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

with lib;
let
  cfg = config.programs.aerc;

  primitive = with types;
    ((type: either type (listOf type)) (nullOr (oneOf [ str int bool float ])))
    // {
      description =
        "values (null, bool, int, string, or float) or a list of values, that will be joined with a comma";
    };

  confSection = types.attrsOf primitive;

  confSections = types.attrsOf confSection;

  sectionsOrLines = types.either types.lines confSections;

  accounts = import ./aerc-accounts.nix {
    inherit config pkgs lib confSection confSections;
  };

  aerc-accounts =
    attrsets.filterAttrs (_: v: v.aerc.enable) config.accounts.email.accounts;

  configDir = if (pkgs.stdenv.isDarwin && !config.xdg.enable) then
    "Library/Preferences/aerc"
  else
    "${config.xdg.configHome}/aerc";

in {
  meta.maintainers = with lib.hm.maintainers; [ lukasngl ];

  options.accounts.email.accounts = accounts.type;

  options.programs.aerc = {

    enable = mkEnableOption "aerc";

    package = mkPackageOption pkgs "aerc" { };

    extraAccounts = mkOption {
      type = sectionsOrLines;
      default = { };
      example = literalExpression
        ''{ Work = { source = "maildir://~/Maildir/work"; }; }'';
      description = ''
        Extra lines added to {file}`$HOME/.config/aerc/accounts.conf`.

        See {manpage}`aerc-config(5)`.
      '';
    };

    extraBinds = mkOption {
      type = sectionsOrLines;
      default = { };
      example = literalExpression ''{ messages = { q = ":quit<Enter>"; }; }'';
      description = ''
        Extra lines added to {file}`$HOME/.config/aerc/binds.conf`.
        Global keybindings can be set in the `global` section.

        See {manpage}`aerc-config(5)`.
      '';
    };

    extraConfig = mkOption {
      type = sectionsOrLines;
      default = { };
      example = literalExpression ''{ ui = { sort = "-r date"; }; }'';
      description = ''
        Extra lines added to {file}`$HOME/.config/aerc/aerc.conf`.

        See {manpage}`aerc-config(5)`.
      '';
    };

    stylesets = mkOption {
      type = with types; attrsOf (either confSection lines);
      default = { };
      example = literalExpression ''
        { default = { ui = { "tab.selected.reverse" = toggle; }; }; };
      '';
      description = ''
        Stylesets added to {file}`$HOME/.config/aerc/stylesets/`.

        See {manpage}`aerc-stylesets(7)`.
      '';
    };

    templates = mkOption {
      type = with types; attrsOf lines;
      default = { };
      example = literalExpression ''
        { new_message = "Hello!"; };
      '';
      description = ''
        Templates added to {file}`$HOME/.config/aerc/templates/`.

        See {manpage}`aerc-templates(7)`.
      '';
    };
  };

  config = let
    joinCfg = cfgs: concatStringsSep "\n" (filter (v: v != "") cfgs);

    toINI = conf: # quirk: global section is prepended w/o section heading
      let
        global = conf.global or { };
        local = removeAttrs conf [ "global" ];
        mkValueString = v:
          if isList v then # join with comma
            concatStringsSep "," (map (generators.mkValueStringDefault { }) v)
          else
            generators.mkValueStringDefault { } v;
        mkKeyValue =
          generators.mkKeyValueDefault { inherit mkValueString; } " = ";
      in joinCfg [
        (generators.toKeyValue { inherit mkKeyValue; } global)
        (generators.toINI { inherit mkKeyValue; } local)
      ];

    mkINI = conf: if isString conf then conf else toINI conf;

    mkStyleset = attrsets.mapAttrs' (k: v:
      let value = if isString v then v else toINI { global = v; };
      in {
        name = "${configDir}/stylesets/${k}";
        value.text = joinCfg [ header value ];
      });

    mkTemplates = attrsets.mapAttrs' (k: v: {
      name = "${configDir}/templates/${k}";
      value.text = v;
    });

    primaryAccount = attrsets.filterAttrs (_: v: v.primary) aerc-accounts;
    otherAccounts = attrsets.filterAttrs (_: v: !v.primary) aerc-accounts;

    primaryAccountAccounts = mapAttrs accounts.mkAccount primaryAccount;

    accountsExtraAccounts = mapAttrs accounts.mkAccount otherAccounts;

    accountsExtraConfig = mapAttrs accounts.mkAccountConfig aerc-accounts;

    accountsExtraBinds = mapAttrs accounts.mkAccountBinds aerc-accounts;

    joinContextual = contextual: joinCfg (map mkINI (attrValues contextual));

    isRecursivelyEmpty = x:
      if isAttrs x then
        all (x: x == { } || isRecursivelyEmpty x) (attrValues x)
      else
        false;

    genAccountsConf = ((cfg.extraAccounts != "" && cfg.extraAccounts != { })
      || !(isRecursivelyEmpty accountsExtraAccounts)
      || !(isRecursivelyEmpty primaryAccountAccounts));

    genAercConf = ((cfg.extraConfig != "" && cfg.extraConfig != { })
      || !(isRecursivelyEmpty accountsExtraConfig));

    genBindsConf = ((cfg.extraBinds != "" && cfg.extraBinds != { })
      || !(isRecursivelyEmpty accountsExtraBinds));

    header = ''
      # Generated by Home Manager.
    '';

  in mkIf cfg.enable {
    warnings = if genAccountsConf
    && (cfg.extraConfig.general.unsafe-accounts-conf or false) == false then [''
      aerc: `programs.aerc.enable` is set, but `...extraConfig.general.unsafe-accounts-conf` is set to false or unset.
      This will prevent aerc from starting; see `unsafe-accounts-conf` in the man page aerc-config(5):
      > By default, the file permissions of accounts.conf must be restrictive and only allow reading by the file owner (0600).
      > Set this option to true to ignore this permission check. Use this with care as it may expose your credentials.
      These permissions are not possible with home-manager, since the generated file is in the nix-store (permissions 0444).
      Therefore, please set `programs.aerc.extraConfig.general.unsafe-accounts-conf = true`.
      This option is safe; if `passwordCommand` is properly set, no credentials will be written to the nix store.
    ''] else
      [ ];

    assertions = [{
      assertion = let
        extraConfigSections = (unique (flatten
          (mapAttrsToList (_: v: attrNames v.aerc.extraConfig) aerc-accounts)));
      in extraConfigSections == [ ] || extraConfigSections == [ "ui" ];
      message = ''
        Only the ui section of $XDG_CONFIG_HOME/aerc.conf supports contextual (per-account) configuration.
        Please configure it with accounts.email.accounts._.aerc.extraConfig.ui and move any other
        configuration to programs.aerc.extraConfig.
      '';
    }];

    home.packages = [ cfg.package ];

    home.file = {
      "${configDir}/accounts.conf" = mkIf genAccountsConf {
        text = joinCfg [
          header
          (mkINI cfg.extraAccounts)
          (mkINI primaryAccountAccounts)
          (mkINI accountsExtraAccounts)
        ];
      };

      "${configDir}/aerc.conf" = mkIf genAercConf {
        text = joinCfg [
          header
          (mkINI cfg.extraConfig)
          (joinContextual accountsExtraConfig)
        ];
      };

      "${configDir}/binds.conf" = mkIf genBindsConf {
        text = joinCfg [
          header
          (mkINI cfg.extraBinds)
          (joinContextual accountsExtraBinds)
        ];
      };
    } // (mkStyleset cfg.stylesets) // (mkTemplates cfg.templates);
  };
}