/**
 * Per-field-most-recent prefill walk.
 *
 * Loads all `Org Engagement Submission` activities for an organization,
 * sorted DESC by activity_date_time. For each field name we care about,
 * walk the list and take the first non-null value found.
 *
 * This closes the v1 prefill gap that Webform CiviCRM cannot express in
 * its admin UI: load latest values per-field across multiple activities,
 * without coupling to update-mode.
 */

import { civi } from "./civicrm";
import type { FieldConfig } from "@/types/form";

interface ActivityRow {
  id: number;
  activity_date_time: string;
  // CiviCRM returns custom fields under their machine names like
  // `custom_42` or `Stage_0_Core.peer_group_participation`.
  [key: string]: unknown;
}

export interface PrefillResult {
  /** Form-side keys → most-recent non-null value. */
  values: Record<string, unknown>;
  /** Number of submission activities walked. */
  activityCount: number;
}

/**
 * Walk Org Engagement Submission activities for the org, returning per-field
 * most-recent values keyed by FieldConfig.name. Only fields with a `civiField`
 * are looked up; transient fields are ignored.
 */
export async function loadPrefill(
  orgId: number,
  fields: FieldConfig[],
  activityTypeName = "Org Engagement Submission",
): Promise<PrefillResult> {
  const civiSelected = fields.filter((f) => f.civiField);

  // CiviCRM File custom fields return a file id by default. To surface a
  // human-readable filename in the prefill (so the prior-attachment
  // indicator can show it), also request the joined `.file_name` for any
  // file-type field.
  const fileFieldRefs = new Set(
    civiSelected.filter((f) => f.type === "file").map((f) => f.civiField!),
  );

  const selectSet = new Set<string>(["id", "activity_date_time"]);
  for (const f of civiSelected) selectSet.add(f.civiField!);
  for (const ref of fileFieldRefs) selectSet.add(`${ref}.file_name`);
  const select = Array.from(selectSet);

  const res = await civi<ActivityRow>("Activity", "get", {
    select,
    where: [
      ["activity_type_id:name", "=", activityTypeName],
      ["target_contact_id", "=", orgId],
    ],
    orderBy: { activity_date_time: "DESC" },
    limit: 200,
  });
  const rows = res.values ?? [];

  const out: Record<string, unknown> = {};
  for (const f of civiSelected) {
    for (const row of rows) {
      const v = row[f.civiField!];
      if (v === null || v === undefined || v === "") continue;
      if (f.type === "file") {
        const fname = row[`${f.civiField!}.file_name`];
        out[f.name] = {
          id: v,
          file_name: typeof fname === "string" ? fname : undefined,
        };
      } else {
        out[f.name] = v;
      }
      break;
    }
  }

  return { values: out, activityCount: rows.length };
}