# https://nixos.org/manual/nixos/stable/index.html#sec-writing-modules
# This is a function with arguments
{
  config,
  lib,
  mylib,
  pkgs,
  ...
}:
# We add stuff from lib to our namespace (mkOption...)
with lib;
with mylib.modules; let
  # This is the current state of the option that this module defines
  # We use it to determine if the config should be changed below
  cfg = config.modules.emacs;
in {
  imports = [];

  # Options is a vector of options this module defines
  # This module defines only the "emacs" option and suboptions "enable" and "doom"
  options.modules.emacs = {
    enable = mkEnableOpt "Emacs module";

    # TODO: Use an enum for this not individual options
    nixpkgs = mkBoolOpt false "Use Emacs from the official repositories";
    nativeComp = mkBoolOpt false "Use Emacs 28.x branch with native comp support";
    pgtkNativeComp = mkBoolOpt false "Use Emacs 29.x branch with native comp and pure gtk support";

    doom = {
      enable = mkEnableOpt "Doom Emacs framework";
      autoSync = mkBoolOpt false "Sync Doom Emacs on nixos-rebuild";
      autoUpgrade = mkBoolOpt false "Upgrade Doom Emacs on nixos-rebuild";
    };
  };

  # Config is the merged set of all module configurations
  # Here we define what happens to the config if the module is active (but only if the module is active)
  # Since this module is for HomeManager, config is not the system config
  # Attribute sets like config can be defined multiple times (every module defines a different config), on
  # building the config they are merged
  # Because config depends on itself recursively (through cfg) we use mkIf instead of the normal if...then...else,
  # as it delays the evaluation (the if is moved inside the assignments inside the set)
  # mkIf can only be used in the config section (like mkMerge, mkForce and co)
  config = mkIf cfg.enable {
    assertions = [
      (mkIf cfg.nativeComp {
        assertion = !cfg.pgtkNativeComp && !cfg.nixpkgs;
        message = "Can't enable more than one Emacs package!";
      })
      (mkIf cfg.pgtkNativeComp {
        assertion = !cfg.nativeComp && !cfg.nixpkgs;
        message = "Can't enable more than one Emacs package!";
      })
      (mkIf cfg.nixpkgs {
        assertion = !cfg.nativeComp && !cfg.pgtkNativeComp;
        message = "Can't enable more than one Emacs package!";
      })
    ];

    # What home packages should be enabled
    home.packages = with pkgs;
      builtins.concatLists [
        (optionals cfg.nativeComp [((emacsPackagesFor emacsNativeComp).emacsWithPackages (epkgs: [epkgs.vterm epkgs.pdf-tools]))])
        (optionals cfg.pgtkNativeComp [((emacsPackagesFor emacsPgtkNativeComp).emacsWithPackages (epkgs: [epkgs.vterm epkgs.pdf-tools]))])
        (optionals cfg.nixpkgs [((emacsPackagesFor emacs).emacsWithPackages (epkgs: [epkgs.vterm epkgs.pdf-tools]))])

        # TODO: Check what hlissner has enabled
        (optionals cfg.doom.enable [
          # emacs-all-the-icons-fonts # Needs to be in fonts.fonts
          (ripgrep.override {withPCRE2 = true;})
          fd
          zstd
          sqlite # Org roam
          inkscape # Org latex preview
          graphviz # Org graphviz support
          gnuplot # Org gnuplot support
          pandoc # Org export formats
          maim
          bashInteractive # For keychain

          # TODO: I don't want to have this here permanently, maybe put in a shell.nix if compilation is needed?
          gcc # Need this for org roam

          # TODO: Conflicts with global python?
          # withPackages expects a function that gets all the packages as argument and returns a list with the packages we want
          (python310.withPackages (ppkgs: [ppkgs.pygments])) # Latex minted
          # TODO: Does it work like this aswell?
          # python310Packages.pygments

          # nixfmt # This belongs in specific flake.nix
          # shellcheck # This belongs in specific flake.nix

          texlive.combined.scheme-full
        ])
      ];

    home.sessionPath = mkIf cfg.doom.enable ["${config.home.homeDirectory}/.emacs.d/bin"];

    # Note: Don't do it this way as the config becomes immutable
    # We tell HomeManager where the config files belong
    # home.file.".config/doom" = {
    #   # With onChange you even could rebuild doom emacs when rebuilding HomeManager but I don't want this to become too slow
    #   recursive = true; # is a directory
    #   source = ../../config/doom;
    # };

    home.activation = mkMerge [
      # The parantheses around mkIf are needed for precedence in this case
      (mkIf cfg.doom.enable {
        # If doom is enabled we want to clone the framework
        # The activation script is being run when home-manager rebuilds
        # Because we write to the filesystem, this script has to be run after HomeManager's writeBoundary
        installDoomEmacs = hm.dag.entryAfter ["writeBoundary"] ''
          if [ ! -d "${config.home.homeDirectory}/.emacs.d" ]; then
            git clone --depth=1 --single-branch "https://github.com/doomemacs/doomemacs" "${config.home.homeDirectory}/.emacs.d"
          fi
        '';

        # With this approach we keep the config mutable as it is not copied and linked from store
        linkDoomConfig =
          hm.dag.entryAfter ["writeBoundary" "installDoomEmacs"]
          (mkLink "${config.home.homeDirectory}/NixFlake/config/doom" "${config.home.homeDirectory}/.config/doom");
      })
      (mkElse cfg.doom.enable {
        unlinkDoomConfig =
          hm.dag.entryAfter ["writeBoundary" "installDoomEmacs"]
          (mkUnlink "${config.home.homeDirectory}/.config/doom");
      })

      (mkIf (cfg.doom.enable && cfg.doom.autoSync) {
        syncDoomEmacs = hm.dag.entryAfter ["writeBoundary" "linkDoomConfig"] ''
          ${config.home.homeDirectory}/.emacs.d/bin/doom sync &
        '';
      })

      (mkIf (cfg.doom.enable && cfg.doom.autoUpgrade) {
        upgradeDoomEmacs = hm.dag.entryAfter ["writeBoundary" "linkDoomConfig"] ''
          ${config.home.homeDirectory}/.emacs.d/bin/doom upgrade -!
        '';
      })
    ];
  };
}