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//! The main logic of JSON extracting
//!
//! It uses matchers to extract a parts of JSON.
//! Nested matches have no meaning here
use crate::{
error,
matcher::MatchMaker,
path::Path,
streamer::{Output, Streamer},
};
use std::mem::swap;
type OptinalPathAndData = (Option<String>, Vec<u8>);
pub struct Extract {
/// Export path as well
export_path: bool,
/// Input idx against total idx
input_start: usize,
/// Buffer index against total idx
buffer_start: usize,
/// Buffer which is used to store collected data
buffer: Vec<u8>,
/// Path which is matched
matched_path: Option<Path>,
/// Path matchers
matchers: Vec<Box<dyn MatchMaker>>,
/// Creates to token stream
streamer: Streamer,
}
impl Default for Extract {
fn default() -> Self {
Self {
export_path: false,
input_start: 0,
buffer_start: 0,
buffer: vec![],
matched_path: None,
matchers: vec![],
streamer: Streamer::new(),
}
}
}
impl Extract {
/// Creates a new `Extract`
///
/// It exracts matched data parts (not nested)
pub fn new() -> Self {
Self::default()
}
/// Sets whether path should be exported with data
///
/// if path is not exported extraction can be a bit faster
pub fn set_export_path(mut self, export: bool) -> Self {
self.export_path = export;
self
}
/// Adds new matcher for data extraction
///
/// # Arguments
/// * `matcher` - matcher which matches the path
///
/// # Example
///
/// ```
/// use streamson_lib::{strategy, matcher};
/// use std::sync::{Arc, Mutex};
///
/// let mut extract = strategy::Extract::new();
/// let matcher = matcher::Simple::new(r#"{"list"}[]"#).unwrap();
/// let mut extract = strategy::Extract::new();
/// extract.add_matcher(
/// Box::new(matcher),
/// );
/// ```
pub fn add_matcher(&mut self, matcher: Box<dyn MatchMaker>) {
self.matchers.push(matcher);
}
/// Processes input data
///
/// # Returns
/// * `Ok(Vec<(Some(r#"{"users"}[0]"#), Vec<u8>)>)` vector containing path and data
/// * `Ok(Vec<(None, Vec<u8>)>)` vector data only
/// * `Err(_)` when input is not correct json
///
/// # Example
/// ```
/// use streamson_lib::strategy;
///
/// let mut extract = strategy::Extract::new();
/// extract.process(br#"{}"#);
/// ```
///
/// # Errors
/// * Error is triggered when incorrect json is detected
/// Note that not all json errors are detected
pub fn process(&mut self, input: &[u8]) -> Result<Vec<OptinalPathAndData>, error::General> {
self.streamer.feed(input);
let mut input_idx = 0;
let mut result = vec![];
loop {
match self.streamer.read()? {
Output::Start(idx) if self.matched_path.is_none() => {
let path = self.streamer.current_path();
// try to check whether it matches
for matcher in self.matchers.iter() {
if matcher.match_path(path) {
// start the buffer
self.buffer_start = idx;
self.matched_path = Some(path.clone());
input_idx = idx - self.input_start;
}
}
}
Output::Pending => {
self.input_start += input.len();
if self.matched_path.is_some() {
self.buffer.extend(&input[input_idx..]);
}
return Ok(result);
}
Output::End(idx) if self.matched_path.is_some() => {
if let Some(path) = self.matched_path.as_ref() {
if path == self.streamer.current_path() {
// extend buffer and update indexes
let to = idx - self.input_start;
self.buffer.extend(&input[input_idx..to]);
input_idx = to;
// Put the buffer to results
let mut buffer = vec![];
swap(&mut self.buffer, &mut buffer);
result.push((
if self.export_path {
Some(path.to_string())
} else {
None
},
buffer,
));
self.matched_path = None
}
}
}
_ => {}
}
}
}
}
#[cfg(test)]
mod tests {
use super::Extract;
use crate::matcher::Simple;
fn get_input() -> Vec<Vec<u8>> {
vec![
br#"{"users": [{"name": "fred"}, {"name": "bob"}], "groups": [{"name": "admins"}]}"#
.iter()
.map(|e| *e)
.collect(),
]
}
#[test]
fn flat() {
// without path
let input = get_input();
let matcher = Simple::new(r#"{}[]{"name"}"#).unwrap();
let mut extract = Extract::new();
extract.add_matcher(Box::new(matcher.clone()));
let mut output = extract.process(&input[0]).unwrap();
assert_eq!(output.len(), 3);
assert_eq!(output[0].0.clone(), None);
assert_eq!(output[1].0.clone(), None);
assert_eq!(output[2].0.clone(), None);
assert_eq!(String::from_utf8(output.remove(0).1).unwrap(), r#""fred""#);
assert_eq!(String::from_utf8(output.remove(0).1).unwrap(), r#""bob""#);
assert_eq!(
String::from_utf8(output.remove(0).1).unwrap(),
r#""admins""#
);
// with path
let input = get_input();
let mut extract = Extract::new().set_export_path(true);
extract.add_matcher(Box::new(matcher));
let mut output = extract.process(&input[0]).unwrap();
assert_eq!(output.len(), 3);
assert_eq!(output[0].0.clone(), Some(r#"{"users"}[0]{"name"}"#.into()));
assert_eq!(output[1].0.clone(), Some(r#"{"users"}[1]{"name"}"#.into()));
assert_eq!(output[2].0.clone(), Some(r#"{"groups"}[0]{"name"}"#.into()));
assert_eq!(String::from_utf8(output.remove(0).1).unwrap(), r#""fred""#);
assert_eq!(String::from_utf8(output.remove(0).1).unwrap(), r#""bob""#);
assert_eq!(
String::from_utf8(output.remove(0).1).unwrap(),
r#""admins""#
);
}
#[test]
fn nested() {
let input = get_input();
let matcher = Simple::new(r#"{}[1]"#).unwrap();
let mut extract = Extract::new();
extract.add_matcher(Box::new(matcher));
let mut output = extract.process(&input[0]).unwrap();
assert_eq!(output.len(), 1);
assert_eq!(
String::from_utf8(output.remove(0).1).unwrap(),
r#"{"name": "bob"}"#
);
}
#[test]
fn pending() {
let input = get_input();
let input1 = &input[0][0..20];
let input2 = &input[0][20..];
let matcher = Simple::new(r#"{}[1]"#).unwrap();
let mut extract = Extract::new();
extract.add_matcher(Box::new(matcher));
let mut result = vec![];
let output = extract.process(input1).unwrap();
result.extend(output);
let output = extract.process(input2).unwrap();
result.extend(output);
assert_eq!(
String::from_utf8(result.into_iter().map(|e| e.1).flatten().collect()).unwrap(),
r#"{"name": "bob"}"#
);
}
}