//! Deriving `NetdocEncodable`

use super::*;

use derive_deftly::{define_derive_deftly, define_derive_deftly_module};

/// Not `Copy`, used to detect when other arguments come after a `rest` field

///

/// Implementation detail of the encoding derives.

#[doc(hidden)]

#[allow(clippy::exhaustive_structs)]

pub struct RestMustComeLastMarker;

/// Displays `T` using the `fmt` function `F`

///

/// Implementation detail of the encoding derives.

#[doc(hidden)]

#[allow(clippy::exhaustive_structs)]

pub struct DisplayHelper<'t, T, F>(pub &'t T, pub F)

where

    F: Fn(&T, &mut fmt::Formatter) -> fmt::Result;

impl<'t, T, F> Display for DisplayHelper<'t, T, F>

where

    F: Fn(&T, &mut fmt::Formatter) -> fmt::Result,

{

}

define_derive_deftly_module! {

    /// Common definitions for `NetdocEncodable` and `NetdocEncodableFields`

    ///

    /// Importer must also import `NetdocSomeItemsDeriveCommon` and `NetdocDeriveAnyCommon`.

    NetdocSomeItemsEncodableCommon beta_deftly:

    ${define P { $crate::encode }}

    // Suffix for error handling - specifically to add field information.

    //

    // Usage:

    //    some_function().$BUG_CONTEXT?;

    ${define BUG_CONTEXT {

        // We use .map_err() rather than .bug_context() so that we nail down the error type

            ${concat "in netdoc " $ttype ", in field " $F_KEYWORD_REPORT}

        ))

    }}

    // Body of an encoding function.

    //

    //    | <- macro conditions and loops are aligned starting here

    //    |         | <- we line up the normal Rust statements starting here

    ${define ENCODE_ITEMS_BODY {

                    $EMIT_DEBUG_PLACEHOLDER

          // Add an item with keyword $F_KEYWORD_STR and value `item`

          ${define ENCODE_ITEM_VALUE {

                    #[allow(unused_mut)]

                    let mut item_out = out.item($F_KEYWORD_STR);

            ${if fmeta(netdoc(with)) {

                    ${fmeta(netdoc(with)) as path}

                        ::${paste_spanned $fname write_item_value_onto}

                        (item, item_out)

                        .$BUG_CONTEXT?;

            } else if fmeta(netdoc(single_arg)) {

                    selector.${paste_spanned $fname check_item_argument_encodable}();

                    ItemArgument::${paste_spanned $fname write_arg_onto}

                        (item, &mut item_out)

                        .$BUG_CONTEXT?;

                    item_out.finish();

            } else {

                    selector.${paste_spanned $fname check_item_value_encodable}();

                    ItemValueEncodable

                        ::${paste_spanned $fname write_item_value_onto}

                        (item, item_out)

                        .$BUG_CONTEXT?;

            }}

          }}

          // Are we skipping encoding default values?

          ${defcond WANT_SKIP_DEFAULT fmeta(netdoc(default(skip)))}

          // If so, provide a function (bound method call) to test defaultness.

          ${define IS_DEFAULT { selector.${paste_spanned $fname is_default} }}

          // Bind `selector` to an appropriate selector ZST.

          ${define LET_SELECTOR {

              ${if WANT_SKIP_DEFAULT {

                         let selector = SingletonMultiplicitySelector::<$ftype>::default();

              } else {

                         let selector = MultiplicitySelector::<$ftype>::default();

              }}

                         let selector = selector.selector();

          }}

          ${for fields {

                    { // Rust block for bindings for this field (notably `selector`, `item`

            // ignore #[deftly(netdoc(default))] precisely like NetdocSomeItemsParseableCommon

            ${if not(F_INTRO) {

                ${if fmeta(netdoc(default)) {}}

            }}

            ${select1

              F_INTRO {

                        #[allow(unused)] // `with` can make this unused

                        let selector = SingletonMultiplicitySelector::<$ftype>::default();

                        let item = &self.$fname;

                        $ENCODE_ITEM_VALUE

              }

              F_NORMAL {

                        $LET_SELECTOR

                        for item in selector.${paste_spanned $fname iter_ordered}(&self.$fname) {

                  ${if WANT_SKIP_DEFAULT {

                            if !$IS_DEFAULT(item)

                  }}

                            {

                                $ENCODE_ITEM_VALUE

                            }

                        }

              }

              F_FLATTEN {

                        <$ftype as NetdocEncodableFields>::encode_fields

                            (&self.$fname, out)

                            .$BUG_CONTEXT?;

              }

              F_SUBDOC {

                        $LET_SELECTOR

                        selector.${paste_spanned $fname check_netdoc_encodable}();

                        for subdoc in selector.iter_ordered(&self.$fname) {

                  ${if WANT_SKIP_DEFAULT {

                            if !$IS_DEFAULT(subdoc)

                  }}

                            {

                                NetdocEncodable::encode_unsigned(subdoc, out)

                                    .$BUG_CONTEXT?;

                            }

                        }

              }

              F_SKIP {

              }

            }

                    } // field block.

          }} // ${for fields ..}

                    Ok(())

    }}

}

define_derive_deftly! {

    use NetdocDeriveAnyCommon;

    use NetdocEntireDeriveCommon;

    use NetdocSomeItemsDeriveCommon;

    use NetdocSomeItemsEncodableCommon;

    /// Derive [`NetdocEncodable`] for a document (or sub-document)

    ///

    // NB there is very similar wording in the NetdocParseable derive docs.

    // If editing any of this derive's documentation, considering editing that too.

    //

    // We could conceivably template this, but without a `$///` string templater in derive-deftly

    // that would be very tiresome, and it might be a bad idea anyway.

    //

    /// ### Expected input structure

    ///

    /// Should be applied named-field struct, where each field is

    /// an Item which may appear in the document,

    /// or a sub-document.

    ///

    /// The first field will be the document's intro Item.

    /// The output Keyword for each Item will be kebab-case of the field name.

    ///

    /// ### Field type

    ///

    /// Each field must be

    ///  * `impl `[`ItemValueEncodable`] for an "exactly once" field,

    ///  * `Vec<T: ItemValueEncodable>` for "zero or more", or

    ///  * `BTreeSet<T: ItemValueEncodable + Ord>`, or

    ///  * `Option<T: ItemValueEncodable>` for "zero or one".

    ///

    /// We don't directly support "at least once"; if the value is empty,

    /// the encoder will produce a structurally correct but semantically invalid document.

    ///

    /// (Multiplicity is implemented via types in the [`multiplicity`] module,

    /// specifically [`MultiplicitySelector`] and [`MultiplicityMethods`].)

    ///

    /// ### Signed documents

    ///

    /// TODO NETDOC ENCODE this is not yet supported.

    ///

    /// ### Top-level attributes:

    ///

    /// * **`#[deftly(netdoc(signatures))]`**:

    ///

    ///   This type is the signatures section of another document.

    ///   TODO NETDOC ENCODE This is not yet supported, and will fail to compile.

    ///

    $DOC_DEBUG_PLACEHOLDER

    ///

    /// # **`#[deftly(netdoc(doctype_for_error = EXPRESSION))]`**:

    ///

    ///   Ignored.  (The encoder does not report errors this way.)

    ///

    ///   Accepted for alignment with `NetdocParseable`,

    ///   so that a struct which only conditionally derives `NetdocParseable`

    ///   does not need to conditionally mark this attribute.

    ///

    /// ### Field-level attributes:

    ///

    /// * **`#[deftly(netdoc(keyword = STR))]`**:

    ///

    ///   Use `STR` as the Keyword for this Item.

    ///

    /// * **`#[deftly(netdoc(single_arg))]`**:

    ///

    ///   The field type implements `ItemArgument`,

    ///   instead of `ItemValueEncodable`,

    ///   and is encoded as if `(FIELD_TYPE,)` had been written.

    ///

    /// * **`#[deftly(netdoc(with = MODULE))]`**:

    ///

    ///   Instead of `ItemValueEncodable`, the item is parsed with

    ///   `MODULE::write_item_value_onto`,

    ///   which must have the same signature as [`ItemValueEncodable::write_item_value_onto`].

    ///

    ///   (Not supported for sub-documents, signature items, or field collections.)

    ///

    /// * **`#[deftly(netdoc(flatten))]`**:

    ///

    ///   This field is a struct containing further individual normal fields.

    ///   The Items for those individual fields appear in this

    ///   outer document here, so interspersed with other normal fields.

    ///

    ///   The field type must implement [`NetdocEncodableFields`].

    ///

    /// * **`#[deftly(netdoc(skip))]`**:

    ///

    ///   This field doesn't really appear in the network document.

    ///   It will be ignored during encoding.

    ///

    /// * **`#[deftly(netdoc(subdoc))]`**:

    ///

    ///   This field is a sub-document.

    ///   The value type `T` must implement [`NetdocEncodable`]

    ///   *instead of* `ItemValueEncodable`.

    ///

    ///   The field name is not used for parsging;

    ///   the sub-document's intro keyword is used instead.

    ///

    /// # **`#[deftly(netdoc(default))]`**:

    ///

    ///   Ignored.  (The encoder always encodes the field, regardless of the value.)

    ///

    ///   Accepted for alignment with `NetdocParseable`.

    ///

    /// # **`#[deftly(netdoc(default(skip)))]`**:

    ///

    ///   Omit encoding this item if the value is [`Eq`] to the [`Default`].

    ///   Forces the multiplicity of the field to be treated as a singleton.

    ///

    ///   Can be combined with `single_arg`, `with`, and with `subdoc`.

    ///

    /// # Example

    ///

    /// TODO NETDOC ENCODE provide an example when signatures are implemented.

    export NetdocEncodable beta_deftly, for struct, meta_quoted rigorous, expect items:

    impl<$tgens> $P::NetdocEncodable for $ttype {

            use $P::*;

            $FIELD_ORDERING_CHECK

            $ENCODE_ITEMS_BODY

    }

}

define_derive_deftly! {

    use NetdocDeriveAnyCommon;

    use NetdocFieldsDeriveCommon;

    use NetdocSomeItemsDeriveCommon;

    use NetdocSomeItemsEncodableCommon;

    /// Derive [`NetdocEncodableFields`] for a struct with individual items

    ///

    /// Similar to

    /// [`#[derive_deftly(NetdocEncodable)]`](derive_deftly_template_NetdocEncodable),

    /// but:

    ///

    ///  * Derives [`NetdocEncodableFields`]

    $DOC_NETDOC_FIELDS_DERIVE_SUPPORTED

    ///

    export NetdocEncodableFields beta_deftly, for struct, meta_quoted rigorous, expect items:

    impl<$tgens> $P::NetdocEncodableFields for $ttype {

            #[allow(unused)] // Not used if there are no fields.

            use $P::*;

            $ENCODE_ITEMS_BODY

    }

}

define_derive_deftly! {

    use NetdocDeriveAnyCommon;

    use NetdocItemDeriveCommon;

    /// Derive `ItemValueEncodable`

    ///

    // NB there is very similar wording in the ItemValuePareable derive docs.

    // If editing any of this derive's documentation, considering editing that too.

    //

    /// Fields in the struct are emitted as keyword line arguments,

    /// in the order they appear in the struct.

    ///

    /// ### Field type

    ///

    /// Each field should be:

    ///

    ///  * `impl `[`ItemArgument`] (one argument),

    ///  * `Option<impl ItemArgument>` (one optional argument), or

    ///  * `Vec<impl ItemArgument + EncodeOrd>` (zero or more arguments).

    ///  * `BTreeSet<impl ItemArgument>` (zero or more arguments).

    ///

    /// `ItemArgument` can be implemented via `impl Display`,

    /// by writing `impl NormalItemArgument`.

    ///

    /// (Multiplicity is implemented via types in the [`multiplicity`] module,

    /// specifically [`MultiplicitySelector`] and [`MultiplicityMethods`].)

    ///

    /// ### Top-level attributes:p

    ///

    ///  * **`#[deftly(netdoc(no_extra_args))]**:

    ///

    ///    Ignored.

    ///    (Obviously, the encoder never emits arguments that aren't in the document struct.)

    ///

    ///    Accepted for alignment with `ItemValueParseable`,

    ///    so that a struct which only conditionally derives `ItemValueParseable`

    ///    does not need to conditionally mark this attribute.

    ///

    ///    (May not be combined with `#[deftly(netdoc(rest))]`.)

    ///

    $DOC_DEBUG_PLACEHOLDER

    ///

    /// ### Field-level attributes:

    ///

    ///  * **`#[deftly(netdoc(rest))]**:

    ///

    ///    The field is the whole rest of the line.

    ///    Must come after any other normal argument fields.

    ///    Only allowed once.

    ///

    ///    The field type must implement `ToString` (normally, via `Display`).

    ///    (I.e. `Vec` , `Option` etc., are not allowed, and `ItemArgumen` is not used.)

    ///

    ///  * **`#[deftly(netdoc(object))]**:

    ///

    ///    The field is the Object.

    ///    It must implement [`ItemObjectEncodable`].

    ///    (or be `Option<impl ItemObjectEncodable>`).

    ///

    ///    Only allowed once.

    ///

    ///  * **`#[deftly(netdoc(object(label = "LABEL")))]**:

    ///

    ///    Sets the expected label for an Object.

    ///    If not supplied, uses [`ItemObjectEncodable::label`].

    ///

    ///  * **`#[deftly(netdoc(with = MODULE)]**:

    ///

    ///    Instead of `ItemArgument`, the argument is encoded with `MODULE::write_arg_onto`,

    ///    which must have the same signature as [`ItemArgument::write_arg_onto`].

    ///

    ///    With `#[deftly(netdoc(rest))]`, `MODULE::fmt_args_rest` replaces `Display::fmt`.

    ///

    ///    With `#[deftly(netdoc(object))]`, uses `MODULE::write_object_onto`

    ///    instead of `tor_netdoc::Writeable::write_onto`.

    ///    LABEL must also be specified unless the object also implements `ItemObjectEncodable`.

    ///

    ///  * **`#[deftly(netdoc(sig_hash = HASH_METHOD))]**:

    ///

    ///    TODO NETDOC ENCODE.  Encoding of signed documents is not yet implemented.

    ///

    ///  * **`#[deftly(netdoc(skip))]**:

    ///

    ///    Do not encode this field.

    export ItemValueEncodable beta_deftly, for struct, meta_quoted rigorous, expect items:

    ${define P { $crate::encode }}

    ${define BUG_CONTEXT {

        // We use .map_err() rather than .bug_context() so that we nail down the error type

            ${concat "in item " $ttype ", in field " $fname}

        ))

    }}

    impl<$tgens> $P::ItemValueEncodable for $ttype {

          //  | <- macro conditions and loops are aligned starting here

          //  |         | <- we line up the normal Rust statements starting here

                        #[allow(unused_imports)]

                        use $P::*;

                        #[allow(unused_imports)]

                        use tor_error::BugContext as _;

                        $EMIT_DEBUG_PLACEHOLDER

                        // ignore #[deftly(netdoc(doctype_for_error = EXPR))]

                        #[allow(unused)]

              ${for fields {

              }}

                // Look at some almost-entirely-ignored attributes.

                ${if tmeta(netdoc(no_extra_args)) {

                }}

              ${for fields {

                ${when F_OBJECT}

                        {

                ${define CHECK_OBJECT_ENCODABLE {

                }}

                            // This is, sort of, a recapitulation of `ItemEncoder::object`.

                            // We can't conveniently just call that because we want to support

                            // overriding the label, even when we're using ItemObjectEncodable.

                            // Bind to `label`

                ${fmeta(netdoc(object(label))) as str, default {

                                {

                                    $CHECK_OBJECT_ENCODABLE

                                }

                }}

                                ;

                            // Obtain the `data`

                      ${fmeta(netdoc(with)) as path, default {

              }}

    }

}