69 lines
2.1 KiB
Rust
69 lines
2.1 KiB
Rust
/// An attachment that extracts metadata from an [Item].
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///
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/// Metadata is exposed as an immutable map of {label: value},
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/// much like a json object.
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#[async_trait::async_trait]
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pub trait ObjectExtractor: Send + Sync {
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/// Get the field at `name` from `item`.
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/// - returns `None` if `name` is not a valid field
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/// - returns `Some(Null)` if `name` is not available
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async fn field(
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&self,
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name: &pile_config::Label,
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) -> Result<Option<crate::value::PileValue>, std::io::Error>;
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/// Return all fields in this extractor.
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/// `Self::field` must return [Some] for all these keys
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/// and [None] for all others.
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async fn fields(&self) -> Result<Vec<pile_config::Label>, std::io::Error>;
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/// Convert this to a JSON value.
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async fn to_json(&self) -> Result<serde_json::Value, std::io::Error> {
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let keys = self.fields().await?;
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let mut map = serde_json::Map::new();
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for k in &keys {
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let v = match self.field(k).await? {
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Some(x) => x,
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None => continue,
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};
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map.insert(k.to_string(), Box::pin(v.to_json()).await?);
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}
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Ok(serde_json::Value::Object(map))
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}
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}
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/// An attachment that extracts metadata from an [Item].
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///
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/// Metadata is exposed as an immutable list of values.
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#[async_trait::async_trait]
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pub trait ListExtractor: Send + Sync {
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/// Get the item at index `idx`.
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/// Indices start at zero, and must be consecutive.
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/// - returns `None` if `idx` is out of range
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/// - returns `Some(Null)` if `None` is at `idx`
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async fn get(&self, idx: usize) -> Result<Option<crate::value::PileValue>, std::io::Error>;
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async fn len(&self) -> Result<usize, std::io::Error>;
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async fn is_empty(&self) -> Result<bool, std::io::Error> {
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Ok(self.len().await? == 0)
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}
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/// Convert this list to a JSON value.
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async fn to_json(&self) -> Result<serde_json::Value, std::io::Error> {
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let len = self.len().await?;
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let mut list = Vec::with_capacity(len);
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for i in 0..len {
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#[expect(clippy::expect_used)]
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let v = self
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.get(i)
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.await?
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.expect("value must be present according to length");
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list.push(Box::pin(v.to_json()).await?);
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}
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Ok(serde_json::Value::Array(list))
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}
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}
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