# class SyntaxSuggest::AroundBlockScan

This class is useful for exploring contents before and after a block

It searches above and below the passed in block to match for whatever criteria you give it:

Example:

    def dog         # 1
      puts "bark"   # 2
      puts "bark"   # 3
    end             # 4

    scan = AroundBlockScan.new(
      code_lines: code_lines
      block: CodeBlock.new(lines: code_lines[1])
    )

    scan.scan_while { true }

    puts scan.before_index # => 0
    puts scan.after_index  # => 3

### Public Class Methods

new (code_lines:, block:)
Source

    # File lib/syntax_suggest/around_block_scan.rb, line 30
    def initialize(code_lines:, block:)
      @code_lines = code_lines
      @orig_indent = block.current_indent

      @stop_after_kw = false
      @force_add_empty = false
      @force_add_hidden = false
      @target_indent = nil

      @scanner = ScanHistory.new(code_lines: code_lines, block: block)
    end

### Public Instance Methods

code_block ()
Source

    # File lib/syntax_suggest/around_block_scan.rb, line 217
    def code_block
      CodeBlock.new(lines: lines)
    end

Return the currently matched lines as a ‘CodeBlock`

When a ‘CodeBlock` is created it will gather metadata about itself, so this is not a free conversion. Avoid allocating more CodeBlock’s than needed

force_add_empty ()
Source

    # File lib/syntax_suggest/around_block_scan.rb, line 60
    def force_add_empty
      @force_add_empty = true
      self
    end

When using this flag, ‘scan_while` will bypass the block it’s given and always add a line that responds truthy to ‘CodeLine#empty?`

Empty lines contain no code, only whitespace such as leading spaces a newline.

force_add_hidden ()
Source

    # File lib/syntax_suggest/around_block_scan.rb, line 49
    def force_add_hidden
      @force_add_hidden = true
      self
    end

When using this flag, ‘scan_while` will bypass the block it’s given and always add a line that responds truthy to ‘CodeLine#hidden?`

Lines are hidden when they’ve been evaluated by the parser as part of a block and found to contain valid code.

inspect ()
Source

    # File lib/syntax_suggest/around_block_scan.rb, line 228
    def inspect
      "#<#{self.class}:0x0000123843lol >"
    end

Manageable rspec errors

lines ()
Source

    # File lib/syntax_suggest/around_block_scan.rb, line 223
    def lines
      @scanner.lines
    end

Returns the lines matched by the current scan as an array of CodeLines

lookahead_balance_one_line ()
Source

    # File lib/syntax_suggest/around_block_scan.rb, line 141
    def lookahead_balance_one_line
      kw_count = 0
      end_count = 0
      lines.each do |line|
        kw_count += 1 if line.is_kw?
        end_count += 1 if line.is_end?
      end

      return self if kw_count == end_count # nothing to balance

      @scanner.commit_if_changed # Rollback point if we don't find anything to optimize

      # Try to eat up empty lines
      @scanner.scan(
        up: ->(line, _, _) { line.hidden? || line.empty? },
        down: ->(line, _, _) { line.hidden? || line.empty? }
      )

      # More ends than keywords, check if we can balance expanding up
      next_up = @scanner.next_up
      next_down = @scanner.next_down
      case end_count - kw_count
      when 1
        if next_up&.is_kw? && next_up.indent >= @target_indent
          @scanner.scan(
            up: ->(line, _, _) { line == next_up },
            down: ->(line, _, _) { false }
          )
          @scanner.commit_if_changed
        end
      when -1
        if next_down&.is_end? && next_down.indent >= @target_indent
          @scanner.scan(
            up: ->(line, _, _) { false },
            down: ->(line, _, _) { line == next_down }
          )
          @scanner.commit_if_changed
        end
      end
      # Rollback any uncommitted changes
      @scanner.stash_changes

      self
    end

Scanning is intentionally conservative because we have no way of rolling back an aggressive block (at this time)

If a block was stopped for some trivial reason, (like an empty line) but the next line would have caused it to be balanced then we can check that condition and grab just one more line either up or down.

For example, below if we’re scanning up, line 2 might cause the scanning to stop. This is because empty lines might denote logical breaks where the user intended to chunk code which is a good place to stop and check validity. Unfortunately it also means we might have a “dangling” keyword or end.

    1 def bark
    2
    3 end

If lines 2 and 3 are in the block, then when this method is run it would see it is unbalanced, but that acquiring line 1 would make it balanced, so that’s what it does.

scan_adjacent_indent ()
Source

    # File lib/syntax_suggest/around_block_scan.rb, line 200
    def scan_adjacent_indent
      before_after_indent = []

      before_after_indent << (@scanner.next_up&.indent || 0)
      before_after_indent << (@scanner.next_down&.indent || 0)

      @target_indent = before_after_indent.min
      scan_while { |line| line.not_empty? && line.indent >= @target_indent }

      self
    end

Scan blocks based on indentation of next line above/below block

Determines indentaion of the next line above/below the current block.

Normally this is called when a block has expanded to capture all “neighbors” at the same (or greater) indentation and needs to expand out. For example the ‘def/end` lines surrounding a method.

scan_neighbors_not_empty ()
Source

    # File lib/syntax_suggest/around_block_scan.rb, line 188
    def scan_neighbors_not_empty
      @target_indent = @orig_indent
      scan_while { |line| line.not_empty? && line.indent >= @target_indent }
    end

Finds code lines at the same or greater indentation and adds them to the block

scan_while () { |line| ... }
Source

    # File lib/syntax_suggest/around_block_scan.rb, line 88
    def scan_while
      stop_next_up = false
      stop_next_down = false

      @scanner.scan(
        up: ->(line, kw_count, end_count) {
          next false if stop_next_up
          next true if @force_add_hidden && line.hidden?
          next true if @force_add_empty && line.empty?

          if @stop_after_kw && kw_count > end_count
            stop_next_up = true
          end

          yield line
        },
        down: ->(line, kw_count, end_count) {
          next false if stop_next_down
          next true if @force_add_hidden && line.hidden?
          next true if @force_add_empty && line.empty?

          if @stop_after_kw && end_count > kw_count
            stop_next_down = true
          end

          yield line
        }
      )

      self
    end

Main work method

The `scan_while` method takes a block that yields lines above and below the block. If the yield returns true, the @before_index or @after_index are modified to include the matched line.

In addition to yielding individual lines, the internals of this object give a mini DSL to handle common situations such as stopping if we’ve found a keyword/end mis-match in one direction or the other.

stop_after_kw ()
Source

    # File lib/syntax_suggest/around_block_scan.rb, line 73
    def stop_after_kw
      @stop_after_kw = true
      self
    end

Tells ‘scan_while` to look for mismatched keyword/end-s

When scanning up, if we see more keywords then end-s it will stop. This might happen when scanning outside of a method body. the first scan line up would be a keyword and this setting would trigger a stop.

When scanning down, stop if there are more end-s than keywords.