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Implement "fields" parameter from the YouTube Data API (#429)

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* Implement fields handling
This commit is contained in:
afrmtbl 2019-03-30 21:18:34 -04:00 committed by Omar Roth
parent 1b78001201
commit a7723e6ded
2 changed files with 258 additions and 0 deletions
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10
src/invidious/helpers/handlers.cr
View File

@ -97,6 +97,16 @@ class APIHandler < Kemal::Handler
if env.response.headers["Content-Type"]?.try &.== "application/json"
response = JSON.parse(response)
if env.params.query["fields"]?
fields_text = env.params.query["fields"]
begin
JSONFilter.filter(response, fields_text)
rescue ex
env.response.status_code = 400
response = {"error" => ex.message}
end
end
if env.params.query["pretty"]? && env.params.query["pretty"] == "1"
response = response.to_pretty_json
else

248
src/invidious/helpers/json_filter.cr Normal file
View File

@ -0,0 +1,248 @@
module JSONFilter
alias BracketIndex = Hash(Int64, Int64)
alias GroupedFieldsValue = String | Array(GroupedFieldsValue)
alias GroupedFieldsList = Array(GroupedFieldsValue)
class FieldsParser
class ParseError < Exception
end
# Returns the `Regex` pattern used to match nest groups
def self.nest_group_pattern : Regex
# uses a '.' character to match json keys as they are allowed
# to contain any unicode codepoint
/(?:|,)(?<groupname>[^,\n]*?)\(/
end
# Returns the `Regex` pattern used to check if there are any empty nest groups
def self.unnamed_nest_group_pattern : Regex
/^\(|\(\(|\/\(/
end
def self.parse_fields(fields_text : String) : Nil
if fields_text.empty?
raise FieldsParser::ParseError.new "Fields is empty"
end
opening_bracket_count = fields_text.count('(')
closing_bracket_count = fields_text.count(')')
if opening_bracket_count != closing_bracket_count
bracket_type = opening_bracket_count > closing_bracket_count ? "opening" : "closing"
raise FieldsParser::ParseError.new "There are too many #{bracket_type} brackets (#{opening_bracket_count}:#{closing_bracket_count})"
elsif match_result = unnamed_nest_group_pattern.match(fields_text)
raise FieldsParser::ParseError.new "Unnamed nest group at position #{match_result.begin}"
end
# first, handle top-level single nested properties: items/id, playlistItems/snippet, etc
parse_single_nests(fields_text) { |nest_list| yield nest_list }
# next, handle nest groups: items(id, etag, etc)
parse_nest_groups(fields_text) { |nest_list| yield nest_list }
end
def self.parse_single_nests(fields_text : String) : Nil
single_nests = remove_nest_groups(fields_text)
if !single_nests.empty?
property_nests = single_nests.split(',')
property_nests.each do |nest|
nest_list = nest.split('/')
if nest_list.includes? ""
raise FieldsParser::ParseError.new "Empty key in nest list: #{nest_list}"
end
yield nest_list
end
# else
# raise FieldsParser::ParseError.new "Empty key in nest list 22: #{fields_text} | #{single_nests}"
end
end
def self.parse_nest_groups(fields_text : String) : Nil
nest_stack = [] of NamedTuple(group_name: String, closing_bracket_index: Int64)
bracket_pairs = get_bracket_pairs(fields_text, true)
text_index = 0
regex_index = 0
while regex_result = self.nest_group_pattern.match(fields_text, regex_index)
raw_match = regex_result[0]
group_name = regex_result["groupname"]
text_index = regex_result.begin
regex_index = regex_result.end
if text_index.nil? || regex_index.nil?
raise FieldsParser::ParseError.new "Received invalid index while parsing nest groups: text_index: #{text_index} | regex_index: #{regex_index}"
end
offset = raw_match.starts_with?(',') ? 1 : 0
opening_bracket_index = (text_index + group_name.size) + offset
closing_bracket_index = bracket_pairs[opening_bracket_index]
content_start = opening_bracket_index + 1
content = fields_text[content_start...closing_bracket_index]
if content.empty?
raise FieldsParser::ParseError.new "Empty nest group at position #{content_start}"
else
content = remove_nest_groups(content)
end
while nest_stack.size > 0 && closing_bracket_index > nest_stack[nest_stack.size - 1][:closing_bracket_index]
if nest_stack.size
nest_stack.pop
end
end
group_name.split('/').each do |group_name|
nest_stack.push({
group_name: group_name,
closing_bracket_index: closing_bracket_index,
})
end
if !content.empty?
properties = content.split(',')
properties.each do |prop|
nest_list = nest_stack.map { |nest_prop| nest_prop[:group_name] }
if !prop.empty?
if prop.includes?('/')
parse_single_nests(prop) { |list| nest_list += list }
else
nest_list.push prop
end
else
raise FieldsParser::ParseError.new "Empty key in nest list: #{nest_list << prop}"
end
yield nest_list
end
end
end
end
def self.remove_nest_groups(text : String) : String
content_bracket_pairs = get_bracket_pairs(text, false)
content_bracket_pairs.each_key.to_a.reverse.each do |opening_bracket|
closing_bracket = content_bracket_pairs[opening_bracket]
last_comma = text.rindex(',', opening_bracket) || 0
text = text[0...last_comma] + text[closing_bracket + 1...text.size]
end
return text.starts_with?(',') ? text[1...text.size] : text
end
def self.get_bracket_pairs(text : String, recursive = true) : BracketIndex
istart = [] of Int64
bracket_index = BracketIndex.new
text.each_char_with_index do |char, index|
if char == '('
istart.push(index.to_i64)
end
if char == ')'
begin
opening = istart.pop
if recursive || (!recursive && istart.size == 0)
bracket_index[opening] = index.to_i64
end
rescue
raise FieldsParser::ParseError.new "No matching opening parenthesis at: #{index}"
end
end
end
if istart.size != 0
idx = istart.pop
raise FieldsParser::ParseError.new "No matching closing parenthesis at: #{idx}"
end
return bracket_index
end
end
class FieldsGrouper
alias SkeletonValue = Hash(String, SkeletonValue)
def self.create_json_skeleton(fields_text : String) : SkeletonValue
root_hash = {} of String => SkeletonValue
FieldsParser.parse_fields(fields_text) do |nest_list|
current_item = root_hash
nest_list.each do |key|
if current_item[key]?
current_item = current_item[key]
else
current_item[key] = {} of String => SkeletonValue
current_item = current_item[key]
end
end
end
root_hash
end
def self.create_grouped_fields_list(json_skeleton : SkeletonValue) : GroupedFieldsList
grouped_fields_list = GroupedFieldsList.new
json_skeleton.each do |key, value|
grouped_fields_list.push key
nested_keys = create_grouped_fields_list(value)
grouped_fields_list.push nested_keys unless nested_keys.empty?
end
return grouped_fields_list
end
end
class FilterError < Exception
end
def self.filter(item : JSON::Any, fields_text : String, in_place : Bool = true)
skeleton = FieldsGrouper.create_json_skeleton(fields_text)
grouped_fields_list = FieldsGrouper.create_grouped_fields_list(skeleton)
filter(item, grouped_fields_list, in_place)
end
def self.filter(item : JSON::Any, grouped_fields_list : GroupedFieldsList, in_place : Bool = true) : JSON::Any
item = item.clone unless in_place
if !item.as_h? && !item.as_a?
raise FilterError.new "Can't filter '#{item}' by #{grouped_fields_list}"
end
top_level_keys = Array(String).new
grouped_fields_list.each do |value|
if value.is_a? String
top_level_keys.push value
elsif value.is_a? Array
if !top_level_keys.empty?
key_to_filter = top_level_keys.last
if item.as_h?
filter(item[key_to_filter], value, in_place: true)
elsif item.as_a?
item.as_a.each { |arr_item| filter(arr_item[key_to_filter], value, in_place: true) }
end
else
raise FilterError.new "Tried to filter while top level keys list is empty"
end
end
end
if item.as_h?
item.as_h.select! top_level_keys
elsif item.as_a?
item.as_a.map { |value| filter(value, top_level_keys, in_place: true) }
end
item
end
end