require 'cairo'
require 'date'

# Convert milimeter to postscript points
def mm2pt(mm) (mm.to_f*360.0)/127.0 end

# Convert a weekday number to a string (sunday is 0)
$weekdays = ['Sø', 'Ma', 'Ti', 'On', 'To', 'Fr', 'Lø']
$months   = ['Januar', 'Februar', 'Marts',
             'April', 'Maj', 'Juni',
             'Juli', 'August', 'September',
             'Oktober', 'November', 'December']

# A collection of events
# You can add an event like
#   events = Events.new
#   date = Date.new(2008, 12, 31)
#   events[date, "New years eve")
# You can now get a list of events for a given day by calling
#   anotherdate = Date.new(2009, 12, 31)
#   e = events[anotherdate]
# Which will return the string from all events (separated by comma)
# matching the day and month, but not the year.
class Events
	# Internal class describing a single event
	class Event
		def initialize(date, str)
			@date = date
			@str = str
		end
		attr_accessor :date, :str
	end
	
	# Create a new list of events
	def initialize
		@events = []
	end
	
	# Look up descriptions of events matching the day and month of the
	# given date. If multiple events exists for that day, they are
	# separated by comma
	def [](date)
		events = []
		for e in @events
			if e.date.month == date.month and e.date.mday == date.mday
				events << e.str
			end
		end
		events.join(', ')
	end
	
	# Add an event to the list
	def []=(date, description)
		e = Event.new(date, description)
		@events << e
	end
end

# An abstraction for Cairo
class GraphicsContext
	# Initialize the graphics context
	def initialize(cr)
		@cr = cr
	end
	
	# Set the color. The supported colors are :black, :white, :lightgray
	# and :darkgray
	def color=(color)
		case color
			when :black     then r = g = b = 0.0
			when :white     then r = g = b = 1.0
			when :lightgray then r = g = b = 0.8
			when :darkgray  then r = g = b = 0.5
			else raise 'Unsupported color'
		end
		@cr.set_source_rgb(r, g, b)
	end
	
	# Set the linewidth. The supported sizes are :thin and :thick
	def line_width=(width)
		case width
			when :thin  then w = 0.15
			when :thick then w = 1.0
			else raise 'Unsupported line width'
		end
		@cr.set_line_width(w)
	end
	
	# Set the font size
	def font_size=(size)
		@cr.set_font_size(size)
	end
	
	# Set the font options (:normal, :bold, :italic)
	def font_options(*options)
		weight = Cairo::FONT_WEIGHT_NORMAL
		slant  = Cairo::FONT_SLANT_NORMAL
		for o in options
			case o
				when :bold   then weight = Cairo::FONT_WEIGHT_BOLD
				when :italic then slant = Cairo::FONT_SLANT_ITALIC
			end
		end
		@cr.select_font_face('sans-serif', slant, weight)
	end
	
	# Draw a line
	def line(x1, y1, x2, y2)
		@cr.move_to(x1, y1)
		@cr.line_to(x2, y2)
		@cr.stroke
	end
	
	# Draw a rectangle
	def rectangle(x1, y1, x2, y2)
		@cr.rectangle(x1, y1, x2 - x1, y2 - y1)
		@cr.fill
	end
	
	# Display some text, and return the x-position where the following
	# text will be placed.
	def text(x, y, str, angle = 0.0)
		radians = angle*Math::PI/180.0
		w, h, a = text_size(str)
		@cr.move_to(x, y)
		@cr.rotate(radians)
		@cr.show_text(str)
		@cr.rotate(-radians)
		return x + w + a
	end
	
	# Return the dimensions of some text
	def text_size(str)
		e = @cr.text_extents(str)
		return e.width, e.height, e.x_advance - e.width
	end
	
	# Return information about a font
	def font_extents
		e = @cr.font_extents
		return e.ascent, e.descent, e.height
	end
end

class Page
	# Draw an empty page (this will be overriden by subclasses)
	def draw(gc,
	         width, height,
	         margin_top, margin_bottom,
	         margin_left, margin_right)
	end
end

# The front page of the calendar
class FrontPage < Page
	# Initialize with the year to display on the front page
	def initialize(title, year)
		@title = title
		@year  = year
	end
	def draw(gc,
	         width, height,
	         margin_top, margin_botom,
	         margin_left, margin_right)
		# Find the position and size
		gc.font_size = 1
		w, h, a = gc.text_size(@title + @year.to_s)
		gc.font_size = (width - margin_left - margin_right)/w
		w, h, a = gc.text_size(@title + @year.to_s)
		x = margin_left
		y = height/2.0 - h
		
		# Show the text
		gc.color = :black
		x = gc.text(x, y,  @title)
		gc.color = :darkgray
		gc.text(x, y, @year.to_s)
	end
end

class NotePage < Page
	def draw(gc,
	         width, height,
	         margin_top, margin_bottom,
	         margin_left, margin_right)
		line_height = (height - margin_top - margin_bottom)/32.0
		
		# Draw the thick line in the top
		gc.color = :black
		gc.line_width = :thick
		x1 = margin_left
		x2 = width - margin_right
		y  = margin_top + line_height
		gc.line(x1, y, x2, y)
		
		# Draw the rest of the lines
		for line in 1..32
			# Draw a thin horizontal line
			x1 = margin_left
			x2 = width - margin_right
			y  = margin_top + line*line_height
			gc.color      = :black
			gc.line_width = :thin
			gc.line(x1, y, x2, y)
		end
	end
end

class MonthPage < Page
	def initialize(year, month, events)
		super() # Initialize the parent class
		@year   = year
		@month  = month
		@days   = []
		@events = events
		first   = Date.new(@year, @month, 1)
		last    = Date.new(@year, @month, -1)
		first.upto(last) do |date|
			@days << date
		end
	end
	@@max_date_width = nil
	@@max_wday_width = nil
	
	def draw(gc,
	         width, height,
	         margin_top, margin_bottom,
	         margin_left, margin_right)
		line_height = (height - margin_top - margin_bottom)/32.0
		
		# Draw the shaded box in weekends
		gc.color = :lightgray
		for day in @days
			# Only draw a box if it's sunday (0) or saturday (6)
			if day.wday == 0 or day.wday == 6
				x1 = margin_left
				y1 = margin_top + (day.mday)*line_height
				x2 = width - margin_right
				y2 = y1 + line_height
				gc.rectangle(x1, y1, x2, y2)
			end
		end
		
		# Calculate the max width of the date
		gc.font_size = line_height*0.8
		if @@max_date_width.nil?
			@@max_date_width = 0
			for i in 1..31
				w, h, a = gc.text_size(day.mday.to_s)
				@@max_date_width = w + a if w + a > @@max_date_width
			end
		end
		
		# Calculate the max width of weekdays
		if @@max_wday_width.nil?
			@@max_wday_width = 0
			for d in $weekdays
				w, h, a = gc.text_size(' ' + d + ' ')
				@@max_wday_width = w + a if w + a > @@max_wday_width
			end
		end
		
		# Draw the month and the year
		gc.color = :black
		gc.line_width = :thick
		x1 = margin_left
		x2 = width - margin_right
		y  = margin_top + line_height
		gc.line(x1, y, x2, y)
		gc.font_options(:bold)
		a, d, h = gc.font_extents
		gc.text(x1, y - d*2, $months[@month-1] + " #{@year}")
		
		# Draw the lines and dates
		gc.font_options(:normal)
		for day in @days
			# Draw a thin horizontal line
			x1 = margin_left
			x2 = width - margin_right
			y  = margin_top + (day.mday + 1)*line_height
			gc.color      = :black
			gc.line_width = :thin
			gc.line(x1, y, x2, y)
			
			# Draw the date and weekday
			gc.font_size = line_height*0.8
			w, h, a = gc.text_size(day.mday.to_s)
			x = margin_left + @@max_date_width - w
			y = y - line_height/2.0 + h/2.0
			x = gc.text(x, y, day.mday.to_s)
			gc.text(x , y, ' ' + $weekdays[day.wday])
			
			# Draw any events on that day
			event = @events[day]
			if event
				x = margin_left + @@max_date_width + @@max_wday_width
				gc.font_size = line_height*0.5
				gc.text(x, y, event)
			end
			
			# Draw the week number on mondays
			if day.wday == 1
				text = day.cweek.to_s
				gc.font_size = line_height*0.8
				w, h, a = gc.text_size(text)
				gc.color = :darkgray
				gc.text(width - margin_right - w, y, text)
			end
		end
	end
end

class LeftMonthPage < Page
	def initialize(year, month, events)
		super() # Initialize the parent class
		@year   = year
		@month  = month
		@days   = []
		@events = events
		first   = Date.new(@year, @month, 1)
		last    = Date.new(@year, @month, -1)
		first.upto(last) do |date|
			@days << date
		end
	end
	@@max_date_width = nil
	@@max_wday_width = nil
	
	def draw(gc,
	         width, height,
	         margin_top, margin_bottom,
	         margin_left, margin_right)
		line_height = (height - margin_top - margin_bottom)/32.0
		
		# Draw the shaded box in weekends
		gc.color = :lightgray
		for day in @days
			# Only draw a box if it's sunday (0) or saturday (6)
			if day.wday == 0 or day.wday == 6
				x1 = margin_left
				y1 = margin_top + (day.mday)*line_height
				x2 = width - margin_right
				y2 = y1 + line_height
				gc.rectangle(x1, y1, x2, y2)
			end
		end
		
		# Calculate the max width of the date
		gc.font_size = line_height*0.8
		if @@max_date_width.nil?
			@@max_date_width = 0
			for i in 1..31
				w, h, a = gc.text_size(day.mday.to_s)
				@@max_date_width = w + a if w + a > @@max_date_width
			end
		end
		
		# Calculate the max width of weekdays
		if @@max_wday_width.nil?
			@@max_wday_width = 0
			for d in $weekdays
				w, h, a = gc.text_size(' ' + d + ' ')
				@@max_wday_width = w + a if w + a > @@max_wday_width
			end
		end
		
		# Draw the month and the year
		gc.color = :black
		gc.line_width = :thick
		x1 = margin_left
		x2 = width - margin_right
		y  = margin_top + line_height
		gc.line(x1, y, x2, y)
		gc.font_options(:bold)
		a, d, h = gc.font_extents
		gc.text(x1, y - d*2, $months[@month-1] + " #{@year}")
		
		# Draw the lines and dates
		gc.font_options(:normal)
		for day in @days
			# Draw a thin horizontal line
			x1 = margin_left
			x2 = width - margin_right
			y  = margin_top + (day.mday + 1)*line_height
			gc.color      = :black
			gc.line_width = :thin
			gc.line(x1, y, x2, y)
			
			# Draw the date and weekday
			gc.font_size = line_height*0.8
			w, h, a = gc.text_size(day.mday.to_s)
			x = margin_left + @@max_date_width - w
			y = y - line_height/2.0 + h/2.0
			x = gc.text(x, y, day.mday.to_s)
			gc.text(x , y, ' ' + $weekdays[day.wday])
			
			# Draw any events on that day
			event = @events[day]
			if event
				x = margin_left + @@max_date_width + @@max_wday_width
				gc.font_size = line_height*0.5
				gc.text(x, y, event)
			end
		end
	end
end

class RightMonthPage < Page
	def initialize(year, month)
		super() # Initialize the parent class
		@year   = year
		@month  = month
		@days   = []
		first   = Date.new(@year, @month, 1)
		last    = Date.new(@year, @month, -1)
		first.upto(last) do |date|
			@days << date
		end
	end
	
	def draw(gc,
	         width, height,
	         margin_top, margin_bottom,
	         margin_left, margin_right)
		line_height = (height - margin_top - margin_bottom)/32.0
		
		# Draw the shaded box in weekends
		gc.color = :lightgray
		for day in @days
			# Only draw a box if it's sunday (0) or saturday (6)
			if day.wday == 0 or day.wday == 6
				x1 = margin_left
				y1 = margin_top + (day.mday)*line_height
				x2 = width - margin_right
				y2 = y1 + line_height
				gc.rectangle(x1, y1, x2, y2)
			end
		end
		
		# Draw the thick line on the top
		gc.color = :black
		gc.line_width = :thick
		x1 = margin_left
		x2 = width - margin_right
		y  = margin_top + line_height
		gc.line(x1, y, x2, y)
		
		# Draw the lines and dates
		gc.font_options(:normal)
		for day in @days
			# Draw a thin horizontal line
			x1 = margin_left
			x2 = width - margin_right
			y  = margin_top + (day.mday + 1)*line_height
			gc.color      = :black
			gc.line_width = :thin
			gc.line(x1, y, x2, y)
			
			# Draw the week number on mondays
			if day.wday == 1
				text = day.cweek.to_s
				gc.font_size = line_height*0.8
				w, h, a = gc.text_size(text)
				gc.color = :darkgray
				gc.text(width - margin_right - 1.5*w, y, text)
			end
		end
		
		# Draw the tab with the month name to the right
		h = height/12.0
		x1 = width - (2.0/3.0)*margin_right
		y1 = h*(@month - 1)
		x2 = width
		y2 = y1 + h
		if @month%2 == 1
			gc.color = :darkgray
		else
			gc.color = :white
		end
		gc.rectangle(x1, y1, x2, y2)
		gc.color = :black
		gc.line_width = :thin
		gc.line(x1, y2, x1, height)
		text = $months[@month - 1][0..2]
		gc.color = :black
		gc.font_size = (1.0/3.0)*margin_right
		tw, th, a = gc.text_size(text)
		x = x1 + (2.0/3.0)*margin_right/2.0 - th/2.0
		y = y1 + h/2.0 - tw/2.0
		gc.text(x, y, text, 90.0)
	end
end

# A booklet with 8 pages printed on one A4 paper
class Booklet
	# Create a new booklet with the specified dimensions (in millimeter)
	def initialize(width, height,
	               margin_top, margin_bottom,
	               margin_inner, margin_outer)
		@w      = width
		@h      = height
		@mt     = margin_top
		@mb     = margin_bottom
		@mi     = margin_inner
		@mo     = margin_outer
		@pages  = []
	end
	
	# Add a page to the booklet
	def add(page)
		@pages << page
	end
	
	# Save to booklet to a file
	def save(filename)
		# Reorder the pages
		pages = reorder
		
		# Calculate the center of the A4 paper
		cx = mm2pt(210)/2.0 + mm2pt(1)
		cy = mm2pt(297)/2.0
		
		# Create a pdf surface with the size of an A4 paper
		pdf = Cairo::PDFSurface.new(filename, mm2pt(210.0), mm2pt(297.0))
		cr  = Cairo::Context.new(pdf)
		gc  = GraphicsContext.new(cr)
		cr.translate(cx, cy)
		for n in 0..(pages.size/8)-1
			# Draw page n, n + 1, n + 4 and n + 5 on this page
			cr.save
			cr.translate(-@w, -@h)
			if n == 0
				# If it is the back page we only use outer margins
				pages[8*n + 0].draw(gc, @w, @h, @mt, @mb, @mo, @mo)
			else
				pages[8*n + 0].draw(gc, @w, @h, @mt, @mb, @mo, @mi)
			end
			cr.translate(@w, 0)
			if n == 0
				# If it is the front page we only use outer margins
				pages[8*n + 1].draw(gc, @w, @h, @mt, @mb, @mo, @mo)
			else
				pages[8*n + 1].draw(gc, @w, @h, @mt, @mb, @mi, @mo)
			end
			cr.translate(-@w, @h)
			pages[8*n + 4].draw(gc, @w, @h, @mt, @mb, @mo, @mi)
			cr.translate(@w, 0)
			pages[8*n + 5].draw(gc, @w, @h, @mt, @mb, @mi, @mo)
			cr.restore
			cr.set_line_width(0.15)
			cr.move_to(-@w - 10, 0)
			cr.line_to(+@w + 10, 0)
			cr.move_to(-@w - 10, -@h)
			cr.line_to(+@w + 10, -@h)
			cr.move_to(-@w - 10, @h)
			cr.line_to(+@w + 10, @h)
			cr.move_to(-@w, -@h - 10)
			cr.line_to(-@w, +@h + 10)
			cr.move_to(+@w, -@h - 10)
			cr.line_to(+@w, +@h + 10)
			cr.stroke
			cr.show_page
			
			# Draw page n + 2, n + 3, n + 6 and n + 7 on the next page
			# (the backside of the first page with a duplex printer)
			cr.save
			cr.translate(-@w, -@h)
			pages[8*n + 2].draw(gc, @w, @h, @mt, @mb, @mo, @mi)
			cr.translate(@w, 0)
			pages[8*n + 3].draw(gc, @w, @h, @mt, @mb, @mi, @mo)
			cr.translate(-@w, @h)
			pages[8*n + 6].draw(gc, @w, @h, @mt, @mb, @mo, @mi)
			cr.translate(@w, 0)
			pages[8*n + 7].draw(gc, @w, @h, @mt, @mb, @mi, @mo)
			cr.restore
			cr.set_line_width(0.5)
			cr.move_to(-@w - 10, 0)
			cr.line_to(+@w + 10, 0)
			cr.move_to(-@w - 10, -@h)
			cr.line_to(+@w + 10, -@h)
			cr.move_to(-@w - 10, @h)
			cr.line_to(+@w + 10, @h)
			cr.move_to(-@w, -@h - 10)
			cr.line_to(-@w, +@h + 10)
			cr.move_to(+@w, -@h - 10)
			cr.line_to(+@w, +@h + 10)
			cr.stroke
			cr.show_page
		end
	end
	
private
	
	# Add blank pages to the end, so the number of pages is divisible
	# with n. The number of pages added is returned
	def add_blanks(n)
		blank_pages = @pages.size%n
		blank_pages = n - blank_pages unless blank_pages == 0
		blank_pages.times { add(Page.new) }
		return blank_pages
	end
	
	# Return an array of reordered pages for the booklet
	def reorder
		# Add blank pages
		blanks = add_blanks(8)
		
		# Reorder the pages
		pages = []
		first = 0
		last  = @pages.size - 1
		while first < last
			pages << @pages[last]
			pages << @pages[first]
			pages << @pages[first + 1]
			pages << @pages[last - 1]
			first += 2
			last  -= 2
		end
		
		# Remove the blank pages again
		blanks.times { @pages.pop }
		
		# Return the reordered pages
		return pages
	end
end