//! Tables related to web page metadata, XRD and JRD, `host-meta`, `WebFinger`, and so on.
//!
//! # Intended usage
//!
//! 1. An user agent requests an application for the descriptor for a given resource;
//! 2. **The application queries the database using these structures to:**
//! 	1. [Determine if a descriptor should be returned, or if it should be handled by another application](MetaSubject);
//! 	2. [Determine which aliases the resource has](MetaAlias);
//! 	3. [Determine which properties the resource has](MetaProperty);
//! 	4. [Determine which links the resource has](MetaLink);
//! 	5. [Determine the titles of each link](MetaLinkTitle);
//! 	6. [Determine the properties of each link](MetaLinkProperty);
//! 3. The application compiles the data in a single structure that the user agent supports
//! 4. The application returns the data to the user agent
//!
//! # Matching
//!
//! Matching is performed for each single record separately, allowing for example a system administrator to define many separate subjects while globally defining a property for all the resources served.
//!
//! # Reference
//!
//! See [`acrate_rd`] for more information on the specification these structures are based on.
//!
//! # Used by
//!
//! - [`acrate_rdserver`]
//!

use diesel::deserialize::FromSql;
use diesel::{AsExpression, Associations, FromSqlRow, Identifiable, Insertable, IntoSql, PgTextExpressionMethods, QueryResult, Queryable, QueryableByName, Selectable, SelectableHelper, ExpressionMethods, BelongingToDsl};
use diesel::pg::{Pg, PgConnection};
use diesel::serialize::{Output, ToSql};
use diesel_async::AsyncPgConnection;
use mediatype::MediaTypeBuf;
use uuid::Uuid;

use crate::schema;
use crate::impl_to_insert;

/// Wrapper to use [`mime::Mime`] with [`diesel`].
#[derive(Debug, Clone, PartialEq, Eq, FromSqlRow, AsExpression)]
#[diesel(sql_type = diesel::sql_types::Text)]
pub struct MediaTypeDatabase(pub MediaTypeBuf);


/// A matchable record denoting the existence of a resource descriptor.
///
/// # See also
///
/// - [`MetaSubjectInsert`]
///
#[derive(Debug, Queryable, QueryableByName, Identifiable, Selectable)]
#[diesel(table_name = schema::meta_subjects)]
#[diesel(check_for_backend(Pg))]
pub struct MetaSubject {
	
	/// The identity column of the record.
	pub id: Uuid,
	
	/// The document the record is valid for.
	pub document: String,
	
	/// The [PostgreSQL ILIKE pattern] to match the search term against for the record to be valid.
	///
	/// [PostgreSQL ILIKE pattern]: https://www.postgresql.org/docs/current/functions-matching.html#FUNCTIONS-LIKE
	pub pattern: String,
	
	/// The value the `subject` property should take when this record is matched.
	///
	/// If [`None`], its value is up for specification by the querying application.
	pub subject: Option<String>,
	
	/// Where the querying application should redirect the user agent to when this record is matched.
	///
	/// If [`Some`], should always override everything else.
	pub redirect: Option<String>,
}

/// An [`Insertable`] version of [`MetaSubject`].
#[derive(Debug, Insertable)]
#[diesel(table_name = schema::meta_subjects)]
#[diesel(check_for_backend(Pg))]
pub struct MetaSubjectInsert {
	
	/// The document the record is valid for.
	pub document: String,
	
	/// The [PostgreSQL ILIKE pattern] to match the search term against for the record to be valid.
	///
	/// [PostgreSQL ILIKE pattern]: https://www.postgresql.org/docs/current/functions-matching.html#FUNCTIONS-LIKE
	pub pattern: String,
	
	/// The value the `subject` property should take when this record is matched.
	///
	/// If [`None`], its value is up for specification by the querying application.
	pub subject: Option<String>,
	
	/// Where the querying application should redirect the user agent to when this record is matched.
	///
	/// If [`Some`], should always override everything else.
	pub redirect: Option<String>,
}

/// A matchable record denoting an alias belonging to a subject.
///
/// # See also
///
/// - [`MetaAliasInsert`]
///
#[derive(Debug, Queryable, QueryableByName, Identifiable, Selectable)]
#[diesel(table_name = schema::meta_aliases)]
#[diesel(check_for_backend(Pg))]
pub struct MetaAlias {
	
	/// The identity column of the record.
	pub id: Uuid,
	
	/// The document the record is valid for.
	pub document: String,
	
	/// The [PostgreSQL ILIKE pattern] to match the search term against for the record to be valid.
	///
	/// [PostgreSQL ILIKE pattern]: https://www.postgresql.org/docs/current/functions-matching.html#FUNCTIONS-LIKE
	pub pattern: String,
	
	/// The alias to **add** to the list of aliases of the resource.
	pub alias: String,
}

/// An [`Insertable`] version of [`MetaAlias`].
#[derive(Debug, Insertable)]
#[diesel(table_name = schema::meta_aliases)]
#[diesel(check_for_backend(Pg))]
pub struct MetaAliasInsert {
	
	/// The document the record is valid for.
	pub document: String,
	
	/// The [PostgreSQL ILIKE pattern] to match the search term against for the record to be valid.
	///
	/// [PostgreSQL ILIKE pattern]: https://www.postgresql.org/docs/current/functions-matching.html#FUNCTIONS-LIKE
	pub pattern: String,
	
	/// The alias to **add** to the list of aliases of the resource.
	pub alias: String,
}

/// A matchable record denoting a link towards another resource someway related with the subject.
///
/// # See also
///
/// - [`MetaLinkInsert`]
///
#[derive(Debug, Queryable, QueryableByName, Identifiable, Selectable)]
#[diesel(table_name = schema::meta_links)]
#[diesel(check_for_backend(Pg))]
pub struct MetaLink {
	
	/// The identity column of the record.
	pub id: Uuid,
	
	/// The document the record is valid for.
	pub document: String,
	
	/// The [PostgreSQL ILIKE pattern] to match the search term against for the record to be valid.
	///
	/// [PostgreSQL ILIKE pattern]: https://www.postgresql.org/docs/current/functions-matching.html#FUNCTIONS-LIKE
	pub pattern: String,
	
	/// The relationship the link establishes between itself and the value of the link.
	pub rel: String,
	
	/// The media type of the value of the link.
	///
	/// Can be [`None`] if it shouldn't be specified.
	pub type_: Option<MediaTypeDatabase>,
	
	/// The URI to the document this property is linking the subject to.
	///
	/// Can be [`None`] if it shouldn't be specified, for example if [`Self::template`] is [`Some`].
	pub href: Option<String>,
	
	/// The template to the document this property is linking the subject to.
	///
	/// Can be [`None`] if it shouldn't be specified, for example if [`Self::href`] is [`Some`].
	pub template: Option<String>,
}

/// An [`Insertable`] version of [`MetaLink`].
#[derive(Debug, Insertable)]
#[diesel(table_name = schema::meta_links)]
#[diesel(check_for_backend(Pg))]
pub struct MetaLinkInsert {
	
	/// The document the record is valid for.
	pub document: String,
	
	/// The [PostgreSQL ILIKE pattern] to match the search term against for the record to be valid.
	///
	/// [PostgreSQL ILIKE pattern]: https://www.postgresql.org/docs/current/functions-matching.html#FUNCTIONS-LIKE
	pub pattern: String,
	
	/// The relationship the link establishes between itself and the value of the link.
	pub rel: String,
	
	/// The media type of the value of the link.
	///
	/// Can be [`None`] if it shouldn't be specified.
	pub type_: Option<MediaTypeDatabase>,
	
	/// The URI to the document this property is linking the subject to.
	///
	/// Can be [`None`] if it shouldn't be specified, for example if [`Self::template`] is [`Some`].
	pub href: Option<String>,
	
	/// The template to the document this property is linking the subject to.
	///
	/// Can be [`None`] if it shouldn't be specified, for example if [`Self::href`] is [`Some`].
	pub template: Option<String>,
}

/// A property that a [`MetaLink`] has.
///
/// # See also
///
/// - [`MetaLinkPropertyInsert`]
///
#[derive(Debug, Queryable, QueryableByName, Identifiable, Selectable, Associations)]
#[diesel(belongs_to(MetaLink))]
#[diesel(table_name = schema::meta_link_properties)]
#[diesel(check_for_backend(Pg))]
pub struct MetaLinkProperty {
	
	/// The identity column of the record.
	pub id: Uuid,
	
	/// The [`MetaLink::id`] this record refers to.
	pub meta_link_id: Uuid,
	
	/// The relationship the property establishes between the [`MetaLink`] and the [`MetaLinkProperty::value`].
	pub rel: String,
	
	/// The value that the property has.
	pub value: Option<String>,
}

/// An [`Insertable`] version of [`MetaLinkProperty`].
#[derive(Debug, Insertable)]
#[diesel(belongs_to(MetaLink))]
#[diesel(table_name = schema::meta_link_properties)]
#[diesel(check_for_backend(Pg))]
pub struct MetaLinkPropertyInsert {
	
	/// The [`MetaLink::id`] this record refers to.
	pub meta_link_id: Uuid,
	
	/// The relationship the property establishes between the [`MetaLink`] and the [`MetaLinkProperty::value`].
	pub rel: String,
	
	/// The value that the property has.
	pub value: Option<String>,
}

/// A title that a [`MetaLink`] has in a certain language.
#[derive(Debug, Queryable, QueryableByName, Identifiable, Selectable, Associations)]
#[diesel(belongs_to(MetaLink))]
#[diesel(table_name = schema::meta_link_titles)]
#[diesel(check_for_backend(Pg))]
pub struct MetaLinkTitle {
	
	/// The identity column of the record.
	pub id: Uuid,
	
	/// The [`MetaLink::id`] this record refers to.
	pub meta_link_id: Uuid,
	
	/// The language of the title.
	pub language: String,
	
	/// The actual contents of the title.
	pub value: String,
}

/// An [`Insertable`] version of [`MetaLinkTitle`].
#[derive(Debug, Insertable)]
#[diesel(belongs_to(MetaLink))]
#[diesel(table_name = schema::meta_link_titles)]
#[diesel(check_for_backend(Pg))]
pub struct MetaLinkTitleInsert {
	
	/// The [`MetaLink::id`] this record refers to.
	pub meta_link_id: Uuid,
	
	/// The language of the title.
	pub language: String,
	
	/// The actual contents of the title.
	pub value: String,
}

/// A matchable record denoting a property that a subject has.
///
/// # See also
///
/// - [`MetaPropertyInsert`]
///
#[derive(Debug, Queryable, QueryableByName, Identifiable, Selectable)]
#[diesel(table_name = schema::meta_properties)]
#[diesel(check_for_backend(Pg))]
pub struct MetaProperty {
	
	/// The identity column of the record.
	pub id: Uuid,
	
	/// The document the record is valid for.
	pub document: String,
	
	/// The [PostgreSQL ILIKE pattern] to match the search term against for the record to be valid.
	///
	/// [PostgreSQL ILIKE pattern]: https://www.postgresql.org/docs/current/functions-matching.html#FUNCTIONS-LIKE
	pub pattern: String,
	
	/// The relationship the property establishes between the [`MetaSubject`] and the [`MetaProperty::value`].
	pub rel: String,
	
	/// The value that the property has.
	pub value: Option<String>,
}

/// An [`Insertable`] version of [`MetaLinkTitle`].
#[derive(Debug, Insertable)]
#[diesel(table_name = schema::meta_properties)]
#[diesel(check_for_backend(Pg))]
pub struct MetaPropertyInsert {
	
	/// The document the record is valid for.
	pub document: String,
	
	/// The [PostgreSQL ILIKE pattern] to match the search term against for the record to be valid.
	///
	/// [PostgreSQL ILIKE pattern]: https://www.postgresql.org/docs/current/functions-matching.html#FUNCTIONS-LIKE
	pub pattern: String,
	
	/// The relationship the property establishes between the [`MetaSubject`] and the [`MetaProperty::value`].
	pub rel: String,
	
	/// The value that the property has.
	pub value: Option<String>,
}

/// Allow [`diesel::sql_types::Text`] values to be parsed as [`MediaTypeDatabase`].
impl<DB> FromSql<diesel::sql_types::Text, DB> for MediaTypeDatabase
	where
		DB: diesel::backend::Backend,
		String: FromSql<diesel::sql_types::Text, DB>,
{
	fn from_sql(bytes: <DB as diesel::backend::Backend>::RawValue<'_>) -> diesel::deserialize::Result<Self> {
		log::trace!("Reading TEXT from the database...");
		let s = <String as FromSql<diesel::sql_types::Text, DB>>::from_sql(bytes)?;
		
		log::trace!("Attempting to parse as a media type: {s:?}");
		let mt: MediaTypeBuf = s.parse()?;
		
		log::trace!("Successfully parsed media type: {mt:?}");
		Ok(Self(mt))
	}
}

/// Allow [`diesel::sql_types::Text`] values to be written to with [`MediaTypeDatabase`].
impl<DB> ToSql<diesel::sql_types::Text, DB> for MediaTypeDatabase
	where
		DB: diesel::backend::Backend,
		str: ToSql<diesel::sql_types::Text, DB>,
{
	fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, DB>) -> diesel::serialize::Result {
		log::trace!("Getting the essence of a media type to prepare for serialization...");
		let mt = self.0.as_str();
		
		log::trace!("Serializing media type as TEXT: {mt:?}");
		<str as ToSql<diesel::sql_types::Text, DB>>::to_sql(mt, out)
	}
}

impl MetaSubject {
	/// Synchronously query the records matching the given document and resource.
	pub fn query_matching(conn: &mut PgConnection, doc: &str, resource: &str) -> QueryResult<Vec<Self>> {
		use diesel::QueryDsl;
		use diesel::RunQueryDsl;
		use schema::meta_subjects::dsl::*;
		
		let document_is_equal = document.eq(doc);
		let resource_matches_pattern = resource.into_sql::<diesel::sql_types::Text>().ilike(pattern);
		
		meta_subjects
			.filter(document_is_equal)
			.filter(resource_matches_pattern)
			.select(Self::as_select())
			.load(conn)
	}
	
	/// Asynchronously query the records matching the given document and resource.
	pub async fn aquery_matching(conn: &mut AsyncPgConnection, doc: &str, resource: &str) -> QueryResult<Vec<Self>> {
		use diesel::QueryDsl;
		use diesel_async::RunQueryDsl;
		use schema::meta_subjects::dsl::*;
		
		let document_is_equal = document.eq(doc);
		let resource_matches_pattern = resource.into_sql::<diesel::sql_types::Text>().ilike(pattern);
		
		meta_subjects
			.filter(document_is_equal)
			.filter(resource_matches_pattern)
			.select(Self::as_select())
			.load(conn)
			.await
	}
}

impl MetaAlias {
	/// Synchronously query the records matching the given document and resource.
	pub fn query_matching(conn: &mut PgConnection, doc: &str, subject: &str) -> QueryResult<Vec<Self>> {
		use diesel::QueryDsl;
		use diesel::RunQueryDsl;
		use schema::meta_aliases::dsl::*;
		
		let document_is_equal = document.eq(doc);
		let subject_matches_pattern = subject.into_sql::<diesel::sql_types::Text>().ilike(pattern);
		
		meta_aliases
			.filter(document_is_equal)
			.filter(subject_matches_pattern)
			.select(Self::as_select())
			.load(conn)
	}
	
	/// Asynchronously query the records matching the given document and resource.
	pub async fn aquery_matching(conn: &mut AsyncPgConnection, doc: &str, subject: &str) -> QueryResult<Vec<Self>> {
		use diesel::QueryDsl;
		use diesel_async::RunQueryDsl;
		use schema::meta_aliases::dsl::*;
		
		let document_is_equal = document.eq(doc);
		let subject_matches_pattern = subject.into_sql::<diesel::sql_types::Text>().ilike(pattern);
		
		meta_aliases
			.filter(document_is_equal)
			.filter(subject_matches_pattern)
			.select(Self::as_select())
			.load(conn)
			.await
	}
}

impl MetaLink {
	/// Synchronously query the records matching the given document and resource.
	pub async fn query_matching(conn: &mut PgConnection, doc: &str, subject: &str) -> QueryResult<Vec<Self>> {
		use diesel::QueryDsl;
		use diesel::RunQueryDsl;
		use schema::meta_links::dsl::*;
		
		let document_is_equal = document.eq(doc);
		let subject_matches_pattern = subject.into_sql::<diesel::sql_types::Text>().ilike(pattern);
		
		meta_links
			.filter(document_is_equal)
			.filter(subject_matches_pattern)
			.select(Self::as_select())
			.load(conn)
	}
	
	/// Asynchronously query the records matching the given document and resource.
	pub async fn aquery_matching(conn: &mut AsyncPgConnection, doc: &str, subject: &str) -> QueryResult<Vec<Self>> {
		use diesel::QueryDsl;
		use diesel_async::RunQueryDsl;
		use schema::meta_links::dsl::*;
		
		let document_is_equal = document.eq(doc);
		let subject_matches_pattern = subject.into_sql::<diesel::sql_types::Text>().ilike(pattern);
		
		meta_links
			.filter(document_is_equal)
			.filter(subject_matches_pattern)
			.select(Self::as_select())
			.load(conn)
			.await
	}
}

impl MetaLinkProperty {
	/// Synchronously query the records belonging to the given [`MetaLink`]s.
	pub fn query_by_link(conn: &mut PgConnection, links: &[MetaLink]) -> QueryResult<Vec<Self>> {
		use diesel::RunQueryDsl;
		
		Self::belonging_to(links)
			.load(conn)
	}
	
	/// Asynchronously query the records belonging to the given [`MetaLink`]s.
	pub async fn aquery_by_link(conn: &mut AsyncPgConnection, links: &[MetaLink]) -> QueryResult<Vec<Self>> {
		use diesel_async::RunQueryDsl;
		
		Self::belonging_to(links)
			.load(conn)
			.await
	}
}

impl MetaLinkTitle {
	/// Synchronously query the records belonging to the given [`MetaLink`]s.
	pub fn query_by_link(conn: &mut PgConnection, links: &[MetaLink]) -> QueryResult<Vec<Self>> {
		use diesel::RunQueryDsl;
		
		Self::belonging_to(links)
			.load(conn)
	}
	
	/// Asynchronously query the records belonging to the given [`MetaLink`]s.
	pub async fn aquery_by_link(conn: &mut AsyncPgConnection, links: &[MetaLink]) -> QueryResult<Vec<Self>> {
		use diesel_async::RunQueryDsl;
		
		Self::belonging_to(links)
			.load(conn)
			.await
	}
}

impl MetaProperty {
	/// Synchronously query the records matching the given document and resource.
	pub fn query_matching(conn: &mut PgConnection, doc: &str, subject: &str) -> QueryResult<Vec<Self>> {
		use diesel::QueryDsl;
		use diesel::RunQueryDsl;
		use schema::meta_properties::dsl::*;
		
		let document_is_equal = document.eq(doc);
		let subject_matches_pattern = subject.into_sql::<diesel::sql_types::Text>().ilike(pattern);
		
		meta_properties
			.filter(document_is_equal)
			.filter(subject_matches_pattern)
			.select(Self::as_select())
			.load(conn)
	}
	
	/// Asynchronously query the records matching the given document and resource.
	pub async fn aquery_matching(conn: &mut AsyncPgConnection, doc: &str, subject: &str) -> QueryResult<Vec<Self>> {
		use diesel::QueryDsl;
		use diesel_async::RunQueryDsl;
		use schema::meta_properties::dsl::*;
		
		let document_is_equal = document.eq(doc);
		let subject_matches_pattern = subject.into_sql::<diesel::sql_types::Text>().ilike(pattern);
		
		meta_properties
			.filter(document_is_equal)
			.filter(subject_matches_pattern)
			.select(Self::as_select())
			.load(conn)
			.await
	}
}

impl_to_insert!(MetaSubjectInsert => MetaSubject: schema::meta_subjects::table);
impl_to_insert!(MetaAliasInsert => MetaAlias: schema::meta_aliases::table);
impl_to_insert!(MetaLinkInsert => MetaLink: schema::meta_links::table);
impl_to_insert!(MetaLinkPropertyInsert => MetaLinkProperty: schema::meta_link_properties::table);
impl_to_insert!(MetaLinkTitleInsert => MetaLinkTitle: schema::meta_link_titles::table);
impl_to_insert!(MetaPropertyInsert => MetaProperty: schema::meta_properties::table);