=begin
This script creates a google chart image as output given acceptable input data.
Usage:
		script <input filename> <output filename> [width [height]]

Input data record format (tab delimited):
		<ISO-date> <chicken-count> <egg-count>

Input data record example:
		2008-09-10	4	1

The chicken count is ignored at the moment and a graph with date on the X,
and egg count on the y is produced.

The only limit is the encoded URL string limit, which on the google end is probably very large.
=end

require 'date'
require 'net/http'

if ARGV.length < 2
	puts "usage: <input-filename> <output-filename> [width [heigth]]"
	exit
end

width = 640
if ARGV.length >= 3
	width = ARGV[2]
end

height = 128
if ARGV.length >= 4
	height = ARGV[3]
end

in_filename = ARGV[0]
out_filename = ARGV[1]
line_count = 0
line_count_valid = 0

date_today = DateTime.now

#pipe_char = '|'
pipe_char = '%7c'
gchart_label = ''
gchart_data = []
gchart_xlabel = ''
data_extent = { 'min' => 0, 'max' => 0 }

File.open( in_filename, "r" ) do |infile|
	while( line = infile.gets )
		line_count = line_count + 1

		#puts "#{line_count}: #{line}"
		#puts line.split( "\t" ).join( '|' )
		line_a = line.split( "\t" )

		# Example
		# 2008-09-10	4	1
		# <date> <chicken-count> <egg-count>
		if line_a.length < 3
			puts '[' + line_count.to_s() + ']: Warning: item_count=' + line_a.length.to_s + ' is not >= 3.'
			next
		end

		date_in = line_a[0]
		if ( date_in =~ /([0-9]{2,4})-([0-9]{1,2})-([0-9]{1,2})/) == nil
			puts '[' + line_count.to_s() + ']: Warning: date="' + date_in + '".'
			next
		end
		date_in_h = { 'year' => $1, 'month' => $2, 'day' => $3 }

		if date_in_h['day'].to_i == 1
			gchart_xlabel << pipe_char << date_in_h['year'] << '-' << date_in_h['month']
		else
			gchart_xlabel << pipe_char
		end
		#puts "y=#{date_in_h['year']}, m=#{date_in_h['month']}, d=#{date_in_h['day']}"
		#puts "line valid: " + line_a.join( pipe_char )

		chicken_count_in = line_a[1].to_i
		egg_count_in = line_a[2].to_i

        if egg_count_in > data_extent['max']
			data_extent['max'] = egg_count_in
		end

		gchart_data << egg_count_in

		line_count_valid = line_count_valid + 1
	end
end

gchart_ylabel = ( data_extent['min'] .. data_extent['max'] ).to_a.join( pipe_char )

# HTTP encoding
# ':' -> %3a
# ',' -> %2c
# '|' -> %7c    (is not "UNRESERVED" in ruby net/http library)
gchart_url_s =
	'/chart' \
	<< '?cht=bvg' \
	<< '&chtt=Egg%20count' \
	<< '&chs=' << width.to_s << 'x' << height.to_s \
	<< '&chxt=x%2cy' \
	<< '&chbh=a%2c0%2c0' \
	<< '&chds=0%2c' << data_extent['max'].to_s \
	<< '&chxl=' << '0%3a' << pipe_char << gchart_xlabel << pipe_char << '1%3a' << pipe_char << gchart_ylabel \
	<< '&chd=t%3a' << gchart_data.join( '%2c' )
#puts 'gchart_url_s=' + gchart_url_s

# Fetch google charts image via HTTP.
url = URI.parse( 'http://chart.apis.google.com/' )
response = Net::HTTP.start( url.host, url.port ) { |http|
	http.get( gchart_url_s )
}

# Save image to file.
File.open( out_filename, 'wb') { |f| f.write( response.body ) }