import { eq } from "drizzle-orm";
import { database } from "~/database/context";
import * as schema from "~/database/schema";
import { DEFAULT_SCORING_RULES } from "~/lib/scoring-types";
import type { ScoringRules } from "~/services/ev-calculator";
import { batchUpsertParticipantEvSnapshots } from "~/models/ev-snapshot";
import { batchUpsertParticipantEVs } from "~/models/participant-expected-value";
import { recalculateStandings } from "~/models/scoring-calculator";
import { findParticipantsBySportsSeasonId } from "~/models/season-participant";
import { findSportsSeasonById, updateSportsSeason } from "~/models/sports-season";
import { calculateEV } from "~/services/ev-calculator";
import { getSimulator, type SimulatorType } from "~/services/simulations/registry";
import { normalizeSimulationResultColumns } from "~/services/simulations/simulation-probabilities";
import {
  getSportsSeasonSimulatorConfig,
  prepareSimulatorInputsForRun,
  validateSimulatorReadiness,
} from "~/models/simulator";

const ZERO_PROBS = {
  probFirst: 0,
  probSecond: 0,
  probThird: 0,
  probFourth: 0,
  probFifth: 0,
  probSixth: 0,
  probSeventh: 0,
  probEighth: 0,
};

async function getPersistenceContext(
  simulatorType: SimulatorType,
  sportsSeason: Awaited<ReturnType<typeof findSportsSeasonById>>
): Promise<{ scoringRules: ScoringRules; source: "elo_simulation" | "performance_model" }> {
  if (simulatorType !== "brackt") {
    return { scoringRules: DEFAULT_SCORING_RULES, source: "elo_simulation" };
  }

  if (!sportsSeason?.fantasySeasonId) {
    throw new Error("Brackt simulations must run against a private per-league sports season, not the global Brackt template.");
  }

  const fantasySeason = await database().query.seasons.findFirst({
    where: eq(schema.seasons.id, sportsSeason.fantasySeasonId),
  });
  if (!fantasySeason) {
    throw new Error("Linked fantasy season not found for Brackt simulation.");
  }

  return {
    source: "performance_model",
    scoringRules: {
      pointsFor1st: fantasySeason.pointsFor1st,
      pointsFor2nd: fantasySeason.pointsFor2nd,
      pointsFor3rd: fantasySeason.pointsFor3rd,
      pointsFor4th: fantasySeason.pointsFor4th,
      pointsFor5th: fantasySeason.pointsFor5th,
      pointsFor6th: fantasySeason.pointsFor6th,
      pointsFor7th: fantasySeason.pointsFor7th,
      pointsFor8th: fantasySeason.pointsFor8th,
    },
  };
}

export interface RunSportsSeasonSimulationResult {
  sportsSeasonId: string;
  simulatorType: SimulatorType;
  simulatedParticipants: number;
  zeroedParticipants: number;
  snapshotDate: string;
}

export async function runSportsSeasonSimulation(
  sportsSeasonId: string
): Promise<RunSportsSeasonSimulationResult> {
  const sportsSeason = await findSportsSeasonById(sportsSeasonId);
  if (!sportsSeason) {
    throw new Error("Sports season not found");
  }
  if (sportsSeason.status === "completed") {
    throw new Error("Completed sports seasons cannot be simulated.");
  }

  const simulatorConfig = await getSportsSeasonSimulatorConfig(sportsSeasonId);
  if (!simulatorConfig) {
    throw new Error(
      "This sport has no simulator type configured. Set a simulator type on the sport in the admin panel before running a simulation."
    );
  }

  if (sportsSeason.simulationStatus === "running") {
    throw new Error("A simulation is already running for this sports season. Please wait for it to complete.");
  }

  const readiness = await validateSimulatorReadiness(sportsSeasonId);
  if (!readiness.canRun) {
    throw new Error(
      `Simulator is not ready: ${readiness.missingInputs.join(", ") || "missing required setup"}.`
    );
  }

  await prepareSimulatorInputsForRun(sportsSeasonId);

  await updateSportsSeason(sportsSeasonId, { simulationStatus: "running" });

  try {
    const simulator = getSimulator(simulatorConfig.simulatorType);
    const results = await simulator.simulate(sportsSeasonId);

    if (results.length === 0) {
      throw new Error("Simulation returned no results. Check that participants have simulator input data.");
    }

    normalizeSimulationResultColumns(results);

    const allSeasonParticipants = await findParticipantsBySportsSeasonId(sportsSeasonId);
    const simulatedIds = new Set(results.map((r) => r.participantId));
    const zeroedParticipants = allSeasonParticipants.filter((p) => !simulatedIds.has(p.id));
    const persistence = await getPersistenceContext(simulatorConfig.simulatorType, sportsSeason);

    await batchUpsertParticipantEVs([
      ...results.map((r) => ({
        participantId: r.participantId,
        sportsSeasonId,
        probabilities: r.probabilities,
        scoringRules: persistence.scoringRules,
        source: persistence.source,
      })),
      ...zeroedParticipants.map((p) => ({
        participantId: p.id,
        sportsSeasonId,
        probabilities: ZERO_PROBS,
        scoringRules: persistence.scoringRules,
        source: persistence.source,
      })),
    ]);

    const seasonSports = await database().query.seasonSports.findMany({
      where: eq(schema.seasonSports.sportsSeasonId, sportsSeasonId),
    });
    await Promise.all(seasonSports.map(({ seasonId }) => recalculateStandings(seasonId)));

    const snapshotDate = new Date().toISOString().slice(0, 10);
    await batchUpsertParticipantEvSnapshots(
      results.map((r) => ({
        participantId: r.participantId,
        sportsSeasonId,
        snapshotDate,
        probFirst: r.probabilities.probFirst,
        probSecond: r.probabilities.probSecond,
        probThird: r.probabilities.probThird,
        probFourth: r.probabilities.probFourth,
        probFifth: r.probabilities.probFifth,
        probSixth: r.probabilities.probSixth,
        probSeventh: r.probabilities.probSeventh,
        probEighth: r.probabilities.probEighth,
        calculatedEV: calculateEV(r.probabilities, persistence.scoringRules),
        source: r.source,
      }))
    );

    await updateSportsSeason(sportsSeasonId, { simulationStatus: "idle" });

    return {
      sportsSeasonId,
      simulatorType: simulatorConfig.simulatorType,
      simulatedParticipants: results.length,
      zeroedParticipants: zeroedParticipants.length,
      snapshotDate,
    };
  } catch (error) {
    await updateSportsSeason(sportsSeasonId, { simulationStatus: "failed" });
    throw error;
  }
}