{ config, pkgs, lib, ... }:

{
  # Fish Shell
  # https://rycee.gitlab.io/home-manager/options.html#opt-programs.fish.enable
  programs.fish.enable = true;

  # Add Fish plugins
  home.packages = builtins.attrValues {
    inherit (pkgs.fishPlugins)
      autopair-fish
      colored-man-pages
      done;
  };
  programs.fish.plugins = [ pkgs.fishPlugins.fisher ];

  xdg.configFile."fish/fish_plugins".text = ''
    jorgebucaran/replay.fish
    americanhanko/fish-spin
    joseluisq/gitnow
    fishpkg/fish-humanize-duration
    oh-my-fish/plugin-bang-bang
    matthewess/fish-autovenv
    Gazorby/fish-abbreviation-tips
  '';

  # Fish functions ----------------------------------------------------------------------------- {{{

  programs.fish.functions = {
    # User functions
    mkdcd = {
      argumentNames = [ "target" ];
      body = ''
        if test -z "$target"
          echo "mkdcd requires an argument" 1>&2
          return 1
        end
        mkdir -p $target
        cd $target
      '';
    };
    unz = {
      argumentNames = [ "target" ];
      body = ''
        # strip extensions
        string match \*.zip $target; and set target (string split -r -m1 . $target)[1]
        unzip -d $target $target
      '';
    };

    # Helpers
    # Toggles `$term_background` between "light" and "dark". Other Fish functions trigger when this
    # variable changes. We use a universal variable so that all instances of Fish have the same
    # value for the variable.
    toggle-background.body = ''
      if test "$term_background" = light
        set -U term_background dark
      else
        set -U term_background light
      end
    '';

    # Set `$term_background` based on whether macOS is light or dark mode. Other Fish functions
    # trigger when this variable changes. We use a universal variable so that all instances of Fish
    # have the same value for the variable.
    set-background-to-macOS.body = ''
      if is-dark-mode
        set -U term_background dark
      else
        set -U term_background light
      end
    '';

    # Set `$term_background` based on an env var.
    set-background-to-env = {
      argumentNames = [ "env_var" ];
      body = ''
        switch $$env_var
        case 1
          echo "Setting dark mode"
          set -U term_background dark
        case 0
          echo "Setting light mode"
          set -U term_background light
        end
      '';
    };

    # Sets Fish Shell to light or dark colorscheme based on `$term_background`.
    set-shell-colors = {
      body = ''
        # Use correct theme for `btm` and `bat`
        if test "$term_background" = light
          alias btm "btm --color default-light"
          set -xg BAT_THEME OneHalfLight
        else
          alias btm "btm --color default"
          set -xg BAT_THEME OneHalfDark
        end
        # Set LS_COLORS
        set -xg LS_COLORS (${pkgs.vivid}/bin/vivid generate one-$term_background)
      '';
      onVariable = "term_background";
    };

    from-dir = {
      argumentNames = [ "dir" ];
      body = ''
        pushd $dir
        set -e argv[1]
        $argv
        popd
      '';
    };

    darwin-rebuild-edit-with = {
      argumentNames = [ "editor" "file" ];
      body = ''
        if test -z "$file"
          set file flake.nix
        end
        from-nix $editor $file
      '';
    };

    nix-unfree = {
      argumentNames = [ "cmd" ];
      body = ''
        env NIX_ALLOW_UNFREE=1 nix $cmd --impure
      '';
    };
  };
  # }}}

  # Fish configuration ------------------------------------------------------------------------- {{{

  # Aliases
  programs.fish.shellAliases =
    let
      inherit (config.home.primaryUser) nixConfigDirectory;
      inherit (pkgs) bat bottom du-dust exa gitAndTools stdenv xh;
    in
    {
      # Nix related
      from-nix = "from-dir ${nixConfigDirectory}";
      # darwin-rebuild build 
      drb = "from-nix darwin-rebuild build --flake .";
      # darwin-rebuild switch full
      drsf = "from-nix darwin-rebuild switch --flake .";
      # darwin-rebuild switch (no homebrew)
      drs = "from-nix darwin-rebuild switch --flake . --override-input homebrew-enabled github:boolean-option/false";
      # edit darwin-rebuild config in code/codium
      drc = "code ${nixConfigDirectory}";
      # edit darwin-rebuild config in vim
      drv = "vim ${nixConfigDirectory}";
      # edit darwin-rebuild config in helix
      drh = "darwin-rebuild-edit-with hx";
      flakeup = "nix flake update ${nixConfigDirectory}/";
      nb = "nix build";
      nd = "nix develop";
      nf = "nix flake";
      nr = "nix run";
      nru = "nix-unfree run";
      ns = "nix search nixpkgs";
      nsh = "nix shell";
      nshu = "nix-unfree shell";
      nrp = "nix repl --expr '{ pkgs = (import <nixpkgs> { }); }'";
      nrpu = "nix repl --expr '{ pkgs = (import <nixpkgs> { config.allowUnfree = true; }); }' --impure";

      # Other
      ".." = "cd ..";
      ":q" = "exit";
      cat = "${bat}/bin/bat --style=plain --paging=never";
      du = "${du-dust}/bin/dust";
      g = "${gitAndTools.git}/bin/git";
      ls = "${exa}/bin/exa";
      ll = "ls -l --time-style long-iso --icons";
      la = "ll -a";
      http = "${xh}/bin/xh";
      https = "${xh}/bin/xhs";
      top = "${bottom}/bin/btm";
      htop = "${bottom}/bin/btm";
      tb = "toggle-background";
    } // lib.optionalAttrs stdenv.isDarwin {
      sb = "set-background-to-macOS";
      conda-init = "eval /opt/homebrew/bin/conda 'shell.fish' 'hook' $argv | source";
    };

  # Configuration that should be above `loginShellInit` and `interactiveShellInit`.
  programs.fish.shellInit = ''
    set -U fish_term24bit 1
    ${lib.optionalString pkgs.stdenv.isDarwin "set-background-to-macOS"}
  '';

  programs.fish.interactiveShellInit = ''
    set -g fish_greeting (set_color blue)"(づ￣ ³￣)づ "(set_color red)"h"(set_color cyan)"e"(set_color yellow)"l"(set_color magenta)"l"(set_color green)"o "(set_color blue)"(づ￣ ³￣)づ"(set_color normal)
    fish_vi_key_bindings
    set VIRTUAL_ENV_DISABLE_PROMPT true
    bind -M insert ! __history_previous_command
    bind -M insert '$' __history_previous_command_arguments
    ${pkgs.thefuck}/bin/thefuck --alias | source
    # Run function to set colors that are dependent on `$term_background` and to register them so
    # they are triggered when the relevent event happens or variable changes.
    set-shell-colors
  '';
  # }}}
}