/**
 * Wikipedia tennis Grand Slam draw adapter.
 *
 * Source of truth: the singles-draw article (e.g.
 * "2025 Wimbledon Championships – Men's singles"), whose full bracket is encoded
 * as MediaWiki bracket templates:
 *   - eight `{{16TeamBracket-Compact-Tennis5}}` sections (Round of 128 → Round
 *     of 16), 16 players each = 128, and
 *   - one `{{8TeamBracket-Tennis5}}` finals bracket (Quarterfinals → Final).
 * (`-Tennis3` best-of-3 variants render women's draws identically for our needs.)
 *
 * The winner of each match is the slot whose `team` value is bolded (`'''…'''`)
 * — losers are never bolded — which lets us derive winner/loser without parsing
 * set scores. Player names come from `[[wikilinks]]`, whose target is a stable
 * cross-year id used to match `seasonParticipants.externalId`.
 *
 * Parsing is split out (pure functions) so it can be unit-tested against a saved
 * wikitext fixture without network access.
 */
import type {
  DrawSyncAdapter,
  FetchedDraw,
  FetchedDrawMatch,
  FetchedPlayer,
  FetchedRound,
} from "./types";

const WIKIPEDIA_API = "https://en.wikipedia.org/w/api.php";
const CONTACT = process.env.WIKIPEDIA_CONTACT_EMAIL ?? "admin@brackt.com";
const USER_AGENT = `Brackt.com tennis draw sync - ${CONTACT}`;

/** Round names for a 16-player draw section, earliest → latest. */
const SECTION_ROUNDS = ["Round of 128", "Round of 64", "Round of 32", "Round of 16"] as const;
/** Round names for the 8-player finals bracket, earliest → latest. */
const FINALS_ROUNDS = ["Quarterfinals", "Semifinals", "Final"] as const;

/**
 * Accept either a plain article title or a pasted Wikipedia URL and return the
 * article title. URLs like
 * `https://en.wikipedia.org/wiki/2025_Wimbledon_Championships_%E2%80%93_Men%27s_singles`
 * become "2025 Wimbledon Championships – Men's singles".
 */
export function articleTitleFromInput(input: string): string {
  const trimmed = input.trim();
  const match = trimmed.match(/\/wiki\/([^?#]+)/);
  if (!match) return trimmed;
  let title = match[1];
  try {
    title = decodeURIComponent(title);
  } catch {
    // leave as-is if it isn't valid percent-encoding
  }
  return title.replace(/_/g, " ").trim();
}

/** Turn an article title into a stable, id-safe slug. */
export function slugifyArticle(title: string): string {
  return title
    .normalize("NFKD")
    .replace(/[̀-ͯ]/g, "") // strip combining diacritics
    .toLowerCase()
    .replace(/[^a-z0-9]+/g, "-")
    .replace(/^-+|-+$/g, "");
}

/**
 * Scan wikitext for `{{<TemplateName>...}}` invocations, returning each body
 * (text between the outer braces) with balanced-brace handling so nested
 * templates like `{{flagicon|ITA}}` don't terminate the capture early.
 */
export function extractTemplates(wikitext: string, namePrefixes: string[]): { name: string; body: string }[] {
  const results: { name: string; body: string }[] = [];
  for (let i = 0; i < wikitext.length - 1; i++) {
    if (wikitext[i] !== "{" || wikitext[i + 1] !== "{") continue;
    const afterBraces = wikitext.slice(i + 2);
    const match = afterBraces.match(/^\s*([A-Za-z0-9 _-]+)/);
    const name = match?.[1]?.trim() ?? "";
    if (!namePrefixes.some((p) => name.startsWith(p))) continue;

    // Walk forward tracking {{ }} depth to find the matching close.
    let depth = 0;
    let j = i;
    for (; j < wikitext.length - 1; j++) {
      if (wikitext[j] === "{" && wikitext[j + 1] === "{") {
        depth++;
        j++;
      } else if (wikitext[j] === "}" && wikitext[j + 1] === "}") {
        depth--;
        j++;
        if (depth === 0) break;
      }
    }
    const body = wikitext.slice(i + 2, j - 1);
    results.push({ name, body });
    i = j; // continue past this template
  }
  return results;
}

/**
 * Split a template body into `key=value` params on top-level `|` only —
 * pipes inside `{{…}}` or `[[…]]` are part of a value (flag templates, piped
 * wikilinks) and must not split.
 */
export function parseTemplateParams(body: string): Map<string, string> {
  const params = new Map<string, string>();
  let braceDepth = 0;
  let linkDepth = 0;
  let current = "";
  const parts: string[] = [];

  for (let i = 0; i < body.length; i++) {
    const two = body.slice(i, i + 2);
    if (two === "{{") { braceDepth++; current += two; i++; continue; }
    if (two === "}}") { braceDepth--; current += two; i++; continue; }
    if (two === "[[") { linkDepth++; current += two; i++; continue; }
    if (two === "]]") { linkDepth--; current += two; i++; continue; }
    if (body[i] === "|" && braceDepth === 0 && linkDepth === 0) {
      parts.push(current);
      current = "";
      continue;
    }
    current += body[i];
  }
  parts.push(current);

  for (const part of parts) {
    const eq = part.indexOf("=");
    if (eq === -1) continue;
    const key = part.slice(0, eq).trim();
    const value = part.slice(eq + 1).trim();
    if (key) params.set(key, value);
  }
  return params;
}

/**
 * Parse a bracket `team` value into a player + whether it won.
 * Returns null for an empty/Bye slot.
 */
export function parsePlayerCell(value: string): { player: FetchedPlayer; isWinner: boolean } | null {
  if (!value) return null;
  // Winner detection: only the winning slot's name is bolded.
  const isWinner = value.includes("'''");
  let text = value.replace(/'''/g, "");

  // Extract the wikilink FIRST, before stripping templates. A team cell may wrap
  // the flag + link in a display template, e.g.
  //   {{nowrap|{{flagicon|ESP}} [[Alejandro Davidovich Fokina|A Davidovich Fokina]]}}
  // Blanket template-stripping would, after removing the inner {{flagicon}}, treat
  // the outer {{nowrap| … [[link]] … }} as a single template and delete the link
  // with it — yielding an empty cell (TBD). Pulling the link out first avoids that.
  const linkMatch = text.match(/\[\[([^\]]+)\]\]/);
  let name: string;
  let externalId: string | null;
  if (linkMatch) {
    const [target, display] = linkMatch[1].split("|");
    externalId = target.trim();
    name = (display ?? target).trim();
  } else {
    // No link: unwrap display templates ({{nowrap|X}}) to their content, drop flag
    // templates, and keep whatever plain text remains (e.g. an unlinked qualifier).
    let prev: string;
    do {
      prev = text;
      text = text.replace(/\{\{\s*(?:nowrap|nobr)\s*\|([^{}]*)\}\}/gi, "$1");
    } while (text !== prev);
    do {
      prev = text;
      text = text.replace(/\{\{[^{}]*\}\}/g, " ");
    } while (text !== prev);
    name = text.replace(/\[\[|\]\]/g, "").trim();
    externalId = null;
  }
  name = name.replace(/\s+/g, " ").trim();
  // Treat empty slots and not-yet-determined placeholders (an unfilled qualifier,
  // a bye, a TBD feeder) as no player → the bracket shows TBD rather than
  // inventing a shared "Qualifier" participant across many slots.
  if (!name || /^(bye|tbd|qualifier|to be determined)$/i.test(name)) return null;
  return { player: { name, externalId, seed: null }, isWinner };
}

/**
 * Build matches for one round of a bracket. Within a round, consecutive slots
 * pair up: (team1,team2)=match1, (team3,team4)=match2, …
 */
function parseRound(
  params: Map<string, string>,
  rdIndex: number,
  roundName: string,
  idPrefix: string,
  matchNumberOffset: number,
): FetchedDrawMatch[] {
  // Collect team slot tokens present for this round, preserving the raw token
  // (slots are zero-padded in the compact section brackets, e.g. "team01", but
  // unpadded in the finals bracket, e.g. "team1"). Sort by numeric value.
  const slots: string[] = [];
  for (const key of params.keys()) {
    const m = key.match(new RegExp(`^RD${rdIndex}-team(\\d+)$`));
    if (m) slots.push(m[1]);
  }
  slots.sort((a, b) => Number(a) - Number(b));

  const matches: FetchedDrawMatch[] = [];
  for (let p = 0; p < slots.length; p += 2) {
    const slot1 = slots[p];
    const slot2 = slots[p + 1];
    const cell1 = parsePlayerCell(params.get(`RD${rdIndex}-team${slot1}`) ?? "");
    const cell2 = slot2 !== undefined ? parsePlayerCell(params.get(`RD${rdIndex}-team${slot2}`) ?? "") : null;

    const seed1 = params.get(`RD${rdIndex}-seed${slot1}`);
    const seed2 = slot2 !== undefined ? params.get(`RD${rdIndex}-seed${slot2}`) : undefined;
    const player1 = cell1 ? { ...cell1.player, seed: parseSeed(seed1) } : null;
    const player2 = cell2 ? { ...cell2.player, seed: parseSeed(seed2) } : null;

    let winner: 1 | 2 | null = null;
    if (cell1?.isWinner) winner = 1;
    else if (cell2?.isWinner) winner = 2;

    const matchNumber = matchNumberOffset + matches.length + 1;
    matches.push({
      externalMatchId: `${idPrefix}:${roundName.replace(/\s+/g, "-")}:m${matchNumber}`,
      round: roundName,
      matchNumber,
      player1,
      player2,
      winner,
    });
  }
  return matches;
}

function parseSeed(raw: string | undefined): number | null {
  if (!raw) return null;
  const n = parseInt(raw.replace(/[^0-9]/g, ""), 10);
  return Number.isFinite(n) ? n : null;
}

/**
 * Parse a full Grand Slam singles draw article into a `FetchedDraw`.
 * @param wikitext raw article wikitext
 * @param articleTitle used to build stable match ids
 */
export function parseTennisDrawWikitext(wikitext: string, articleTitle: string): FetchedDraw {
  const slug = slugifyArticle(articleTitle);
  const sectionBrackets = extractTemplates(wikitext, ["16TeamBracket"]);
  const finalsBrackets = extractTemplates(wikitext, ["8TeamBracket"]);

  if (finalsBrackets.length !== 1 || sectionBrackets.length !== 8) {
    throw new Error(
      `Unexpected tennis draw layout in "${articleTitle}": found ${sectionBrackets.length} ` +
        `16-team section bracket(s) and ${finalsBrackets.length} 8-team finals bracket(s); ` +
        "expected 8 sections + 1 finals. Template variant may be unsupported.",
    );
  }

  // Accumulate matches per round across all sections (section order is cosmetic).
  const roundMatches = new Map<string, FetchedDrawMatch[]>();
  const pushMatches = (round: string, ms: FetchedDrawMatch[]) => {
    const existing = roundMatches.get(round) ?? [];
    roundMatches.set(round, existing.concat(ms));
  };

  sectionBrackets.forEach((bracket, sectionIdx) => {
    const params = parseTemplateParams(bracket.body);
    SECTION_ROUNDS.forEach((roundName, rdIdx) => {
      const offset = roundMatches.get(roundName)?.length ?? 0;
      pushMatches(roundName, parseRound(params, rdIdx + 1, roundName, `${slug}:s${sectionIdx}`, offset));
    });
  });

  const finalsParams = parseTemplateParams(finalsBrackets[0].body);
  FINALS_ROUNDS.forEach((roundName, rdIdx) => {
    pushMatches(roundName, parseRound(finalsParams, rdIdx + 1, roundName, `${slug}:f`, 0));
  });

  const orderedRoundNames = [...SECTION_ROUNDS, ...FINALS_ROUNDS];
  const rounds: FetchedRound[] = orderedRoundNames.map((roundName) => ({
    roundName,
    matches: roundMatches.get(roundName) ?? [],
  }));

  return { templateId: "tennis_128", rounds };
}

export class WikipediaTennisAdapter implements DrawSyncAdapter {
  async fetchDraw(sourceKey: string): Promise<FetchedDraw> {
    const title = articleTitleFromInput(sourceKey);
    const url = `${WIKIPEDIA_API}?action=parse&prop=wikitext&format=json&formatversion=2&redirects=1&page=${encodeURIComponent(title)}`;
    const response = await fetch(url, { headers: { "User-Agent": USER_AGENT } });
    if (!response.ok) {
      throw new Error(`Wikipedia API returned ${response.status}: ${response.statusText}`);
    }
    const json = (await response.json()) as {
      error?: { info?: string };
      parse?: { wikitext?: string };
    };
    if (json.error) {
      throw new Error(`Wikipedia API error for "${title}": ${json.error.info ?? "unknown error"}`);
    }
    const wikitext = json.parse?.wikitext;
    if (!wikitext) {
      throw new Error(`No wikitext returned for "${title}"`);
    }
    return parseTennisDrawWikitext(wikitext, title);
  }
}