Genarrative/src/data/playerProgression.ts

import type { PlayerProgressionState } from '../types';

export interface LevelBenchmark {
  level: number;
  xpToNextLevel: number;
  cumulativeXpRequired: number;
  referenceStrength: number;
  baseHp: number;
  baseMana: number;
  baselineDamageScale: number;
}

export const MAX_PLAYER_LEVEL = 20;

function clampNonNegativeInteger(value: unknown) {
  if (typeof value !== 'number' || !Number.isFinite(value)) {
    return 0;
  }

  return Math.max(0, Math.floor(value));
}

function clampLevel(value: unknown) {
  if (typeof value !== 'number' || !Number.isFinite(value)) {
    return 1;
  }

  return Math.min(MAX_PLAYER_LEVEL, Math.max(1, Math.floor(value)));
}

function roundMetric(value: number, digits = 3) {
  return Number(value.toFixed(digits));
}

function computeXpToNextLevel(level: number) {
  const scale = Math.max(0, level - 1);
  return 60 + 20 * scale + 8 * scale * scale;
}

function buildLevelBenchmarks(maxLevel: number) {
  const benchmarks: LevelBenchmark[] = [];
  let cumulativeXpRequired = 0;

  for (let level = 1; level <= maxLevel; level += 1) {
    const scale = level - 1;
    const xpToNextLevel = level >= maxLevel ? 0 : computeXpToNextLevel(level);

    benchmarks.push({
      level,
      xpToNextLevel,
      cumulativeXpRequired,
      referenceStrength: 100 + 16 * scale + 6 * scale * scale,
      baseHp: 180 + 24 * scale + 10 * scale * scale,
      baseMana: 80 + 14 * scale + 6 * scale * scale,
      baselineDamageScale: roundMetric(1 + 0.12 * scale + 0.03 * scale * scale),
    });

    cumulativeXpRequired += xpToNextLevel;
  }

  return benchmarks;
}

const LEVEL_BENCHMARKS = buildLevelBenchmarks(MAX_PLAYER_LEVEL);
const LEVEL_BENCHMARKS_BY_LEVEL = new Map(
  LEVEL_BENCHMARKS.map((benchmark) => [benchmark.level, benchmark]),
);

export function getLevelBenchmark(level: number) {
  return (
    LEVEL_BENCHMARKS_BY_LEVEL.get(clampLevel(level)) ?? LEVEL_BENCHMARKS[0]!
  );
}

export function getPlayerXpToNextLevel(level: number) {
  return getLevelBenchmark(level).xpToNextLevel;
}

function resolveLevelFromTotalXp(totalXp: number) {
  let resolvedLevel = 1;

  for (let level = 2; level <= MAX_PLAYER_LEVEL; level += 1) {
    if (totalXp < getLevelBenchmark(level).cumulativeXpRequired) {
      break;
    }

    resolvedLevel = level;
  }

  return resolvedLevel;
}

function buildProgressionStateFromTotalXp(
  totalXp: number,
  lastGrantedSource: PlayerProgressionState['lastGrantedSource'] = null,
): PlayerProgressionState {
  const normalizedTotalXp = clampNonNegativeInteger(totalXp);
  const level = resolveLevelFromTotalXp(normalizedTotalXp);
  const benchmark = getLevelBenchmark(level);

  if (level >= MAX_PLAYER_LEVEL) {
    return {
      level,
      currentLevelXp: 0,
      totalXp: normalizedTotalXp,
      xpToNextLevel: 0,
      pendingLevelUps: 0,
      lastGrantedSource,
    };
  }

  return {
    level,
    currentLevelXp: Math.max(
      0,
      normalizedTotalXp - benchmark.cumulativeXpRequired,
    ),
    totalXp: normalizedTotalXp,
    xpToNextLevel: benchmark.xpToNextLevel,
    pendingLevelUps: 0,
    lastGrantedSource,
  };
}

export function createInitialPlayerProgressionState(): PlayerProgressionState {
  return buildProgressionStateFromTotalXp(0);
}

export function normalizePlayerProgressionState(
  value: Partial<PlayerProgressionState> | null | undefined,
): PlayerProgressionState {
  if (!value) {
    return createInitialPlayerProgressionState();
  }

  const explicitLevel = clampLevel(value.level);
  const explicitCurrentLevelXp = clampNonNegativeInteger(value.currentLevelXp);
  const totalXp = clampNonNegativeInteger(value.totalXp);
  const hasExplicitProgress = explicitLevel > 1 || explicitCurrentLevelXp > 0;
  const derivedTotalXp =
    totalXp > 0 || !hasExplicitProgress
      ? totalXp
      : getLevelBenchmark(explicitLevel).cumulativeXpRequired +
        Math.min(explicitCurrentLevelXp, getPlayerXpToNextLevel(explicitLevel));
  const lastGrantedSource =
    value.lastGrantedSource === 'quest' ||
    value.lastGrantedSource === 'hostile_npc'
      ? value.lastGrantedSource
      : null;

  return {
    ...buildProgressionStateFromTotalXp(derivedTotalXp, lastGrantedSource),
    pendingLevelUps: clampNonNegativeInteger(value.pendingLevelUps),
  };
}