Class: Gitlab::Triage::ExpandCondition::Expansion

Inherits:
Object
  • Object
show all
Defined in:
lib/gitlab/triage/expand_condition/expansion.rb

Instance Method Summary collapse

Constructor Details

#initialize(pattern, &compile) ⇒ Expansion

into a list of results.

Please see the comments for #perform to see actual example.



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# File 'lib/gitlab/triage/expand_condition/expansion.rb', line 12

def initialize(pattern, &compile)
  @pattern = pattern
  @compile = compile
end

Instance Method Details

#expand(string, items) ⇒ Object

This recursive method does the heavy lifting. It substitutes the sequence patterns in a string with a picked number from the sequence, and collect all the results. Here’s an example:

expand(“a:Gitlab::Triage::ExpandCondition::Expansion.0.0..1:Gitlab::Triage::ExpandCondition::Expansion.2.2..3”, [0..1, 2..3])

This means that we want to pick the numbers from the sequences, and fill them back to the string containing the pattern in the respective order. We don’t care which pattern it is because the order should have spoken for it. The result will be:

%w[

a:0:2
a:0:3
a:1:2
a:1:3

]

We start by picking the first sequence, which is 0..1 here. We want all the possible picks, thus we flat_map on it, substituting the first pattern with the picked number. This means we get:

“a:0:Gitlab::Triage::ExpandCondition::Expansion.2.2..3”

For the first iteration. Before we jump to the next pick from the sequence, we recursively do this again on the current string, which only has one sequence pattern left. It will be called like:

expand(“a:0:Gitlab::Triage::ExpandCondition::Expansion.2.2..3”, [2..3])

Because we also dropped the first sequence we have already used. On the next recursive call, we don’t have any sequences left, therefore we just return the current string: “a:0:2”.

Flattening the recursion, it might look like this:

(0..1).flat_map do |x|

(2..3).flat_map do |y|
  "a:{0..1}:{2..3}".sub(PATTERN, x.to_s).sub(PATTERN, y.to_s)
end

end

So here we could clearly see that we go deep first, substituting the least significant pattern first, and then go back to the previous one, until there’s nothing more to pick.



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# File 'lib/gitlab/triage/expand_condition/expansion.rb', line 191

def expand(string, items)
  if items.empty?
    [string]
  else
    remainings = items.drop(1)

    items.first.flat_map do |item|
      expand(string.sub(@pattern, item.to_s), remainings)
    end
  end
end

#expand_patterns(string) ⇒ Object

This method expands the string from the sequences. For example, giving it “a:Gitlab::Triage::ExpandCondition::Expansion.0.0..1:Gitlab::Triage::ExpandCondition::Expansion.2.2..3” will return:

%w[

a:0:2
a:0:3
a:1:2
a:1:3

]



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# File 'lib/gitlab/triage/expand_condition/expansion.rb', line 134

def expand_patterns(string)
  expand(string, scan_patterns(string))
end

#perform(strings) ⇒ Object

This method will take a list of strings, which contains some kind of pattern, described by @pattern and expand them into each possible matches via @compile. For example, suppose @pattern is:

/\{(\d+)\.\.(\d+)\}/

And @compile is:

do |(lower, upper)|
  Integer(lower)..Integer(upper)
end

And the input is:

  • a:Gitlab::Triage::ExpandCondition::Expansion.0.0..1

  • b:Gitlab::Triage::ExpandCondition::Expansion.2.2..3

  • c

The result would be:

    • a:0

    • b:2

    • c

    • a:0

    • b:3

    • c

    • a:1

    • b:2

    • c

    • a:1

    • b:3

    • c

We get this by picking the 1st number from the 1st string, which is 0 from “a:Gitlab::Triage::ExpandCondition::Expansion.0.0..1”, and the 1st number from the 2nd string, which is 2 from “b:Gitlab::Triage::ExpandCondition::Expansion.2.2..3”, and since the 3rd string is just a fixed string, we just pick it.

This way we have the first possible match, that is:

  • a:0

  • b:2

  • c

Then we repeat the process by picking the next number for the next possible match, starting from the least significant string, which is c, but there’s nothing more to pick. Then we go to the next one, which will be the 2nd string: “b:Gitlab::Triage::ExpandCondition::Expansion.2.2..3”, and we pick the 2nd number for it: 3. Since we have a new pick, we have a new possible match:

  • a:0

  • b:3

  • c

Again we repeat the process, and 2nd string doesn’t have more choices therefore we need to go to the 1st string now. When this happens, we’ll need to reset the picks from the previous string, thus 2nd string will go back to 2. The next number for the 1st string is 1, and then we form the new match:

  • a:1

  • b:2

  • c

The next step will be the last match by picking the next number from the 2nd string again: 3, and we get:

  • a:1

  • b:3

  • c

The method will stop here because it had walked through all the possible combinations. The total number of results is the product of numbers of sequences.

Note that a string can contain multiple sequences, and it will also walk through them one by one. For example, given:

  • a:Gitlab::Triage::ExpandCondition::Expansion.0.0..1:Gitlab::Triage::ExpandCondition::Expansion.2.2..3

  • c

We’ll get:

    • a:0:2

    • c

    • a:0:3

    • c

    • a:1:2

    • c

    • a:1:3

    • c



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# File 'lib/gitlab/triage/expand_condition/expansion.rb', line 110

def perform(strings)
  expanded_strings =
    strings.map(&:strip).map(&method(:expand_patterns))

  product_of_all(expanded_strings)
end

#product_of_all(expanded_strings) ⇒ Object

This method returns the product of list of lists. For example, giving it [%w[a:0 a:1], %w[b:2 b:3], %w] will return:

%w[a:0 b:2 c], %w[a:0 b:3 c], %w[a:1 b:2 c], %w[a:1 b:3 c] 


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# File 'lib/gitlab/triage/expand_condition/expansion.rb', line 121

def product_of_all(expanded_strings)
  expanded_strings.first.product(*expanded_strings.drop(1))
end

#scan_patterns(string) ⇒ Object

This method extracts the sequences from the string. For example, giving it “a:Gitlab::Triage::ExpandCondition::Expansion.0.0..1:Gitlab::Triage::ExpandCondition::Expansion.2.2..3” will return:

0..1, 2..3 


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# File 'lib/gitlab/triage/expand_condition/expansion.rb', line 142

def scan_patterns(string)
  string.scan(@pattern).map(&@compile)
end