#!/usr/bin/perl

use File::Basename;
use File::Find;
use Digest::SHA qw(sha1_hex);

# This script is designed to introspect C files and generate a makefile to use.

sub header_deps {
  my $file = @_[0];
  my @headers;

  if (open(my $fh, '<:encoding(UTF-8)', $file)) {
    print STDERR "\x1b[35m[Trace] - Reading file $file\x1b[00m\n";
    push(@headers, $file);

    while (<$fh>) {
      /#include\s+"(.*)"\s*$/ && push(@headers, header_deps("include/$1"));
    }
  }

  return @headers;
}

my @files;
find(sub {
    push @files, "$File::Find::name" if $_ =~ /.*\.c/
  }, "src/");

my @test_files;
find(sub {
    push @test_files, "$File::Find::name" if $_ =~ /.*\.c/
  }, "tests/");

my @header_files;
find(sub {
    push @header_files, "$File::Find::name" if $_ =~ /.*\.h/;
  }, "include/" );

my $idempotency_hash=sha1_hex("@files @test_files @header_files");

if ("$ARGV[0]" eq "hash") {
  print "$idempotency_hash\n";
  exit 0
}

my @obj_files;

open(my $fh, '<:encoding(UTF-8)', "Makefile.preamble")
    or die "Missing Makefile.preamble";

while (<$fh>) {
  print "$_";
}

# Emit a rule that will rerun genmake if the c files do not match.
my $idempotency_cmd_make =
    "/usr/bin/perl ./genmake.pl hash";

print "IDEMPOTENCY_HASH=$idempotency_hash\n";

my $arch_obs_dir = "_\$(PREFIX)_obs";
print "CHEAT_PRE_MAKE := \$(shell mkdir -p $arch_obs_dir)\n";

foreach $file (@files) {
  my $c_file = $file;
  (my $file_no_ext = $file) =~ s/src\/(.*)\.c$/\1/g;

  my $obj_file = "$arch_obs_dir/${file_no_ext}.o";
  my $s_file = "${file_no_ext}.s";

  push(@obj_files, $obj_file);
  my @deps = header_deps($c_file);

  my $deps_as_join = join(" ", @deps);

  # Emit the rule to make the object file.
  print "$obj_file: $deps_as_join\n\t";
  print "\@mkdir -p " . dirname($obj_file) . "\n\t";
  print '$(CC) -c ' . $c_file . ' -o ' . $obj_file . ' $(CFLAGS)' . "\n\n";

  # Emit the rule to make the assembly file.
  print "$s_file: $deps_as_join\n\t";
  print "\@mkdir -p " . dirname($obj_file) . "\n\t";
  print '$(CC) -S ' . $c_file . ' -o ' . $s_file . ' $(CFLAGS)' . "\n\n";
}

my $obj_files_deps = join(' ', @obj_files);

my @tests_tgts;
foreach $file (@test_files) {
  my $c_file = $file;

  my($basename, $directories, $suffix) = fileparse($file, qr/\.[^.]*/);

  my $outdir = $directories . "build/";
  my $outbinary = $outdir . $basename;

  my @deps = header_deps($c_file);
  my $deps_as_join = join(" ", @deps);

  push (@test_tgts, "${outbinary}");
  print "${outbinary}: $deps_as_join $obj_files_deps test_harness/test_harness.a\n\t";
  print "mkdir -p " . dirname($outbinary) . "\n\t";
  print '$(CC) $(CFLAGS) -o' . ${outbinary} . ' ' . $c_file . ' ' . $obj_files_deps . " test_harness/test_harness.a\n\n";

  print "$directories$basename:\n\t";
  print 'mkdir -p ' . $outdir . "\n\t";
  print 'PREFIX=$(TEST_PREFIX) CFLAGS="$(TEST_CFLAGS)" $(MAKE) ' . $outbinary . "\n\t";
  print $outbinary . "\n\n";
}

print "test_harness/test_harness.a: test_harness/test_harness.h test_harness/test_harness.c\n\t";
print 'cd test_harness; $(MAKE) test_harness.a; cd ..' . "\n\n";

print "tests_: " . join(" ", @test_tgts) . "\n\t";
print "" . join("\n\t", @test_tgts) . "\n\n";

print ".PHONY: tests\n";
print "tests:\n\t";
print 'PREFIX=$(TEST_PREFIX) CFLAGS="$(TEST_CFLAGS)" $(MAKE) tests_' . "\n\n";

print "FORCE:\n\t\n\n";
print "$arch_obs_dir/main.elf: FORCE $obj_files_deps linker/linker_script.ld\n\t";
print "([ \"\$\$($idempotency_cmd_make)\" != \"\$(IDEMPOTENCY_HASH)\" ] "
        . "&& ./genmake.pl > Makefile && make $arch_obs_dir/main.elf ) "
        . "|| "
        . "\$(LD) -o $arch_obs_dir/main.elf \$(LD_FLAGS) $obj_files_deps\n\n";