Module: ObjectPatch::Generator

Defined in:
lib/object_patch/generator.rb

Overview

This module handles the generation of patches between two objects.

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.array_compare(src_ary, tgt_ary, current_path) ⇒ Object 



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# File 'lib/object_patch/generator.rb', line 64

def array_compare(src_ary, tgt_ary, current_path)
  operations = []

  if src_ary.size > tgt_ary.size
    # We'll need to remove some elements
    base_size = tgt_ary.size
    src_ary[base_size..-1].each_with_index do |itm, idx|
      path = Pointer.encode(current_path + Array(base_size + idx))
      operations.push(
        Operations::Test.new("path" => path, "value" => src_ary[base_size + idx]),
        Operations::Remove.new("path" => path)
      )
    end
  elsif src_ary.size < tgt_ary.size
    # We'll need to add some elements
    base_size = tgt_ary.size
    src_ary[base_size..-1].each_with_index do |itm, idx|
      path = Pointer.encode(current_path + Array(base_size + idx))
      operations.push(
        Operations::Add.new("path" => path, "value" => tgt_ary[base_size + idx]),
      )
    end
  end

  # Compare the existing values in the array
  smallest_length = (src_ary.size > tgt_ary.size) ? tgt_ary.size : src_ary.size
  smallest_length.times do |n|
    # Handle arrays and hashes in a special way as their values are
    # potentially not going to be able to hold up to a comparison.
    if src_ary[n].is_a?(Array) || src_ary[n].is_a?(Hash) || tgt_ary[n].is_a?(Array) || tgt_ary[n].is_a?(Hash)
      operations.push(*generate(src_ary[n], tgt_ary[n], current_path + Array(n)))
      next
    end

    # We've gotten the complicated cases out, this is a simple test and
    # replace.
    unless src_ary[n] == tgt_ary[n]
      path = Pointer.encode(current_path + Array(n))
      operations.push(
        Operations::Test.new("path" => path, "value" => src_ary[n]),
        Operations::Replace.new("path" => path, "value" => tgt_ary[n]),
      )
    end
  end

  operations
end

.generate(source, target, current_path = []) ⇒ Array<Hash>

TODO:

This doesn’t do anything yet…

Generate a series of patch operations that describe the changes from the source object to the target object.

Parameters:

  • source (Object) —

    The source document

  • target (Object) —

    The target document we’ll generate the differences for.

Returns:

  • (Array<Hash>) 


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# File 'lib/object_patch/generator.rb', line 15

def generate(source, target, current_path = [])
  if source.class != target.class
    # The simplest of cases is that we have incompatible types, in which
    # case we'll full replace the root. This of course could be optimized
    # for situations where the root as moved to a child element but that is
    # harder to detect...
    return [Operations::Replace.new("path" => Pointer.encode(current_path), "value" => target)]
  end

  case source.class.to_s
  when "Hash"
    return hash_compare(source, target, current_path)
  when "Array"
    return array_compare(source, target, current_path)
  else
    # A scaler value
    return [] if source == target
    return [Operations::Replace.new("path" => Pointer.encode(current_path), "value" => target)]
  end
end

.hash_compare(src_hash, tgt_hash, current_path) ⇒ Object 



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# File 'lib/object_patch/generator.rb', line 36

def hash_compare(src_hash, tgt_hash, current_path)
  operations = []

  # Keys to remove
  (src_hash.keys - tgt_hash.keys).each do |k|
    path = Pointer.encode(current_path + Array(k))
    operations.push(
      Operations::Test.new("path" => path, "value" => src_hash[k]),
      Operations::Remove.new("path" => path)
    )
  end

  # Missing keys to add
  (tgt_hash.keys - src_hash.keys).each do |k|
    path = Pointer.encode(current_path + Array(k))
    operations.push(
      Operations::Add.new("path" => path, "value" => tgt_hash[k])
    )
  end

  # When both hashes share the same key we need to go deeper...
  (src_hash.keys & tgt_hash.keys).each do |k|
    operations += generate(src_hash[k], tgt_hash[k], current_path + Array(k))
  end

  operations
end

Instance Method Details

#array_compare(src_ary, tgt_ary, current_path) ⇒ Object (private) 



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# File 'lib/object_patch/generator.rb', line 64

def array_compare(src_ary, tgt_ary, current_path)
  operations = []

  if src_ary.size > tgt_ary.size
    # We'll need to remove some elements
    base_size = tgt_ary.size
    src_ary[base_size..-1].each_with_index do |itm, idx|
      path = Pointer.encode(current_path + Array(base_size + idx))
      operations.push(
        Operations::Test.new("path" => path, "value" => src_ary[base_size + idx]),
        Operations::Remove.new("path" => path)
      )
    end
  elsif src_ary.size < tgt_ary.size
    # We'll need to add some elements
    base_size = tgt_ary.size
    src_ary[base_size..-1].each_with_index do |itm, idx|
      path = Pointer.encode(current_path + Array(base_size + idx))
      operations.push(
        Operations::Add.new("path" => path, "value" => tgt_ary[base_size + idx]),
      )
    end
  end

  # Compare the existing values in the array
  smallest_length = (src_ary.size > tgt_ary.size) ? tgt_ary.size : src_ary.size
  smallest_length.times do |n|
    # Handle arrays and hashes in a special way as their values are
    # potentially not going to be able to hold up to a comparison.
    if src_ary[n].is_a?(Array) || src_ary[n].is_a?(Hash) || tgt_ary[n].is_a?(Array) || tgt_ary[n].is_a?(Hash)
      operations.push(*generate(src_ary[n], tgt_ary[n], current_path + Array(n)))
      next
    end

    # We've gotten the complicated cases out, this is a simple test and
    # replace.
    unless src_ary[n] == tgt_ary[n]
      path = Pointer.encode(current_path + Array(n))
      operations.push(
        Operations::Test.new("path" => path, "value" => src_ary[n]),
        Operations::Replace.new("path" => path, "value" => tgt_ary[n]),
      )
    end
  end

  operations
end

#generate(source, target, current_path = []) ⇒ Array<Hash> (private)

TODO:

This doesn’t do anything yet…

Generate a series of patch operations that describe the changes from the source object to the target object.

Parameters:

  • source (Object) —

    The source document

  • target (Object) —

    The target document we’ll generate the differences for.

Returns:

  • (Array<Hash>) 


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# File 'lib/object_patch/generator.rb', line 15

def generate(source, target, current_path = [])
  if source.class != target.class
    # The simplest of cases is that we have incompatible types, in which
    # case we'll full replace the root. This of course could be optimized
    # for situations where the root as moved to a child element but that is
    # harder to detect...
    return [Operations::Replace.new("path" => Pointer.encode(current_path), "value" => target)]
  end

  case source.class.to_s
  when "Hash"
    return hash_compare(source, target, current_path)
  when "Array"
    return array_compare(source, target, current_path)
  else
    # A scaler value
    return [] if source == target
    return [Operations::Replace.new("path" => Pointer.encode(current_path), "value" => target)]
  end
end

#hash_compare(src_hash, tgt_hash, current_path) ⇒ Object (private) 



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# File 'lib/object_patch/generator.rb', line 36

def hash_compare(src_hash, tgt_hash, current_path)
  operations = []

  # Keys to remove
  (src_hash.keys - tgt_hash.keys).each do |k|
    path = Pointer.encode(current_path + Array(k))
    operations.push(
      Operations::Test.new("path" => path, "value" => src_hash[k]),
      Operations::Remove.new("path" => path)
    )
  end

  # Missing keys to add
  (tgt_hash.keys - src_hash.keys).each do |k|
    path = Pointer.encode(current_path + Array(k))
    operations.push(
      Operations::Add.new("path" => path, "value" => tgt_hash[k])
    )
  end

  # When both hashes share the same key we need to go deeper...
  (src_hash.keys & tgt_hash.keys).each do |k|
    operations += generate(src_hash[k], tgt_hash[k], current_path + Array(k))
  end

  operations
end