# YAMD
# Copyright (C) 2025 kp2pml30
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

module YAMD
	class Renderer
		attr_reader :buf

		def initialize()
			@buf = String.new
		end

		def finalize
			@buf.freeze
		end
	end

	class Output
		def initialize()
			@buf = String.new

			#@buf << "Proc.new {\n"

			@ind = 0
		end

		def add_static(s)
			return if s.empty?

			@buf << ("\t" * @ind) << "str " << s.dump << "\n"
		end

		def add_expr(e)
			@buf << ("\t" * @ind) << "str((#{e}).to_s)"
		end

		def add_code_nl(c)
			c = c.strip

			if c.start_with?("}")
				@ind -= 1
			end

			@buf << ("\t" * @ind) << c << "\n"

			if c.end_with?("{")
				@ind += 1
			end
		end

		def finalize()
			#@buf << "}"

			@buf.freeze

			@buf
		end
	end

	class State
		attr_reader :output

		def initialize(io)
			@io = io
			@lineStart = false
			@lineNo = 0
			nextLine

			@output = Output.new
		end

		def errCtx
			{
				line: @lineNo
			}
		end

		def eol?()
			@line.empty?
		end

		def eof?()
			eol? and @io.eof?
		end

		def lineStart?()
			@lineStart
		end

		def nextLine()
			@lineNo += 1

			@lineStart = true
			@line = @io.gets()
			if @line.nil?
				@line = String.new
			end

			if @line.end_with?("\n")
				@line.chop!
			end

			if @line.end_with?("\r")
				@line.chop!
			end

			@line.freeze

			line
		end

		def line()
			@line
		end

		def consume(cnt)
			@lineStart = false
			@line = @line[cnt..]
		end
	end

	class Context
		attr_reader :indent, :indent_str

		def initialize(indent)
			@indent = indent
			@indent_str = "\t" * indent
			self.freeze
		end

		def indented()
			Context.new(@indent + 1)
		end
	end

	def self.parseRaw(state, ctx)
		raw = String.new
		loop {
			if state.eof?
				break
			end
			if not state.line.start_with? ctx.indent_str
				# whitespace line == empty line
				if state.line =~ /^\s*$/
					raw << "\n"
					state.nextLine
					next
				end
				# skip comment
				if state.line =~ /^\s*#(?:|\s.*)$/
					state.nextLine
					next
				end
				break
			end

			state.consume(ctx.indent) # skip indent
			raw << state.line
			raw << "\n"
			state.nextLine
		}

		raw.rstrip!
		raw.freeze
	end

	def loopIndentedContent(state, ctx)
		loop {
			if not state.lineStart?
				yield state.line
				state.nextLine

				next
			end
			if state.line =~ /^#(?:|\s.*)$/
				state.nextLine
				#yield ' '
				next
			end
		}
	end

	def self.parseContent(state, ctx)
		strBuf = String.new

		flushStrBuf = Proc.new {
			if strBuf != ''
				if strBuf.end_with?(' ')
					strBuf.chop!
				end
				state.output.add_static(strBuf)
				strBuf = String.new
			end
		}

		addWs = Proc.new {
			if not strBuf.end_with? ' '
				strBuf << ' '
			end
		}

		prevParagraph = false

		while not state.eof?
			if state.lineStart?
				if state.line =~ /^\s*$/
					if not prevParagraph
						prevParagraph = true
						flushStrBuf.()

						state.output.add_code_nl("new_line")
					end
					state.nextLine
					next
				end

				if state.line =~ /^\s*#(?:|\s.*)$/
					addWs.()
					state.nextLine
					next
				end

				prevParagraph = false

				if not state.line.start_with?(ctx.indent_str)
					flushStrBuf.()
					return
				end

				state.consume(ctx.indent)
				if state.line.start_with?("\t")
					raise "unexpected indent at #{state.errCtx}"
				end

				if state.line.start_with?("#!")
					flushStrBuf.()
					state.consume(2)

					state.output.add_code_nl("" + state.line.strip + " {")
					state.nextLine
					parseContent(state, ctx.indented)
					state.output.add_code_nl("}")

					next
				elsif state.line.start_with?('#$')
					flushStrBuf.()
					state.consume(2)

					line = state.line.strip
					state.nextLine
					state.output.add_code_nl("" + line.strip + " {")
					state.output.add_code_nl("next " + parseRaw(state, ctx.indented).dump)
					state.output.add_code_nl("}")

					next
				elsif state.line.start_with?("#%")
					flushStrBuf.()

					state.consume(2)

					state.output.add_code_nl(state.line)

					state.nextLine
					next
				elsif state.line.start_with?("#. ") or state.line == "#."
					flushStrBuf.()
					state.consume(2)

					state.output.add_code_nl("list_item {")
					parseContent state, ctx.indented
					state.output.add_code_nl("}")

					next
				end
			end

			prevParagraph = false

			if state.eol?
				addWs.()
				state.nextLine
			elsif state.line.start_with?('##')
				strBuf << '#'
				state.consume 2
			elsif state.line.start_with?('}#')
				flushStrBuf.()

				return
			elsif state.line[0] == '#'
				state.output.add_static(strBuf)
				strBuf = String.new

				self.handle_hash state, ctx
			else
				strBuf << state.line[0]
				state.consume 1
			end
		end

		flushStrBuf.()
	end

	def self.handle_hash(state, ctx)
		if state.line.start_with?('#`')
			state.consume(2)
			code = String.new
			while state.line.size > 0 and state.line[0] != '`'
				code << state.line[0]
				state.consume 1
			end
			if not state.line.start_with?('`')
				raise "unterminated \#` at #{state.errCtx}"
			end
			state.consume 1
			state.output.add_code_nl("inline_code(#{code.dump})")
		elsif state.line.start_with?('#{')
			state.consume 2
			expr = read_balanced(state, ctx)
			if not state.line.start_with?('}')
				raise "unterminated \#{} at #{state.errCtx}"
			end
			state.consume 1

			state.output.add_expr expr
		elsif state.line.start_with?('#(')
			state.consume 2
			expr = read_balanced(state, ctx)
			if not state.line.start_with?(')')
				raise "unterminated \#() at #{state.errCtx}"
			end
			state.consume 1

			state.output.add_code_nl "inline_math #{expr.dump}"
		elsif state.line.start_with?(/^\#[a-zA-Z_]/)
			exprBuf = String.new
			state.consume 1

			while not state.line.empty?
				if state.line[0] == '('
					exprBuf << '('
					state.consume 1
					exprBuf << read_balanced(state, ctx)
					raise "unbalanced () at #{state.errCtx}" if state.line[0] != ')'
					state.consume 1
					exprBuf << ')'
				elsif state.line.start_with?('#{')
					state.consume 2
					exprBuf << " {"
					state.output.add_code_nl(exprBuf)

					while state.line[0] == ' '
						state.consume 1
					end

					self.parseContent(state, ctx.indented)

					raise "unmatched \#{ }\# at #{state.errCtx}" if not state.line.start_with?('}#')
					state.consume 2
					state.output.add_code_nl("}")

					return
				else
					exprBuf << state.line[0]
					state.consume 1
				end
			end
			state.output.add_code_nl exprBuf
			# expression
		else
			raise "unexpected hash at #{state.errCtx}"
		end
	end

	def self.read_balanced(state, ctx)
		ret = String.new

		stack = []

		flipper = {
			"(" => ")",
			"{" => "}",
		}

		revFlipper = {}
		flipper.each { |k, v|
			revFlipper[v] = k
		}

		while state.line.size > 0 and state.line[0] != '`'
			chr = state.line[0]

			fromFlipper = flipper[chr]
			fromRevFlipper = revFlipper[chr]

			if not fromFlipper.nil?
				stack.push fromFlipper
			end
			if not fromRevFlipper.nil?
				return ret.freeze if stack.empty?

				have = stack.pop
				if have != chr
					raise "unbalanced #{have}, got #{chr}"
				end
			end

			ret << chr
			state.consume 1
		end

		ret.freeze
	end
end