{ lib
, runCommand
, jq
, yq
}:

{ pname ? null

  # A list of dependency package names.
, dependencies

  # An attribute set of package names to sources.
, dependencySources
}:

let
  packages = lib.genAttrs dependencies (dependency: rec {
    src = dependencySources.${dependency};
    inherit (src) packageRoot;
  });
in
(runCommand "${lib.optionalString (pname != null) "${pname}-"}package-config.json" {
  inherit packages;

  nativeBuildInputs = [ jq yq ];

  __structuredAttrs = true;
}) ''
  declare -A packageSources
  declare -A packageRoots
  while IFS=',' read -r name src packageRoot; do
    packageSources["$name"]="$src"
    packageRoots["$name"]="$packageRoot"
  done < <(jq -r '.packages | to_entries | map("\(.key),\(.value.src),\(.value.packageRoot)") | .[]' "$NIX_ATTRS_JSON_FILE")

  for package in "''${!packageSources[@]}"; do
    if [ ! -e "''${packageSources["$package"]}/''${packageRoots["$package"]}/pubspec.yaml" ]; then
      echo >&2 "The package sources for $package are missing. Is the following path inside the source derivation?"
      echo >&2 "Source path: ''${packageSources["$package"]}/''${packageRoots["$package"]}/pubspec.yaml"
      exit 1
    fi

    languageConstraint="$(yq -r .environment.sdk "''${packageSources["$package"]}/''${packageRoots["$package"]}/pubspec.yaml")"
    if [[ "$languageConstraint" =~ ^[[:space:]]*(\^|>=|>)?[[:space:]]*([[:digit:]]+\.[[:digit:]]+)\.[[:digit:]]+.*$ ]]; then
      languageVersionJson="\"''${BASH_REMATCH[2]}\""
    elif [ "$languageConstraint" = 'any' ]; then
      languageVersionJson='null'
    else
      # https://github.com/dart-lang/pub/blob/68dc2f547d0a264955c1fa551fa0a0e158046494/lib/src/language_version.dart#L106C35-L106C35
      languageVersionJson='"2.7"'
    fi

    jq --null-input \
      --arg name "$package" \
      --arg path "''${packageSources["$package"]}/''${packageRoots["$package"]}" \
      --argjson languageVersion "$languageVersionJson" \
      '{
        name: $name,
        rootUri: "file://\($path)",
        packageUri: "lib/",
        languageVersion: $languageVersion,
      }'
  done | jq > "$out" --slurp '{
    configVersion: 2,
    generator: "nixpkgs",
    packages: .,
  }'
''