{ pkgs
, options
, config
, version
, revision
, nixpkgsRevision
, extraSources ? []
, prefix ? ../..
}:

with pkgs;

let
  lib = pkgs.lib;

  gitHubDeclaration = user: repo: ref: subpath:
    # Default to `master` if we don't know what revision the system
    # configuration is using (custom nixpkgs, etc.).
    let urlRef = if ref != null then ref else "master";
    in {
      url = "https://github.com/${user}/${repo}/blob/${urlRef}/${subpath}";
      name = "<${repo}/${subpath}>";
    };

  optionsDoc = buildPackages.nixosOptionsDoc {
    inherit options;
    transformOptions = opt: opt // {
      # Clean up declaration sites to not refer to the nix-darwin source tree.
      # TODO: handle `extraSources`? (it's not set anywhere)
      declarations = map
        (decl:
          if lib.hasPrefix (toString prefix) (toString decl) then
            gitHubDeclaration "LnL7" "nix-darwin" revision
              (lib.removePrefix "/"
                (lib.removePrefix (toString prefix) (toString decl)))
          # TODO: handle this in a better way (may require upstream
          # changes to nixpkgs)
          else if decl == "lib/modules.nix" then
            gitHubDeclaration "NixOS" "nixpkgs" nixpkgsRevision decl
          else decl)
        opt.declarations;
    };
  };

in rec {
  # TODO: Use `optionsDoc.optionsJSON` directly once upstream
  # `nixosOptionsDoc` is more customizable.
  optionsJSON = runCommand "options.json"
    { meta.description = "List of nix-darwin options in JSON format"; }
    ''
      mkdir -p $out/{share/doc,nix-support}
      cp -a ${optionsDoc.optionsJSON}/share/doc/nixos $out/share/doc/darwin
      substitute \
        ${optionsDoc.optionsJSON}/nix-support/hydra-build-products \
        $out/nix-support/hydra-build-products \
        --replace \
          '${optionsDoc.optionsJSON}/share/doc/nixos' \
          "$out/share/doc/darwin"
    '';

  # Generate the nix-darwin manual.
  manualHTML = runCommand "darwin-manual-html"
    { nativeBuildInputs = [ buildPackages.nixos-render-docs ];
      styles = lib.sourceFilesBySuffices (pkgs.path + "/doc") [ ".css" ];
      meta.description = "The Darwin manual in HTML format";
      allowedReferences = ["out"];
    }
    ''
      # Generate the HTML manual.
      dst=$out/share/doc/darwin
      mkdir -p $dst

      cp $styles/style.css $dst
      cp -r ${pkgs.documentation-highlighter} $dst/highlightjs

      substitute ${./manual.md} manual.md \
        --replace '@DARWIN_VERSION@' "${version}" \
        --replace \
          '@DARWIN_OPTIONS_JSON@' \
          ${optionsJSON}/share/doc/darwin/options.json

      # TODO: --manpage-urls?
      nixos-render-docs -j $NIX_BUILD_CORES manual html \
        --manpage-urls ${pkgs.writeText "manpage-urls.json" "{}"} \
        --revision ${lib.escapeShellArg revision} \
        --generator "nixos-render-docs ${lib.version}" \
        --stylesheet style.css \
        --stylesheet highlightjs/mono-blue.css \
        --script ./highlightjs/highlight.pack.js \
        --script ./highlightjs/loader.js \
        --toc-depth 1 \
        --chunk-toc-depth 1 \
        ./manual.md \
        $dst/index.html

      mkdir -p $out/nix-support
      echo "nix-build out $out" >> $out/nix-support/hydra-build-products
      echo "doc manual $dst" >> $out/nix-support/hydra-build-products
    '';

  # Index page of the nix-darwin manual.
  manualHTMLIndex = "${manualHTML}/share/doc/darwin/index.html";

  manualEpub = builtins.throw "The nix-darwin EPUB manual has been removed.";

  # Generate the nix-darwin manpages.
  manpages = runCommand "darwin-manpages"
    { nativeBuildInputs = [ buildPackages.nixos-render-docs ];
      allowedReferences = ["out"];
    }
    ''
      # Generate manpages.
      mkdir -p $out/share/man/man5
      nixos-render-docs -j $NIX_BUILD_CORES options manpage \
        --revision ${lib.escapeShellArg revision} \
        ${optionsJSON}/share/doc/darwin/options.json \
        $out/share/man/man5/configuration.nix.5

      # TODO: get these parameterized in upstream nixos-render-docs
      sed -i -e '
        /^\.TH / s|NixOS|nix-darwin|g

        /^\.SH "NAME"$/ {
          N
          s|NixOS|nix-darwin|g
        }

        /^\.SH "DESCRIPTION"$/ {
          N; N
          s|/etc/nixos/configuration|configuration|g
          s|NixOS|nix-darwin|g
          s|nixos|nix-darwin|g
        }

        /\.SH "AUTHORS"$/ {
          N; N
          s|Eelco Dolstra and the Nixpkgs/NixOS contributors|Daiderd Jordan and the nix-darwin contributors|g
        }
      ' $out/share/man/man5/configuration.nix.5
    '';
}