From 4d080bacd8c91e145d0f99672d12c785c3e38491 Mon Sep 17 00:00:00 2001
From: Pavel Shevaev <pacha.shevaev@gmail.com>
Date: Tue, 25 Feb 2025 20:03:52 +0300
Subject: [PATCH] Better parsing error reporting

---
 jzon.inc.php | 55 +++++++++++++++++++++++++++++++---------------------
 1 file changed, 33 insertions(+), 22 deletions(-)

diff --git a/jzon.inc.php b/jzon.inc.php
index d9e493b..76e0a37 100644
--- a/jzon.inc.php
+++ b/jzon.inc.php
@@ -6,29 +6,38 @@ if(!defined('JZON_VERSION'))
   define('JZON_EXT_VERSION', phpversion('jzon'));
 }
 
-function jzon_show_position($p, $in, $context_chars)
+function jzon_show_position(int $p, string $in, int $context_lines = 5) : string
 {
-  $pre = str_replace("\n", '', jzon_get_past_input($p, $in, $context_chars));
-  $c = str_repeat('-', max(0, strlen($pre) - 1));
+  $out = array();
+  $lines = explode("\n", $in);
+  //let's find out the maximum leading zeros for line numbers
+  $fmt_num = (int)round(log10(count($lines)));
+  foreach($lines as $line_idx => $line)
+  {
+    //adding line numbers and handling tabs
+    $out[] = sprintf('%0'.$fmt_num.'d', $line_idx) . ' ' . str_replace("\t", "    ", $line);
+    $left = $p - (strlen($line) + 1/*taking into account \n*/);
+    //var_dump($left, $p, $line, $fmt_num);
+    if($left < 0)
+    {
+      $arrow = str_repeat('-', $fmt_num) . '-'; //line numbers
+      for($i=0;$i<$p;++$i)
+        $arrow .= ($line[$i] === "\t" ? '----' : '-');
+      $arrow .= '^';
 
-  return $pre . str_replace("\n", '', jzon_get_upcoming_input($p, $in, $context_chars)) . "\n" . $c . "^";
-}
-
-function jzon_get_past_input($c, $in, $context_chars)
-{
-  $past = substr($in, 0, $c+1);
-  return (strlen($past) > $context_chars ? '...' : '') . substr($past, -$context_chars);
-}
-
-function jzon_get_upcoming_input($c, $in, $context_chars)
-{
-  $next = substr($in, $c+1);
-  return substr($next, 0, $context_chars) . (strlen($next) > $context_chars ? '...' : '');
+      $out[] = $arrow;
+      break;
+    }
+    $p = $left;
+  }
+  if(count($out) > $context_lines)
+    $out = array_slice($out, -$context_lines);
+  return implode("\n", $out);
 }
 
 class jzonParser
 {
-  const ERR_CONTEXT_CHARS = 200;
+  const ERR_CONTEXT_LINES = 5;
 
   private $in;
   private $len;
@@ -86,9 +95,9 @@ class jzonParser
   private function _error($error)
   {
     if($this->c < $this->len)
-      throw new Exception("Parse error: $error\n" . jzon_show_position($this->c, $this->in, self::ERR_CONTEXT_CHARS));
+      throw new Exception("Parse error: $error\n" . jzon_show_position($this->c, $this->in, self::ERR_CONTEXT_LINES));
     else
-      throw new Exception("Parse error: $error\n" . jzon_show_position($this->len-1, $this->in, self::ERR_CONTEXT_CHARS));
+      throw new Exception("Parse error: $error\n" . jzon_show_position($this->len-1, $this->in, self::ERR_CONTEXT_LINES));
   }
 
   private function skip_whitespace()
@@ -337,13 +346,13 @@ class jzonParser
     else
       $this->_error("'null' expected");
   }
-
 }
 
-function jzon_parse($str)
+function jzon_parse($str, ?int &$parser = null) : array
 {
   //NOTE: using super fast built-in implementation and making a gracefull fallback to a slower and
   //      more relaxed implementation
+  $parser = 1;
   $res = json_decode($str, true);
   if(is_array($res))
     return $res;
@@ -351,13 +360,15 @@ function jzon_parse($str)
   //NOTE: only allowing extension implementation if versions match
   if(defined('JZON_EXT_VERSION') && JZON_EXT_VERSION === JZON_VERSION)
   {
+    $parser = 2;
     list($ok, $err, $err_pos, $res) = jzon_parse_c($str);
     if(!$ok)
-      throw new Exception($err . "\n" . jzon_show_position($err_pos, $str, jzonParser::ERR_CONTEXT_CHARS));
+      throw new Exception($err . "\n" . jzon_show_position($err_pos, $str, jzonParser::ERR_CONTEXT_LINES));
     return $res;
   }
   else
   {
+    $parser = 3;
     $p = new jzonParser($str);
     $res = $p->parse();
     return $res;