documenso/packages/lib/utils/recipient-groups.ts

import type { Recipient } from '@prisma/client';
import { SigningStatus } from '@prisma/client';

import { isCcRecipient } from './recipients';

/**
 * A recipient "step" is the set of non-CC recipients sharing a signing order.
 * A step with 2 or more members is a "signing group": members may act in any
 * order among themselves, and the next step only unlocks once every member of
 * the group has completed their action.
 */

type GroupableRecipient = Pick<Recipient, 'role'> & {
  signingOrder?: number | null;
};

export type RecipientStep<T> = {
  /**
   * The signing order shared by all members of the step.
   */
  order: number;
  members: T[];
};

const UNORDERED = Number.MAX_SAFE_INTEGER;

/**
 * The signing order to sort and group by — a missing order means LAST.
 */
export const effectiveSigningOrder = (recipient: { signingOrder?: number | null }) =>
  recipient.signingOrder ?? UNORDERED;

/**
 * Derives the ordered list of steps from a list of recipients.
 *
 * - Non-CC recipients who share a signing order form a signing group.
 * - Recipients without a signing order share a single tail group.
 * - CC recipients are returned separately and never belong to a group.
 */
export const groupRecipientsBySigningOrder = <T extends GroupableRecipient>(recipients: T[]) => {
  const ccRecipients = recipients.filter((recipient) => isCcRecipient(recipient));
  const nonCcRecipients = recipients.filter((recipient) => !isCcRecipient(recipient));

  const membersByOrder = new Map<number, T[]>();

  for (const recipient of nonCcRecipients) {
    const order = effectiveSigningOrder(recipient);
    const members = membersByOrder.get(order) ?? [];

    members.push(recipient);
    membersByOrder.set(order, members);
  }

  const steps: RecipientStep<T>[] = [...membersByOrder.entries()]
    .sort(([orderA], [orderB]) => orderA - orderB)
    .map(([order, members]) => ({ order, members }));

  return { steps, ccRecipients };
};

/**
 * Index of the last step containing a locked (non-updatable) recipient, or -1.
 */
export const getLastLockedStepIndex = <T extends GroupableRecipient>(
  steps: RecipientStep<T>[],
  canUpdateRecipient: (recipient: T) => boolean = () => true,
): number =>
  steps.reduce(
    (lastIndex, step, index) => (step.members.some((member) => !canUpdateRecipient(member)) ? index : lastIndex),
    -1,
  );

/**
 * Dense-renumbers steps to 1..K while preserving groups (duplicate orders).
 *
 * - Locked steps keep their persisted order
 * - Editable steps never collide into a locked step's number
 * - CC recipients move to the tail with an undefined order
 * - The returned array is re-ordered by step sequence
 */
export const normalizeGroupedSigningOrders = <T extends GroupableRecipient>(
  recipients: T[],
  canUpdateRecipient: (recipient: T) => boolean = () => true,
): Array<T & { signingOrder?: number }> => {
  const { steps, ccRecipients } = groupRecipientsBySigningOrder(recipients);

  const lastLockedStepIndex = getLastLockedStepIndex(steps, canUpdateRecipient);

  let nextOrder = 1;

  const normalizedSteps = steps.map((step, index) => {
    // Locked steps hold persisted orders. Keep them exactly as they are, even
    // when sparse.
    if (index <= lastLockedStepIndex) {
      const order = step.order === UNORDERED ? undefined : step.order;

      if (order !== undefined) {
        nextOrder = Math.max(nextOrder, order + 1);
      }

      return { order, members: step.members };
    }

    const order = nextOrder;

    nextOrder += 1;

    return { order, members: step.members };
  });

  return [
    ...normalizedSteps.flatMap((step) => step.members.map((member) => ({ ...member, signingOrder: step.order }))),
    ...ccRecipients.map((recipient) => ({ ...recipient, signingOrder: undefined })),
  ];
};

type EditorRecipient = GroupableRecipient & { formId: string };

/**
 * Merges all members of the source step into the target step.
 */
export const mergeSteps = <T extends EditorRecipient>(
  recipients: T[],
  sourceStepIndex: number,
  targetStepIndex: number,
  canUpdateRecipient?: (recipient: T) => boolean,
): Array<T & { signingOrder?: number }> => {
  const { steps } = groupRecipientsBySigningOrder(recipients);

  const sourceStep = steps[sourceStepIndex];
  const targetStep = steps[targetStepIndex];
  const lastLockedStepIndex = getLastLockedStepIndex(steps, canUpdateRecipient);

  if (
    !sourceStep ||
    !targetStep ||
    sourceStepIndex === targetStepIndex ||
    sourceStepIndex <= lastLockedStepIndex ||
    targetStepIndex <= lastLockedStepIndex
  ) {
    return normalizeGroupedSigningOrders(recipients, canUpdateRecipient);
  }

  const sourceFormIds = new Set(sourceStep.members.map((member) => member.formId));

  // Source members join after the target step's existing members.
  const remaining = recipients.filter((recipient) => !sourceFormIds.has(recipient.formId));
  const lastMemberFormId = targetStep.members[targetStep.members.length - 1].formId;
  const insertAfterIndex = remaining.findIndex((recipient) => recipient.formId === lastMemberFormId);

  const movedMembers = sourceStep.members.map((member) => ({ ...member, signingOrder: targetStep.order }));

  const updated = [
    ...remaining.slice(0, insertAfterIndex + 1),
    ...movedMembers,
    ...remaining.slice(insertAfterIndex + 1),
  ];

  return normalizeGroupedSigningOrders(updated, canUpdateRecipient);
};

/**
 * Moves a single recipient into the target step (joins the group).
 */
export const moveRecipientToStep = <T extends EditorRecipient>(
  recipients: T[],
  formId: string,
  targetStepIndex: number,
  canUpdateRecipient?: (recipient: T) => boolean,
): Array<T & { signingOrder?: number }> => {
  const { steps } = groupRecipientsBySigningOrder(recipients);

  const targetStep = steps[targetStepIndex];
  const mover = recipients.find((recipient) => recipient.formId === formId);
  const lastLockedStepIndex = getLastLockedStepIndex(steps, canUpdateRecipient);
  const moverStepIndex = steps.findIndex((step) => step.members.some((member) => member.formId === formId));

  if (!targetStep || !mover || isCcRecipient(mover)) {
    return normalizeGroupedSigningOrders(recipients, canUpdateRecipient);
  }

  // Neither the recipient nor the destination may sit in the locked region.
  if (targetStepIndex <= lastLockedStepIndex || moverStepIndex <= lastLockedStepIndex) {
    return normalizeGroupedSigningOrders(recipients, canUpdateRecipient);
  }

  if (targetStep.members.some((member) => member.formId === formId)) {
    return normalizeGroupedSigningOrders(recipients, canUpdateRecipient);
  }

  const remaining = recipients.filter((recipient) => recipient.formId !== formId);
  const lastMemberFormId = targetStep.members[targetStep.members.length - 1].formId;
  const insertAfterIndex = remaining.findIndex((recipient) => recipient.formId === lastMemberFormId);

  const updated = [
    ...remaining.slice(0, insertAfterIndex + 1),
    { ...mover, signingOrder: targetStep.order },
    ...remaining.slice(insertAfterIndex + 1),
  ];

  return normalizeGroupedSigningOrders(updated, canUpdateRecipient);
};

/**
 * Extracts a recipient into its own standalone step at the given gap position.
 *
 * - Gap N sits before step N
 * - An out-of-bounds gap appends to the end
 */
export const extractRecipientToNewStep = <T extends EditorRecipient>(
  recipients: T[],
  formId: string,
  insertStepIndex: number,
  canUpdateRecipient?: (recipient: T) => boolean,
): Array<T & { signingOrder?: number }> => {
  const { steps } = groupRecipientsBySigningOrder(recipients);

  const mover = recipients.find((recipient) => recipient.formId === formId);

  if (!mover || isCcRecipient(mover)) {
    return normalizeGroupedSigningOrders(recipients, canUpdateRecipient);
  }

  const currentStepIndex = steps.findIndex((step) => step.members.some((member) => member.formId === formId));
  const isSoloStep = currentStepIndex !== -1 && steps[currentStepIndex].members.length === 1;
  const lastLockedStepIndex = getLastLockedStepIndex(steps, canUpdateRecipient);

  // Dropping a solo step into the gap directly above or below itself is a no-op.
  if (isSoloStep && (insertStepIndex === currentStepIndex || insertStepIndex === currentStepIndex + 1)) {
    return normalizeGroupedSigningOrders(recipients, canUpdateRecipient);
  }

  // Gap N sits before step N, so inserting at or before the last locked step
  // would land the recipient inside the locked region.
  if (insertStepIndex <= lastLockedStepIndex || currentStepIndex <= lastLockedStepIndex) {
    return normalizeGroupedSigningOrders(recipients, canUpdateRecipient);
  }

  const insertOrder =
    insertStepIndex >= steps.length ? (steps[steps.length - 1]?.order ?? 0) + 1 : steps[insertStepIndex].order - 0.5;

  const updated = recipients.map((recipient) =>
    recipient.formId === formId ? { ...recipient, signingOrder: insertOrder } : recipient,
  );

  return normalizeGroupedSigningOrders(updated, canUpdateRecipient);
};

/**
 * Moves a whole step (group) to a new position in the step sequence.
 *
 * - Refused when either end sits in the locked region; only the unlocked
 *   tail can be rearranged.
 */
export const reorderStep = <T extends EditorRecipient>(
  recipients: T[],
  fromStepIndex: number,
  toStepIndex: number,
  canUpdateRecipient: (recipient: T) => boolean = () => true,
): Array<T & { signingOrder?: number }> => {
  const { steps, ccRecipients } = groupRecipientsBySigningOrder(recipients);

  const lastLockedStepIndex = getLastLockedStepIndex(steps, canUpdateRecipient);

  if (
    !steps[fromStepIndex] ||
    fromStepIndex === toStepIndex ||
    fromStepIndex <= lastLockedStepIndex ||
    toStepIndex <= lastLockedStepIndex
  ) {
    return normalizeGroupedSigningOrders(recipients, canUpdateRecipient);
  }

  const reorderedSteps = [...steps];
  const [movedStep] = reorderedSteps.splice(fromStepIndex, 1);

  reorderedSteps.splice(Math.min(toStepIndex, reorderedSteps.length), 0, movedStep);

  // Locked steps cannot be the source or destination, so they keep both their
  // position and their persisted order. The moved tail is numbered above the
  // highest locked order so it still sorts after them.
  const highestLockedOrder = reorderedSteps
    .slice(0, lastLockedStepIndex + 1)
    .reduce((highest, step) => (step.order === UNORDERED ? highest : Math.max(highest, step.order)), 0);

  const updated = [
    ...reorderedSteps.flatMap((step, index) => {
      if (index <= lastLockedStepIndex) {
        return step.members;
      }

      const order = highestLockedOrder + (index - lastLockedStepIndex);

      return step.members.map((member) => ({ ...member, signingOrder: order }));
    }),
    ...ccRecipients,
  ];

  return normalizeGroupedSigningOrders(updated, canUpdateRecipient);
};

type SignableRecipient = Pick<Recipient, 'role' | 'signingStatus'> & {
  signingOrder?: number | null;
};

/**
 * Whether it is the recipient's turn to act under SEQUENTIAL signing.
 *
 * - A recipient may act if no non-CC recipient with a lower order is still unsigned
 * - Recipients sharing a signing order never block each other.
 * - Callers must check the document is in SEQUENTIAL mode.
 */
export const isRecipientTurnBySigningOrder = <T extends SignableRecipient>(
  recipients: T[],
  currentRecipient: { signingOrder?: number | null },
): boolean => {
  const currentOrder = effectiveSigningOrder(currentRecipient);

  return !recipients.some(
    (recipient) =>
      !isCcRecipient(recipient) &&
      recipient.signingStatus !== SigningStatus.SIGNED &&
      effectiveSigningOrder(recipient) < currentOrder,
  );
};

/**
 * Every pending recipient sharing the lowest pending signing order — the "active step".
 *
 * - Two or more members form a signing group and act in parallel.
 * - Pending means non-CC and NOT_SIGNED; rejected recipients are excluded so
 *   the flow never re-activates somebody who declined.
 * - Pass the full recipient list: filtering happens here so every caller
 *   agrees on what "pending" means.
 */
export const getRecipientsInActiveSigningStep = <T extends SignableRecipient>(recipients: T[]): T[] => {
  const pendingRecipients = recipients.filter(
    (recipient) => !isCcRecipient(recipient) && recipient.signingStatus === SigningStatus.NOT_SIGNED,
  );

  if (pendingRecipients.length === 0) {
    return [];
  }

  const minOrder = Math.min(...pendingRecipients.map((recipient) => effectiveSigningOrder(recipient)));

  return pendingRecipients.filter((recipient) => effectiveSigningOrder(recipient) === minOrder);
};

/**
 * The single recipient that the current recipient may dictate (rename) on
 * completion, or null when dictation does not apply:
 *
 * - the current recipient must be the last unsigned member of their step, and
 * - the next step must contain exactly one recipient.
 */
export const getNextDictatableRecipient = <T extends SignableRecipient & Pick<Recipient, 'id'>>({
  recipients,
  currentRecipientId,
}: {
  recipients: T[];
  currentRecipientId: number;
}): T | null => {
  const currentRecipient = recipients.find((recipient) => recipient.id === currentRecipientId);

  if (!currentRecipient || isCcRecipient(currentRecipient)) {
    return null;
  }

  const currentOrder = effectiveSigningOrder(currentRecipient);

  const hasUnsignedPeers = recipients.some(
    (recipient) =>
      recipient.id !== currentRecipientId &&
      !isCcRecipient(recipient) &&
      effectiveSigningOrder(recipient) === currentOrder &&
      recipient.signingStatus !== SigningStatus.SIGNED,
  );

  if (hasUnsignedPeers) {
    return null;
  }

  // Only the step matters here; `getRecipientsInActiveSigningStep` drops
  // CCs and anyone who has already signed or rejected.
  const laterRecipients = recipients.filter((recipient) => effectiveSigningOrder(recipient) > currentOrder);

  const nextStep = getRecipientsInActiveSigningStep(laterRecipients);

  if (nextStep.length !== 1) {
    return null;
  }

  return nextStep[0];
};

/**
 * Dissolves a group into consecutive standalone steps preserving relative order.
 */
export const ungroupStep = <T extends EditorRecipient>(
  recipients: T[],
  stepIndex: number,
  canUpdateRecipient?: (recipient: T) => boolean,
): Array<T & { signingOrder?: number }> => {
  const { steps } = groupRecipientsBySigningOrder(recipients);

  const step = steps[stepIndex];

  // Splitting a locked step would rewrite persisted orders.
  if (!step || step.members.length < 2 || stepIndex <= getLastLockedStepIndex(steps, canUpdateRecipient)) {
    return normalizeGroupedSigningOrders(recipients, canUpdateRecipient);
  }

  const offsetByFormId = new Map(step.members.map((member, index) => [member.formId, index]));

  const updated = recipients.map((recipient) => {
    const offset = offsetByFormId.get(recipient.formId);

    if (offset === undefined) {
      return recipient;
    }

    return { ...recipient, signingOrder: step.order + offset / (step.members.length + 1) };
  });

  return normalizeGroupedSigningOrders(updated, canUpdateRecipient);
};