import { convertFuturesToElo } from "~/services/probability-engine";
import { simulatorInputLabel, type SimulatorManifestProfile } from "./manifest";
import { logger } from "~/lib/logger";

export type MissingEloStrategy = "block" | "fallbackElo" | "averageKnown" | "worstKnownMinus";
export type MissingRatingStrategy = "block" | "fallbackRating" | "averageKnown" | "worstKnownMinus";

/**
 * "Base" strength sources — the ways to produce a participant's underlying Elo
 * before any futures-odds blend. These are *substitutes* (a season rarely has
 * more than one), so they are tried in order and the first available one wins.
 * Futures odds are not in this list: they blend on top of the base Elo via
 * `oddsWeight`, rather than being one more interchangeable base.
 */
export type BaseEloKey = "sourceElo" | "projectedWins" | "projectedTablePoints";

export const BASE_ELO_KEYS: readonly BaseEloKey[] = [
  "sourceElo",
  "projectedWins",
  "projectedTablePoints",
];

/** Default order for choosing the base Elo: raw Elo, then projections. */
export const DEFAULT_BASE_ELO_PRIORITY: BaseEloKey[] = [
  "sourceElo",
  "projectedWins",
  "projectedTablePoints",
];

export interface SimulatorInputPolicy {
  missingEloStrategy: MissingEloStrategy;
  missingRatingStrategy: MissingRatingStrategy;
  /** Order for choosing the base strength Elo from its substitutable sources. */
  baseEloPriority: BaseEloKey[];
  /**
   * Weight (0–1) of the futures-odds-derived Elo when blending with the base Elo
   * into the single Elo that feeds every simulator. `0` = base only (Elo /
   * projections), `1` = futures fully override the base, in between = blend.
   */
  oddsWeight: number;
  fallbackElo: number;
  fallbackEloDelta: number;
  eloMin: number;
  eloMax: number;
  fallbackRating: number;
  fallbackRatingDelta: number;
  ratingMin: number;
  ratingMax: number;
}

export interface ParticipantInputForPolicy {
  participantId: string;
  sourceOdds: number | null;
  sourceElo: number | null;
  rating: number | null;
  projectedWins: number | null;
  projectedTablePoints: number | null;
}

export interface ResolvedSourceElo {
  participantId: string;
  sourceElo: number;
  method: "direct" | "projectedWins" | "projectedTablePoints" | "sourceOdds" | "blend" | MissingEloStrategy;
}

export interface ResolvedRating {
  participantId: string;
  rating: number;
  method: "direct" | "sourceOdds" | "blend" | MissingRatingStrategy;
}

const DEFAULT_ODDS_WEIGHT = 0.3;

const DEFAULT_POLICY: SimulatorInputPolicy = {
  missingEloStrategy: "block",
  missingRatingStrategy: "block",
  baseEloPriority: DEFAULT_BASE_ELO_PRIORITY,
  oddsWeight: DEFAULT_ODDS_WEIGHT,
  fallbackElo: 1400,
  fallbackEloDelta: 25,
  eloMin: 1100,
  eloMax: 1900,
  fallbackRating: 0,
  fallbackRatingDelta: 5,
  ratingMin: -20,
  ratingMax: 40,
};

function isRecord(value: unknown): value is Record<string, unknown> {
  return typeof value === "object" && value !== null && !Array.isArray(value);
}

function optionalNumber(value: unknown, fallback: number): number {
  return typeof value === "number" && Number.isFinite(value) ? value : fallback;
}

function clamp(value: number, min: number, max: number): number {
  return Math.min(max, Math.max(min, value));
}

function toWinRate(projection: number, maxProjection: number): number {
  if (maxProjection <= 0) return 0.5;
  return clamp(projection / maxProjection, 0.01, 0.99);
}

function projectionToElo(
  projection: number,
  maxProjection: number,
  parityFactor: number,
  policy: SimulatorInputPolicy
): number {
  const rate = toWinRate(projection, maxProjection);
  const elo = 1500 + parityFactor * Math.log10(rate / (1 - rate));
  return clamp(Math.round(elo), policy.eloMin, policy.eloMax);
}

function parseBaseEloPriority(value: unknown, fallback: BaseEloKey[]): BaseEloKey[] {
  if (!Array.isArray(value)) return fallback;
  const seen = new Set<BaseEloKey>();
  const parsed: BaseEloKey[] = [];
  for (const entry of value) {
    if (typeof entry === "string" && (BASE_ELO_KEYS as readonly string[]).includes(entry) && !seen.has(entry as BaseEloKey)) {
      seen.add(entry as BaseEloKey);
      parsed.push(entry as BaseEloKey);
    }
  }
  return parsed.length > 0 ? parsed : fallback;
}

export function getSimulatorInputPolicy(config: Record<string, unknown>): SimulatorInputPolicy {
  const rawPolicy = isRecord(config.inputPolicy) ? config.inputPolicy : {};
  const eloStrategy = rawPolicy.missingEloStrategy;
  const ratingStrategy = rawPolicy.missingRatingStrategy;

  return {
    missingEloStrategy:
      eloStrategy === "fallbackElo" || eloStrategy === "averageKnown" || eloStrategy === "worstKnownMinus"
        ? eloStrategy
        : "block",
    missingRatingStrategy:
      ratingStrategy === "fallbackRating" || ratingStrategy === "averageKnown" || ratingStrategy === "worstKnownMinus"
        ? ratingStrategy
        : "block",
    baseEloPriority: parseBaseEloPriority(rawPolicy.baseEloPriority, DEFAULT_POLICY.baseEloPriority),
    // The futures blend weight lives only under inputPolicy (single home).
    oddsWeight: clamp(optionalNumber(rawPolicy.oddsWeight, DEFAULT_POLICY.oddsWeight), 0, 1),
    fallbackElo: optionalNumber(rawPolicy.fallbackElo, DEFAULT_POLICY.fallbackElo),
    fallbackEloDelta: optionalNumber(rawPolicy.fallbackEloDelta, DEFAULT_POLICY.fallbackEloDelta),
    eloMin: optionalNumber(rawPolicy.eloMin, DEFAULT_POLICY.eloMin),
    eloMax: optionalNumber(rawPolicy.eloMax, DEFAULT_POLICY.eloMax),
    fallbackRating: optionalNumber(rawPolicy.fallbackRating, DEFAULT_POLICY.fallbackRating),
    fallbackRatingDelta: optionalNumber(rawPolicy.fallbackRatingDelta, DEFAULT_POLICY.fallbackRatingDelta),
    ratingMin: optionalNumber(rawPolicy.ratingMin, DEFAULT_POLICY.ratingMin),
    ratingMax: optionalNumber(rawPolicy.ratingMax, DEFAULT_POLICY.ratingMax),
  };
}

export function sourceEloRequirementLabel(profile: SimulatorManifestProfile): string {
  const alternatives = profile.derivableInputs?.sourceElo ?? [];
  // Omit "configured fallback" from the label: if a participant appears in
  // missingInputs it means no fallback resolved it, so mentioning fallback
  // as an option would be misleading.
  return ["Elo rating", ...alternatives.map(simulatorInputLabel)].join(" / ");
}

export function ratingRequirementLabel(profile: SimulatorManifestProfile): string {
  const alternatives = profile.derivableInputs?.rating ?? [];
  return ["rating", ...alternatives.map(simulatorInputLabel)].join(" / ");
}

/**
 * Combine a participant's base strength value and its odds-derived value into the
 * single value that feeds the simulator, by `oddsWeight`: 0 = base only,
 * 1 = odds only, in between = weighted blend. Odds-derived and blended results
 * pass through `clampDerived` (they are mapped onto the configured band by
 * design); a base value is returned untouched (a directly entered Elo/rating is
 * trusted as-is, a projection-derived Elo was already clamped upstream). Returns
 * undefined when neither source is present (the caller falls back to its
 * missing-input strategy). Shared by Elo and rating resolution.
 */
function blendBaseAndOdds<M extends string>(
  base: { value: number; method: M } | undefined,
  odds: number | undefined,
  oddsWeight: number,
  clampDerived: (value: number) => number
): { value: number; method: M | "sourceOdds" | "blend" } | undefined {
  if (base !== undefined && odds !== undefined) {
    if (oddsWeight <= 0) return { value: base.value, method: base.method };
    if (oddsWeight >= 1) return { value: clampDerived(odds), method: "sourceOdds" };
    return { value: clampDerived((1 - oddsWeight) * base.value + oddsWeight * odds), method: "blend" };
  }
  if (base !== undefined) return { value: base.value, method: base.method };
  if (odds !== undefined) return { value: clampDerived(odds), method: "sourceOdds" };
  return undefined;
}

export function resolveSourceElos(
  inputs: ParticipantInputForPolicy[],
  profile: Pick<SimulatorManifestProfile, "derivableInputs">,
  config: Record<string, unknown>
): Map<string, ResolvedSourceElo> {
  const policy = getSimulatorInputPolicy(config);
  const resolved = new Map<string, ResolvedSourceElo>();
  const alternatives = new Set(profile.derivableInputs?.sourceElo ?? []);
  const parityFactor = optionalNumber(config.parityFactor, 400);

  // 1. Base Elo: the first available *substitutable* source per baseEloPriority.
  //    `sourceElo` (raw) is always permitted; projections must be declared in
  //    the profile's derivableInputs.sourceElo.
  const baseElo = new Map<string, { elo: number; method: ResolvedSourceElo["method"] }>();
  for (const source of policy.baseEloPriority) {
    if (source !== "sourceElo" && !alternatives.has(source)) continue;

    if (source === "sourceElo") {
      for (const input of inputs) {
        if (baseElo.has(input.participantId)) continue;
        if (input.sourceElo !== null && input.sourceElo !== undefined) {
          baseElo.set(input.participantId, { elo: input.sourceElo, method: "direct" });
        }
      }
    } else if (source === "projectedWins") {
      const seasonGames = optionalNumber(config.seasonGames, Math.max(...inputs.map((input) => input.projectedWins ?? 0), 1));
      for (const input of inputs) {
        if (baseElo.has(input.participantId) || input.projectedWins === null || input.projectedWins === undefined) continue;
        baseElo.set(input.participantId, {
          elo: projectionToElo(input.projectedWins, seasonGames, parityFactor, policy),
          method: "projectedWins",
        });
      }
    } else if (source === "projectedTablePoints") {
      const seasonGames = optionalNumber(config.seasonGames, 38);
      const maxPoints = optionalNumber(config.maxTablePoints, seasonGames * 3);
      for (const input of inputs) {
        if (baseElo.has(input.participantId) || input.projectedTablePoints === null || input.projectedTablePoints === undefined) continue;
        baseElo.set(input.participantId, {
          elo: projectionToElo(input.projectedTablePoints, maxPoints, parityFactor, policy),
          method: "projectedTablePoints",
        });
      }
    }
  }

  // 2. Odds-derived Elo (field-relative): only when futures odds are a permitted
  //    source and at least two participants have odds (a spread is required).
  const oddsElo = new Map<string, number>();
  if (alternatives.has("sourceOdds")) {
    const oddsInputs = inputs
      .filter((input) => input.sourceOdds !== null && input.sourceOdds !== undefined)
      .map((input) => ({ participantId: input.participantId, odds: input.sourceOdds as number }));
    if (oddsInputs.length === 1) {
      logger.warn(
        `resolveSourceElos: only 1 participant has sourceOdds (${oddsInputs[0].participantId}). ` +
        `convertFuturesToElo requires at least 2 to derive a meaningful Elo spread — ignoring the lone odds value.`
      );
    }
    if (oddsInputs.length >= 2) {
      for (const [participantId, elo] of convertFuturesToElo(oddsInputs)) {
        oddsElo.set(participantId, elo);
      }
    }
  }

  // 3. Blend base + odds into the single Elo that feeds the simulator.
  //    Directly entered Elos (some sports use ratings above the default ceiling,
  //    e.g. snooker ~2450) pass through unclamped; only derived values are
  //    clamped onto [eloMin, eloMax].
  const clampDerived = (elo: number): number => clamp(Math.round(elo), policy.eloMin, policy.eloMax);
  for (const input of inputs) {
    const base = baseElo.get(input.participantId);
    const blended = blendBaseAndOdds(
      base ? { value: base.elo, method: base.method } : undefined,
      oddsElo.get(input.participantId),
      policy.oddsWeight,
      clampDerived
    );
    if (!blended) continue;
    resolved.set(input.participantId, {
      participantId: input.participantId,
      sourceElo: blended.value,
      method: blended.method,
    });
  }

  const knownElos = [...resolved.values()].map((value) => value.sourceElo);
  const averageKnown = knownElos.length > 0
    ? knownElos.reduce((sum, elo) => sum + elo, 0) / knownElos.length
    : policy.fallbackElo;
  const worstKnown = knownElos.length > 0 ? Math.min(...knownElos) : policy.fallbackElo;

  for (const input of inputs) {
    if (resolved.has(input.participantId) || policy.missingEloStrategy === "block") continue;

    let sourceElo: number;
    if (policy.missingEloStrategy === "averageKnown") {
      sourceElo = averageKnown;
    } else if (policy.missingEloStrategy === "worstKnownMinus") {
      sourceElo = worstKnown - policy.fallbackEloDelta;
    } else {
      sourceElo = policy.fallbackElo;
    }

    resolved.set(input.participantId, {
      participantId: input.participantId,
      sourceElo: clamp(Math.round(sourceElo), policy.eloMin, policy.eloMax),
      method: policy.missingEloStrategy,
    });
  }

  return resolved;
}

export function resolveRatings(
  inputs: ParticipantInputForPolicy[],
  profile: Pick<SimulatorManifestProfile, "derivableInputs">,
  config: Record<string, unknown>
): Map<string, ResolvedRating> {
  const policy = getSimulatorInputPolicy(config);
  const resolved = new Map<string, ResolvedRating>();
  const alternatives = new Set(profile.derivableInputs?.rating ?? []);

  // Ratings follow the same single-value blend as Elo: the base is the direct
  // `rating`; futures odds (when permitted, scaled onto the rating range) blend
  // on top by oddsWeight. `0` = rating only, `1` = futures override.
  const baseRating = new Map<string, number>();
  for (const input of inputs) {
    if (input.rating !== null && input.rating !== undefined) {
      baseRating.set(input.participantId, input.rating);
    }
  }

  const oddsRating = new Map<string, number>();
  if (alternatives.has("sourceOdds")) {
    const oddsInputs = inputs
      .filter((input) => input.sourceOdds !== null && input.sourceOdds !== undefined)
      .map((input) => ({ participantId: input.participantId, odds: input.sourceOdds as number }));
    if (oddsInputs.length === 1) {
      logger.warn(
        `resolveRatings: only 1 participant has sourceOdds (${oddsInputs[0].participantId}). ` +
        `convertFuturesToElo requires at least 2 to derive a meaningful rating — ignoring the lone odds value.`
      );
    }
    if (oddsInputs.length >= 2) {
      const converted = convertFuturesToElo(oddsInputs, "american", {
        exponent: 0.33,
        eloMin: policy.ratingMin,
        eloMax: policy.ratingMax,
      });
      for (const [participantId, rating] of converted) {
        oddsRating.set(participantId, rating);
      }
    }
  }

  // As with Elo: a directly entered rating passes through untouched; only
  // derived values are clamped onto the rating band.
  const clampDerived = (rating: number): number => clamp(rating, policy.ratingMin, policy.ratingMax);
  for (const input of inputs) {
    const base = baseRating.get(input.participantId);
    const blended = blendBaseAndOdds(
      base !== undefined ? { value: base, method: "direct" as const } : undefined,
      oddsRating.get(input.participantId),
      policy.oddsWeight,
      clampDerived
    );
    if (!blended) continue;
    resolved.set(input.participantId, {
      participantId: input.participantId,
      rating: blended.value,
      method: blended.method,
    });
  }

  const knownRatings = [...resolved.values()].map((value) => value.rating);
  const averageKnown = knownRatings.length > 0
    ? knownRatings.reduce((sum, rating) => sum + rating, 0) / knownRatings.length
    : policy.fallbackRating;
  const worstKnown = knownRatings.length > 0 ? Math.min(...knownRatings) : policy.fallbackRating;

  for (const input of inputs) {
    if (resolved.has(input.participantId) || policy.missingRatingStrategy === "block") continue;

    let rating: number | null;
    if (policy.missingRatingStrategy === "averageKnown") {
      rating = averageKnown;
    } else if (policy.missingRatingStrategy === "worstKnownMinus") {
      rating = knownRatings.length > 0 ? worstKnown - policy.fallbackRatingDelta : null;
    } else {
      rating = policy.fallbackRating;
    }

    if (rating === null) continue;

    resolved.set(input.participantId, {
      participantId: input.participantId,
      rating: clamp(rating, policy.ratingMin, policy.ratingMax),
      method: policy.missingRatingStrategy,
    });
  }

  return resolved;
}