/**
 * Model for Participant Expected Values
 *
 * Manages probability distributions and calculated EVs for participants
 * in sports seasons.
 */

import { database } from "~/database/context";
import { participantExpectedValues } from "~/database/schema";
import { eq, and } from "drizzle-orm";
import type { ProbabilityDistribution, ScoringRules } from "~/services/ev-calculator";
import { calculateEV, validateProbabilities, normalizeProbabilities } from "~/services/ev-calculator";

export type ProbabilitySource = "manual" | "futures_odds" | "elo_simulation" | "performance_model";

export interface ParticipantEV {
  id: string;
  participantId: string;
  sportsSeasonId: string;
  probFirst: string;
  probSecond: string;
  probThird: string;
  probFourth: string;
  probFifth: string;
  probSixth: string;
  probSeventh: string;
  probEighth: string;
  expectedValue: string;
  source: ProbabilitySource | null;
  sourceOdds: number | null;
  calculatedAt: Date;
  updatedAt: Date;
}

export interface CreateProbabilityInput {
  participantId: string;
  sportsSeasonId: string;
  probabilities: ProbabilityDistribution;
  scoringRules: ScoringRules;
  source?: ProbabilitySource;
  sourceOdds?: number; // American odds if source is futures_odds
}

export interface UpdateProbabilityInput {
  probabilities: ProbabilityDistribution;
  scoringRules: ScoringRules;
  source?: ProbabilitySource;
}

/**
 * Create or update participant probabilities and calculate EV
 *
 * @param input - Probabilities, scoring rules, and metadata
 * @returns Created/updated participant EV record
 * @throws Error if probabilities don't sum to 1.0 (within tolerance)
 */
export async function upsertParticipantEV(
  input: CreateProbabilityInput
): Promise<ParticipantEV> {
  const { participantId, sportsSeasonId, probabilities, scoringRules, source = "manual", sourceOdds } = input;

  // Validate probabilities (only for manual entry)
  // For futures_odds/ICM, probabilities may sum to <1.0 for teams unlikely to finish top 8
  if (source === "manual" && !validateProbabilities(probabilities)) {
    const sum = Object.values(probabilities).reduce((a, b) => a + b, 0);
    throw new Error(
      `Probabilities must sum to 1.0 (±0.01). Current sum: ${sum.toFixed(4)} (${(sum * 100).toFixed(1)}%)`
    );
  }

  // Always validate probabilities don't exceed 1.0
  const sum = Object.values(probabilities).reduce((a, b) => a + b, 0);
  if (sum > 1.01) {
    throw new Error(
      `Probabilities cannot sum to more than 1.0. Current sum: ${sum.toFixed(4)} (${(sum * 100).toFixed(1)}%)`
    );
  }

  // Calculate EV
  const expectedValue = calculateEV(probabilities, scoringRules);

  const db = database();

  // Check if record exists
  const existing = await db
    .select()
    .from(participantExpectedValues)
    .where(
      and(
        eq(participantExpectedValues.participantId, participantId),
        eq(participantExpectedValues.sportsSeasonId, sportsSeasonId)
      )
    )
    .limit(1);

  const now = new Date();

  if (existing.length > 0) {
    // Update existing
    const updated = await db
      .update(participantExpectedValues)
      .set({
        probFirst: probabilities.probFirst.toString(),
        probSecond: probabilities.probSecond.toString(),
        probThird: probabilities.probThird.toString(),
        probFourth: probabilities.probFourth.toString(),
        probFifth: probabilities.probFifth.toString(),
        probSixth: probabilities.probSixth.toString(),
        probSeventh: probabilities.probSeventh.toString(),
        probEighth: probabilities.probEighth.toString(),
        expectedValue: expectedValue.toString(),
        source,
        sourceOdds: sourceOdds ?? null,
        calculatedAt: now,
        updatedAt: now,
      })
      .where(eq(participantExpectedValues.id, existing[0].id))
      .returning();

    return updated[0];
  } else {
    // Create new
    const created = await db
      .insert(participantExpectedValues)
      .values({
        participantId,
        sportsSeasonId,
        probFirst: probabilities.probFirst.toString(),
        probSecond: probabilities.probSecond.toString(),
        probThird: probabilities.probThird.toString(),
        probFourth: probabilities.probFourth.toString(),
        probFifth: probabilities.probFifth.toString(),
        probSixth: probabilities.probSixth.toString(),
        probSeventh: probabilities.probSeventh.toString(),
        probEighth: probabilities.probEighth.toString(),
        expectedValue: expectedValue.toString(),
        source,
        sourceOdds: sourceOdds ?? null,
        calculatedAt: now,
        updatedAt: now,
      })
      .returning();

    return created[0];
  }
}

/**
 * Create or update with auto-normalization
 * Automatically normalizes probabilities if they don't sum to 100%
 */
export async function upsertParticipantEVWithNormalization(
  input: CreateProbabilityInput
): Promise<ParticipantEV> {
  const normalized = normalizeProbabilities(input.probabilities);

  return upsertParticipantEV({
    ...input,
    probabilities: normalized,
  });
}

/**
 * Get participant EV for a specific sports season
 */
export async function getParticipantEV(
  participantId: string,
  sportsSeasonId: string
): Promise<ParticipantEV | null> {
  const db = database();
  const result = await db
    .select()
    .from(participantExpectedValues)
    .where(
      and(
        eq(participantExpectedValues.participantId, participantId),
        eq(participantExpectedValues.sportsSeasonId, sportsSeasonId)
      )
    )
    .limit(1);

  return result[0] || null;
}

/**
 * Get all participant EVs for a sports season
 */
export async function getAllParticipantEVsForSeason(
  sportsSeasonId: string
): Promise<ParticipantEV[]> {
  const db = database();
  return db
    .select()
    .from(participantExpectedValues)
    .where(eq(participantExpectedValues.sportsSeasonId, sportsSeasonId));
}

/**
 * Delete participant EV
 */
export async function deleteParticipantEV(
  participantId: string,
  sportsSeasonId: string
): Promise<void> {
  const db = database();
  await db
    .delete(participantExpectedValues)
    .where(
      and(
        eq(participantExpectedValues.participantId, participantId),
        eq(participantExpectedValues.sportsSeasonId, sportsSeasonId)
      )
    );
}

/**
 * Batch upsert multiple participant EVs
 * Useful for updating all participants after generating probabilities
 */
export async function batchUpsertParticipantEVs(
  inputs: CreateProbabilityInput[]
): Promise<ParticipantEV[]> {
  const results: ParticipantEV[] = [];

  // Process in batches to avoid overwhelming the database
  const batchSize = 50;
  for (let i = 0; i < inputs.length; i += batchSize) {
    const batch = inputs.slice(i, i + batchSize);
    const batchResults = await Promise.all(
      batch.map((input) => upsertParticipantEV(input))
    );
    results.push(...batchResults);
  }

  return results;
}

/**
 * Convert database record to ProbabilityDistribution
 */
export function toProbabilityDistribution(ev: ParticipantEV): ProbabilityDistribution {
  return {
    probFirst: parseFloat(ev.probFirst),
    probSecond: parseFloat(ev.probSecond),
    probThird: parseFloat(ev.probThird),
    probFourth: parseFloat(ev.probFourth),
    probFifth: parseFloat(ev.probFifth),
    probSixth: parseFloat(ev.probSixth),
    probSeventh: parseFloat(ev.probSeventh),
    probEighth: parseFloat(ev.probEighth),
  };
}

/**
 * Recalculate EV for a participant with new scoring rules
 * Keeps probabilities the same, only updates EV based on new scoring
 */
export async function recalculateEV(
  participantId: string,
  sportsSeasonId: string,
  newScoringRules: ScoringRules
): Promise<ParticipantEV | null> {
  const existing = await getParticipantEV(participantId, sportsSeasonId);

  if (!existing) {
    return null;
  }

  const probabilities = toProbabilityDistribution(existing);
  const newEV = calculateEV(probabilities, newScoringRules);

  const db = database();
  const updated = await db
    .update(participantExpectedValues)
    .set({
      expectedValue: newEV.toString(),
      calculatedAt: new Date(),
      updatedAt: new Date(),
    })
    .where(eq(participantExpectedValues.id, existing.id))
    .returning();

  return updated[0];
}

/**
 * Recalculate EVs for all participants in a sports season
 * Used when scoring rules change
 */
export async function recalculateAllEVsForSeason(
  sportsSeasonId: string,
  newScoringRules: ScoringRules
): Promise<number> {
  const allEVs = await getAllParticipantEVsForSeason(sportsSeasonId);

  await Promise.all(
    allEVs.map((ev) =>
      recalculateEV(ev.participantId, sportsSeasonId, newScoringRules)
    )
  );

  return allEVs.length;
}