64030a40ac
This should help Twitter's horribly broken URL detection algorithm not screw up shortlinks from OSM.
41 lines
1.7 KiB
Ruby
41 lines
1.7 KiB
Ruby
require File.dirname(__FILE__) + '/../test_helper'
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class ShortLinkTest < ActiveSupport::TestCase
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##
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# tests that encoding and decoding are working to within
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# the acceptable quantisation range.
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def test_encode_decode
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cases = Array.new
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1000.times do
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cases << [ 180.0 * rand - 90.0, 360.0 * rand - 180.0, (18 * rand).to_i ]
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end
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cases.each do |lat, lon, zoom|
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lon2, lat2, zoom2 = ShortLink.decode(ShortLink.encode(lon, lat, zoom))
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# zooms should be identical
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assert_equal zoom, zoom2, "Decoding a encoded short link gives different zoom for (#{lat}, #{lon}, #{zoom})."
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# but the location has a quantisation error introduced at roughly
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# one pixel (i.e: zoom + 8). the sqrt(5) is because each position
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# has an extra bit of accuracy in the lat coordinate, due to the
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# smaller range.
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distance = Math.sqrt((lat - lat2) ** 2 + (lon - lon2) ** 2)
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max_distance = 360.0 / (1 << (zoom + 8)) * 0.5 * Math.sqrt(5)
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assert max_distance > distance, "Maximum expected error exceeded: #{max_distance} <= #{distance} for (#{lat}, #{lon}, #{zoom})."
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end
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end
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##
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# test that links are backwards-compatible, so any old links with
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# the deprecated @ characters in them still work properly.
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def test_deprecated_at_sign
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cases = [["~v2juONc--", "@v2juONc--"],
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["as3I3GpG~-", "as3I3GpG@-"],
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["D~hV--", "D@hV--"],
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["CO0O~m8--", "CO0O@m8--"]]
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cases.each do |new_code, old_code|
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assert_equal ShortLink.decode(old_code), ShortLink.decode(new_code),
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"old (#{old_code}) and new (#{new_code}) should decode to the same location."
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end
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end
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end
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