/+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  Mallard 0.1
  An object-oriented CGI platform.
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  Getting/setting environment variables via the Environment singleton.
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module mallard.environment;

/+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  Imports
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// standard imports
private import std.string   ;
private import std.c.stdlib ; // for getenv()

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  Aliases
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alias std.string.toString stdToString;

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  Externs
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private extern(C) int putenv(char*);

/+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  Constants
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// CGI environment variable names - useful to make typos compile-time errors
public const char[]
  DOCUMENT_ROOT         = `DOCUMENT_ROOT`         ,
  GATEWAY_INTERFACE     = `GATEWAY_INTERFACE`     ,
  HTTP_ACCEPT           = `HTTP_ACCEPT`           ,
  HTTP_ACCEPT_CHARSET   = `HTTP_ACCEPT_CHARSET`   ,
  HTTP_ACCEPT_ENCODING  = `HTTP_ACCEPT_ENCODING`  ,
  HTTP_ACCEPT_LANGUAGE  = `HTTP_ACCEPT_LANGUAGE`  ,
  HTTP_CONNECTION       = `HTTP_CONNECTION`       ,
  HTTP_HOST             = `HTTP_HOST`             ,
  HTTP_KEEP_ALIVE       = `HTTP_KEEP_ALIVE`       ,
  HTTP_USER_AGENT       = `HTTP_USER_AGENT`       ,
  PATH_INFO             = `PATH_INFO`             ,
  PATH_TRANSLATED       = `PATH_TRANSLATED`       ,
  QUERY_STRING          = `QUERY_STRING`          ,
  REDIRECT_QUERY_STRING = `REDIRECT_QUERY_STRING` ,
  REDIRECT_STATUS       = `REDIRECT_STATUS`       ,
  REDIRECT_URL          = `REDIRECT_URL`          ,
  REMOTE_ADDR           = `REMOTE_ADDR`           ,
  REMOTE_PORT           = `REMOTE_PORT`           ,
  REQUEST_METHOD        = `REQUEST_METHOD`        ,
  REQUEST_URI           = `REQUEST_URI`           ,
  SCRIPT_FILENAME       = `SCRIPT_FILENAME`       ,
  SCRIPT_NAME           = `SCRIPT_NAME`           ,
  SERVER_ADDR           = `SERVER_ADDR`           ,
  SERVER_ADMIN          = `SERVER_ADMIN`          ,
  SERVER_NAME           = `SERVER_NAME`           ,
  SERVER_PORT           = `SERVER_PORT`           ,
  SERVER_PROTOCOL       = `SERVER_PROTOCOL`       ,
  SERVER_SIGNATURE      = `SERVER_SIGNATURE`      ,
  SERVER_SOFTWARE       = `SERVER_SOFTWARE`       ;

/+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  Singleton Environment
  TODO:
    Implement a method to enumerate the entire environment (or a least its keys).
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public abstract class Environment { static:

  /+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    Getting environment variable values.
    NOTE: Defaults to an empty string.
    USAGE:
      char[] var;
      var = Environment.get("some key");
      var = Environment["some key"];
  +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++/
  public char[] get (in char[] key) {
    return stdToString(getenv(toStringz(key)));
  }

  public alias get opIndex;

  /+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    Setting environment variable values.
    USAGE:
      char[] key = "some key", value = "some value";
      Environment.set(key, value);
      Environment[key] = value;
  +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++/
  public int set (in char[] key, in char[] value) {
    return putenv(toStringz(format("%s=%s", key, value)));
  }

  // can't use alias because the params are backward to support variable-length keysets
  public int opIndexAssign (in char[] value, in char[] key) {
    return set(key, value);
  }

  /+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    An array of the CGI keys.  Can be useful for stepping through them all easily.
    For an example, see the opApply overload below.
  +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++/
  public const char[][] STD_CGI_KEYS = [
    DOCUMENT_ROOT         ,
    GATEWAY_INTERFACE     ,
    HTTP_ACCEPT           ,
    HTTP_ACCEPT_CHARSET   ,
    HTTP_ACCEPT_ENCODING  ,
    HTTP_ACCEPT_LANGUAGE  ,
    HTTP_CONNECTION       ,
    HTTP_HOST             ,
    HTTP_KEEP_ALIVE       ,
    HTTP_USER_AGENT       ,
    PATH_INFO             ,
    PATH_TRANSLATED       ,
    QUERY_STRING          ,
    REDIRECT_QUERY_STRING ,
    REDIRECT_STATUS       ,
    REDIRECT_URL          ,
    REMOTE_ADDR           ,
    REMOTE_PORT           ,
    REQUEST_METHOD        ,
    REQUEST_URI           ,
    SCRIPT_FILENAME       ,
    SCRIPT_NAME           ,
    SERVER_ADDR           ,
    SERVER_ADMIN          ,
    SERVER_NAME           ,
    SERVER_PORT           ,
    SERVER_PROTOCOL       ,
    SERVER_SIGNATURE      ,
    SERVER_SOFTWARE       
  ];

  // For array-like syntax.  Some people like that.
  public alias STD_CGI_KEYS keys;

  /+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    Make the Environment foreach'able.
    Just steps through the standard CGI keys.
  +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++/
  // for just keys
  public int opApply(int delegate(inout char[]) dg) {
    int result ;

    foreach (char[] key; STD_CGI_KEYS) {
      result = dg(key);
      if (result)
        break;
    }
    return result;
  }

  // for key->value pairs
  public int opApply(int delegate(inout char[], inout char[]) dg) {
    int    result ;
    char[] key    ,
           value  ;

    foreach (char[] key; STD_CGI_KEYS) {
      value  = get (key       ) ;
      result = dg  (key, value) ;
      if (result)
        break;
    }
    return result;
  }

} // end singleton Environment

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