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

with lib;

let

  cfg = config.programs.starship;

  tomlFormat = pkgs.formats.toml { };

  starshipCmd = "${config.home.profileDirectory}/bin/starship";

in {
  meta.maintainers = [ maintainers.marsam ];

  options.programs.starship = {
    enable = mkEnableOption "starship";

    package = mkOption {
      type = types.package;
      default = pkgs.starship;
      defaultText = literalExpression "pkgs.starship";
      description = "The package to use for the starship binary.";
    };

    settings = mkOption {
      type = with types;
        let
          prim = either bool (either int str);
          primOrPrimAttrs = either prim (attrsOf prim);
          entry = either prim (listOf primOrPrimAttrs);
          entryOrAttrsOf = t: either entry (attrsOf t);
          entries = entryOrAttrsOf (entryOrAttrsOf entry);
        in attrsOf entries // { description = "Starship configuration"; };
      default = { };
      example = literalExpression ''
        {
          add_newline = false;
          format = lib.concatStrings [
            "$line_break"
            "$package"
            "$line_break"
            "$character"
          ];
          scan_timeout = 10;
          character = {
            success_symbol = "➜";
            error_symbol = "➜";
          };
        }
      '';
      description = ''
        Configuration written to
        <filename>$XDG_CONFIG_HOME/starship.toml</filename>.
        </para><para>
        See <link xlink:href="https://starship.rs/config/" /> for the full list
        of options.
      '';
    };

    enableBashIntegration = mkEnableOption "Bash integration" // {
      default = true;
    };

    enableZshIntegration = mkEnableOption "Zsh integration" // {
      default = true;
    };

    enableFishIntegration = mkEnableOption "Fish integration" // {
      default = true;
    };

    enableIonIntegration = mkEnableOption "Ion integration" // {
      default = true;
    };

    enableNushellIntegration = mkEnableOption "Nushell integration" // {
      default = true;
    };
  };

  config = mkIf cfg.enable {
    assertions = [{
      assertion = cfg.enableNushellIntegration
        -> versionAtLeast config.programs.nushell.package.version "0.73";
      message = ''
        Nushell integration for starship requires nushell 0.73 or later.
      '';
    }];

    home.packages = [ cfg.package ];

    xdg.configFile."starship.toml" = mkIf (cfg.settings != { }) {
      source = tomlFormat.generate "starship-config" cfg.settings;
    };

    programs.bash.initExtra = mkIf cfg.enableBashIntegration ''
      if [[ $TERM != "dumb" && (-z $INSIDE_EMACS || $INSIDE_EMACS == "vterm") ]]; then
        eval "$(${starshipCmd} init bash --print-full-init)"
      fi
    '';

    programs.zsh.initExtra = mkIf cfg.enableZshIntegration ''
      if [[ $TERM != "dumb" && (-z $INSIDE_EMACS || $INSIDE_EMACS == "vterm") ]]; then
        eval "$(${starshipCmd} init zsh)"
      fi
    '';

    programs.fish.interactiveShellInit = mkIf cfg.enableFishIntegration ''
      if test "$TERM" != "dumb"  -a \( -z "$INSIDE_EMACS"  -o "$INSIDE_EMACS" = "vterm" \)
        eval (${starshipCmd} init fish)
      end
    '';

    programs.ion.initExtra = mkIf cfg.enableIonIntegration ''
      if test $TERM != "dumb" && not exists -s INSIDE_EMACS || test $INSIDE_EMACS = "vterm"
        eval $(${starshipCmd} init ion)
      end
    '';

    programs.nushell = mkIf cfg.enableNushellIntegration {
      # Unfortunately nushell doesn't allow conditionally sourcing nor
      # conditionally setting (global) environment variables, which is why the
      # check for terminal compatibility (as seen above for the other shells) is
      # not done here.
      extraEnv = ''
        let starship_cache = "${config.xdg.cacheHome}/starship"
        if not ($starship_cache | path exists) {
          mkdir $starship_cache
        }
        ${starshipCmd} init nu | save --force ${config.xdg.cacheHome}/starship/init.nu
      '';
      extraConfig = ''
        source ${config.xdg.cacheHome}/starship/init.nu
      '';
    };
  };
}