/**
 * Progress dashboard island — the expanded, always-current version of the
 * daily email footer. Rendered on /progress; fetches campaign state from the
 * SRS Worker at page load, entirely client-side, so `blume build` never
 * depends on the API being up. API_BASE is a placeholder stamped in after the
 * Worker deploys — do not inline it anywhere else.
 *
 * Invariants: the component never throws on malformed API data (a shape guard
 * downgrades to the error state), and the first frame is always the loading
 * state so server and client render identically.
 */
import { useEffect, useState, type CSSProperties } from "react";

export const client = "load";

const API_BASE = "https://srs-api.prdlk.workers.dev";

// ── /api/stats response shape ────────────────────────────────────

const STAGES = ["new", "+2", "+5", "+10", "retired"] as const;

type Stage = (typeof STAGES)[number];

interface Stats {
  generated: string;
  campaign: { day: number; week: number; start: string; days: number };
  phases: {
    milestone: number;
    name: string;
    core_done: number;
    core_total: number;
    optional_done: number;
    optional_total: number;
    deferred_done: number;
    deferred_total: number;
  }[];
  ladder: Record<Stage, number>;
  gates: {
    week: number;
    issue: number | null;
    pass_rate: number | null;
    closed_on: string | null;
  }[];
  streak: number;
  queue: { date: string; due: number }[];
  recent: { date: string; attempts: number; passes: number }[];
}

function isStats(value: unknown): value is Stats {
  if (typeof value !== "object" || value === null) return false;
  const v = value as Record<string, unknown>;
  return (
    typeof v.campaign === "object" &&
    v.campaign !== null &&
    typeof v.ladder === "object" &&
    v.ladder !== null &&
    Array.isArray(v.phases) &&
    Array.isArray(v.gates) &&
    Array.isArray(v.queue) &&
    Array.isArray(v.recent) &&
    typeof v.streak === "number"
  );
}

// ── formatting ───────────────────────────────────────────────────

/** Legacy gates stored integer percent; the Worker may emit a 0–1 fraction. */
function percent(rate: number): string {
  return `${Math.round(rate <= 1 ? rate * 100 : rate)}%`;
}

/** "2026-08-24" → "Mon 24" without timezone drift. */
function dayLabel(iso: string): string {
  const d = new Date(`${iso}T00:00:00`);
  const weekday = d.toLocaleDateString("en-US", { weekday: "short" });
  return `${weekday} ${iso.slice(8)}`;
}

// ── shared styles (theme tokens only — no hand-rolled palette) ───

const card: CSSProperties = {
  border: "1px solid var(--blume-border)",
  borderRadius: "var(--blume-radius)",
  padding: "0.75rem 1rem",
  marginBottom: "1rem",
};

const muted: CSSProperties = {
  color: "var(--blume-muted-foreground)",
  fontSize: "0.85em",
};

const heading: CSSProperties = {
  fontWeight: 600,
  marginBottom: "0.5rem",
};

function Bar({ done, total }: { done: number; total: number }) {
  const ratio = total > 0 ? Math.min(done / total, 1) : 0;
  return (
    <span
      style={{
        display: "inline-block",
        width: "10rem",
        maxWidth: "40vw",
        height: "0.5rem",
        borderRadius: "var(--blume-radius)",
        background: "var(--blume-muted)",
        verticalAlign: "middle",
        overflow: "hidden",
      }}
    >
      <span
        style={{
          display: "block",
          width: `${ratio * 100}%`,
          height: "100%",
          background: "var(--blume-accent)",
        }}
      />
    </span>
  );
}

// ── sections ─────────────────────────────────────────────────────

function Header({ stats }: { stats: Stats }) {
  const { campaign, streak } = stats;
  return (
    <div style={{ ...card, display: "flex", gap: "1.5rem", flexWrap: "wrap" }}>
      <span>
        <strong>
          Day {campaign.day}/{campaign.days}
        </strong>
      </span>
      <span>Week {campaign.week}</span>
      <span>
        Streak: <strong>{streak}</strong> day{streak === 1 ? "" : "s"}
      </span>
      <span style={muted}>started {campaign.start}</span>
    </div>
  );
}

function Phases({ stats }: { stats: Stats }) {
  return (
    <div style={card}>
      <div style={heading}>Phases</div>
      <table style={{ borderCollapse: "collapse", width: "100%" }}>
        <tbody>
          {stats.phases.map((p) => (
            <tr key={p.milestone}>
              <td style={{ padding: "0.2rem 1rem 0.2rem 0" }}>{p.name}</td>
              <td style={{ padding: "0.2rem 1rem 0.2rem 0" }}>
                <Bar done={p.core_done} total={p.core_total} />{" "}
                <span style={muted}>
                  core {p.core_done}/{p.core_total}
                </span>
              </td>
              <td style={{ padding: "0.2rem 0" }}>
                <span style={muted}>
                  optional {p.optional_done}/{p.optional_total}
                  {p.deferred_total > 0 &&
                    ` · deferred ${p.deferred_done}/${p.deferred_total}`}
                </span>
              </td>
            </tr>
          ))}
        </tbody>
      </table>
    </div>
  );
}

function Ladder({ stats }: { stats: Stats }) {
  return (
    <div style={card}>
      <div style={heading}>SRS ladder</div>
      <div style={{ display: "flex", gap: "0.5rem", flexWrap: "wrap" }}>
        {STAGES.map((stage) => (
          <span
            key={stage}
            style={{
              background: "var(--blume-muted)",
              borderRadius: "var(--blume-radius)",
              padding: "0.35rem 0.75rem",
            }}
          >
            <span style={muted}>{stage}</span>{" "}
            <strong>{stats.ladder[stage] ?? 0}</strong>
          </span>
        ))}
      </div>
    </div>
  );
}

function Queue({ stats }: { stats: Stats }) {
  const max = Math.max(1, ...stats.queue.map((q) => q.due));
  return (
    <div style={card}>
      <div style={heading}>Review queue — next 14 days</div>
      <table style={{ borderCollapse: "collapse" }}>
        <tbody>
          {stats.queue.map((q) => (
            <tr key={q.date}>
              <td style={{ ...muted, padding: "0.1rem 1rem 0.1rem 0" }}>
                {dayLabel(q.date)}
              </td>
              <td style={{ padding: "0.1rem 0.75rem 0.1rem 0" }}>
                <Bar done={q.due} total={max} />
              </td>
              <td>{q.due}</td>
            </tr>
          ))}
        </tbody>
      </table>
    </div>
  );
}

function Gates({ stats }: { stats: Stats }) {
  return (
    <div style={card}>
      <div style={heading}>Gate log</div>
      {stats.gates.length === 0 ? (
        <span style={muted}>No gates yet.</span>
      ) : (
        <table style={{ borderCollapse: "collapse", width: "100%" }}>
          <thead>
            <tr>
              {["Week", "Issue", "Pass rate", "Closed"].map((h) => (
                <th key={h} style={{ ...muted, textAlign: "left", padding: "0.2rem 1rem 0.2rem 0" }}>
                  {h}
                </th>
              ))}
            </tr>
          </thead>
          <tbody>
            {stats.gates.map((g) => (
              <tr key={g.week}>
                <td style={{ padding: "0.2rem 1rem 0.2rem 0" }}>{g.week}</td>
                <td style={{ padding: "0.2rem 1rem 0.2rem 0" }}>
                  {g.issue === null ? (
                    <span style={muted}>—</span>
                  ) : (
                    <a
                      href={`https://github.com/prdlk/leetcode/issues/${g.issue}`}
                      target="_blank"
                      rel="noreferrer"
                    >
                      #{g.issue}
                    </a>
                  )}
                </td>
                <td style={{ padding: "0.2rem 1rem 0.2rem 0" }}>
                  {g.pass_rate === null ? (
                    <span style={muted}>open</span>
                  ) : (
                    percent(g.pass_rate)
                  )}
                </td>
                <td style={{ padding: "0.2rem 0" }}>
                  {g.closed_on ?? <span style={muted}>—</span>}
                </td>
              </tr>
            ))}
          </tbody>
        </table>
      )}
    </div>
  );
}

function Recent({ stats }: { stats: Stats }) {
  return (
    <div style={card}>
      <div style={heading}>Last 7 days</div>
      <div style={{ display: "flex", gap: "0.5rem", flexWrap: "wrap" }}>
        {stats.recent.map((r) => (
          <span
            key={r.date}
            style={{
              border: "1px solid var(--blume-border)",
              borderRadius: "var(--blume-radius)",
              padding: "0.35rem 0.6rem",
              textAlign: "center",
            }}
          >
            <span style={{ ...muted, display: "block" }}>{dayLabel(r.date)}</span>
            <strong>{r.passes}</strong>
            <span style={muted}>/{r.attempts}</span>
          </span>
        ))}
      </div>
      <div style={{ ...muted, marginTop: "0.4rem" }}>passes / attempts</div>
    </div>
  );
}

// ── dashboard ────────────────────────────────────────────────────

type Load =
  | { phase: "loading" }
  | { phase: "error" }
  | { phase: "ready"; stats: Stats };

export default function ProgressDashboard() {
  const [load, setLoad] = useState<Load>({ phase: "loading" });

  useEffect(() => {
    const controller = new AbortController();
    fetch(`${API_BASE}/api/stats`, { signal: controller.signal })
      .then((res) => {
        if (!res.ok) throw new Error(`HTTP ${res.status}`);
        return res.json();
      })
      .then((body: unknown) => {
        setLoad(isStats(body) ? { phase: "ready", stats: body } : { phase: "error" });
      })
      .catch(() => {
        if (!controller.signal.aborted) setLoad({ phase: "error" });
      });
    return () => controller.abort();
  }, []);

  if (load.phase === "loading") {
    return <p style={muted}>Loading progress…</p>;
  }
  if (load.phase === "error") {
    return (
      <p style={muted}>
        API unreachable — stats are served live from the SRS Worker and it did
        not respond.
      </p>
    );
  }

  const { stats } = load;
  return (
    <div>
      <Header stats={stats} />
      <Phases stats={stats} />
      <Ladder stats={stats} />
      <Queue stats={stats} />
      <Gates stats={stats} />
      <Recent stats={stats} />
      <p style={muted}>Generated {stats.generated}</p>
    </div>
  );
}