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* AgentKits — Workflow Engine
*
* Define and execute multi-step workflows with LLM calls, tool calls,
* conditional branches, parallel execution, retry, and fallback.
*
* Usage:
* import { createWorkflow, runWorkflow } from 'agentkits/workflow';
*/
import { createChat } from '../llm/index.js';
import type { ChatConfig } from '../llm/index.js';
// ── Types ──────────────────────────────────────────────────────────
export type StepType = 'llm' | 'tool' | 'condition' | 'parallel' | 'transform' | 'delay';
export interface RetryPolicy {
maxRetries?: number;
delayMs?: number;
backoff?: 'fixed' | 'exponential';
}
export interface WorkflowStep {
id: string;
type: StepType;
/** For 'llm': chat config */
llm?: ChatConfig & { prompt?: string; systemPrompt?: string };
/** For 'tool': function to call */
tool?: {
name: string;
handler: (input: any, context: WorkflowContext) => Promise<any>;
};
/** For 'condition': branch based on result */
condition?: {
/** Expression evaluated against context.variables — or a function */
check: string | ((context: WorkflowContext) => boolean);
ifTrue: string; // step id
ifFalse: string; // step id
};
/** For 'parallel': run multiple steps concurrently */
parallel?: string[]; // step ids
/** For 'transform': transform data */
transform?: (input: any, context: WorkflowContext) => any;
/** For 'delay': wait ms */
delayMs?: number;
/** Next step id (for linear flows) */
next?: string;
/** Retry policy */
retry?: RetryPolicy;
/** Fallback step id on error */
fallback?: string;
/** Input mapping: keys from context.variables */
input?: string | ((context: WorkflowContext) => any);
/** Output variable name to store result */
output?: string;
}
export interface WorkflowDefinition {
name: string;
description?: string;
version?: string;
/** First step id */
startStep: string;
steps: WorkflowStep[];
/** Global variables / initial context */
variables?: Record<string, any>;
}
export interface WorkflowContext {
variables: Record<string, any>;
stepResults: Record<string, any>;
currentStep: string;
history: Array<{ stepId: string; status: 'success' | 'error' | 'skipped'; result?: any; error?: string; durationMs: number }>;
}
export interface WorkflowResult {
success: boolean;
context: WorkflowContext;
finalOutput: any;
totalDurationMs: number;
stepsExecuted: number;
}
export interface WorkflowEngine {
/** Run the workflow */
run(initialVars?: Record<string, any>): Promise<WorkflowResult>;
/** Validate workflow definition */
validate(): string[];
}
// ── Step Executors ─────────────────────────────────────────────────
async function executeLLMStep(step: WorkflowStep, context: WorkflowContext): Promise<any> {
const cfg = step.llm!;
const chat = createChat({ provider: cfg.provider, model: cfg.model, apiKey: cfg.apiKey, baseUrl: cfg.baseUrl, temperature: cfg.temperature, maxTokens: cfg.maxTokens });
const prompt = resolveTemplate(cfg.prompt ?? '', context);
const messages: Array<{ role: 'system' | 'user'; content: string }> = [];
if (cfg.systemPrompt) messages.push({ role: 'system', content: resolveTemplate(cfg.systemPrompt, context) });
messages.push({ role: 'user', content: prompt });
return await chat.chat(messages);
}
async function executeToolStep(step: WorkflowStep, context: WorkflowContext): Promise<any> {
const input = resolveInput(step, context);
return await step.tool!.handler(input, context);
}
async function executeConditionStep(step: WorkflowStep, context: WorkflowContext): Promise<string> {
const cond = step.condition!;
let result: boolean;
if (typeof cond.check === 'function') {
result = cond.check(context);
} else {
// Simple expression: check if variable is truthy
result = !!context.variables[cond.check];
}
return result ? cond.ifTrue : cond.ifFalse;
}
async function executeParallelStep(step: WorkflowStep, allSteps: Map<string, WorkflowStep>, context: WorkflowContext): Promise<any> {
const results = await Promise.all(
step.parallel!.map(async (stepId) => {
const s = allSteps.get(stepId);
if (!s) throw new Error(`Parallel step not found: ${stepId}`);
return executeStep(s, allSteps, context);
})
);
return results;
}
function resolveTemplate(template: string, context: WorkflowContext): string {
return template.replace(/\{\{(\w+(?:\.\w+)*)\}\}/g, (_, key) => {
const parts = key.split('.');
let val: any = { ...context.variables, ...context.stepResults };
for (const p of parts) {
val = val?.[p];
}
return val !== undefined ? String(val) : `{{${key}}}`;
});
}
function resolveInput(step: WorkflowStep, context: WorkflowContext): any {
if (!step.input) return context.variables;
if (typeof step.input === 'function') return step.input(context);
return context.variables[step.input] ?? context.stepResults[step.input];
}
async function executeStep(step: WorkflowStep, allSteps: Map<string, WorkflowStep>, context: WorkflowContext): Promise<any> {
switch (step.type) {
case 'llm': return executeLLMStep(step, context);
case 'tool': return executeToolStep(step, context);
case 'transform': return step.transform!(resolveInput(step, context), context);
case 'delay': await new Promise(r => setTimeout(r, step.delayMs ?? 1000)); return null;
case 'parallel': return executeParallelStep(step, allSteps, context);
case 'condition': return executeConditionStep(step, context);
default: throw new Error(`Unknown step type: ${step.type}`);
}
}
async function executeWithRetry(step: WorkflowStep, allSteps: Map<string, WorkflowStep>, context: WorkflowContext): Promise<any> {
const policy = step.retry ?? { maxRetries: 0 };
const maxRetries = policy.maxRetries ?? 0;
const delayMs = policy.delayMs ?? 1000;
const backoff = policy.backoff ?? 'exponential';
let lastError: Error | null = null;
for (let attempt = 0; attempt <= maxRetries; attempt++) {
try {
return await executeStep(step, allSteps, context);
} catch (e: any) {
lastError = e;
if (attempt < maxRetries) {
const wait = backoff === 'exponential' ? delayMs * Math.pow(2, attempt) : delayMs;
await new Promise(r => setTimeout(r, wait));
}
}
}
throw lastError;
}
// ── Factory ────────────────────────────────────────────────────────
export function createWorkflow(definition: WorkflowDefinition): WorkflowEngine {
const stepMap = new Map<string, WorkflowStep>();
for (const step of definition.steps) {
stepMap.set(step.id, step);
}
return {
validate(): string[] {
const errors: string[] = [];
if (!stepMap.has(definition.startStep)) errors.push(`Start step '${definition.startStep}' not found`);
for (const step of definition.steps) {
if (step.next && !stepMap.has(step.next)) errors.push(`Step '${step.id}' references unknown next '${step.next}'`);
if (step.fallback && !stepMap.has(step.fallback)) errors.push(`Step '${step.id}' references unknown fallback '${step.fallback}'`);
if (step.condition) {
if (!stepMap.has(step.condition.ifTrue)) errors.push(`Condition step '${step.id}' references unknown ifTrue '${step.condition.ifTrue}'`);
if (!stepMap.has(step.condition.ifFalse)) errors.push(`Condition step '${step.id}' references unknown ifFalse '${step.condition.ifFalse}'`);
}
if (step.parallel) {
for (const pid of step.parallel) {
if (!stepMap.has(pid)) errors.push(`Parallel step '${step.id}' references unknown step '${pid}'`);
}
}
}
return errors;
},
async run(initialVars?: Record<string, any>): Promise<WorkflowResult> {
const startTime = Date.now();
const context: WorkflowContext = {
variables: { ...definition.variables, ...initialVars },
stepResults: {},
currentStep: definition.startStep,
history: [],
};
let currentStepId: string | undefined = definition.startStep;
let stepsExecuted = 0;
let finalOutput: any = null;
const maxSteps = 100; // safety limit
while (currentStepId && stepsExecuted < maxSteps) {
const step = stepMap.get(currentStepId);
if (!step) throw new Error(`Step '${currentStepId}' not found`);
context.currentStep = currentStepId;
const stepStart = Date.now();
stepsExecuted++;
try {
const result = await executeWithRetry(step, stepMap, context);
// Store result
if (step.output) context.variables[step.output] = result;
context.stepResults[step.id] = result;
finalOutput = result;
context.history.push({
stepId: step.id,
status: 'success',
result,
durationMs: Date.now() - stepStart,
});
// Determine next step
if (step.type === 'condition') {
currentStepId = result as string; // condition returns next step id
} else {
currentStepId = step.next;
}
} catch (e: any) {
context.history.push({
stepId: step.id,
status: 'error',
error: e.message,
durationMs: Date.now() - stepStart,
});
if (step.fallback) {
currentStepId = step.fallback;
} else {
return {
success: false,
context,
finalOutput: null,
totalDurationMs: Date.now() - startTime,
stepsExecuted,
};
}
}
}
return {
success: true,
context,
finalOutput,
totalDurationMs: Date.now() - startTime,
stepsExecuted,
};
},
};
}
// ── YAML/JSON Definition Parser ────────────────────────────────────
/** Parse a workflow from a JSON object (e.g., loaded from YAML/JSON file) */
export function parseWorkflowJSON(json: any, toolHandlers?: Record<string, (input: any, ctx: WorkflowContext) => Promise<any>>): WorkflowDefinition {
const steps: WorkflowStep[] = (json.steps ?? []).map((s: any) => {
const step: WorkflowStep = {
id: s.id,
type: s.type,
next: s.next,
output: s.output,
input: s.input,
retry: s.retry,
fallback: s.fallback,
delayMs: s.delayMs,
};
if (s.type === 'llm') step.llm = s.llm;
if (s.type === 'tool' && toolHandlers?.[s.tool]) {
step.tool = { name: s.tool, handler: toolHandlers[s.tool] };
}
if (s.type === 'condition') step.condition = s.condition;
if (s.type === 'parallel') step.parallel = s.parallel;
return step;
});
return {
name: json.name ?? 'unnamed',
description: json.description,
version: json.version,
startStep: json.startStep ?? steps[0]?.id,
steps,
variables: json.variables,
};
}
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