nvf/modules/plugins/languages/kotlin.nix

{
  config,
  pkgs,
  lib,
  ...
}: let
  inherit (lib.options) mkEnableOption mkOption;
  inherit (lib.modules) mkIf mkMerge;
  inherit (lib.meta) getExe;
  inherit (lib.nvim.languages) diagnosticsToLua;
  inherit (lib.types) package enum;
  inherit (lib.attrsets) attrNames;
  inherit (lib.nvim.types) mkGrammarOption diagnostics;
  inherit (lib.lists) isList;
  inherit (lib.nvim.lua) expToLua;

  cfg = config.vim.languages.kotlin;

  # Creating a version of the LSP with access to the kotlin binary.
  # This is necessary for the LSP to load the standard library
  kotlinLspWithRuntime = pkgs.symlinkJoin {
    name = "kotlin-language-server-with-runtime";
    paths = [
      pkgs.kotlin-language-server
      pkgs.kotlin
    ];
    buildInputs = [pkgs.makeWrapper];
    postBuild = ''
      wrapProgram $out/bin/kotlin-language-server \
        --prefix PATH : ${pkgs.lib.makeBinPath [pkgs.kotlin]}
    '';
  };

  defaultFormat = "ktlint";
  formats = {
    ktlint = {
      package = pkgs.ktlint;
      nullConfig = ''
        table.insert(
          ls_sources,
          null_ls.builtins.formatting.ktlint.with({
            command = "${cfg.format.package}/bin/ktlint",
          })
        )
      '';
    };
    ktfmt = {
      package = pkgs.ktfmt;
      nullConfig = ''
        table.insert(
          ls_sources,
          null_ls.builtins.formatting.ktlint.with({
            command = "${cfg.format.package}/bin/ktfmt",
          })
        )
      '';
    };
  };
  defaultDiagnosticsProvider = ["ktlint"];
  diagnosticsProviders = {
    ktlint = {
      package = pkgs.ktlint;
      nullConfig = pkg: ''
        table.insert(
          ls_sources,
          null_ls.builtins.diagnostics.ktlint.with({
            command = "${getExe pkg}",
          })
        )
      '';
    };
  };
in {
  options.vim.languages.kotlin = {
    enable = mkEnableOption "Kotlin/HCL support";

    treesitter = {
      enable = mkEnableOption "Kotlin treesitter" // {default = config.vim.languages.enableTreesitter;};
      package = mkGrammarOption pkgs "kotlin";
    };

    lsp = {
      enable = mkEnableOption "Kotlin LSP support (kotlin_language_server)" // {default = config.vim.languages.enableLSP;};

      package = mkOption {
        description = "kotlin_language_server package with Kotlin runtime";
        type = package;
        default = kotlinLspWithRuntime;
      };
    };

    format = {
      enable = mkEnableOption "Kotlin document formatting" // {default = config.vim.languages.enableFormat;};

      type = mkOption {
        description = "Kotlin formatter to use";
        type = enum (attrNames formats);
        default = defaultFormat;
      };

      package = mkOption {
        description = "Kotlin formatter package";
        type = package;
        default = formats.${cfg.format.type}.package;
      };
    };

    extraDiagnostics = {
      enable = mkEnableOption "extra Kotlin diagnostics" // {default = config.vim.languages.enableExtraDiagnostics;};

      types = diagnostics {
        langDesc = "Kotlin";
        inherit diagnosticsProviders;
        inherit defaultDiagnosticsProvider;
      };
    };
  };
  config = mkIf cfg.enable (mkMerge [
    (mkIf cfg.treesitter.enable {
      vim.treesitter.enable = true;
      vim.treesitter.grammars = [cfg.treesitter.package];
    })

    # (mkIf cfg.format.enable {
    #   vim.lsp.null-ls.enable = true;
    #   vim.lsp.null-ls.sources.kotlin-format = formats.${cfg.format.type}.nullConfig;
    # })

    (mkIf cfg.extraDiagnostics.enable {
      vim.lsp.null-ls.enable = true;
      vim.lsp.null-ls.sources = diagnosticsToLua {
        lang = "ts";
        config = cfg.extraDiagnostics.types;
        inherit diagnosticsProviders;
      };
    })

    (mkIf cfg.lsp.enable {
      vim.lsp.lspconfig.enable = true;
      vim.lsp.lspconfig.sources.kotlin_language_server = ''
        lspconfig.kotlin_language_server.setup {
          capabilities = capabilities,
          root_dir = lspconfig.util.root_pattern("main.kt", ".git"),
          on_attach=default_on_attach,
          init_options = {
          -- speeds up the startup time for the LSP
            storagePath = "vim.fn.stdpath('state') .. '/kotlin'",
          },
          cmd = ${
          if isList cfg.lsp.package
          then expToLua cfg.lsp.package
          else ''{"${cfg.lsp.package}/bin/kotlin-language-server"}''
        },
        }
      '';
    })
  ]);
}