Module: Textus::Protocol::Diff

Defined in:
lib/textus/protocol/diff.rb

Class Method Summary collapse

Class Method Details

.backtrack(trace, x_pos, y_pos) ⇒ Object 



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# File 'lib/textus/protocol/diff.rb', line 67

def backtrack(trace, x_pos, y_pos)
  script = []
  d = trace.size - 1
  return script if d.negative?

  k = x_pos - y_pos
  while d.positive?
    prev_v = trace[d - 1]
    prev_k = if k == -d || (k != d && (prev_v[k - 1] || -1) < (prev_v[k + 1] || -1))
               k + 1
             else
               k - 1
             end
    prev_x = prev_v[prev_k] || 0
    prev_y = prev_x - prev_k

    while x_pos > prev_x && y_pos > prev_y
      script.unshift([:eq, x_pos - 1, y_pos - 1])
      x_pos -= 1
      y_pos -= 1
    end

    if x_pos > prev_x
      script.unshift([:del, x_pos - 1, nil])
      x_pos -= 1
    elsif y_pos > prev_y
      script.unshift([:ins, nil, y_pos - 1])
      y_pos -= 1
    end

    d -= 1
    k = prev_k
    x_pos = prev_x
    y_pos = prev_y
  end

  script
end

.body(a_text, b_text) ⇒ Object 



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# File 'lib/textus/protocol/diff.rb', line 6

def body(a_text, b_text)
  a_lines = (a_text || "").lines.map(&:chomp)
  b_lines = (b_text || "").lines.map(&:chomp)
  hunks = build_hunks(myers_diff(a_lines, b_lines), a_lines, b_lines)
  { "type" => "body", "hunks" => hunks, "stats" => stats(hunks) }
end

.build_hunks(script, a_lines, b_lines) ⇒ Object 



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# File 'lib/textus/protocol/diff.rb', line 106

def build_hunks(script, a_lines, b_lines)
  return [] if script.empty?

  hunks = []
  i = 0
  while i < script.size
    next_context = find_next_change(script, i)
    break unless next_context

    start = [next_context - 3, 0].max
    hunk_end_script = find_hunk_end(script, next_context)
    hunk_end = [hunk_end_script + 3, script.size - 1].min

    a_start = nil
    b_start = nil
    a_lines_hunk = []
    b_lines_hunk = []

    (start..hunk_end).each do |j|
      op, ai, bi = script[j]
      a_start ||= ai if ai
      b_start ||= bi if bi

      case op
      when :eq
        a_lines_hunk << { "type" => "context", "line" => a_lines[ai] }
        b_lines_hunk << { "type" => "context", "line" => b_lines[bi] }
      when :del
        a_lines_hunk << { "type" => "deletion", "line" => a_lines[ai] }
      when :ins
        b_lines_hunk << { "type" => "addition", "line" => b_lines[bi] }
      end
    end

    hunks << {
      "a_start" => a_start, "b_start" => b_start,
      "a_lines" => a_lines_hunk, "b_lines" => b_lines_hunk
    }

    i = hunk_end + 1
  end

  hunks
end

.find_hunk_end(script, from) ⇒ Object 



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# File 'lib/textus/protocol/diff.rb', line 155

def find_hunk_end(script, from)
  last_change = from
  (from...[script.size, from + 6].min).each do |i|
    last_change = i if script[i][0] != :eq
  end
  last_change
end

.find_next_change(script, from) ⇒ Object 



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# File 'lib/textus/protocol/diff.rb', line 151

def find_next_change(script, from)
  (from...script.size).find { |i| script[i][0] != :eq }
end

.meta(a_hash, b_hash) ⇒ Object 



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# File 'lib/textus/protocol/diff.rb', line 13

def meta(a_hash, b_hash)
  a = a_hash || {}
  b = b_hash || {}
  all_keys = (a.keys + b.keys).uniq.sort
  changes = all_keys.filter_map do |k|
    av = a[k]
    bv = b[k]
    next if av == bv

    { "key" => k.to_s, "old" => av, "new" => bv }
  end
  { "type" => "meta", "changes" => changes, "stats" => { "changed" => changes.size } }
end

.myers_diff(a_lines, b_lines) ⇒ Object 



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# File 'lib/textus/protocol/diff.rb', line 39

def myers_diff(a_lines, b_lines)
  a_count = a_lines.size
  b_count = b_lines.size
  max_d = a_count + b_count
  v = Hash.new(0)
  v[1] = 0
  trace = []

  (0..max_d).each do |d|
    (-d..d).step(2).each do |k|
      x = if k == -d || (k != d && v[k - 1] < v[k + 1])
            v[k + 1]
          else
            v[k - 1] + 1
          end
      y = x - k
      while x < a_count && y < b_count && a_lines[x] == b_lines[y]
        x += 1
        y += 1
      end
      v[k] = x
      return backtrack(trace, x, y) if x >= a_count && y >= b_count
    end
    trace << v.dup
  end
  []
end

.schema(a_schema, b_schema) ⇒ Object 



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# File 'lib/textus/protocol/diff.rb', line 27

def schema(a_schema, b_schema)
  meta(a_schema, b_schema).merge("type" => "schema")
end

.stats(hunks) ⇒ Object 



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# File 'lib/textus/protocol/diff.rb', line 163

def stats(hunks)
  additions = hunks.sum { |h| h["b_lines"].count { |l| l["type"] == "addition" } }
  deletions = hunks.sum { |h| h["a_lines"].count { |l| l["type"] == "deletion" } }
  { "additions" => additions, "deletions" => deletions, "hunks" => hunks.size }
end

.summary(diff_result) ⇒ Object 



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# File 'lib/textus/protocol/diff.rb', line 31

def summary(diff_result)
  parts = []
  parts << "#{diff_result.dig("body", "stats", "additions") || 0}+" if diff_result["body"]
  parts << "#{diff_result.dig("body", "stats", "deletions") || 0}-" if diff_result["body"]
  parts << "#{diff_result.dig("meta", "stats", "changed") || 0}~" if diff_result["meta"]
  parts.join(" ")
end