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use std::error::Error;
use std::mem::discriminant;
use serde_json::{Map, Value};
use log::{trace, error, debug};
use crate::error::{ErrorKind, ProcessingError};
pub struct OutputMessage {
pub key: Option<String>,
value: Value,
}
impl Default for OutputMessage {
fn default() -> Self {
Self::new()
}
}
impl OutputMessage {
pub fn new() -> OutputMessage {
OutputMessage {
key: None,
value: Value::Null,
}
}
}
pub trait ObjectTree {
fn get_val(&self, key: &[ObjectKey]) -> Result<&Value, ProcessingError>;
fn insert_val(&mut self, key: &[ObjectKey], value: Value) -> Result<(), ProcessingError>;
}
#[derive(Debug, Clone)]
pub enum ObjectKey {
Index(usize),
Key(String),
}
impl ObjectTree for OutputMessage {
fn get_val(&self, key: &[ObjectKey]) -> Result<&Value, ProcessingError> {
self.value.get_val(key)
}
fn insert_val(&mut self, key: &[ObjectKey], value: Value) -> Result<(), ProcessingError> {
if key.is_empty() {
return Err(ErrorKind::EmptyKey.into());
}
if let Value::Null = self.value {
self.value = match key[0] {
ObjectKey::Key(_) => Value::Object(Map::new()),
ObjectKey::Index(_) => Value::Array(vec![]),
};
}
self.value.insert_val(key, value)
}
}
impl ObjectTree for Value {
fn get_val(&self, key: &[ObjectKey]) -> Result<&Value, ProcessingError> {
if key.is_empty() {
return Err(ErrorKind::EmptyKey.into());
}
let mut node = Some(self);
for k in key {
node = node.and_then(|n| match k {
ObjectKey::Index(i) => n.get(i),
ObjectKey::Key(k) => n.get(k),
})
}
node.ok_or_else(|| ErrorKind::FieldNotFound { key: key.to_vec()}.into())
}
fn insert_val(&mut self, key: &[ObjectKey], value: Value) -> Result<(), ProcessingError> {
if key.is_empty() {
return Err(ErrorKind::EmptyKey.into());
}
if let Value::Null = self {
return Err(ErrorKind::InvalidObjectTree {
invalid_key: key.to_vec(),
reason: "Root node is null.".to_string(),
}.into());
}
let mut cur_value = self;
for i in 0..key.len() - 1 {
cur_value = insert_node(cur_value, &key[i], &key[i + 1])
.map_err(|e| fill_key_in_error(e, key))?;
}
insert_child(cur_value, key.last().unwrap(), value)
.map_err(|e| fill_key_in_error(e, key))?;
Ok(())
}
}
fn fill_key_in_error(e: ProcessingError, key: &[ObjectKey]) -> ProcessingError {
match e.inner {
ErrorKind::InvalidObjectTree { reason, .. } => ErrorKind::InvalidObjectTree {
invalid_key: key.to_vec(),
reason
}.into(),
_ => e,
}
}
fn insert_node<'a>(node: &'a mut Value, key: &ObjectKey, child: &ObjectKey) -> Result<&'a mut Value, ProcessingError> {
let child = match child {
ObjectKey::Key(_) => Value::Object(Map::new()),
ObjectKey::Index(_) => Value::Array(vec![]),
};
insert_child(node, key, child)
}
fn insert_child<'a>(node: &'a mut Value, key: &ObjectKey, child: Value) -> Result<&'a mut Value, ProcessingError> {
if let Value::Null = node {
return Err(ErrorKind::InvalidObjectTree {
invalid_key: vec![key.clone()],
reason: "Node is null.".to_string(),
}.into());
}
match key {
ObjectKey::Key(k) => {
if let Value::Object(values) = node {
let cur_node = values.get(k).unwrap_or(&Value::Null);
verify_type_compatibility(cur_node, &child)?;
values.insert(k.clone(), child);
Ok(values.get_mut(k).unwrap())
} else {
Err(ErrorKind::InvalidObjectTree {
invalid_key: vec![key.clone()],
reason: "Node has incompatible type, Object expected.".to_string(),
}.into())
}
}
ObjectKey::Index(i) => {
let i = *i;
if let Value::Array(values) = node {
while values.len() <= i {
values.push(Value::Null);
}
verify_type_compatibility(&values[i], &child)?;
values[i] = child;
Ok(&mut values[i])
} else {
Err(ErrorKind::InvalidObjectTree {
invalid_key: vec![key.clone()],
reason: "Node has incompatible type, Array expected.".to_string(),
}.into())
}
}
}
}
fn verify_type_compatibility(node: &Value, child: &Value) -> Result<(), ProcessingError> {
let child_discriminant = discriminant(child);
let node_discriminant = discriminant(node);
match node {
Value::Object(_) | Value::Array(_) => {
if node_discriminant != child_discriminant {
return Err(ErrorKind::InvalidObjectTree {
invalid_key: vec![],
reason: format!("Child node has incompatible type, cannot merge {child_discriminant:?} into {node_discriminant:?}."),
}.into());
}
}
_ => {}
}
Ok(())
}
pub struct SerializedOutputMessage {
pub key: String,
pub message: String,
}
pub type ProcessingResult<T> = Result<T, Box<dyn Error>>;
pub type Processor = &'static (dyn Fn(&Value, &mut OutputMessage) -> Result<(), ProcessingError> + Sync + Send);
pub fn process_payload(id: String, payload: &[u8], processors: &[Processor]) -> ProcessingResult<SerializedOutputMessage> {
trace!("[{id}] Start of processing.");
let source: Value = serde_json::from_slice(payload)?;
let mut message: OutputMessage = OutputMessage::new();
for (i, process) in processors.iter().enumerate() {
if let Err(e) = process(&source, &mut message) {
let e: ProcessingError = e;
match e.inner {
ErrorKind::FieldNotFound { .. } =>
debug!("[{id}]#{i} {e}. Skipping processor."),
ErrorKind::ProcessorSkipped { .. } =>
debug!("[{id}]#{i} {e}"),
_ =>
error!("[{id}]#{i} Cannot process message. Reason: {e}"),
}
}
}
trace!("[{id}] End of processing - serializing message.");
Ok(SerializedOutputMessage {
key: message.key.unwrap_or(id),
message: serde_json::to_string(&message.value)?,
})
}