// SPDX-License-Identifier: MIT
// Copyright © 2022 The Tvix Authors
syntax = "proto3";

package tvix.store.v1;

import "castore/protos/castore.proto";

option go_package = "code.tvl.fyi/tvix/store-go;storev1";

// PathInfo shows information about a Nix Store Path.
// That's a single element inside /nix/store.
message PathInfo {
  // The path can be a directory, file or symlink.
  tvix.castore.v1.Node node = 1;

  // List of references (output path hashes)
  // This really is the raw *bytes*, after decoding nixbase32, and not a
  // base32-encoded string.
  repeated bytes references = 2;

  // see below.
  NARInfo narinfo = 3;
}

// Represents a path in the Nix store (a direct child of STORE_DIR).
// It is commonly formatted by a nixbase32-encoding the digest, and
// concatenating the name, separated by a `-`.
message StorePath {
  // The string after digest and `-`.
  string name = 1;

  // The digest (20 bytes).
  bytes digest = 2;
}

// Nix C++ uses NAR (Nix Archive) as a format to transfer store paths,
// and stores metadata and signatures in NARInfo files.
// Store all these attributes in a separate message.
//
// This is useful to render .narinfo files to clients, or to preserve/validate
// these signatures.
// As verifying these signatures requires the whole NAR file to be synthesized,
// moving to another signature scheme is desired.
// Even then, it still makes sense to hold this data, for old clients.
message NARInfo {
  // This represents a (parsed) signature line in a .narinfo file.
  message Signature {
    string name = 1;
    bytes data = 2;
  }

  // This size of the NAR file, in bytes.
  uint64 nar_size = 1;

  // The sha256 of the NAR file representation.
  bytes nar_sha256 = 2;

  // The signatures in a .narinfo file.
  repeated Signature signatures = 3;

  // A list of references. To validate .narinfo signatures, a fingerprint needs
  // to be constructed.
  // This fingerprint doesn't just contain the hashes of the output paths of all
  // references (like PathInfo.references), but their whole (base)names, so we
  // need to keep them somewhere.
  repeated string reference_names = 4;

  // The StorePath of the .drv file producing this output.
  // The .drv suffix is omitted in its `name` field.
  StorePath deriver = 5;

  // The CA field in the .narinfo.
  // Its textual representations seen in the wild are one of the following:
  //  - `fixed:r:sha256:1gcky5hlf5vqfzpyhihydmm54grhc94mcs8w7xr8613qsqb1v2j6`
  //    fixed-output derivations using "recursive" `outputHashMode`.
  //  - `fixed:sha256:19xqkh72crbcba7flwxyi3n293vav6d7qkzkh2v4zfyi4iia8vj8
  //    fixed-output derivations using "flat" `outputHashMode`
  //  - `text:sha256:19xqkh72crbcba7flwxyi3n293vav6d7qkzkh2v4zfyi4iia8vj8`
  //    Text hashing, used for uploaded .drv files and outputs produced by
  //    builtins.toFile.
  //
  // Semantically, they can be split into the following components:
  //  - "content address prefix". Currently, "fixed" and "text" are supported.
  //  - "hash mode". Currently, "flat" and "recursive" are supported.
  //  - "hash type". The underlying hash function used.
  //    Currently, sha1, md5, sha256, sha512.
  //  - "digest". The digest itself.
  //
  // There are some restrictions on the possible combinations.
  // For example, `text` and `fixed:recursive` always imply sha256.
  //
  // We use an enum to encode the possible combinations, and optimize for the
  // common case, `fixed:recursive`, identified as `NAR_SHA256`.
  CA ca = 6;

  message CA {
    enum Hash {
      // produced when uploading fixed-output store paths using NAR-based
      // hashing (`outputHashMode = "recursive"`).
      NAR_SHA256 = 0;
      NAR_SHA1 = 1;
      NAR_SHA512 = 2;
      NAR_MD5 = 3;

      // Produced when uploading .drv files or outputs produced by
      // builtins.toFile.
      // Produces equivalent digests as FLAT_SHA256, but is a separate
      // hashing type in Nix, affecting output path calculation.
      TEXT_SHA256 = 4;

      // Produced when using fixed-output derivations with
      // `outputHashMode = "flat"`.
      FLAT_SHA1 = 5;
      FLAT_MD5 = 6;
      FLAT_SHA256 = 7;
      FLAT_SHA512 = 8;

      // TODO: what happens in Rust if we introduce a new enum kind here?
    }

    // The hashing type used.
    Hash type = 1;

    // The digest, in raw bytes.
    bytes digest = 2;
  }
}