# Generates the documentation for library functions using nixdoc.
# See https://github.com/nix-community/nixdoc
{
  lib,
  runCommand,
  writers,
  nixdoc,
  nixvim,
  pageSpecs ? ./pages.nix,
}:

let
  pageConfiguration = lib.evalModules {
    modules = [
      pageSpecs
      {
        freeformType = lib.types.attrsOf (
          lib.types.submoduleWith {
            modules = [ ../modules/page.nix ];
          }
        );
      }
    ];
  };
  pages = pageConfiguration.config;

  # Collect all page nodes into a list of page entries
  collectPages =
    pages:
    builtins.concatMap (
      node:
      let
        children = builtins.removeAttrs node [ "_page" ];
      in
      lib.optional (node ? _page) node._page ++ lib.optionals (children != { }) (collectPages children)
    ) (builtins.attrValues pages);

  # Normalised page specs
  pageList = collectPages pages;
  pagesToRender = builtins.filter (page: page.hasContent) pageList;

  result =
    runCommand "nixvim-lib-docs"
      {
        nativeBuildInputs = [
          nixdoc
        ];

        locations = writers.writeJSON "locations.json" (
          import ./function-locations.nix {
            inherit lib;
            rootPath = nixvim;
            functionSet = lib.extend nixvim.lib.overlay;
            pathsToScan = lib.pipe pageList [
              (map (x: x.functions))
              (builtins.filter (x: x.file != null))
              (map (x: x.loc))
            ];
            revision = nixvim.rev or "main";
          }
        );

        passthru.config = pageConfiguration;

        passthru.menu = import ./menu.nix {
          inherit lib pages;
        };

        passthru.pages = map (page: "${result}/${page.target}") pagesToRender;
      }
      ''
        function docgen {
          md_file="$1"
          in_file="$2"
          name="$3"
          out_file="$out/$4"
          title="$5"

          if [[ -z "$in_file" ]]; then
            if [[ -z "$md_file" ]]; then
              >&2 echo "No markdown or nix file for $name"
              exit 1
            fi
          elif [[ -f "$in_file/default.nix" ]]; then
            in_file+="/default.nix"
          elif [[ ! -f "$in_file" ]]; then
            >&2 echo "File not found: $in_file"
            exit 1
          fi

          if [[ -n "$in_file" ]]; then
            nixdoc \
              --file "$in_file" \
              --locs "$locations" \
              --category "$name" \
              --description "REMOVED BY TAIL" \
              --prefix "lib" \
              --anchor-prefix "" \
            | tail --lines +2 \
            > functions.md
          fi

          default_heading="# $name"
          if [[ -n "$title" ]]; then
            default_heading+=": $title"
          fi

          print_heading=true
          if [[ -f "$md_file" ]] && [[ "$(head --lines 1 "$md_file")" == '# '* ]]; then
            >&2 echo "NOTE: markdown file for $name starts with a <h1> heading. Skipping default heading \"$default_heading\"."
            >&2 echo "      Found \"$(head --lines 1 "$md_file")\" in: $md_file"
            print_heading=false
          fi

          mkdir -p $(dirname "$out_file")
          (
            if [[ "$print_heading" = true ]]; then
              echo "$default_heading"
              echo
            fi
            if [[ -f "$md_file" ]]; then
              cat "$md_file"
              echo
            fi
            if [[ -f functions.md ]]; then
              cat functions.md
            fi
          ) > "$out_file"
        }

        mkdir -p "$out"

        ${lib.concatMapStringsSep "\n" (
          {
            functions,
            source,
            target,
            title ? "",
            ...
          }:
          lib.escapeShellArgs [
            "docgen"
            "${lib.optionalString (source != null) source}" # md_file
            "${lib.optionalString (functions.file != null) functions.file}" # in_file
            (lib.showAttrPath functions.loc) # name
            target # out_file
            title # title
          ]
        ) pagesToRender}
      '';
in
result