import {
	isWorkflowAllowed,
	type WorkflowPolicyResolution,
} from "../../shared/workflow-policy.ts";
import {
	getTopWorkflow,
	type WorkflowChain,
	type WorkflowDefinition,
	type WorkflowState,
} from "./workflow.ts";

export const WORKFLOW_CREATE_TOOL = "workflow_create";
export const WORKFLOW_ACTIVATE_TOOL = "workflow_activate";
export const WORKFLOW_GET_STAGE_TOOL = "workflow_get_stage";
export const WORKFLOW_EDIT_STAGE_TOOL = "workflow_edit_stage";
export const WORKFLOW_TRANSITION_TOOL = "workflow_transition";
/** Identifies the explicit workflow lifecycle tool. */
export const WORKFLOW_EXIT_TOOL = "workflow_exit";

export type WorkflowToolName =
	| typeof WORKFLOW_CREATE_TOOL
	| typeof WORKFLOW_ACTIVATE_TOOL
	| typeof WORKFLOW_GET_STAGE_TOOL
	| typeof WORKFLOW_EDIT_STAGE_TOOL
	| typeof WORKFLOW_TRANSITION_TOOL
	| typeof WORKFLOW_EXIT_TOOL;

/** Inputs required to resolve workflow capabilities without using Pi runtime state. */
export interface WorkflowAvailabilityInput {
	readonly catalog: readonly WorkflowDefinition[];
	readonly catalogValid: boolean;
	readonly policy: WorkflowPolicyResolution;
	readonly chain: WorkflowChain;
}

/** One internally consistent view of workflow tools and provider-context data. */
export interface WorkflowAvailability {
	readonly activationOptions: readonly WorkflowDefinition[];
	readonly projectedState: WorkflowState | undefined;
	readonly availableToolNames: ReadonlySet<WorkflowToolName>;
}

/** Resolves workflow capabilities from catalog, policy, and session state. */
export function resolveWorkflowAvailability(
	input: WorkflowAvailabilityInput,
): WorkflowAvailability {
	// A malformed policy cannot safely authorize any catalog or session capability.
	if (input.policy.kind === "error") {
		return {
			activationOptions: [],
			projectedState: undefined,
			availableToolNames: new Set(),
		};
	}

	const policy = input.policy.policy;
	// Catalog errors block capabilities that require a complete ID namespace.
	const allowedCatalog = input.catalogValid
		? input.catalog.filter(({ id }) => isWorkflowAllowed(policy, id))
		: [];

	// A resolved workflow policy restricts new catalog activation, not the saved active state.
	const projectedState = getTopWorkflow(input.chain);

	const availableToolNames = new Set<WorkflowToolName>();
	if (input.catalogValid) {
		availableToolNames.add(WORKFLOW_CREATE_TOOL);
	}
	if (allowedCatalog.length > 0) {
		availableToolNames.add(WORKFLOW_ACTIVATE_TOOL);
	}
	if (projectedState?.source === "dynamic") {
		availableToolNames.add(WORKFLOW_GET_STAGE_TOOL);
		availableToolNames.add(WORKFLOW_EDIT_STAGE_TOOL);
	}
	if (projectedState !== undefined || allowedCatalog.length > 0) {
		availableToolNames.add(WORKFLOW_TRANSITION_TOOL);
		availableToolNames.add(WORKFLOW_EXIT_TOOL);
	}

	// Running workflows stay in the options, so a start or an exit leaves the published list unchanged; the chain rejects a running ID.
	return {
		activationOptions: allowedCatalog,
		projectedState,
		availableToolNames,
	};
}