#!/usr/bin/perl

# dwim (do what i mean) is my own plan9-like plumber

use v5.24;
use warnings;
use strict;
use subs qw/arguments dir env fail handle path run/;

my ($DEBUG, $handler, $phrase);

while ($_ = shift @ARGV) {
	if (/^-d$/) {
		$DEBUG = 1;
	} elsif (/^-/) {
		die "usage: $0 [-d] [phrase]\n";
	} else {
		$phrase = $_;
	}
}

$phrase = `xsel -o` if not defined $phrase;

my @OPENER		= ('xtopen');
my @EDITOR		= (@OPENER, 'vi');
my @PDF_VIEWER		= ('xpdf');
my @MAN_VIEWER		= (@OPENER, 'man');
my @MAILER		= (@OPENER, 'mutt');
my @BROWSER		= (@OPENER, 'w3m -title');
my @FILE_BROWSER	= ('rox');
my @MAILDIR_VIEWER	= (@OPENER, 'mutt -f');
my $MAILROOT		= env MAILROOT => '/home/john/mail/';

for ($phrase) {
	if (/^(https?:\/?\/?\S+)$/) {
		handle 'web address';
		run @BROWSER, $1
	}

	if (/^(mailto:\S+)$/ or /^(\S+@.+\.\w+)$/) {
		handle 'e-mail address';
		run @MAILER, $1
	}

	if (/^(.+?):(\d+).*?$/) {
		handle 'file:line (like grep -n)';
		my $p = path $1;
		run @EDITOR, "+$2", $p
	}

	if (/^(.+) line (\d+)\.?$/) {
		handle 'FILE line LINE (like perl)';
		my $p = path $1;
		run @EDITOR, "+$2", $p
	}

	if (/^(.+):(.+)$/) {
		handle 'file:query (like grep)';
		my $p = path $1;
		run @EDITOR, "+/$2", $p if -e $p;
		fail 'file not found' if $DEBUG;
		# otherwise fall through
	}

	if (/^([-_A-Za-z]+)\((\d+)\)[):,.]*$/) {
		handle 'manual(section)';
		run @MAN_VIEWER, $2, $1;
	}

	if (/^([-_A-Za-z]+)\.([1-9])$/) {
		handle 'manual.section';
		my $p = path "$1.$2";
		run @MAN_VIEWER, $p if -e $p;
		run @MAN_VIEWER, $2, $1;
	}

	if (/^([A-Za-z_][A-Za-z0-9_]*)\(/) {
		handle 'function(call';
		my $dir = dir;
		s/\(.*//;
		for (`grep -n '^$_' "$dir"/*.c "$dir"/*.h`) {
			run @EDITOR, "+$2", $1 if /([^:]+):(\d+):/;
		}
	}

	if (/^<(\S+)>$/) {
		handle '<header.h>';
		open my $h, 'find / -maxdepth 3 -type d -name include 2>&-|'
			or fail 'could not search include directories';
		while (<$h>) {
			chomp;
			if (-e "$_/$1") {
				close $h;
				run @EDITOR, "$_/$1";
			}
		}
		close $h;
		fail 'header file not found';
	}

	if (/^(\S+)$/) {
		handle 'maildir / directory / file';
		my $p = path $1;
		run @MAILDIR_VIEWER, $p if $p =~ /^$MAILROOT/; # maildir
		run @FILE_BROWSER, $p if -d $p; # directory
		run @PDF_VIEWER, $p if -e $p and $p =~ /\.pdf$/; # pdf
		run @EDITOR, $p if -e $p; # file
		fail 'file not found' if $DEBUG;
		# otherwise fall through
	}

	# otherwise
	die "no handler matched by: $phrase\n"
}

sub dir {
	for (`xtitle`) {
		chomp;
		s/.*\(([^(]+)\)$/$1/;
		s,^~([^/]+),/home/$1,;
		s,^~,/home/$ENV{USER},;
		die "couldn't retrieve current directory\n"
			if ! -d $_ and ! -d ($_ = dirname($_));
		return $_;
	}
	die "couldn't retrieve current directory: xtitle not installed\n";
}

sub path {
	my $n = shift;
	$n =~ s,^~([^/]+),/home/$1,;
	$n =~ s,^~,/home/$ENV{USER},;
	return $n if $n =~ /^\// or $n =~ /^~/;
	return dir . "/$n";
}

# take K => V and return environment variable K if defined, otherwise V
sub env {
	my %h = @_;
	my $k = (keys %h)[0];
	return $ENV{$k} if defined ${ENV}{$k};
	return $h{$k};
}

sub handle {
	$handler = shift;
	print STDERR "$handler MATCHED\n" if $DEBUG;
}

sub fail {
	my $msg = shift;
	print STDERR "$handler FAILED: $msg\n";
}

sub run {
	if ($DEBUG) {
		my @argv = @_;
		s/(\s)/\\$1/g for @argv; # escape whitespace
		print STDERR "@argv\n";
	}
	system "@_ &";
	exit;
}

sub dirname {
	my $path = shift;
	$path =~ s,/[^/]+,,;
	return $path;
}