<?php

$hash = hash("md5", $_SERVER['PHP_SELF']);
$basedir = sys_get_temp_dir() . "/$hash";

if (!is_dir($basedir))
  mkdir($basedir);

try {
  function isValidFileName($filename) {
    return preg_match("/^[_a-zA-Z0-9]*\.JPG$/i", $filename) == 1;
  }

  function parseVal($s) {
    $major = strstr($s, '/', true);
    $minor = substr(strstr($s, '/'), 1);
    return intval($major) / intval($minor);
  }

  function parseDeg($val) {
    $deg = parseVal($val[0]);
    $min = parseVal($val[1]);
    $sec = parseVal($val[2]);
    return $deg + $min/60 + $sec / 3600;
  }

  function processFile($filename) {
    global $basedir;
    $cacheFile = "$basedir/$filename.geojson";

    if (!isValidFileName($filename)) {
      throw new InvalidArgumentException("Invalid file name: $filename");
    }

    if (is_readable($cacheFile)) {
      $s = file_get_contents($cacheFile);
      // echo "cacheFile=$cacheFile, s=$s\n";
      if ($s !== false) {
        $j = json_decode($s);
        if ($j !== null) {
          return $j;
        } else {
          // echo "Could not decode JSON\n";
        }
      }
    }

    $exif = exif_read_data($filename, 0, true);
    if (!$exif) {
      throw new InvalidArgumentException("Could not open file: $filename");
    }

    $json = ["type" => "Feature", "id" => $filename];

    foreach ($exif as $key => $section) {
      foreach ($section as $name => $val) {
        switch("$key.$name") {
          case "FILE.FileSize": $filesize_bytes = $val; break;
          case "COMPUTED.Height": $height = $val; break;
          case "COMPUTED.Width": $width = $val; break;
          case "GPS.GPSLongitude": $lon = parseDeg($val); break;
          case "GPS.GPSLatitude": $lat = parseDeg($val); break;
          case "IFD0.Orientation": $orientation = $val; break;
          case "EXIF.MakerNote":
          case "EXIF.ComponentsConfiguration":
          case "GPS.GPSVersion":
          case "GPS.GPSAltitudeRef":
            break;
          default:
//            echo "$key.$name=$val\n";
        }
      }
    }

    if (isset($lon) && isset($lat)) {
      $json["geometry"] = [
        "type" => "Point",
        "coordinates" => [$lon, $lat]
      ];
    }

    $properties = [
    ];
    if (isset($filesize_bytes)) {
      $properties["filesize_bytes"] = $filesize_bytes;
    }
    if (isset($height)) {
      $properties["height_px"] = $height;
    }
    if (isset($width)) {
      $properties["width_px"] = $width;
    }
    if (isset($orientation)) {
      if($orientation == 1) {
        $properties["orientation"] = 0;
      } else if($orientation == 3) {
        $properties["orientation"] = -180;
      } else if($orientation == 6) {
        $properties["orientation"] = 90;
      } else if($orientation == 8) {
        $properties["orientation"] = -90;
      }
    }
    $json["properties"] = $properties;

    $s = json_encode($json);
    file_put_contents($cacheFile, $s);

    return $json;
  }

  if (!isset($_GET["file"])) {
    $d = dir(".");
    $features = [];
    while (false !== ($entry = $d->read())) {
      if(!isValidFilename($entry)) {
        continue;
      }
      array_push($features, processFile($entry));
    }
    $json = ["type" => "FeatureCollection", "features" => $features];
  } else {
    $filename = $_GET["file"];
    $json = processFile($filename);
  }

  header('Content-Type: application/vnd.geo+json');
  header('Access-Control-Allow-Origin: *');
  echo json_encode($json, JSON_PRETTY_PRINT);
  echo "\n";
} catch(InvalidArgumentException $e) {
  header('HTTP/1.1 400 bad request');
}
?>