51 lines
1.9 KiB
Ruby
51 lines
1.9 KiB
Ruby
module Api
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module V0
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class CommentsController < ApiController
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respond_to :json
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before_action :set_cache_control_headers, only: %i[index show]
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def index
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article = Article.find(params[:a_id])
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@comments = article.comments.
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includes(:user).
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select(ATTRIBUTES_FOR_SERIALIZATION).
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arrange
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set_surrogate_key_header article.record_key, Comment.table_key, edge_cache_keys(@comments)
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end
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def show
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tree_with_root_comment = Comment.subtree_of(params[:id].to_i(26)).
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includes(:user).
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select(ATTRIBUTES_FOR_SERIALIZATION).
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arrange
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# being only one tree we know that the root comment is the first (and only) key
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@comment = tree_with_root_comment.keys.first
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@comments = tree_with_root_comment[@comment]
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set_surrogate_key_header Comment.table_key, edge_cache_keys(tree_with_root_comment)
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end
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ATTRIBUTES_FOR_SERIALIZATION = %i[id processed_html user_id ancestry].freeze
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private_constant :ATTRIBUTES_FOR_SERIALIZATION
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private
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# ancestry wraps a single or multiple trees of comments into a single hash,
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# in the case of an article comments, the hash has multiple keys (the root comments),
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# in the case of a comment and its descendants, the hash has only one key.
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# Either way, we need to use recursion to extract all the comment cache keys
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# collecting both the keys of each level of root comments and their descendants
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# NOTE: the objects are already loaded in memory by "ancestry",
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# so no additional SQL query is performed during this extraction, avoiding N+1s
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def edge_cache_keys(comments_trees)
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comments_trees.keys.flat_map do |comment|
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Array.wrap(comment.record_key) + edge_cache_keys(comments_trees[comment])
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end
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end
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end
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end
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end
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