{pkgs, lib, config, system, ...}:
let inherit (builtins) toString toFile;
    inherit (lib) types;
    inherit (pkgs.lib) unlines;
    inherit (config.services) dovecot2 postfix x509 openldap;
    when        = x: y: if x == null then "" else y;
    extSep      = postfix.recipientDelimiter;
    dirSep      = extSep;
    libDir      = "/var/lib/dovecot";
    mailDir     = "${libDir}/mail";
    sieveDir    = "${libDir}/sieve";
    authDir     = "${libDir}/auth";
    authUser    = dovecot2.mailUser;  # TODO: php_roundcube
    authGroup   = dovecot2.mailGroup; # TODO: php_roundcube
    escapeGroup = lib.stringAsChars (c: if "a"<=c && c<="z"
                                        || "0"<=c && c<="9"
                                        || c=="-"
                                        then c else "_");
    etc_dovecot = [
      { target = "dovecot/${config.networking.domain}/dovecot-ldap.conf";
        source = pkgs.writeText "dovecot-ldap.conf" ''
          ${lib.optionalString dovecot2.debug ''
            debug_level = 1
          ''}

          # LDAP database
          uris = ldapi://
          base = ou=posix,${openldap.domainSuffix}
          scope = subtree
          deref = never
          blocking = no
            # NOTE: sufficient for small systems and uses less resources.

          # LDAP auth
          sasl_bind = yes
          sasl_mech = EXTERNAL
          #dn = cn=admin,${openldap.domainSuffix}
          #dnpass = useless with sasl_mech=EXTERNAL
          auth_bind = no
          #auth_bind_userdn = cn=%n,ou=accounts,ou=posix,dc=${openldap.domainSuffix}

          # dovecot passdb query
          pass_filter = (&(objectClass=posixAccount)(uid=%n))
          pass_attrs = userPassword=password,\
                       uidNumber=userdb_uid,\
                       gidNumber=userdb_gid,\
                       mailGroupMember=mail_access_groups,\
                       =user=%n@%d
                       #homeDirectory=userdb_home
                       #quotaBytes=userdb_quota_rule=*:bytes=%{ldap:quotaBytes}
            # TODO: userdb_quota_rule=*:storage=
            # TODO: userdb_mail_access_groups
            # DOC: http://wiki2.dovecot.org/PasswordDatabase/ExtraFields
          default_pass_scheme = CRYPT

          # dovecot userdb query
          user_filter = (&(objectClass=posixAccount)(uid=%n))
          #user_filter = (&(objectClass=inetOrgPerson)(uid=%n)(mailEnabled=TRUE))
          #  # DOC: http://wiki2.dovecot.org/Variables
          #user_attrs = homeDirectory=home,uidNumber=uid,gidNumber=gid
          #user_attrs = mailHomeDirectory=home,\
          #              mailStorageDirectory=mail,\
          #              mailUidNumber=uid,\
          #              mailGidNumber=gid,\
          #              mailQuota=quota_rule=*:bytes=%$
          #  # DOC: http://wiki2.dovecot.org/UserDatabase/ExtraFields

          # doveadm user query
          iterate_attrs = =user=%{ldap:uid}@${config.networking.domain}
          iterate_filter = (objectClass=posixAccount)
        '';
      }
    ];
in
{
imports = [
  dovecot/autoconfig.nix
];
config = {
  systemd.services.dovecot2.after = [ "postfix.service" ];
  systemd.services.dovecot2.restartTriggers =
    map (f: f.source) etc_dovecot;
  environment.etc = etc_dovecot;
  #services.postfix.mapFiles."transport-dovecot" =
  #  toFile "transport-dovecot"
  #   (unlines
  #     (lib.mapAttrsToList
  #       (dom: {...}: "${transportSubDomain}.${dom} lmtp:unix:private/dovecot-lmtp")
  #       dovecot2.domains));
  #users.extraUsers = [
  #  { name        = "dovecot";
  #    uid         = config.ids.uids.dovecot2;
  #    description = "Dovecot user";
  #    group       = dovecot2.group;
  #  }
  #];
  users.extraGroups =
    lib.mapAttrs
     (domain: {...}:
      { name = escapeGroup "${dovecot2.mailGroup}-${domain}";
      })
     dovecot2.domains;
  systemd.services.dovecot2.preStart =
    let sieveList =
          pkgs.writeText "list.sieve" ''
          require
           [ "date"
           , "fileinto"
           , "mailbox"
           , "variables"
           ];

          if currentdate :matches "year"  "*" { set "year"  "''${1}"; }
          if currentdate :matches "month" "*" { set "month" "''${1}"; }

          if exists "List-ID" {
            if header :matches "List-ID" "*<*.*.*.*>*" {
              set "list"   "''${2}";
              set "domain" "''${4}";
            }
            elsif header :matches "List-ID" "*<*.*.*>*" {
              set "list"   "''${2}";
              set "domain" "''${3}";
            }
            fileinto :create "Listes+''${domain}+''${list}+''${year}+''${month}";
            stop;
           }
          '';
        sieveSpam =
          pkgs.writeText "spam.sieve" ''
          require
           [ "imap4flags"
           ];

          if header :contains "X-Spam-Level" "***" {
            addflag "Junk";
          }
          '';
        sieveExtension =
          pkgs.writeText "extension.sieve" ''
          require
           [ "envelope"
           , "fileinto"
           , "mailbox"
           , "subaddress"
           , "variables"
           ];
          if envelope :matches :detail "TO" "*" {
            set "extension" "''${1}";
          }
          if not string :is "''${extension}" "" {
            fileinto :create "Plus+''${extension}";
            stop;
          }
          '';
        dovecot-virtual =
          pkgs.writeText "dovecot-virtual" ''
          all
          all+*
            all
          '';
        installSieve = ''
          # SEE: http://wiki2.dovecot.org/SharedMailboxes/Permissions
          # NOTE: the sticky bit is to allow the acl.db{.lock,} done by dovecot
          install -D -d -m 2771 \
           -o ${dovecot2.mailUser} \
           -g ${dovecot2.mailGroup} \
           ${mailDir}

          # Install global sieves
          install -D -d -m 0755 \
           -o root \
           -g root \
           ${sieveDir} \
           ${sieveDir}/after.d \
           ${sieveDir}/before.d \
           ${sieveDir}/global.d
          ln -fns ${sieveList}      ${sieveDir}/global.d/list.sieve
          ln -fns ${sieveExtension} ${sieveDir}/global.d/extension.sieve
          ln -fns ${sieveSpam}      ${sieveDir}/global.d/spam.sieve
          for f in ${sieveDir}/*/*.sieve
           do ${pkgs.dovecot_pigeonhole}/bin/sievec $f
           done
        '';
        installPOP3 = ''
          # Install pop3 Inbox
          install -D -m 0644 \
           -o root \
           -g root \
           ${dovecot-virtual} \
           ${libDir}/pop3/INBOX/dovecot-virtual
        '';
        installDomains = ''
          # Install domains
          new_uid=5000
          ''
          + unlines (lib.mapAttrsToList (domain: {accounts, ...}:
            let domainGroup = escapeGroup "${dovecot2.mailGroup}-${domain}"; in
            ''
            install -D -d -m 1770 \
             -o ${dovecot2.mailUser} \
             -g ${domainGroup} \
             ${mailDir}/${domain} \
             ${libDir}/control/${domain} \
             ${libDir}/index/${domain}
            install -D -d -m 1770 \
             -o ${dovecot2.mailUser} \
             -g ${authGroup} \
             ${libDir}/auth \
             ${libDir}/auth/${domain}
            dir_passwd=${authDir}/${domain}
            old_passwd=$dir_passwd/passwd
            new_passwd=$(TMPDIR= mktemp --tmpdir=$dir_passwd -t passwd.XXXXXXXX.tmp)

            # Install users
            ''
            + unlines (lib.mapAttrsToList (user: acct: ''
              (
              home=${mailDir}/${domain}/${user}
              gecos=
              shell=/run/current-system/sw/bin/nologin
              if test -e $home
               then
                uid=$(stat -c %u $home)
                gid=$(stat -c %g $home)
               fi
              [ "''${uid:+set}" ] || {
                while test exists = "$(find $(dirname $home) -mindepth 1 -maxdepth 1 -uid $new_uid -printf exists -quit)"
                 do new_uid=$((new_uid + 1))
                 done
                uid=$new_uid
                gid=$new_uid
              }
              install -D -d -o $uid -g $gid -m 2770 $home $home/Maildir
              install    -d -o $uid -g $gid -m 0700 $home/sieve
              ''
              + unlines (lib.mapAttrsToList
                  (n: v: ''
                    install -D -m 640 -o $uid -g $gid \
                     ${pkgs.writeText "${n}.sieve" v} \
                     $home/sieve/${n}.sieve
                    ${pkgs.dovecot_pigeonhole}/bin/sievec \
                     $home/sieve/${n}.sieve
                  '')
                  acct.sieves)
              + ''
              mail_access_groups=${lib.concatStringsSep "," ([domainGroup] ++ acct.groups)}
              quota=${if lib.isString acct.quota
                      then ''"userdb_quota_rule=*:storage=${acct.quota}"''
                      else ""}
              extra_fields="userdb_uid=$uid userdb_gid=$gid userdb_mail_access_groups=$mail_access_groups $quota"
              #test ! -e $old_passwd || {
              #  # Preserve password changed by another mechanism, eg. roundcube.
              #  # But this also does not overwrite any old password set by this config.
              #  pass="$(sed -ne "s/^${user}:\([^:]*\):.*/\1/p" $old_passwd)"
              #}
              [ "''${pass:+set}" ] || {
                pass=${lib.escapeShellArg acct.password}
              }
              printf '%s\n' >>$new_passwd \
               "${user}:$pass:$uid:$gid:$gecos:$home:$shell:$extra_fields"
              )
            '') accounts)
            + ''
            install -o ${authUser} -g ${authGroup} -m 0640 $new_passwd $old_passwd
            rm $new_passwd
            ''
          ) dovecot2.domains);
    in
    unlines [
      installSieve
      installPOP3
      installDomains
    ];
  services.dovecot2 = {
    enable    = true;
    debug     = true;
    mailUser  = "dovemail";
    mailGroup = "dovemail";
    modules   = [
      #pkgs.dovecot_antispam
      pkgs.dovecot_pigeonhole
    ];
    configFile = toString (pkgs.writeText "dovecot.conf" ''
      passdb {
        driver = ldap
        args = /etc/dovecot/${config.networking.domain}/dovecot-ldap.conf
        default_fields =
        override_fields =
      }
      userdb {
        driver = prefetch
      }
      userdb {
        # NOTE: this userdb is only used by lda.
        driver = ldap
        args = /etc/dovecot/${config.networking.domain}/dovecot-ldap.conf
        default_fields =
        override_fields =
        skip = found
      }
      #passdb {
      #  driver = passwd-file
      #  args   = scheme=crypt username_format=%n ${authDir}/%d/passwd
      #}
      #userdb {
      #  # NOTE: this userdb is only used by lda.
      #  driver = passwd-file
      #  args = username_format=%n ${authDir}/%d/passwd
      #  #default_fields = home=${mailDir}/%d/%n
      #  skip = found
      #}
      mail_home = ${mailDir}/%d/%n
        # NOTE: if needed, may be overrided by userdb_mail
      mail_location = maildir:${mailDir}/%d/%n/Maildir:LAYOUT=fs:INDEX=${libDir}/index/%d/%n:CONTROL=${libDir}/control/%d/%n
        # NOTE: if needed, may be overrided by userdb_mail
        # NOTE: INDEX and CONTROL are on a partition without quota, as explain in the doc.
        # SEE: http://wiki2.dovecot.org/Quota/FS
      auth_mechanisms = plain login
      auth_ssl_require_client_cert = no
        # NOTE: postfix does not supply a client cert.
      auth_ssl_username_from_cert = yes
      auth_verbose = yes
      auth_username_format = %Lu
        # NOTE: lowercase the username, help with LDAP?
      ${lib.optionalString dovecot2.debug ''
        auth_debug  = yes
        mail_debug  = yes
        verbose_ssl = yes
      ''}
      default_internal_user = ${dovecot2.user}
      default_internal_group = ${dovecot2.group}
      disable_plaintext_auth = yes
      first_valid_uid = 1000
      lda_mailbox_autocreate = yes
      lda_mailbox_autosubscribe = yes
      listen = *
      log_timestamp = "%Y-%m-%d %H:%M:%S "
      #maildir_copy_with_hardlinks = yes
      namespace inbox {
        # NOTE: here because protocol sieve {namespace inbox{}} does not seem to work.
        inbox     = yes
        location  =
        list      = yes
        prefix    =
        separator = ${dirSep}
      }
      namespace {
        #list          = children
        list          = yes
        location      = maildir:${mailDir}/%d/%n/Maildir:LAYOUT=fs:INDEX=${libDir}/index/%d/%n/Shared/%n:CONTROL=${libDir}/control/%d/%n/Shared/%n
          # FIXME: %d not working
        prefix        = Partages+%%n+
        separator     = ${dirSep}
        subscriptions = yes
        type          = shared
      }
      mail_plugins = $mail_plugins acl quota virtual
      #mail_uid = ${dovecot2.mailUser}
      #mail_gid = ${dovecot2.mailGroup}
        # NOTE: each user has a dedicated (uid,gid) pair
      #mail_privileged_group = mail
      #mail_access_groups =
      plugin {
        acl = vfile:/etc/dovecot/acl/global.d
        acl_anyone = allow
        acl_shared_dict = file:${mailDir}/%d/acl.db
          # NOTE: to let users LIST mailboxes shared by other users,
          #       Dovecot needs a shared mailbox dictionary.
          # FIXME: %d not working with userdb ldap
        ##antispam_allow_append_to_spam = yes
        # # NOTE: pour offlineimap
        #antispam_backend = pipe
        ##antispam_crm_args = -u;${mailDir}/%d/.crm114;/usr/share/crm114/mailfilter.crm
        #antispam_crm_args = -u;${mailDir}/crm114;/usr/share/crm114/mailfilter.crm
        #antispam_crm_binary = /usr/bin/crm
        #antispam_debug_target = syslog
        ##antispam_crm_env = HOME=%h;USER=%u
        #antispam_ham_keywords = NonJunk
        #antispam_pipe_program = /usr/bin/crm
        #antispam_pipe_program_args = -u;${mailDir}/crm114;/usr/share/crm114/mailfilter.crm;--stats_only;--force
        #antispam_pipe_program_notspam_arg = --learnnonspam
        #antispam_pipe_program_spam_arg = --learnspam
        #antispam_pipe_program_unlearn_spam_args = --unlearn;--learnspam
        #antispam_pipe_program_unlearn_notspam_args = --unlearn;--learnnonspam
        #antispam_pipe_tmpdir = ${mailDir}/crm114/tmp
        #antispam_signature = X-CRM114-CacheID
        #antispam_signature_missing = move
        #antispam_spam = Junk
        #antispam_spam_keywords = Junk
        #antispam_trash = Trash
        #antispam_unsure = Unsure
        #antispam_verbose_debug = 0
        quota = maildir:User quota
        quota_rule = *:storage=256M
        quota_rule2 = Trash:storage=+64M
        quota_max_mail_size = 20M
        #quota_exceeded_message = </path/to/quota_exceeded_message.txt
        quota_warning  = storage=95%% quota-warning 95 %u
        quota_warning2 = storage=80%% quota-warning 80 %u
        quota_warning3 = -storage=100%% quota-warning below %u
         # NOTE: user is no longer over quota
        recipient_delimiter = ${extSep}
        sieve = file:${mailDir}/%d/%n/sieve;active=${mailDir}/%d/%n/sieve/main.sieve
        #sieve_default = file:${mailDir}/%u/default.sieve
        #sieve_default_name = default
        sieve_after  = ${sieveDir}/after.d/
        sieve_before = ${sieveDir}/before.d/
        sieve_dir = ${mailDir}/%d/%n/sieve/
        #sieve_extensions = +spamtest +spamtestplus
        sieve_global_dir = ${sieveDir}/global.d/
        sieve_max_script_size = 1M
        sieve_quota_max_scripts = 0
        sieve_quota_max_storage = 10M
        sieve_spamtest_max_value = 10
        sieve_spamtest_status_header = X-Spam-Score
        sieve_spamtest_status_type = strlen
        sieve_user_log = /var/log/dovecot/%d/sieve.%n.log
      }
      service quota-warning {
        executable = script ${
          pkgs.writeScript "quota-warning" ''
            #!/bin/sh -eu
            PERCENT=$1
            USER=$2
            cat << EOF | ${pkgs.dovecot}/libexec/dovecot/dovecot-lda -d $USER -o
            "plugin/quota=maildir:User quota:noenforcing"
            From: postmaster@${config.networking.domain}
            Subject: [WARNING] your mailbox is now $PERCENT% full.

            Please remove some mails to make room for new ones.
            EOF
          ''
        }
        # use some unprivileged user for executing the quota warnings
        user = ${dovecot2.user}
        unix_listener quota-warning {
        }
      }
      protocol imap {
        #mail_max_userip_connections = 10
        mail_plugins = $mail_plugins imap_acl imap_quota # antispam
        namespace inbox {
          inbox = yes
          location =
          list = yes
          mailbox Drafts {
            special_use = \Drafts
          }
          mailbox Junk {
            special_use = \Junk
          }
          mailbox Sent {
            special_use = \Sent
          }
          mailbox "Sent Messages" {
            special_use = \Sent
          }
          mailbox Trash {
            special_use = \Trash
          }
          prefix =
          separator = ${dirSep}
        }
      }
      protocol lda {
        auth_socket_path = /var/run/dovecot/auth-userdb
        hostname         = ${config.networking.domain}
        info_log_path    =
        log_path         =
        mail_plugins     = $mail_plugins sieve
        namespace inbox {
          inbox     = yes
          location  =
          list      = yes
          prefix    =
          separator = ${dirSep}
        }
        postmaster_address = postmaster${extSep}dovecot${extSep}lda@${config.networking.domain}
        syslog_facility = mail
      }
      protocol lmtp {
        #info_log_path = /tmp/dovecot-lmtp.log
        mail_plugins = $mail_plugins sieve
        namespace inbox {
          inbox     = yes
          location  =
          list      = yes
          prefix    =
          separator = ${dirSep}
        }
        postmaster_address = postmaster${extSep}dovecot${extSep}lmtp@${config.networking.domain}
      }
      protocol pop3 {
        #mail_max_userip_connections = 10
        namespace all {
          # NOTE: used by ${libDir}/pop3/INBOX/dovecot-virtual
          hidden    = yes
          list      = no
          location  =
          prefix    = all+
          separator = ${dirSep}
        }
        # Virtual namespace for the virtual INBOX.
        # Use a global directory for dovecot-virtual files.
        namespace inbox {
          inbox     = yes
          hidden    = yes
          list      = no
          location  = virtual:${libDir}/pop3:INDEX=${libDir}/index/%d/%n/POP3:LAYOUT=fs
          prefix    = pop3+
          separator = ${dirSep}
        }
        pop3_client_workarounds =
        pop3_fast_size_lookups = yes
        pop3_lock_session = yes
        pop3_no_flag_updates = yes
        # Use GUIDs to avoid accidental POP3 UIDL changes instead of IMAP UIDs.
        pop3_uidl_format = %g
      }
      protocol sieve {
        #mail_max_userip_connections = 10
        #managesieve_implementation_string = Dovecot Pigeonhole
        managesieve_max_compile_errors = 5
        #managesieve_max_line_length = 65536
        #managesieve_notify_capability = mailto
        #managesieve_sieve_capability = fileinto reject envelope encoded-character vacation subaddress comparator-i;ascii-numeric relational regex imap4flags copy include variables body enotify environment mailbox date ihave
      }
      protocols = imap lmtp pop3 sieve
      service lmtp {
        #executable = lmtp -L
        process_min_avail = 2
        unix_listener /var/lib/postfix/queue/private/dovecot-lmtp {
          user  = ${postfix.user}
          group = ${postfix.group}
          mode  = 0600
        }
        #user = mail
      }
      service auth {
        user = root
          # FIXME: may be user=dovecot-auth with LDAP?
        unix_listener auth-userdb {
          user  = ${dovecot2.user}
          group = ${dovecot2.group}
          mode  = 0660
        }
        unix_listener /var/lib/postfix/queue/private/auth {
          user  = ${postfix.user}
          group = ${postfix.group}
          mode  = 0660
        }
      }
      service imap {
        # Most of the memory goes to mmap()ing files.
        # You may need to increase this limit if you have huge mailboxes.
        #vsz_limit =
        process_limit = 1024
      }
      service imap-login {
        #inet_listener imap {
        #  address = 127.0.0.1
        #  port    = 143
        #  ssl     = no
        #}
        inet_listener imaps {
          port = 993
          ssl  = yes
        }
      }
      service pop3 {
        process_limit = 1024
      }
      service pop3-login {
        inet_listener pop3s {
          port = 995
          ssl  = yes
        }
      }
      ssl = required
      ssl_dh = <${x509.dir}/dh.pem
      ssl_cipher_list = HIGH:!LOW:!SSLv2:!EXP:!aNULL
      ssl_cert = <${x509.cert}
      ssl_key = <${x509.key}
      #ssl_ca   = <''${caPath}
      #ssl_verify_client_cert = yes
    '');
      #${lib.concatMapStringsSep "\n"
      #    (dom: ''
      #      local_name mail.${dom} {
      #        #ssl_ca   = <''${caPath}
      #        ssl_cert = <${x509.cert dom}
      #        ssl_key  = <${x509.key dom}
      #        }
      #    '')
      #    dovecot2.domains
      #}
  };
};
}