Struct Context 

pub struct Context { /* private fields */ }

Context for sharing data between tasks in a graph execution.

Provides thread-safe storage for workflow state and dedicated chat history management. The context is shared across all tasks in a workflow execution (cloning a Context is cheap and yields a handle to the same state).

All methods are synchronous - see the module docs for rationale.

Examples

use graph_flow::Context;

let context = Context::new();

// Typed key-value state
context.set("user_id", 12345)?;
let user_id: Option<i32> = context.get("user_id");

// Chat history
context.add_user_message("Hello".to_string());
let history = context.get_chat_history();

Implementations

impl Context

pub fn new() -> Self

Create a new empty context.

pub fn with_max_chat_messages(max: usize) -> Self

Create a new context with a maximum chat history size.

When the chat history exceeds this size, older messages are automatically removed.

pub fn set(&self, key: impl Into<String>, value: impl Serialize) -> Result<()>

Set a value in the context.

Returns Err(GraphError::ContextError) if the value cannot be serialized to JSON (e.g. a map with non-string keys).

Examples

use graph_flow::Context;
use serde::{Serialize, Deserialize};

#[derive(Serialize, Deserialize)]
struct UserData {
    id: u32,
    name: String,
}

let context = Context::new();

// Store primitive types
context.set("count", 42)?;
context.set("name", "Alice".to_string())?;

// Store complex types
let user = UserData { id: 1, name: "Bob".to_string() };
context.set("user", user)?;

pub fn get<T: DeserializeOwned>(&self, key: &str) -> Option<T>

Get a value from the context.

Returns None if the key doesn’t exist or if the stored value cannot be deserialized to the requested type (a warning is logged for the latter, since it usually indicates a type mismatch bug).

Examples

use graph_flow::Context;

let context = Context::new();
context.set("count", 42)?;

let count: Option<i32> = context.get("count");
assert_eq!(count, Some(42));

let missing: Option<String> = context.get("missing");
assert_eq!(missing, None);

pub fn remove(&self, key: &str) -> Option<Value>

Remove a value from the context.

Returns the removed value if it existed.

pub fn clear(&self)

Clear all regular context data (does not affect chat history).

pub fn add_user_message(&self, content: String)

Add a user message to the chat history.

pub fn add_assistant_message(&self, content: String)

Add an assistant message to the chat history.

pub fn add_system_message(&self, content: String)

Add a system message to the chat history.

pub fn get_chat_history(&self) -> ChatHistory

Get a clone of the current chat history.

pub fn clear_chat_history(&self)

Clear the chat history.

pub fn chat_history_len(&self) -> usize

Get the number of messages in the chat history.

pub fn is_chat_history_empty(&self) -> bool

Check if the chat history is empty.

pub fn get_last_messages(&self, n: usize) -> Vec<SerializableMessage>

Get the last N messages from chat history, oldest first.

pub fn get_all_messages(&self) -> Vec<SerializableMessage>

Get all messages from chat history, oldest first.

Trait Implementations

impl Clone for Context

fn clone(&self) -> Context

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Context

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Context

fn default() -> Self

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for Context

fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Serialize for Context

fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.