syntax = "proto3";

package envoy.type.matcher;

import "google/protobuf/wrappers.proto";

import "udpa/annotations/status.proto";
import "validate/validate.proto";

option java_package = "io.envoyproxy.envoy.type.matcher";
option java_outer_classname = "RegexProto";
option java_multiple_files = true;
option go_package = "github.com/envoyproxy/go-control-plane/envoy/type/matcher";
option (udpa.annotations.file_status).package_version_status = FROZEN;

// [#protodoc-title: Regex matcher]

// A regex matcher designed for safety when used with untrusted input.
message RegexMatcher {
  // Google's `RE2 <https://github.com/google/re2>`_ regex engine. The regex string must adhere to
  // the documented `syntax <https://github.com/google/re2/wiki/Syntax>`_. The engine is designed
  // to complete execution in linear time as well as limit the amount of memory used.
  //
  // Envoy supports program size checking via runtime. The runtime keys ``re2.max_program_size.error_level``
  // and ``re2.max_program_size.warn_level`` can be set to integers as the maximum program size or
  // complexity that a compiled regex can have before an exception is thrown or a warning is
  // logged, respectively. ``re2.max_program_size.error_level`` defaults to 100, and
  // ``re2.max_program_size.warn_level`` has no default if unset (will not check/log a warning).
  //
  // Envoy emits two stats for tracking the program size of regexes: the histogram `re2.program_size`,
  // which records the program size, and the counter `re2.exceeded_warn_level`, which is incremented
  // each time the program size exceeds the warn level threshold.
  message GoogleRE2 {
    // This field controls the RE2 "program size" which is a rough estimate of how complex a
    // compiled regex is to evaluate. A regex that has a program size greater than the configured
    // value will fail to compile. In this case, the configured max program size can be increased
    // or the regex can be simplified. If not specified, the default is 100.
    //
    // This field is deprecated; regexp validation should be performed on the management server
    // instead of being done by each individual client.
    google.protobuf.UInt32Value max_program_size = 1 [deprecated = true];
  }

  oneof engine_type {
    option (validate.required) = true;

    // Google's RE2 regex engine.
    GoogleRE2 google_re2 = 1 [(validate.rules).message = {required: true}];
  }

  // The regex match string. The string must be supported by the configured engine.
  string regex = 2 [(validate.rules).string = {min_len: 1}];
}

// Describes how to match a string and then produce a new string using a regular
// expression and a substitution string.
message RegexMatchAndSubstitute {
  // The regular expression used to find portions of a string (hereafter called
  // the "subject string") that should be replaced. When a new string is
  // produced during the substitution operation, the new string is initially
  // the same as the subject string, but then all matches in the subject string
  // are replaced by the substitution string. If replacing all matches isn't
  // desired, regular expression anchors can be used to ensure a single match,
  // so as to replace just one occurrence of a pattern. Capture groups can be
  // used in the pattern to extract portions of the subject string, and then
  // referenced in the substitution string.
  RegexMatcher pattern = 1;

  // The string that should be substituted into matching portions of the
  // subject string during a substitution operation to produce a new string.
  // Capture groups in the pattern can be referenced in the substitution
  // string. Note, however, that the syntax for referring to capture groups is
  // defined by the chosen regular expression engine. Google's `RE2
  // <https://github.com/google/re2>`_ regular expression engine uses a
  // backslash followed by the capture group number to denote a numbered
  // capture group. E.g., ``\1`` refers to capture group 1, and ``\2`` refers
  // to capture group 2.
  string substitution = 2;
}
