Class: Underpass::WayChain

Inherits:
Object
  • Object
show all
Defined in:
lib/underpass/way_chain.rb

Overview

Chains way node sequences that share endpoints into complete rings.

Used internally by Shape.multipolygon_from_relation to merge multiple way segments into closed linear rings.

Constant Summary collapse

MERGE_STRATEGIES =

This constant is part of a private API. You should avoid using this constant if possible, as it may be removed or be changed in the future. 

[
  ->(cur, seq) { cur.last == seq.first ? cur + seq[1..] : nil },
  ->(cur, seq) { cur.last == seq.last ? cur + seq.reverse[1..] : nil },
  ->(cur, seq) { cur.first == seq.last ? seq + cur[1..] : nil },
  ->(cur, seq) { cur.first == seq.first ? seq.reverse + cur[1..] : nil }
].freeze

Instance Method Summary collapse

Constructor Details

#initialize(way_ids, ways) ⇒ WayChain

Creates a new WayChain from way IDs and a way lookup table.

Parameters:

  • way_ids (Array<Integer>) —

    IDs of the ways to chain

  • ways (Hash{Integer => Hash}) —

    way lookup table



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# File 'lib/underpass/way_chain.rb', line 21

def initialize(way_ids, ways)
  @sequences = way_ids.filter_map do |way_id|
    way = ways[way_id]
    next unless way

    way[:nodes].dup
  end
end

Instance Method Details

#merged_sequences ⇒ Array<Array<Integer>>

Merges node sequences that share endpoints into continuous rings.

Returns:

  • (Array<Array<Integer>>) —

    the merged node ID sequences



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# File 'lib/underpass/way_chain.rb', line 33

def merged_sequences
  return @sequences if @sequences.empty?

  remaining = @sequences.dup
  current = remaining.shift
  current, remaining = merge_all(current, remaining)
  [current, *remaining]
end