#! /usr/bin/perl

#
# FXData
# manages all data regarding currencies 
#
#

package FXData;

#use LWP::Simple;
use strict;


my $URL = "http://finance.yahoo.com/d/quotes.csv?s=%s=X&f=sl1d1t1ba&e=.csv";

# FXData(fx rate file name, currency file name)
sub new {
    my $class = shift;
    my $self = {};

    $self->{rate_file} = shift;  # fx transactions file
    $self->{cur_file}  = shift;	 # currencies file

    # listing of currency symbols (keys)
    # and descriptions (values)
    $self->{listing} = {};

    # just the currency symbols.
    $self->{symbols} = []; 

    # table of all fx transactions
    # available.
    $self->{spot_table} = {};

    $self->{field_sep} = ":"; 
    
    bless ($self, $class);

    $self->load();

    return $self;
}

# set_rate_file(rate file name)
sub set_rate_file {
    my $self = shift;
    $self->{rate_file} = shift;
}

# set_currency_file(currency file name)
sub set_currency_file {
    my $self = shift;
    $self->{cur_file} = shift;
}

# down_load()
# download data from Yahoo! finance.
sub down_load {
    my $self = shift;

    my @symlist = @{$self->{symbols}};

    my %fx_table;

    my $from_sym;
    foreach $from_sym (@symlist) {
        my $to_sym;
        foreach $to_sym (@symlist) {
            next if $from_sym eq $to_sym;

            my $url = sprintf $URL, $from_sym . $to_sym;

            my @data = split ",", `./wget.py "$url"`; 

            $data[0] =~ /"(.*?)\=/;

            my $pair = $1; # pairs of currencies like USDJPY
            my $rate = $data[1]; # spot rate

            $fx_table{$pair} = $rate;
        }
    }
    $self->{rate_table} = {%fx_table};
    $self->dump_spotrates();
}

# utility method for writing a hash table into a file
sub write_table {
    my $self = shift;
    my $filename = shift;
    my %data = @_;

    open FILE, ">$filename" || die $!;

    my $key;
    while ($key = each %data) {
        print FILE "$key", $self->{field_sep}, $data{$key}, "\n";
    }

    close FILE;
}

# utility method for reading a table from 
# a file and loading it into a hash data structure.
sub read_table {
    my $self = shift;
    my $filename = shift;

    open FILE, $filename || die "could not open file $filename$!";

    my %table = ();
    while (<FILE>) {
    	chomp;
        my ($key, $val) = split $self->{field_sep};
        $table{$key} = $val;
    }

    close FILE;
    return %table;
}

# load_currencies()
# loads currency file
sub load_currencies {
    my $self = shift;
    $self->{listing} = {$self->read_table($self->{cur_file})};
    $self->{symbols} = [keys %{$self->{listing}}];
}

# load_spotrates()
# loads fx rates file
sub load_spotrates {
    my $self = shift;
    $self->{rate_table} = {$self->read_table($self->{rate_file})};
}

# dump_currencies()
# writes currency file
sub dump_currencies {
    my $self = shift;
    $self->write_table($self->{cur_file}, 
                       %{$self->{listing}}
                      );
}

# dump_spotrates()
# writes rates file
sub dump_spotrates {
    my $self = shift;
    $self->write_table($self->{rate_file}, 
                       %{$self->{rate_table}}
                      );
}

# load()
# loads all files and downloads
# data if none exists 
sub load {
    my $self = shift;
    $self->down_load() unless -e $self->{rate_file}; 
    $self->load_currencies();
    $self->load_spotrates();
}

#
# Public Functions
#

# sync_rates()
# updates fx rates
sub sync_rates {
    my $self = shift;
    unlink $self->{rate_file};
    $self->down_load();
    $self->dump_spotrates();
}

# currency_listing()
# returns a hashtable of currency 
# listings of the format { SYMBOL => DESCRIPTION }
sub currency_listing {
    my $self = shift;
    return $self->{listing};
}

# rate_table()
# returns a hash table of currency pairs
# and their exchange rate in the format
# { S1S2 => Rate }
# S1 = currency exchanging from
# S2 = currency exchanging to
sub rate_table {
    my $self = shift;
    return %{$self->{rate_table}};
}



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