{ depot, pkgs, lib, ... }:

let
  # dependency imports

  inherit (depot.nix) getBins;
  inherit (depot.third_party) rustsec-advisory-db;

  bins = getBins pkgs.jq [
    "jq"
  ] // getBins pkgs.coreutils [
    "cat"
    "printf"
    "tee"
    "test"
    "wc"
  ] // getBins pkgs.gnugrep [
    "grep"
  ] // getBins pkgs.cargo-audit [
    "cargo-audit"
  ] // getBins pkgs.ansi2html [
    "ansi2html"
  ] // {
    eprintf = depot.tools.eprintf;
  };

  # buildRustPackage handling

  /* Predicate by which we identify rust packages we are interested in,
     i. e. built using `buildRustPackage`.

     Type :: drv -> bool
  */
  isRustPackage = v: v ? cargoDeps;

  /* Takes a buildRustPackage derivation and returns a derivation which
     builds extracts the `Cargo.lock` of its `cargoDeps` derivation or
     `null` if it has none.

     Type: drv -> option<drv>
  */
  # TODO(sterni): support cargoVendorDir?
  extractCargoLock = drv:
    if !(drv ? cargoDeps.outPath)
    then null
    else pkgs.runCommandNoCC "${drv.name}-Cargo.lock" {} ''
      if test -d "${drv.cargoDeps}"; then
        cp "${drv.cargoDeps}/Cargo.lock" "$out"
      fi

      if test -f "${drv.cargoDeps}"; then
        tar -xO \
          --no-wildcards-match-slash --wildcards \
          -f "${drv.cargoDeps}" \
          '*/Cargo.lock' \
          > "$out"
      fi
    '';

  # nixpkgs traversal

  # Condition for us to recurse: Either at top-level or recurseForDerivation.
  recurseInto = path: x: path == [] ||
    (lib.isAttrs x && (x.recurseForDerivations or false));

  # Returns the value or false if an eval error occurs.
  tryEvalOrFalse = v: (builtins.tryEval v).value;

  /* Traverses nixpkgs as instructed by `recurseInto` and collects
     the attribute and lockfile derivation of every rust package it
     encounters into a list.

     Type :: attrs
          -> list {
               attr :: list<str>;
               lock :: option<drv>;
               maintainers :: list<maintainer>;
             }
  */
  allLockFiles =
    let
      go = path: x:
        let
          isDrv = tryEvalOrFalse (lib.isDerivation x);
          doRec = tryEvalOrFalse (recurseInto path x);
          isRust = tryEvalOrFalse (isRustPackage x);
        in
          if doRec then lib.concatLists (
            lib.mapAttrsToList (n: go (path ++ [ n ])) x
          ) else if isDrv && isRust then [
            {
              attr = path;
              lock = extractCargoLock x;
              maintainers = x.meta.maintainers or [];
            }
          ] else [];
    in go [];

  # Report generation and formatting

  reportFor = { attr, lock, ... }: let
    # naïve attribute path to Nix syntax conversion
    strAttr = lib.concatStringsSep "." attr;
  in
    if lock == null
    then pkgs.emptyFile
    else depot.nix.runExecline "${strAttr}-vulnerability-report" {} [
      "pipeline" [
        bins.cargo-audit
        "audit" "--json"
        "-n" "--db" rustsec-advisory-db
        "-f" lock
      ]
      "importas" "out" "out"
      "redirfd" "-w" "1" "$out"
      bins.jq "-rj" "-f" ./format-audit-result.jq "--arg" "attr" strAttr
    ];

  # GHMF in issues splits paragraphs on newlines
  description = lib.concatMapStringsSep "\n\n" (
    builtins.replaceStrings [ "\n" ] [ " " ]
  ) [
    ''
      The vulnerability report below was generated by
      [nixpkgs-crate-holes](https://code.tvl.fyi/tree/users/sterni/nixpkgs-crate-holes)
      which extracts the `Cargo.lock` file of each package in nixpkgs with a
      `cargoDeps` attribute and passes it to
      [cargo-audit](https://github.com/RustSec/rustsec/tree/main/cargo-audit)
      using RustSec's
      [advisory-db at ${builtins.substring 0 7 rustsec-advisory-db.rev}](https://github.com/RustSec/advisory-db/tree/${rustsec-advisory-db.rev}/).
    ''
    ''
      Feel free to report any problems or suggest improvements (I have an email
      address on my profile and hang out on Matrix/libera.chat as sterni)!
      Tick off any reports that have been fixed in the meantime.
    ''
    ''
      Note: A vulnerability in a dependency does not necessarily mean the dependent
      package is vulnerable, e. g. when a vulnerable function isn't used.
    ''
  ];

  runInstructions = ''
    <details>
    <summary>
    Generating Cargo.lock vulnerability reports

    </summary>

    If you have a checkout of [depot](https://code.tvl.fyi/about/), you can generate this report using:

    ```
    nix-build -A users.sterni.nixpkgs-crate-holes.full \
      --argstr nixpkgsPath /path/to/nixpkgs
    ```

    If you want a more detailed report for a single attribute of nixpkgs, use:

    ```
    nix-build -A users.sterni.nixpkgs-crate-holes.single \
      --argstr nixpkgsPath /path/to/nixpkgs --arg attr '[ "ripgrep" ]'
    ```

    </details>
  '';

  defaultNixpkgsArgs = { allowBroken = false; };

  reportForNixpkgs =
    { nixpkgsPath
    , nixpkgsArgs ? defaultNixpkgsArgs
    }@args:

    let
      reports = builtins.map reportFor (
        allLockFiles (import nixpkgsPath nixpkgsArgs)
      );
    in

    depot.nix.runExecline "nixpkgs-rust-pkgs-vulnerability-report.md" {
      stdin = lib.concatMapStrings (report: "${report}\n") reports;
    } [
      "importas" "out" "out"
      "redirfd" "-w" "1" "$out"
      # Print introduction paragraph for the issue
      "if" [ bins.printf "%s\n\n" description ]
      # Print all reports
      "foreground" [
        "forstdin" "-E" "report" bins.cat "$report"
      ]
      # Print stats at the end (mostly as a gimmick), we already know how many
      # attributes there are and count the attributes with vulnerability by
      # finding the number of checkable list entries in the output.
      "backtick" "-E" "vulnerableCount" [
        "pipeline" [
          bins.grep "^- \\[ \\]" "$out"
        ]
        bins.wc "-l"
      ]
      "if" [
        bins.printf
        "\n%s of %s checked attributes have vulnerable dependencies.\n\n"
        "$vulnerableCount"
        (toString (builtins.length reports))
      ]
      "if" [
        bins.printf "%s\n\n" runInstructions
      ]
    ];

  singleReport =
    { # Attribute to check: string or list of strings (attr path)
      attr
      # Path to importable nixpkgs checkout
    , nixpkgsPath
      # Arguments to pass to nixpkgs
    , nixpkgsArgs ? defaultNixpkgsArgs
    }:

    let
      attr' = if builtins.isString attr then [ attr ] else attr;
      drv = lib.getAttrFromPath attr' (import nixpkgsPath nixpkgsArgs);
      lockFile = extractCargoLock drv;
      strAttr = lib.concatStringsSep "." attr';
    in

    depot.nix.runExecline "${strAttr}-report.html" {} [
      "importas" "out" "out"
      "backtick" "-I" "-E" "-N" "report" [
        bins.cargo-audit "audit"
        "--quiet"
        "-n" "--db" rustsec-advisory-db
        "-f" lockFile
      ]
      "pipeline" [
        "ifte" [
          bins.printf "%s" "$report"
        ] [
          bins.printf "%s\n" "No vulnerabilities found"
        ]
        bins.test "-n" "$report"
      ]
      "pipeline" [
        bins.tee "/dev/stderr"
      ]
      "redirfd" "-w" "1" "$out"
      bins.ansi2html
    ];

in {
  full = reportForNixpkgs;
  single = singleReport;

  inherit
    extractCargoLock
    allLockFiles
  ;

  # simple sanity check, doesn't cover everything, but testing the full report
  # is quite expensive in terms of evaluation.
  testSingle = singleReport {
    nixpkgsPath = depot.third_party.nixpkgs.path;
    attr = [ "ripgrep" ];
  };

  meta.targets = [ "testSingle" ];
}