137 lines
4.0 KiB
Rust
137 lines
4.0 KiB
Rust
//! Types for Relay-compliant server
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mod connection_type;
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mod cursor;
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mod edge;
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mod page_info;
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use std::fmt::Display;
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use std::future::Future;
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use crate::{Result, SimpleObject};
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pub use connection_type::Connection;
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pub use cursor::CursorType;
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pub use edge::Edge;
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pub use page_info::PageInfo;
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/// Empty additional fields
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#[derive(SimpleObject)]
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#[graphql(internal, dummy)]
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pub struct EmptyFields;
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/// Parses the parameters and executes the query.
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///
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/// # Examples
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///
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/// ```rust
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/// use async_graphql::*;
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/// use async_graphql::connection::*;
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///
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/// struct QueryRoot;
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///
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/// struct Numbers;
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///
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/// #[derive(SimpleObject)]
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/// struct Diff {
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/// diff: i32,
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/// }
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///
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/// #[Object]
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/// impl QueryRoot {
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/// async fn numbers(&self,
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/// after: Option<String>,
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/// before: Option<String>,
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/// first: Option<i32>,
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/// last: Option<i32>
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/// ) -> Result<Connection<usize, i32, EmptyFields, Diff>> {
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/// query(after, before, first, last, |after, before, first, last| async move {
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/// let mut start = after.map(|after| after + 1).unwrap_or(0);
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/// let mut end = before.unwrap_or(10000);
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/// if let Some(first) = first {
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/// end = (start + first).min(end);
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/// }
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/// if let Some(last) = last {
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/// start = if last > end - start {
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/// end
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/// } else {
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/// end - last
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/// };
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/// }
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/// let mut connection = Connection::new(start > 0, end < 10000);
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/// connection.append(
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/// (start..end).into_iter().map(|n|
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/// Edge::with_additional_fields(n, n as i32, Diff{ diff: (10000 - n) as i32 })),
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/// );
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/// Ok(connection)
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/// }).await
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/// }
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/// }
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///
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/// tokio::runtime::Runtime::new().unwrap().block_on(async {
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/// let schema = Schema::new(QueryRoot, EmptyMutation, EmptySubscription);
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///
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/// assert_eq!(schema.execute("{ numbers(first: 2) { edges { node diff } } }").await.into_result().unwrap().data, value!({
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/// "numbers": {
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/// "edges": [
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/// {"node": 0, "diff": 10000},
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/// {"node": 1, "diff": 9999},
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/// ]
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/// },
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/// }));
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///
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/// assert_eq!(schema.execute("{ numbers(last: 2) { edges { node diff } } }").await.into_result().unwrap().data, value!({
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/// "numbers": {
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/// "edges": [
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/// {"node": 9998, "diff": 2},
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/// {"node": 9999, "diff": 1},
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/// ]
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/// },
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/// }));
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/// });
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/// ```
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pub async fn query<Cursor, Node, ConnectionFields, EdgeFields, F, R>(
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after: Option<String>,
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before: Option<String>,
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first: Option<i32>,
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last: Option<i32>,
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f: F,
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) -> Result<Connection<Cursor, Node, ConnectionFields, EdgeFields>>
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where
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Cursor: CursorType + Send + Sync,
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<Cursor as CursorType>::Error: Display + Send + Sync + 'static,
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F: FnOnce(Option<Cursor>, Option<Cursor>, Option<usize>, Option<usize>) -> R,
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R: Future<Output = Result<Connection<Cursor, Node, ConnectionFields, EdgeFields>>>,
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{
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if first.is_some() && last.is_some() {
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return Err("The \"first\" and \"last\" parameters cannot exist at the same time".into());
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}
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let first = match first {
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Some(first) if first < 0 => {
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return Err("The \"first\" parameter must be a non-negative number".into());
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}
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Some(first) => Some(first as usize),
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None => None,
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};
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let last = match last {
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Some(last) if last < 0 => {
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return Err("The \"last\" parameter must be a non-negative number".into());
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}
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Some(last) => Some(last as usize),
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None => None,
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};
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let before = match before {
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Some(before) => Some(Cursor::decode_cursor(&before)?),
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None => None,
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};
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let after = match after {
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Some(after) => Some(Cursor::decode_cursor(&after)?),
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None => None,
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};
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f(after, before, first, last).await
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}
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