Class: DiffLineMapper

Inherits:
Object
  • Object
show all
Defined in:
lib/vimamsa/diff_buffer.rb

Overview

Map a “line number in a unified diff output” to the corresponding line in the new/changed file (the + side), together with the file it belongs to.

Handles multi-file diffs: each — / +++ pair sets the active file; each @@ hunk header resets the line counters. Walking hunk lines:

' ' => old++, new++
'-' => old++
'+' => new++

Returns [new_path, old_path, line_no] or nil for deleted / unmappable lines.

Constant Summary collapse

HUNK_RE = 
/^@@\s+-(\d+)(?:,(\d+))?\s+\+(\d+)(?:,(\d+))?\s+@@/

Instance Method Summary collapse

Constructor Details

#initialize(diff_text) ⇒ DiffLineMapper

Returns a new instance of DiffLineMapper.



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# File 'lib/vimamsa/diff_buffer.rb', line 15

def initialize(diff_text)
  @lines = diff_text.lines
end

Instance Method Details

#new_line_for_diff_lineno(diff_lineno) ⇒ Object

Given a 1-based line number in the diff output, return:

- [new_path, old_path, Integer]: raw +++ path, raw --- path, 1-based new-file line
- nil: if the diff line is a deletion ('-') or cannot be mapped

Raises:

  • (ArgumentError) 


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# File 'lib/vimamsa/diff_buffer.rb', line 22

def new_line_for_diff_lineno(diff_lineno)
  raise ArgumentError, "diff line number must be >= 1" if diff_lineno.to_i < 1
  idx = diff_lineno.to_i - 1
  return nil if idx >= @lines.length

  old_path = nil
  new_path = nil
  old = nil
  new_ = nil
  in_hunk = false

  @lines.each_with_index do |line, i|
    # File headers reset hunk state and record current file paths.
    # These appear outside hunks, but guard against malformed diffs too.
    if line.start_with?('--- ')
      old_path = line[4..].split("\t").first.strip
      in_hunk = false
      old = new_ = nil
      next
    end

    if line.start_with?('+++ ')
      new_path = line[4..].split("\t").first.strip
      in_hunk = false
      old = new_ = nil
      next
    end

    if (m = line.match(HUNK_RE))
      old = m[1].to_i
      new_ = m[3].to_i
      in_hunk = true
      next
    end

    next unless in_hunk

    if i == idx
      return nil unless new_
      case line.getbyte(0)
      when '+'.ord then return [new_path, old_path, new_]
      when ' '.ord then return [new_path, old_path, new_]
      when '-'.ord then return nil
      else              return nil
      end
    end

    next unless old && new_

    case line.getbyte(0)
    when ' '.ord then old += 1; new_ += 1
    when '-'.ord then old += 1
    when '+'.ord then new_ += 1
    end
  end

  nil
end