import { NotificationLevels } from "discourse/lib/notification-levels";
import {
  default as computed,
  on
} from "ember-addons/ember-computed-decorators";
import { defaultHomepage } from "discourse/lib/utilities";
import PreloadStore from "preload-store";

function isNew(topic) {
  return (
    topic.last_read_post_number === null &&
    ((topic.notification_level !== 0 && !topic.notification_level) ||
      topic.notification_level >= NotificationLevels.TRACKING)
  );
}

function isUnread(topic) {
  return (
    topic.last_read_post_number !== null &&
    topic.last_read_post_number < topic.highest_post_number &&
    topic.notification_level >= NotificationLevels.TRACKING
  );
}

const TopicTrackingState = Discourse.Model.extend({
  messageCount: 0,

  @on("init")
  _setup() {
    this.unreadSequence = [];
    this.newSequence = [];
    this.states = {};
  },

  establishChannels() {
    const tracker = this;

    const process = data => {
      if (data.message_type === "delete") {
        tracker.removeTopic(data.topic_id);
        tracker.incrementMessageCount();
      }

      if (["new_topic", "latest"].includes(data.message_type)) {
        const muted_category_ids = Discourse.User.currentProp(
          "muted_category_ids"
        );
        if (
          muted_category_ids &&
          muted_category_ids.includes(data.payload.category_id)
        ) {
          return;
        }
      }

      // fill parent_category_id we need it for counting new/unread
      if (data.payload && data.payload.category_id) {
        var category = Discourse.Category.findById(data.payload.category_id);

        if (category && category.parent_category_id) {
          data.payload.parent_category_id = category.parent_category_id;
        }
      }

      if (data.message_type === "latest") {
        tracker.notify(data);
      }

      if (["new_topic", "unread", "read"].includes(data.message_type)) {
        tracker.notify(data);
        const old = tracker.states["t" + data.topic_id];

        // don't add tracking state for read stuff that was not tracked in first place
        if (old || data.message_type !== "read") {
          if (!_.isEqual(old, data.payload)) {
            tracker.states["t" + data.topic_id] = data.payload;
            tracker.incrementMessageCount();
          }
        }
      }
    };

    this.messageBus.subscribe("/new", process);
    this.messageBus.subscribe("/latest", process);
    if (this.currentUser) {
      this.messageBus.subscribe(
        "/unread/" + this.currentUser.get("id"),
        process
      );
    }

    this.messageBus.subscribe("/delete", msg => {
      const old = tracker.states["t" + msg.topic_id];
      if (old) {
        old.deleted = true;
      }
      tracker.incrementMessageCount();
    });

    this.messageBus.subscribe("/recover", msg => {
      const old = tracker.states["t" + msg.topic_id];
      if (old) {
        delete old.deleted;
      }
      tracker.incrementMessageCount();
    });
  },

  updateSeen(topicId, highestSeen) {
    if (!topicId || !highestSeen) {
      return;
    }
    const state = this.states["t" + topicId];
    if (
      state &&
      (!state.last_read_post_number ||
        state.last_read_post_number < highestSeen)
    ) {
      state.last_read_post_number = highestSeen;
      this.incrementMessageCount();
    }
  },

  notify(data) {
    if (!this.newIncoming) {
      return;
    }
    if (data.payload && data.payload.archetype === "private_message") {
      return;
    }

    const filter = this.filter;
    const filterCategory = this.filterCategory;
    const categoryId = data.payload && data.payload.category_id;

    if (filterCategory && filterCategory.get("id") !== categoryId) {
      const category = categoryId && Discourse.Category.findById(categoryId);
      if (
        !category ||
        category.get("parentCategory.id") !== filterCategory.get("id")
      ) {
        return;
      }
    }

    if (filter === defaultHomepage()) {
      const suppressed_from_latest_category_ids = Discourse.Site.currentProp(
        "suppressed_from_latest_category_ids"
      );
      if (
        suppressed_from_latest_category_ids &&
        suppressed_from_latest_category_ids.includes(data.payload.category_id)
      ) {
        return;
      }
    }

    if (
      ["all", "latest", "new"].includes(filter) &&
      data.message_type === "new_topic"
    ) {
      this.addIncoming(data.topic_id);
    }

    if (["all", "unread"].includes(filter) && data.message_type === "unread") {
      const old = this.states["t" + data.topic_id];
      if (!old || old.highest_post_number === old.last_read_post_number) {
        this.addIncoming(data.topic_id);
      }
    }

    if (filter === "latest" && data.message_type === "latest") {
      this.addIncoming(data.topic_id);
    }

    this.set("incomingCount", this.newIncoming.length);
  },

  addIncoming(topicId) {
    if (this.newIncoming.indexOf(topicId) === -1) {
      this.newIncoming.push(topicId);
    }
  },

  resetTracking() {
    this.newIncoming = [];
    this.set("incomingCount", 0);
  },

  // track how many new topics came for this filter
  trackIncoming(filter) {
    this.newIncoming = [];
    const split = filter.split("/");

    if (split.length >= 4) {
      filter = split[split.length - 1];
      // c/cat/subcat/l/latest
      var category = Discourse.Category.findSingleBySlug(
        split.splice(1, split.length - 3).join("/")
      );
      this.set("filterCategory", category);
    } else {
      this.set("filterCategory", null);
    }

    this.set("filter", filter);
    this.set("incomingCount", 0);
  },

  @computed("incomingCount")
  hasIncoming(incomingCount) {
    return incomingCount && incomingCount > 0;
  },

  removeTopic(topic_id) {
    delete this.states["t" + topic_id];
  },

  // If we have a cached topic list, we can update it from our tracking information.
  updateTopics(topics) {
    if (Ember.isEmpty(topics)) {
      return;
    }

    const states = this.states;
    topics.forEach(t => {
      const state = states["t" + t.get("id")];

      if (state) {
        const lastRead = t.get("last_read_post_number");
        if (lastRead !== state.last_read_post_number) {
          const postsCount = t.get("posts_count");
          let newPosts = postsCount - state.highest_post_number,
            unread = postsCount - state.last_read_post_number;

          if (newPosts < 0) {
            newPosts = 0;
          }
          if (!state.last_read_post_number) {
            unread = 0;
          }
          if (unread < 0) {
            unread = 0;
          }

          t.setProperties({
            highest_post_number: state.highest_post_number,
            last_read_post_number: state.last_read_post_number,
            new_posts: newPosts,
            unread: unread,
            unseen: !state.last_read_post_number
          });
        }
      }
    });
  },

  sync(list, filter) {
    const tracker = this,
      states = tracker.states;

    if (!list || !list.topics) {
      return;
    }

    // compensate for delayed "new" topics
    // client side we know they are not new, server side we think they are
    for (let i = list.topics.length - 1; i >= 0; i--) {
      const state = states["t" + list.topics[i].id];
      if (state && state.last_read_post_number > 0) {
        if (filter === "new") {
          list.topics.splice(i, 1);
        } else {
          list.topics[i].set("unseen", false);
          list.topics[i].set("dont_sync", true);
        }
      }
    }

    list.topics.forEach(function(topic) {
      const row = tracker.states["t" + topic.id] || {};
      row.topic_id = topic.id;
      row.notification_level = topic.notification_level;

      if (topic.unseen) {
        row.last_read_post_number = null;
      } else if (topic.unread || topic.new_posts) {
        row.last_read_post_number =
          topic.highest_post_number -
          ((topic.unread || 0) + (topic.new_posts || 0));
      } else {
        if (!topic.dont_sync) {
          delete tracker.states["t" + topic.id];
        }
        return;
      }

      row.highest_post_number = topic.highest_post_number;
      if (topic.category) {
        row.category_id = topic.category.id;
      }

      tracker.states["t" + topic.id] = row;
    });

    // Correct missing states, safeguard in case message bus is corrupt
    if ((filter === "new" || filter === "unread") && !list.more_topics_url) {
      const ids = {};
      list.topics.forEach(r => (ids["t" + r.id] = true));

      Object.keys(tracker.states).forEach(k => {
        // we are good if we are on the list
        if (ids[k]) {
          return;
        }

        const v = tracker.states[k];

        if (filter === "unread" && isUnread(v)) {
          // pretend read
          v.last_read_post_number = v.highest_post_number;
        }

        if (filter === "new" && isNew(v)) {
          // pretend not new
          v.last_read_post_number = 1;
        }
      });
    }

    this.incrementMessageCount();
  },

  incrementMessageCount() {
    this.incrementProperty("messageCount");
  },

  countNew(category_id) {
    return _.chain(this.states)
      .filter(isNew)
      .filter(
        topic =>
          topic.archetype !== "private_message" &&
          !topic.deleted &&
          (topic.category_id === category_id ||
            topic.parent_category_id === category_id ||
            !category_id)
      )
      .value().length;
  },

  resetNew() {
    Object.keys(this.states).forEach(id => {
      if (this.states[id].last_read_post_number === null) {
        delete this.states[id];
      }
    });
  },

  countUnread(category_id) {
    return _.chain(this.states)
      .filter(isUnread)
      .filter(
        topic =>
          topic.archetype !== "private_message" &&
          !topic.deleted &&
          (topic.category_id === category_id ||
            topic.parent_category_id === category_id ||
            !category_id)
      )
      .value().length;
  },

  countCategory(category_id) {
    let sum = 0;
    Object.values(this.states).forEach(topic => {
      if (topic.category_id === category_id && !topic.deleted) {
        sum +=
          topic.last_read_post_number === null ||
          topic.last_read_post_number < topic.highest_post_number
            ? 1
            : 0;
      }
    });
    return sum;
  },

  lookupCount(name, category) {
    if (name === "latest") {
      return (
        this.lookupCount("new", category) + this.lookupCount("unread", category)
      );
    }

    let categoryId = category ? Ember.get(category, "id") : null;
    let categoryName = category ? Ember.get(category, "name") : null;

    if (name === "new") {
      return this.countNew(categoryId);
    } else if (name === "unread") {
      return this.countUnread(categoryId);
    } else {
      categoryName = name.split("/")[1];
      if (categoryName) {
        return this.countCategory(categoryId);
      }
    }
  },

  loadStates(data) {
    const states = this.states;
    const idMap = Discourse.Category.idMap();

    // I am taking some shortcuts here to avoid 500 gets for a large list
    if (data) {
      data.forEach(topic => {
        var category = idMap[topic.category_id];
        if (category && category.parent_category_id) {
          topic.parent_category_id = category.parent_category_id;
        }
        states["t" + topic.topic_id] = topic;
      });
    }
  }
});

export function startTracking(tracking) {
  const data = PreloadStore.get("topicTrackingStates");
  tracking.loadStates(data);
  tracking.initialStatesLength = data && data.length;
  tracking.establishChannels();
  PreloadStore.remove("topicTrackingStates");
}

export default TopicTrackingState;