wp-calypso/client/state/comments/README.md

Comments

This store has the following structure

comments = {
    items: Immutable.Map<CommentTargetId, Immutable.List<Comment>>, // Comment is a Immutable.Map in the shape that returned by wpcom, ordered by date DESC
    requests: Immutable.Map<CommentTargetId, Map<RequestId, ActionType>>,
    totalCommentsCount: Immutable.Map<CommentTargetId, Number>
}>;

Types

    CommentTargetId: `${siteId}-${postId}`;
    RequestId: `${siteId}-${postId}-${stringify(query)}`; // query is the query to wpcom replies()

Selectors

All selectors receive redux state and { siteId, postId }. The more "complex" ones, like getPostCommentsTree implemented with lib/combine-selector.

getPostCommentsTree - returns a memoized comments tree of the form:

    Tree: Map<CommentId, CommentNode>;
    in addition to the CommentId => CommentNode map, it has the following property:
        children: List<CommentId> // root-level comments ordered by date

    CommentNode: Map<> {
        children: List<CommentId>,
        data: Map | undefined, // the comment as received from wpcom API, if not yet received: undefined
        parentId: CommentId | null | undefined, // if we don't know yet, set to undefined. if comment has parent then set to number else to null
    }

Simple selectors

getPostCommentItems - gets items of siteId, postId; getPostTotalCommentsCount - gets totalCommentsCount of siteId, postId

Compute selectors

getPostMostRecentCommentDate - gets the date of most recent comment getPostOldestCommentDate - gets the date of the earliest comment getPostCommentsTree - computes a comments tree haveMoreCommentsToFetch - concludes whether there are more comments to fetch according to totalCommentsCount and items.size

How it works

Comments fetching

We pull from the API in reverse chronological order (going back in time with before field) via actions#requestPostComments(), building up the comment tree (reducer#tree) as we process each comment.

Since replies have to happen after the initial comment, we'll process all replies to a comment before the comment itself, util we have seen an actual node, a placeholder CommentNode with parentId === undefined and data === undefined is placed on the tree.

Note: Since we haven't seen the parent of the placeholder CommentNode, that node won't be reachable from the root children list, but can be reached directly by ID.