/**
 * Human-readable mission progression markdown + BeatSaver / BeatLeader URLs.
 * BeatLeader logic mirrors plebsaber.stream (MapActionButtons + player-playlist-gaps).
 */

import { join } from "@std/path";
import type {
  CampainMapPosition,
  CampaignInventory,
  ChallengeRequirement,
  InventoryMission,
} from "./campaign-types.ts";
import { DIFFICULTY_LABELS } from "./campaign-types.ts";

const BEATLEADER_API_HASH_BASE = "https://api.beatleader.com/leaderboards/hash/";
const FETCH_TIMEOUT_MS = 20_000;

export type BLDifficulty = {
  modeName?: string;
  difficultyName?: string;
  value?: number;
  ModeName?: string;
  DifficultyName?: string;
  Value?: number;
};

export type BLLeaderboardInfo = {
  id?: string | number | null;
  Id?: string | number | null;
  leaderboardId?: string | number | null;
  LeaderboardId?: string | number | null;
  difficulty?: BLDifficulty;
  Difficulty?: BLDifficulty;
};

function normalizeName(name?: string | null): string {
  return (name ?? "").toString().toLowerCase().replace(/\s+/g, "");
}

function difficultyRankIndex(diffName?: string | null): number {
  const order = ["easy", "normal", "hard", "expert", "expert+", "expertplus"];
  const n = normalizeName(diffName).replace("expertplus", "expert+");
  const idx = order.indexOf(n);
  return idx === -1 ? -1 : idx;
}

export function getDifficulty(obj?: BLDifficulty | null): BLDifficulty {
  const o = obj ?? {} as BLDifficulty;
  return {
    modeName: (o.modeName ?? (o as Record<string, unknown>).ModeName) as
      | string
      | undefined,
    difficultyName: (o.difficultyName ?? (o as Record<string, unknown>).DifficultyName) as
      | string
      | undefined,
    value: (o.value ?? (o as Record<string, unknown>).Value) as number | undefined,
  };
}

/** Prefer Standard mode; ExpertPlus; else highest known difficulty / value (playlist-gaps). */
export function pickPreferredLeaderboard(
  lbs: BLLeaderboardInfo[] | null | undefined,
): BLLeaderboardInfo | null {
  if (!Array.isArray(lbs) || lbs.length === 0) return null;
  const getDiff = (lb: BLLeaderboardInfo) =>
    getDifficulty(lb.difficulty ?? (lb as Record<string, unknown>).Difficulty as BLDifficulty | undefined);
  const isStandard = (lb: BLLeaderboardInfo) =>
    normalizeName(getDiff(lb)?.modeName) === "standard";
  const inStandard = lbs.filter(isStandard);
  const pool = inStandard.length > 0 ? inStandard : lbs;
  const expertPlus = pool.find((lb) => {
    const n = normalizeName(getDiff(lb)?.difficultyName);
    return n === "expertplus" || n === "expert+";
  });
  if (expertPlus) return expertPlus;
  const byKnownOrder = [...pool].sort((a, b) =>
    difficultyRankIndex(getDiff(a)?.difficultyName) -
      difficultyRankIndex(getDiff(b)?.difficultyName)
  );
  const bestByOrder = byKnownOrder[byKnownOrder.length - 1];
  if (
    bestByOrder && difficultyRankIndex(getDiff(bestByOrder)?.difficultyName) >= 0
  ) {
    return bestByOrder;
  }
  const byValue = [...pool].sort((a, b) =>
    (getDiff(a)?.value ?? 0) - (getDiff(b)?.value ?? 0)
  );
  return byValue[byValue.length - 1] ?? pool[0] ?? null;
}

function characteristicMatches(
  modeName: string | undefined,
  characteristic: string,
): boolean {
  return normalizeName(modeName) === normalizeName(characteristic);
}

function difficultyLabelMatches(
  difficultyName: string | undefined,
  difficultyIndex: number,
): boolean {
  const label = DIFFICULTY_LABELS[difficultyIndex] ?? "ExpertPlus";
  const want = normalizeName(label).replace("expertplus", "expert+");
  const got = normalizeName(difficultyName).replace("expertplus", "expert+");
  return got === want ||
    (label === "ExpertPlus" && (got === "expert+" || got === "expertplus"));
}

/** Stable pick when multiple leaderboards match (deterministic markdown). */
function pickFirstStableById(lbs: BLLeaderboardInfo[]): BLLeaderboardInfo {
  return [...lbs].sort((a, b) =>
    String(extractLeaderboardId(a) ?? "").localeCompare(
      String(extractLeaderboardId(b) ?? ""),
    )
  )[0];
}

/**
 * Prefer exact characteristic + difficulty match, then characteristic pool + preferred diff,
 * then global preferred leaderboard.
 */
export function pickLeaderboardForMission(
  lbs: BLLeaderboardInfo[] | null | undefined,
  characteristic: string,
  difficultyIndex: number,
): BLLeaderboardInfo | null {
  if (!Array.isArray(lbs) || lbs.length === 0) return null;
  const getDiff = (lb: BLLeaderboardInfo) =>
    getDifficulty(lb.difficulty ?? (lb as Record<string, unknown>).Difficulty as BLDifficulty | undefined);

  const exact = lbs.filter((lb) => {
    const d = getDiff(lb);
    return characteristicMatches(d.modeName, characteristic) &&
      difficultyLabelMatches(d.difficultyName, difficultyIndex);
  });
  if (exact.length > 0) return pickFirstStableById(exact);

  const charOnly = lbs.filter((lb) =>
    characteristicMatches(getDiff(lb).modeName, characteristic)
  );
  if (charOnly.length > 0) return pickPreferredLeaderboard(charOnly);

  return pickPreferredLeaderboard(lbs);
}

export function extractLeaderboardId(lb: BLLeaderboardInfo | null): string | null {
  if (!lb) return null;
  const anyLb = lb as Record<string, unknown>;
  const id = anyLb.id ?? anyLb.leaderboardId ?? anyLb.Id ?? anyLb.LeaderboardId;
  return id != null ? String(id) : null;
}

export function buildBeatLeaderUrlFromLeaderboard(
  lb: BLLeaderboardInfo | null,
  hash: string,
): string {
  const id = extractLeaderboardId(lb);
  if (id && id.length > 0) {
    return `https://beatleader.com/leaderboard/global/${id}`;
  }
  return `https://beatleader.com/leaderboards?search=${encodeURIComponent(hash)}`;
}

/** Hash + diff query variant (MapActionButtons fallback when no leaderboard id). */
export function buildBeatLeaderUrlHashQuery(params: {
  hash: string;
  diffName: string;
  modeName: string;
}): string {
  const { hash, diffName, modeName } = params;
  return `https://beatleader.com/leaderboard/global/${hash}?diff=${encodeURIComponent(diffName)}&mode=${encodeURIComponent(modeName)}`;
}

export function buildBeatSaverUrl(
  songid: string | undefined,
  hash: string | undefined,
): string | null {
  const key = songid?.trim();
  if (key) return `https://beatsaver.com/maps/${key}`;
  const h = hash?.trim().toLowerCase();
  if (h && /^[a-f0-9]{40}$/.test(h)) {
    return `https://beatsaver.com/search/hash/${h}`;
  }
  return null;
}

export async function fetchLeaderboardsByHash(
  hash: string,
  fetchImpl: typeof fetch = fetch,
): Promise<BLLeaderboardInfo[] | null> {
  const h = hash.trim().toLowerCase();
  if (!/^[a-f0-9]{40}$/.test(h)) return null;
  try {
    const res = await fetchImpl(
      BEATLEADER_API_HASH_BASE + encodeURIComponent(h),
      { signal: AbortSignal.timeout(FETCH_TIMEOUT_MS) },
    );
    if (!res.ok) return null;
    const data = await res.json() as Record<string, unknown>;
    const leaderboards = data.leaderboards ?? data.Leaderboards;
    return Array.isArray(leaderboards)
      ? leaderboards as BLLeaderboardInfo[]
      : null;
  } catch {
    return null;
  }
}

function escapeMarkdownHeader(text: string): string {
  return text.replace(/\r?\n/g, " ").trim();
}

function formatRequirementsOneLine(reqs: ChallengeRequirement[]): string {
  if (!reqs.length) return "_None_";
  return reqs.map((r) =>
    `${r.type}: ${r.count}${r.isMax ? " (max)" : ""}`
  ).join(" · ");
}

function formatLinksOneLine(urls: ResolvedMissionUrls | undefined): string {
  const bl = urls?.beatLeaderUrl
    ? `[BeatLeader](${urls.beatLeaderUrl})`
    : "_unavailable_";
  const bs = urls?.beatSaverUrl
    ? `[BeatSaver](${urls.beatSaverUrl})`
    : "_unavailable_";
  return `- **Links:** ${bl} · ${bs}`;
}

export type ResolvedMissionUrls = {
  beatLeaderUrl: string | null;
  beatSaverUrl: string | null;
};

export async function resolveMissionUrls(
  mission: InventoryMission,
  leaderboardsByHash: Map<string, BLLeaderboardInfo[] | null>,
  fetchImpl: typeof fetch,
  warnings: string[],
): Promise<ResolvedMissionUrls> {
  const beatSaverUrl = buildBeatSaverUrl(mission.songid, mission.hash);
  if (!beatSaverUrl) {
    warnings.push(
      `Mission ${mission.index}: BeatSaver URL skipped (need songid or 40-char hash).`,
    );
  }

  const h = mission.hash?.trim().toLowerCase();
  const hashOk = Boolean(h && /^[a-f0-9]{40}$/.test(h));

  if (!hashOk) {
    const search = mission.songid?.trim() || mission.name?.trim() || "";
    if (search) {
      warnings.push(
        `Mission ${mission.index}: BeatLeader hash missing/invalid; using site search.`,
      );
      return {
        beatSaverUrl,
        beatLeaderUrl:
          `https://beatleader.com/leaderboards?search=${encodeURIComponent(search)}`,
      };
    }
    warnings.push(
      `Mission ${mission.index}: BeatLeader URL skipped (no valid hash or search term).`,
    );
    return { beatSaverUrl, beatLeaderUrl: null };
  }

  let lbs = leaderboardsByHash.get(h!);
  if (lbs === undefined) {
    lbs = await fetchLeaderboardsByHash(h!, fetchImpl);
    leaderboardsByHash.set(h!, lbs);
  }

  if (!lbs || lbs.length === 0) {
    warnings.push(
      `Mission ${mission.index}: BeatLeader API returned no leaderboards for hash; using hash+diff URL.`,
    );
    const diffName = DIFFICULTY_LABELS[mission.difficulty] ?? "ExpertPlus";
    return {
      beatSaverUrl,
      beatLeaderUrl: buildBeatLeaderUrlHashQuery({
        hash: h!,
        diffName,
        modeName: mission.characteristic || "Standard",
      }),
    };
  }

  const picked = pickLeaderboardForMission(
    lbs,
    mission.characteristic || "Standard",
    mission.difficulty,
  );
  const id = extractLeaderboardId(picked);
  if (!id) {
    warnings.push(
      `Mission ${mission.index}: No leaderboard id from API; using hash+diff URL.`,
    );
    const diffName = DIFFICULTY_LABELS[mission.difficulty] ?? "ExpertPlus";
    return {
      beatSaverUrl,
      beatLeaderUrl: buildBeatLeaderUrlHashQuery({
        hash: h!,
        diffName,
        modeName: mission.characteristic || "Standard",
      }),
    };
  }

  return {
    beatSaverUrl,
    beatLeaderUrl: buildBeatLeaderUrlFromLeaderboard(picked, h!),
  };
}

export function formatMissionProgressionMarkdown(params: {
  inv: CampaignInventory;
  mapPositions: CampainMapPosition[];
  missions: InventoryMission[];
  urlsByMissionIndex: Map<number, ResolvedMissionUrls>;
}): string {
  const { inv, mapPositions, missions, urlsByMissionIndex } = params;
  const lines: string[] = [];

  lines.push(`# ${escapeMarkdownHeader(inv.info.name)}`);
  lines.push("");
  if (inv.info.desc?.trim()) {
    lines.push(inv.info.desc.trim());
    lines.push("");
  }
  if (inv.info.bigDesc?.trim()) {
    lines.push(inv.info.bigDesc.trim());
    lines.push("");
  }

  lines.push("## Missions");
  lines.push("");

  if (missions.length === 0) {
    lines.push("_No missions._");
    lines.push("");
    return lines.join("\n");
  }

  const diffLabel = (i: number) => DIFFICULTY_LABELS[i] ?? String(i);

  for (const m of missions) {
    const urls = urlsByMissionIndex.get(m.index);
    const children = mapPositions[m.index]?.childNodes ?? [];
    const nextLabel = children.length
      ? [...children].sort((a, b) => a - b).join(", ")
      : "_none (end)_";

    lines.push(`### Mission ${m.index}: ${escapeMarkdownHeader(m.name)}`);
    lines.push("");
    lines.push(
      `- **Difficulty:** ${diffLabel(m.difficulty)} · **Characteristic:** ${escapeMarkdownHeader(m.characteristic)}`,
    );
    if (m.purpose?.trim()) {
      lines.push(`- **Purpose:** ${m.purpose.trim()}`);
    }
    if (m.notes?.trim()) {
      lines.push(`- **Notes:** ${m.notes.trim()}`);
    }
    lines.push(formatLinksOneLine(urls));
    lines.push(
      `- **Requirements:** ${formatRequirementsOneLine(m.requirements ?? [])}`,
    );
    lines.push("");
    lines.push(`**Unlocks missions:** ${nextLabel}`);
    lines.push("");
    lines.push("---");
    lines.push("");
  }

  return lines.join("\n").replace(/\n---\n\n$/, "\n");
}

export const MISSION_PROGRESSION_FILENAME = "mission-progression.md";

export async function writeMissionProgressionMarkdown(
  outDir: string,
  inv: CampaignInventory,
  mapPositions: CampainMapPosition[],
  sortedMissions: InventoryMission[],
  options?: { fetchImpl?: typeof fetch },
): Promise<{ warnings: string[]; markdownPath: string }> {
  const warnings: string[] = [];
  const fetchImpl = options?.fetchImpl ?? fetch;
  const leaderboardsByHash = new Map<string, BLLeaderboardInfo[] | null>();
  const urlsByMissionIndex = new Map<number, ResolvedMissionUrls>();

  for (const m of sortedMissions) {
    const resolved = await resolveMissionUrls(
      m,
      leaderboardsByHash,
      fetchImpl,
      warnings,
    );
    urlsByMissionIndex.set(m.index, resolved);
  }

  const body = formatMissionProgressionMarkdown({
    inv,
    mapPositions,
    missions: sortedMissions,
    urlsByMissionIndex,
  });

  const markdownPath = join(outDir, MISSION_PROGRESSION_FILENAME);
  await Deno.writeTextFile(markdownPath, body.endsWith("\n") ? body : body + "\n");

  return { warnings, markdownPath };
}