(); };
      head.appendChild(link);
    });
  },

  function getModDir () {
    return window.__pleromaModLoader.config.modDirectory;
  }
].forEach((fn) => { PleromaModLoader[fn.name] = fn; });

function PleromaMod (name) {
  this.name = name;
  this.instance = null;
}
[
  function getClassName () {
    let className = "PleromaMod";
    const nameParts = this.name.split("-");
    for (const namePart of nameParts) {
      className += namePart.substring(0, 1).toUpperCase();
      className += namePart.substring(1);
    }
    return className;
  },

  function include () {
    console.log("loading " + this.name);
    PleromaModLoader.includeScript(
      PleromaModLoader.getModDir() + "pleroma-mod-" + this.name + "/mod.js"
    ).then(() => {
      this.modLoaded();
    });
  },

  function modLoaded () {
    console.log(this.name + " loaded");
    this.instance = new window.__pleromaModLoader.classes[this.getClassName()]();
    this.run();
  },

  function run () {
    if (this.instance) {
      this.instance.run();
    }
  }
].forEach((fn) => { PleromaMod.prototype[fn.name] = fn; });

window.__pleromaModLoader = new PleromaModLoader();
window.__pleromaModLoader.waitUntilReady();