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use quote::quote_spanned;
use super::{
FloType, OpInstGenerics, OperatorCategory, OperatorConstraints, OperatorInstance,
OperatorWriteOutput, RANGE_0, RANGE_1, WriteContextArgs,
};
/// > 0 input streams, 1 output stream
///
/// > Arguments: An [`AsRef`](https://doc.rust-lang.org/std/convert/trait.AsRef.html)`<`[`Path`](https://doc.rust-lang.org/nightly/std/path/struct.Path.html)`>`
/// > for a file to read as json. This will emit the parsed value one time.
///
/// `source_json` may take one generic type argument, the type of the value to be parsed, which must implement [`Deserialize`](https://docs.rs/serde/latest/serde/de/trait.Deserialize.html).
///
/// ```dfir
/// source_json("example.json") -> for_each(|json: dfir_rs::serde_json::Value| println!("{:#?}", json));
/// ```
pub const SOURCE_JSON: OperatorConstraints = OperatorConstraints {
name: "source_json",
categories: &[OperatorCategory::Source],
hard_range_inn: RANGE_0,
soft_range_inn: RANGE_0,
hard_range_out: RANGE_1,
soft_range_out: RANGE_1,
num_args: 1,
persistence_args: RANGE_0,
type_args: &(0..=1),
is_external_input: true,
has_singleton_output: false,
flo_type: Some(FloType::Source),
ports_inn: None,
ports_out: None,
input_delaytype_fn: |_| None,
write_fn: |wc @ &WriteContextArgs {
root,
op_span,
ident,
op_inst:
OperatorInstance {
generics: OpInstGenerics { type_args, .. },
..
},
arguments,
..
},
_| {
let generic_type = type_args.first().map(|ty| quote_spanned!(op_span=> : #ty));
let ident_jsonread = wc.make_ident("jsonread");
let write_prologue = quote_spanned! {op_span=>
// Note that reading the entire file to memory is (probably still) faster than using a
// reader: https://github.com/serde-rs/json/issues/160
let mut #ident_jsonread = {
let string = ::std::fs::read_to_string(#arguments).unwrap();
let value #generic_type = #root::serde_json::from_str(&string).unwrap();
#root::dfir_pipes::pull::once(value)
};
};
let write_iterator = quote_spanned! {op_span=>
let #ident = &mut #ident_jsonread;
};
Ok(OperatorWriteOutput {
write_prologue,
write_iterator,
..Default::default()
})
},
};