1 files changed, 142 insertions, 0 deletions
diff --git a/json-format.pl b/json-format.pl
new file mode 100755
index 0000000..feeb77f
--- /dev/null
+++ b/json-format.pl
@@ -0,0 +1,142 @@
+#!/usr/bin/env perl
+# To speed up processing of large files, GNU parallel can be used:
+#   $ parallel --pipe -k json-format.pl INPUT
+use strict;
+use warnings;
+use Term::ANSIColor;
+use Getopt::Long;
+
+my $reset = color('reset');
+my %format = (
+  FIELD  => color('bold'),
+  NULL   => color('cyan'),
+  BOOL   => color('red'),
+  NUMBER => color('magenta'),
+  STRING => color('blue'),
+  ERROR  => color('bold white on_red'),
+);
+
+my $color = 'auto';
+my $help;
+if (!GetOptions('color=s' => \$color, 'help' => \$help) || $help) {
+  print STDERR
+    "Usage: $0 [OPTION...] [FILE...]\n" .
+	"Pretty-print and colorify JSON\n" .
+    "\n" .
+    "  --help         print this help\n" .
+    "  --color=COLOR  'always', 'never' or 'auto' (the default)\n";
+  exit 2;
+}
+
+%format = ()
+  if $color eq 'never' || $color eq 'auto' && !-t STDOUT;
+
+# Hash lookup is the fastest way to qualify tokens, however it cannot be used
+# for everything and we need to fall back to regular expressions
+my %lookup = (
+  '[' => 'LBRACKET', '{' => 'LBRACE',
+  ']' => 'RBRACKET', '}' => 'RBRACE',
+  ':' => 'COLON', ',' => 'COMMA',
+  'true' => 'BOOL', 'false' => 'BOOL', 'null' => 'NULL',
+);
+my @pats = (
+  ['"(?:[^\\\\"]*|\\\\(?:u[\da-f]{4}|["\\\\/bfnrt]))*"' => 'STRING'],
+  ['-?\d+(?:\.\d+)?(?:[eE][-+]?\d+)?' => 'NUMBER'],
+  ['[ \t\r\n]+' => 'WS'],
+);
+my @tokens = map {[qr/^$_->[0]$/s, $_->[1]]} @pats;
+
+# m//g is the fastest way to explode text into tokens in the first place
+# and we need to construct an all-encompassing regular expression for it
+my @all_pats = map {$_->[0]} @pats;
+push @all_pats, quotemeta for keys %lookup;
+my $any_token = qr/\G(${\join '|', @all_pats})/;
+
+# FIXME: this probably shouldn't be a global variable
+my $indent = 0;
+
+sub nexttoken ($) {
+  my $ref = shift;
+  return unless @$ref;
+  my $text = shift @$ref;
+  if (my $s = $lookup{$text}) {
+    return $s, $text;
+  }
+  for my $s (@tokens) {
+    return $s->[1], $text if $text =~ $s->[0];
+  }
+  return 'ERROR', $text;
+}
+
+sub printindent () {
+  print "\n";
+  print '  ' x $indent;
+}
+
+sub do_value ($$$);
+sub do_object ($) {
+  my $json = shift;
+  my $in_field_name = 1;
+  while (my ($token, $text) = nexttoken $json) {
+    if ($token eq 'COLON') {
+      $in_field_name = 0;
+    } elsif ($token eq 'COMMA') {
+      $in_field_name = 1;
+    } elsif ($token eq 'STRING') {
+      $token = 'FIELD' if $in_field_name;
+    }
+    if ($token eq 'RBRACE') {
+      $indent--;
+      printindent;
+    }
+    do_value $token, $text, $json;
+    return if $token eq 'RBRACE';
+  }
+}
+
+sub do_array ($) {
+  my $json = shift;
+  while (my ($token, $text) = nexttoken $json) {
+    if ($token eq 'RBRACKET') {
+      $indent--;
+      printindent;
+    }
+    do_value $token, $text, $json;
+    return if $token eq 'RBRACKET';
+  }
+}
+
+sub do_value ($$$) {
+  my ($token, $text, $json) = @_;
+  if (my $format = $format{$token}) {
+    print $format, $text, $reset;
+  } else {
+    print $text;
+  }
+  if ($token eq 'LBRACE') {
+    $indent++;
+    printindent;
+    do_object $json;
+  } elsif ($token eq 'LBRACKET') {
+    $indent++;
+    printindent;
+    do_array $json;
+  } elsif ($token eq 'COMMA') {
+    printindent;
+  } elsif ($token eq 'COLON') {
+    print ' ';
+  }
+}
+
+while (<>) {
+    my $json = $_;
+
+    my @matches = $json =~ /$any_token/gsc;
+    push @matches, substr $json, pos $json
+      if pos $json != length $json;
+    while (my ($token, $text) = nexttoken \@matches) {
+      next if $token eq 'WS';
+      do_value $token, $text, \@matches;
+    }
+    print "\n";
+}