# Heading parser factory
class MdHeadingParserFactory
	super MdBlockParserFactory

	redef fun try_start(state, matched_block_parser) do
		if state.indent >= 4 then return null

		var next_non_space = state.next_non_space_index
		var line = state.line_string
		var paragraph = null
		if matched_block_parser isa MdParagraphParser then
			paragraph = matched_block_parser.content
		end

		var line_content = line.substring(next_non_space, line.length - next_non_space)
		var match = line_content.search(re_atx_heading)
		if match != null then
			# ATX heading
			var new_offset = next_non_space + match.subs.first.as(not null).length
			var level = match.subs.first.as(not null).to_s.trim.length
			# remove trailing ###s
			var after_leading = line.substring(new_offset, line.length - new_offset)
			var trailing = after_leading.search(re_atx_trailing)
			var has_trailing = trailing != null
			var trailing_length = if trailing != null then trailing.length else 0
			var content = after_leading.replace(re_atx_trailing, "")
			return (new MdBlockStart(
				[new MdHeadingParser(
					state.line,
					next_non_space + 1,
					new_offset + 1,
					state.line,
					new_offset + content.length + trailing_length,
					level,
					content,
					has_trailing, false)])
				).at_index(line.length)
		end

		if paragraph ==  null then return null

		match = line_content.search(re_setext_heading)
		if match == null then return null
		var level = 2
		if match.subs.first.as(not null).to_s.chars.first == '=' then level = 1
		var content = paragraph.to_s
		return (new MdBlockStart(
			[new MdHeadingParser(
				state.line - 1,
				next_non_space + 1,
				0,
				state.line,
				state.column + match.length,
				level,
				content,
				false, true)])
			).at_index(line.length).replacing_active_block_parser
	end
end