import { getLevelBenchmark, MAX_PLAYER_LEVEL } from './levelBenchmarks.js';

type JsonRecord = Record<string, unknown>;

export type PlayerProgressionGrantSource = 'quest' | 'hostile_npc';

export interface PlayerProgressionState {
  level: number;
  currentLevelXp: number;
  totalXp: number;
  xpToNextLevel: number;
  pendingLevelUps?: number;
  lastGrantedSource?: PlayerProgressionGrantSource | null;
}

export interface PlayerExperienceGrantResult {
  state: PlayerProgressionState;
  grantedXp: number;
  previousLevel: number;
  nextLevel: number;
  levelUps: number;
  leveledUp: boolean;
  reachedMaxLevel: boolean;
}

function isRecord(value: unknown): value is JsonRecord {
  return typeof value === 'object' && value !== null && !Array.isArray(value);
}

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 normalizeLastGrantedSource(value: unknown) {
  return value === 'quest' || value === 'hostile_npc' ? value : null;
}

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: PlayerProgressionGrantSource | null = 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: unknown,
): PlayerProgressionState {
  if (!isRecord(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,
          getLevelBenchmark(explicitLevel).xpToNextLevel,
        );

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

export function grantPlayerExperience(
  value: unknown,
  amount: number,
  options: {
    source: PlayerProgressionGrantSource;
  },
): PlayerExperienceGrantResult {
  const currentState = normalizePlayerProgressionState(value);
  const grantedXp = clampNonNegativeInteger(amount);

  if (grantedXp <= 0) {
    return {
      state: {
        ...currentState,
        pendingLevelUps: 0,
      },
      grantedXp: 0,
      previousLevel: currentState.level,
      nextLevel: currentState.level,
      levelUps: 0,
      leveledUp: false,
      reachedMaxLevel: currentState.level >= MAX_PLAYER_LEVEL,
    };
  }

  const nextState = buildProgressionStateFromTotalXp(
    currentState.totalXp + grantedXp,
    options.source,
  );
  const levelUps = Math.max(0, nextState.level - currentState.level);

  return {
    state: {
      ...nextState,
      pendingLevelUps: 0,
    },
    grantedXp,
    previousLevel: currentState.level,
    nextLevel: nextState.level,
    levelUps,
    leveledUp: levelUps > 0,
    reachedMaxLevel: nextState.level >= MAX_PLAYER_LEVEL,
  };
}

export function buildExperienceGrantResultText(
  result: PlayerExperienceGrantResult,
) {
  if (result.grantedXp <= 0) {
    return '';
  }

  const parts = [`经验 +${result.grantedXp}`];

  if (result.leveledUp) {
    parts.push(
      result.levelUps > 1
        ? `连升 ${result.levelUps} 级，达到 Lv.${result.nextLevel}`
        : `升至 Lv.${result.nextLevel}`,
    );
  }

  return `${parts.join('，')}。`;
}