"use client";

import type { FieldHistoryEntry, StageSectionConfig } from "@/types/form";
import { formatShortDate } from "./FieldHistory";

/**
 * Date-grouped timeline strip at the top of the report. Walks every
 * date-type field across all stage sections (0–5), pulls each field's
 * most-recent entered date, and plots events into six horizontal swim
 * lanes — one per stage. Stage 5's `Date_Opened` gets visual emphasis
 * as the journey's anchor at the right end of the time axis. A faint
 * "Today" tick anchors the reader if today falls within the range, and
 * an adaptive month/year axis runs beneath the lanes. Each dot exposes
 * a tooltip on hover or keyboard focus.
 */
export function DateTimeline({
  sections,
  fieldHistory,
}: {
  sections: StageSectionConfig[];
  fieldHistory: Record<string, FieldHistoryEntry[]>;
}) {
  type Event = {
    rank: number;
    fieldLabel: string;
    date: string; // YYYY-MM-DD or full ISO
    isOpened: boolean;
  };
  const events: Event[] = [];
  for (const section of sections) {
    if (section.rank < 0 || section.rank > 5) continue;
    for (const f of section.fields) {
      if (f.type !== "date") continue;
      const history = fieldHistory[f.name];
      if (!history || history.length === 0) continue;
      const v = history[0].value;
      if (typeof v !== "string" || v.length === 0) continue;
      events.push({
        rank: section.rank,
        fieldLabel: f.label,
        date: v,
        isOpened: f.name === "Date_Opened",
      });
    }
  }
  if (events.length === 0) return null;

  const times = events.map((e) => new Date(e.date).getTime()).filter(Number.isFinite);
  if (times.length === 0) return null;

  const openedEvent = events.find((e) => e.isOpened);
  const openedTime = openedEvent ? new Date(openedEvent.date).getTime() : undefined;
  const minT = Math.min(...times);
  // If Date_Opened is set, anchor the right edge there; if any other event
  // is later, extend so nothing falls off the chart.
  const maxT = Math.max(...times, openedTime ?? -Infinity);
  const tRange = maxT - minT || 1;
  const todayT = Date.now();
  const todayPct =
    todayT >= minT && todayT <= maxT ? ((todayT - minT) / tRange) * 100 : null;

  const ticks = generateAxisTicks(minT, maxT);

  return (
    <section
      aria-labelledby="timeline-heading"
      className="rounded-lg border border-rule bg-paper-2/30 px-6 py-5 sm:px-7 sm:py-6"
    >
      <div className="flex items-baseline justify-between gap-4">
        <h2
          id="timeline-heading"
          className="font-display text-base font-medium leading-tight text-ink"
        >
          Timeline
        </h2>
        <p className="text-[11px] uppercase tracking-[0.12em] text-ink-mute tabular-nums">
          {formatShortDate(new Date(minT).toISOString())}
          {" → "}
          {formatShortDate(new Date(maxT).toISOString())}
        </p>
      </div>
      <ol className="mt-4 space-y-2">
        {[0, 1, 2, 3, 4, 5].map((rank) => {
          const rowEvents = events.filter((e) => e.rank === rank);
          const isEmpty = rowEvents.length === 0;
          return (
            <li
              key={rank}
              className="grid grid-cols-[3.5rem_1fr] items-center gap-3 sm:grid-cols-[4.5rem_1fr]"
            >
              <span className="text-[10px] uppercase tracking-[0.14em] font-medium text-ink-mute">
                Stage {rank}
              </span>
              <div className="relative h-5">
                <span
                  aria-hidden
                  className={
                    "absolute inset-x-0 top-1/2 -translate-y-1/2 h-px " +
                    (isEmpty ? "bg-rule-soft/60" : "bg-rule-soft")
                  }
                />
                {todayPct !== null && (
                  <span
                    aria-hidden
                    style={{ left: `${todayPct}%` }}
                    className="absolute top-0 bottom-0 w-px -translate-x-1/2 border-l border-dashed border-clay-300/70"
                  />
                )}
                {rowEvents.map((e, i) => {
                  const t = new Date(e.date).getTime();
                  if (!Number.isFinite(t)) return null;
                  const x = ((t - minT) / tRange) * 100;
                  return (
                    <TimelineDot
                      key={i}
                      rank={rank}
                      event={e}
                      x={x}
                    />
                  );
                })}
              </div>
            </li>
          );
        })}
      </ol>

      {/* Adaptive month/year axis. Render only when we have ≥2 ticks so a
          single tick doesn't dangle. Today gets its own labeled mark when
          it falls within range. */}
      {ticks.length >= 2 && (
        <div className="mt-3 grid grid-cols-[3.5rem_1fr] items-start gap-3 sm:grid-cols-[4.5rem_1fr]">
          <span aria-hidden />
          <div className="relative h-7">
            <span
              aria-hidden
              className="absolute inset-x-0 top-0 h-px bg-rule-soft"
            />
            {ticks.map((tk, i) => {
              const x = ((tk.t - minT) / tRange) * 100;
              // Edge labels shift so they don't overflow the row.
              const alignClass =
                x < 6
                  ? "left-0 origin-top-left"
                  : x > 94
                    ? "right-0 origin-top-right text-right"
                    : "left-1/2 -translate-x-1/2 text-center";
              return (
                <span
                  key={i}
                  style={{ left: `${x}%` }}
                  className="absolute top-0 -translate-x-1/2"
                >
                  <span
                    aria-hidden
                    className="block h-1.5 w-px bg-rule mx-auto"
                  />
                  <span
                    className={
                      "absolute top-2 block whitespace-nowrap text-[9px] uppercase tracking-[0.08em] tabular-nums text-ink-mute " +
                      alignClass
                    }
                  >
                    {tk.label}
                  </span>
                </span>
              );
            })}
            {todayPct !== null && (
              <span
                style={{ left: `${todayPct}%` }}
                className="absolute top-0 -translate-x-1/2"
              >
                <span
                  aria-hidden
                  className="block h-1.5 w-px bg-clay-500 mx-auto"
                />
                <span className="absolute top-2 left-1/2 -translate-x-1/2 block whitespace-nowrap text-[9px] font-medium uppercase tracking-[0.08em] text-clay-700">
                  Today
                </span>
              </span>
            )}
          </div>
        </div>
      )}
      {/* Accessible event list — invisible to sighted users but readable by SR */}
      <ul className="sr-only">
        {events.map((e, i) => (
          <li key={i}>
            Stage {e.rank}: {e.fieldLabel} — {formatShortDate(e.date)}
            {e.isOpened ? " (opened)" : ""}
          </li>
        ))}
      </ul>
    </section>
  );
}

function stageDotBg(rank: number): string {
  switch (rank) {
    case 0:
      return "bg-leaf-200";
    case 1:
      return "bg-leaf-300";
    case 2:
      return "bg-leaf-500";
    case 3:
      return "bg-leaf-600";
    case 4:
      return "bg-leaf-700";
    case 5:
      return "bg-clay-700";
    default:
      return "bg-leaf-600";
  }
}

/**
 * A single dot on the timeline plus its hover/focus tooltip. Keyboard
 * users can Tab to each dot and the tooltip will appear via
 * `group-focus-within`. The tooltip is anchored above the dot; for dots
 * near the left or right edge of the row, anchor flips so the card
 * doesn't overflow.
 */
function TimelineDot({
  rank,
  event,
  x,
}: {
  rank: number;
  event: { fieldLabel: string; date: string; isOpened: boolean };
  x: number;
}) {
  const isOpened = event.isOpened;
  const bg = isOpened ? "bg-clay-700" : stageDotBg(rank);
  const size = isOpened ? "h-3.5 w-3.5" : "h-2.5 w-2.5";
  const ring = isOpened ? "ring-2" : "ring-1";
  const tipAlign =
    x < 18
      ? "left-0"
      : x > 82
        ? "right-0"
        : "left-1/2 -translate-x-1/2";
  return (
    <span
      role="img"
      tabIndex={0}
      aria-label={`${event.fieldLabel}, ${formatShortDate(event.date)}${isOpened ? " (opened)" : ""}, stage ${rank}`}
      style={{ left: `${x}%` }}
      className={
        "group/dot absolute top-1/2 -translate-x-1/2 -translate-y-1/2 rounded-full shadow-sm focus:outline-none focus-visible:ring-2 focus-visible:ring-leaf-500/40 " +
        `${ring} ring-paper ${size} ${bg}`
      }
    >
      <span
        role="tooltip"
        className={
          "pointer-events-none absolute bottom-full z-30 mb-2 hidden whitespace-nowrap rounded-md bg-ink/95 px-2.5 py-1.5 text-[11px] leading-snug text-paper shadow-lg group-hover/dot:block group-focus-within/dot:block " +
          tipAlign
        }
      >
        <span className="block font-medium">{event.fieldLabel}</span>
        <span className="mt-0.5 block tabular-nums text-paper-2/80">
          {formatShortDate(event.date)}
          <span className="ml-2 uppercase tracking-[0.08em] text-paper-2/60">
            Stage {rank}
          </span>
        </span>
        {isOpened && (
          <span className="mt-0.5 block text-clay-200 uppercase tracking-[0.08em]">
            Opened
          </span>
        )}
      </span>
    </span>
  );
}

/**
 * Pick a "nice" tick interval for the time axis based on the visible
 * span, then walk that interval from min to max producing labeled ticks.
 * Uses months for shorter spans, years for longer ones; January-bordered
 * month ticks include the year so the reader has an anchor.
 */
export function generateAxisTicks(minT: number, maxT: number): Array<{ t: number; label: string }> {
  const range = maxT - minT;
  const monthMs = 30.4375 * 24 * 3600 * 1000;
  const months = range / monthMs;

  type Step = { unit: "month" | "year"; step: number };
  let plan: Step;
  if (months < 4) plan = { unit: "month", step: 1 };
  else if (months < 12) plan = { unit: "month", step: 2 };
  else if (months < 24) plan = { unit: "month", step: 3 };
  else if (months < 48) plan = { unit: "month", step: 6 };
  else if (months / 12 < 12) plan = { unit: "year", step: 1 };
  else plan = { unit: "year", step: 2 };

  const ticks: Array<{ t: number; label: string }> = [];
  const start = new Date(minT);
  let y = start.getFullYear();
  let m =
    plan.unit === "year"
      ? 0
      : Math.floor(start.getMonth() / plan.step) * plan.step;
  // Don't skip a tick that sits right at minT — start from minT-aligned step.
  while (true) {
    const t = new Date(y, m, 1).getTime();
    if (t > maxT) break;
    if (t >= minT) {
      const d = new Date(y, m, 1);
      const label =
        plan.unit === "year"
          ? String(y)
          : m === 0
            ? d.toLocaleDateString("en-US", { month: "short", year: "numeric" })
            : d.toLocaleDateString("en-US", { month: "short" });
      ticks.push({ t, label });
    }
    if (plan.unit === "year") {
      y += plan.step;
    } else {
      m += plan.step;
      while (m > 11) {
        m -= 12;
        y += 1;
      }
    }
  }
  return ticks;
}