import { convertEpisodes } from "./convert.ts";
import { applyRule, selectRule } from "./rules.ts";
import { airDateOf, daysBetween } from "./table.ts";
import {
  type CanonicalEpisodes,
  type EpisodeResolution,
  MAIN_CONTENT_TYPES,
  type ResolveEpisodesInput,
} from "./types.ts";
import { validateEpisodes } from "./validate.ts";

/** 换算结果与「元数据滞后」冲突时,发布时间与换算后那集播出日期相差不超过这么多天才认换算 */
export const CONVERSION_NEAR_DAYS = 7;

/**
 * 集数解析总入口(设计文档判定流程 1→4)。纯函数,时间等事实由调用方传入。
 * 1 有适用规则 → 按规则换算并校验;fail → unresolved(规则照写的用,不回退到确定性换算,也不停用规则)
 * 2 原号校验 pass → raw
 * 3 确定性换算(只取唯一解):原号 fail 时唯一解即采用;原号滞后放行(unverified)时,
 *   唯一解还要发布时间贴近目标集播出日期(按日期对集的除外),否则按滞后放行
 * 4 仍不行 → unresolved
 */
export function resolveEpisodes(input: ResolveEpisodesInput): EpisodeResolution {
  const { parsed, kind, table, rules } = input;
  const publishedAt = input.publishedAt ?? null;
  const source: EpisodeResolution["source"] = {};
  if (parsed.season !== undefined) source.season = parsed.season;
  if (parsed.episodes) source.episodes = parsed.episodes;
  if (parsed.airDate) source.airDate = parsed.airDate;
  const result = (r: Omit<EpisodeResolution, "source">): EpisodeResolution => ({ source, ...r });
  const skipped = (why: string) => result({ method: "skipped", canonical: null, evidence: [why] });

  if (kind !== "series" && kind !== "variety") return skipped(`kind:${kind}`);
  if (!MAIN_CONTENT_TYPES.includes(parsed.contentType)) return skipped(`content_type:${parsed.contentType}`);
  if (parsed.season === 0) return skipped("season:0");
  const episodes = parsed.episodes ?? null;
  const airDate = parsed.airDate ?? null;
  if (!episodes && !airDate) return skipped("no_episode");

  // 有集号无季号按第 1 季推定(与解析器一致)
  const season = parsed.season ?? (episodes ? 1 : null);
  const seasonInferred = parsed.seasonInferred === true || (parsed.season === undefined && season !== null);
  const evidence: string[] = [];

  // 1 规则
  const rule = selectRule(rules, season, parsed.releaseGroup?.name ?? null);
  if (rule && season !== null) {
    const ref = {
      ruleId: rule.id,
      ...(rule.line !== undefined ? { ruleLine: rule.line } : {}),
      ...(rule.text !== undefined ? { ruleText: rule.text } : {}),
    };
    const applied = applyRule(rule, season, episodes);
    if (applied.kind === "special") {
      return result({
        method: "rule",
        canonical: null,
        ...ref,
        special: applied.special,
        evidence: [`rule:special:${applied.special}`],
      });
    }
    if (applied.kind === "error") {
      return result({ method: "unresolved", canonical: null, ...ref, evidence: [applied.evidence] });
    }
    const v = validateEpisodes(applied.canonical.season, applied.canonical.episodes, table);
    if (v === "fail") {
      return result({
        method: "unresolved",
        canonical: null,
        ...ref,
        evidence: [applied.evidence, "rule:validate_fail"],
      });
    }
    return result({
      method: "rule",
      canonical: applied.canonical,
      ...ref,
      evidence: [applied.evidence, `validate:${v}`],
    });
  }

  // 2 原号校验
  let rawStatus: "unverified" | "fail" | null = null;
  let rawCanonical: CanonicalEpisodes | null = null;
  if (episodes && season !== null) {
    rawCanonical = { season, episodes };
    const v = validateEpisodes(season, episodes, table);
    if (v === "pass") return result({ method: "raw", canonical: rawCanonical, evidence: ["validate:pass"] });
    rawStatus = v;
    evidence.push(`validate:${v}`);
  }

  // 3 确定性换算
  const conv = convertEpisodes({ season, seasonInferred, episodes, airDate, variety: kind === "variety", table });
  evidence.push(...conv.evidence);
  const unique = conv.candidates.length === 1 ? conv.candidates[0]! : null;
  if (conv.candidates.length > 1)
    evidence.push(`conversion:ambiguous:${conv.candidates.map((c) => c.evidence).join(",")}`);

  if (rawStatus === "unverified" && rawCanonical) {
    if (unique) {
      if (unique.method === "air_date") return accepted(unique);
      const target = airDateOf(table, unique.canonical.season, unique.canonical.episodes.start);
      const d = target && publishedAt ? daysBetween(publishedAt, target) : null;
      if (d !== null && d <= CONVERSION_NEAR_DAYS) return accepted(unique, `published_near:${d}d`);
      evidence.push(`${unique.evidence}:${d === null ? "no_date" : `published_far:${d}d`}`);
    }
    return result({ method: "unverified", canonical: rawCanonical, evidence });
  }
  if (unique) return accepted(unique);

  // 只有播出日期、对不上:元数据没覆盖到这一天(没有每集日期、或作品未完结、或日期晚于已知最后一集)按滞后放行,
  // canonical 为空表示照用解析结果;只有已完结且已知日期覆盖到这一天才转待确认
  if (!episodes && airDate && conv.candidates.length === 0 && !coveredAirDate(airDate)) {
    return result({ method: "unverified", canonical: null, evidence: [...evidence, "air_date:not_covered"] });
  }

  // 4 待确认
  if (conv.candidates.length === 0) evidence.push("conversion:none");
  return result({ method: "unresolved", canonical: null, evidence });

  function coveredAirDate(d: string): boolean {
    if (!table.ended) return false;
    const iso = d.replace(/^(\d{4})-?(\d{2})-?(\d{2})$/, "$1-$2-$3");
    return table.seasons.some((s) => (s.episodes ?? []).some((e) => e.airDate !== null && e.airDate >= iso));
  }

  function accepted(c: (typeof conv.candidates)[number], extra?: string): EpisodeResolution {
    return result({
      method: c.method,
      canonical: c.canonical,
      evidence: [...evidence, c.evidence, ...(extra ? [extra] : [])],
    });
  }
}