import type { ActivitySummary } from "@/types/form";

/**
 * CiviCRM activity stage values → Framework Stage rank (1..5). "Inquiry"
 * predates Stage 1 and is conventionally rank 0 (pre-engagement); callers
 * that render stage lanes 1..5 should treat 0 as "no rank in scope".
 */
export const STAGE_RANK: Record<string, number> = {
  Inquiry: 0,
  Organizing: 1,
  Feasibility: 2,
  "Business feasibility": 3,
  "Store Implementation": 4,
  "Stabilize newly opened co-op": 5,
};

/**
 * Build a resolver that returns the co-op's Framework Stage rank at a given
 * point in time, derived from the activity stream. Only activities that
 * carry a non-empty `stage` value are stage transitions; their stage holds
 * from that activity's date forward until the next transition.
 *
 * Returns `null` when the date precedes any known transition (i.e. we have
 * no evidence of which stage the co-op was in at that point) — callers can
 * fall back to a field-section default in that case.
 */
export function buildStageRankAtDate(
  activities: ActivitySummary[]
): (isoDate: string) => number | null {
  const transitions = activities
    .filter(
      (a): a is ActivitySummary & { stage: string } =>
        typeof a.stage === "string" && a.stage.length > 0
    )
    .map((a) => ({ t: new Date(a.date).getTime(), stage: a.stage }))
    .filter((tr) => Number.isFinite(tr.t))
    .sort((a, b) => a.t - b.t);

  return (isoDate: string) => {
    const t = new Date(isoDate).getTime();
    if (!Number.isFinite(t)) return null;
    let last: number | null = null;
    for (const tr of transitions) {
      if (tr.t > t) break;
      const r = STAGE_RANK[tr.stage];
      if (typeof r === "number") last = r;
    }
    return last;
  };
}

export interface StageRange {
  rank: number;
  /** ISO date this stage period begins (the stage-transition activity). */
  startDate: string;
  /**
   * ISO date the period ends — the next chronologically-later activity with
   * a higher stage rank. `null` means the period is open-ended (still in
   * effect today); the chart should extend it to the right edge.
   */
  endDate: string | null;
  activityId: number;
  subject: string | null;
}

/**
 * Derive per-activity stage ranges from the activity stream. Each
 * stage-transition activity (one with a non-empty `stage`) produces one
 * range: start = the activity's date, end = the date of the next
 * chronologically-following activity whose stage rank is *strictly higher*.
 * If no later activity has a higher rank, the range is open-ended.
 *
 * Multiple activities at the same stage each yield their own range; they'll
 * share the same end date if they sit between the same two higher-rank
 * boundaries.
 */
export function computeStageRanges(activities: ActivitySummary[]): StageRange[] {
  type Item = {
    t: number;
    rank: number;
    activityId: number;
    isoDate: string;
    subject: string | null;
  };
  const items: Item[] = [];
  for (const a of activities) {
    if (typeof a.stage !== "string" || a.stage.length === 0) continue;
    const r = STAGE_RANK[a.stage];
    if (typeof r !== "number" || r < 1 || r > 5) continue;
    const t = new Date(a.date).getTime();
    if (!Number.isFinite(t)) continue;
    items.push({
      t,
      rank: r,
      activityId: a.id,
      isoDate: a.date,
      subject: a.subject ?? null,
    });
  }
  items.sort((x, y) => x.t - y.t);

  const ranges: StageRange[] = [];
  for (let i = 0; i < items.length; i++) {
    const cur = items[i];
    let endIso: string | null = null;
    for (let j = i + 1; j < items.length; j++) {
      if (items[j].rank > cur.rank) {
        endIso = items[j].isoDate;
        break;
      }
    }
    ranges.push({
      rank: cur.rank,
      startDate: cur.isoDate,
      endDate: endIso,
      activityId: cur.activityId,
      subject: cur.subject,
    });
  }
  return ranges;
}