#!/usr/bin/env ruby
# vim:encoding=UTF-8:
$KCODE = "u" if RUBY_VERSION < "1.9" # json use this

require 'uri'
require 'net/http'
require 'stringio'
require 'zlib'
require 'nkf'

class ThreadData
	class UnknownThread < StandardError; end

	attr_accessor :uri
	attr_accessor :last_modified, :size

	Line = Struct.new(:n, :name, :mail, :misc, :body, :opts, :id) do
		def aa?
			body = self.body
			return false if body.count("\n") < 3

			significants = body.scan(/[>\n0-9a-z０-９A-Zａ-ｚＡ-Ｚぁ-んァ-ン一-龠]/u).size.to_f
			body_length  = body.scan(/./u).size
			is_aa = 1 - significants / body_length

			is_aa > 0.6
		end
	end

	def initialize(thread_uri)
		@uri = URI(thread_uri)
		_, _, _, @board, @num, = *@uri.path.split('/')
		@dat = []
	end

	def length
		@dat.length
	end

	def subject
		retrieve(true) if @dat.size.zero?
		self[1].opts || ""
	end

	def [](n)
		l = @dat[n - 1]
		return nil unless l
		name, mail, misc, body, opts = * l.split(/<>/)
		id = misc[/ID:([^\s]+)/, 1]

		body.gsub!(/<br>/, "\n")
		body.gsub!(/<[^>]+>/, "")
		body.gsub!(/^\s+|\s+$/, "")
		body.gsub!(/&(gt|lt|amp|nbsp);/) {|s|
			{ 'gt' => ">", 'lt' => "<", 'amp' => "&", 'nbsp' => " " }[$1]
		}

		Line.new(n, name, mail, misc, body, opts, id)
	end

	def dat
		@num
	end

	def retrieve(force=false)
		@dat = [] if @force

		res = Net::HTTP.start(@uri.host, @uri.port) do |http|
			req = Net::HTTP::Get.new('/%s/dat/%d.dat' % [@board, @num])
			req['User-Agent']        = 'Monazilla/1.00 (2ig.rb/0.0e)'
			req['Accept-Encoding']   = 'gzip' unless @size
			unless force
				req['If-Modified-Since'] = @last_modified if @last_modified
				req['Range']             = "bytes=%d-" % @size if @size
			end

			http.request(req)
		end

		ret = nil
		case res.code.to_i
		when 200, 206
			body = res.body
			if res['Content-Encoding'] == 'gzip'
				body = StringIO.open(body, 'rb') {|io| Zlib::GzipReader.new(io).read }
			end

			@last_modified = res['Last-Modified']
			if res.code == '206'
				@size += body.size
			else
				@size  = body.size
			end

			body = NKF.nkf('-w', body)

			curr = @dat.size + 1
			@dat.concat(body.split(/\n/))
			last = @dat.size

			(curr..last).map {|n|
				self[n]
			}
		when 416 # たぶん削除が発生
			p ['416']
			retrieve(true)
			[]
		when 304 # Not modified
			[]
		when 302 # dat 落ち
			p ['302', res['Location']]
			raise UnknownThread
		else
			p ['Unknown Status:', res.code]
			[]
		end
	end

	def canonicalize_subject(subject)
		subject.gsub(/[Ａ-Ｚａ-ｚ０-９]/u) {|c|
			c.unpack("U*").map {|i| i - 65248 }.pack("U*")
		}
	end

	def guess_next_thread
		res = Net::HTTP.start(@uri.host, @uri.port) do |http|
			req = Net::HTTP::Get.new('/%s/subject.txt' % @board)
			req['User-Agent']        = 'Monazilla/1.00 (2ig.rb/0.0e)'
			http.request(req)
		end

		recent_posted_threads = (900..999).inject({}) {|r,i|
			line = self[i]
			line.body.scan(%r|ttp://#{@uri.host}/test/read.cgi/[^/]+/\d+/|).each do |uri|
				r["h#{uri}"] = i
			end if line
			r
		}

		current_subject    = canonicalize_subject(self.subject)
		current_thread_rev = current_subject.scan(/\d+/).map {|d| d.to_i }
		current            = current_subject.scan(/./u)

		body = NKF.nkf('-w', res.body)
		threads = body.split(/\n/).map {|l|
			dat, rest = *l.split(/<>/)
			dat.sub!(/\.dat$/, "")

			uri = "http://#{@uri.host}/test/read.cgi/#{@board}/#{dat}/"

			subject, n = */(.+?) \((\d+)\)/.match(rest).captures
			canonical_subject = canonicalize_subject(subject)
			thread_rev     = canonical_subject[/\d+/].to_i

			distance       = (dat     == self.dat)     ? Float::MAX :
			                 (subject == self.subject) ? 0 :
			                 levenshtein(canonical_subject.scan(/./u), current)
			continuous_num = current_thread_rev.find {|rev| rev == thread_rev - 1 }
			appear_recent  = recent_posted_threads[uri]

			score = distance
			score -= 10 if continuous_num
			score -= 10 if appear_recent
			score += 10 if dat.to_i < self.dat.to_i
			{
				:uri            => uri,
				:dat            => dat,
				:subject        => subject,
				:distance       => distance,
				:continuous_num => continuous_num,
				:appear_recent  => appear_recent,
				:score          => score.to_f
			}
		}.sort_by {|o|
			o[:score]
		}

		threads
	end

	def levenshtein(a, b)
		case
		when a.empty?
			b.length
		when b.empty?
			a.length
		when a == b
			0
		else
			d = Array.new(a.length + 1) { |s|
				Array.new(b.length + 1, 0)
			}

			(0..a.length).each do |i|
				d[i][0] = i
			end

			(0..b.length).each do |j|
				d[0][j] = j
			end

			(1..a.length).each do |i|
				(1..b.length).each do |j|
					cost = (a[i - 1] == b[j - 1]) ? 0 : 1
					d[i][j] = [
						d[i-1][j  ] + 1,
						d[i  ][j-1] + 1,
						d[i-1][j-1] + cost
					].min
				end
			end

			d[a.length][b.length]
		end
	end
end

if __FILE__ == $0
	require 'pp'
	thread = ThreadData.new(ARGV[0])
	pp thread.guess_next_thread.reverse

	p thread.subject
end