import type {
  CustomWorldProfile,
  SceneActBlueprint,
  SceneActStage,
  SceneChapterBlueprint,
} from '../custom-world/runtimeTypes.js';

type JsonRecord = Record<string, unknown>;

type ChapterStateLike = {
  id: string;
  stage: SceneActStage;
  sceneId: string | null;
};

type SceneActRuntimeStateLike = {
  sceneId: string;
  chapterId: string;
  currentActId: string;
  currentActIndex: number;
};

export type ChapterPaceBand =
  | 'opening_fast'
  | 'steady'
  | 'pressure'
  | 'finale_dense';

export interface ChapterProgressionPlan {
  chapterId: string;
  chapterIndex: number;
  totalChapters: number;
  entryPseudoLevel: number;
  exitPseudoLevel: number;
  entryLevel: number;
  exitLevel: number;
  totalXpBudget: number;
  questXpBudget: number;
  hostileXpBudget: number;
  expectedHostileDefeatCount: number;
  paceBand: ChapterPaceBand;
}

export interface ChapterProgressionContext {
  plan: ChapterProgressionPlan;
  activeChapter: SceneChapterBlueprint;
  activeAct: SceneActBlueprint | null;
  stage: SceneActStage;
}

const DEFAULT_STAGE: SceneActStage = 'opening';
const DEFAULT_TERMINAL_STORY_LEVEL = 15;
const MIN_TERMINAL_STORY_LEVEL = 5;
const PSEUDO_LEVEL_CURVE_EXPONENT = 0.92;

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

function readString(value: unknown) {
  return typeof value === 'string' && value.trim() ? value.trim() : '';
}

function readNumber(value: unknown) {
  return typeof value === 'number' && Number.isFinite(value) ? value : null;
}

function roundToNearestFive(value: number) {
  return Math.round(value / 5) * 5;
}

function normalizeStage(value: unknown): SceneActStage | null {
  return value === 'opening' ||
    value === 'expansion' ||
    value === 'turning_point' ||
    value === 'climax' ||
    value === 'aftermath'
    ? value
    : null;
}

function readChapterState(value: unknown): ChapterStateLike | null {
  if (!isRecord(value)) {
    return null;
  }

  const id = readString(value.id);
  const stage = normalizeStage(value.stage);
  if (!id || !stage) {
    return null;
  }

  return {
    id,
    stage,
    sceneId: readString(value.sceneId) || null,
  };
}

function readSceneActRuntimeState(value: unknown): SceneActRuntimeStateLike | null {
  if (!isRecord(value)) {
    return null;
  }

  const sceneId = readString(value.sceneId);
  const chapterId = readString(value.chapterId);
  const currentActId = readString(value.currentActId);
  const currentActIndex = readNumber(value.currentActIndex);
  if (!sceneId || !chapterId || !currentActId || currentActIndex === null) {
    return null;
  }

  return {
    sceneId,
    chapterId,
    currentActId,
    currentActIndex: Math.max(0, Math.round(currentActIndex)),
  };
}

function readStoryEngineMemoryChapter(value: unknown) {
  return readChapterState(isRecord(value) ? value.currentChapter : null);
}

function readStoryEngineMemoryActState(value: unknown) {
  return readSceneActRuntimeState(
    isRecord(value) ? value.currentSceneActState : null,
  );
}

function getChapterBlueprints(
  profile: CustomWorldProfile | null | undefined,
) {
  return (profile?.sceneChapterBlueprints ?? []).filter(
    (entry): entry is SceneChapterBlueprint =>
      Boolean(entry?.id && entry.sceneId && Array.isArray(entry.acts)),
  );
}

function resolveExplicitStage(params: {
  chapterState?: unknown;
  storyEngineMemory?: unknown;
}) {
  return (
    readChapterState(params.chapterState)?.stage ??
    readStoryEngineMemoryChapter(params.storyEngineMemory)?.stage ??
    null
  );
}

function pickActStage(act: SceneActBlueprint | null) {
  if (!act) {
    return null;
  }

  return act.stageCoverage
    .map((stage) => normalizeStage(stage))
    .find((stage): stage is SceneActStage => Boolean(stage)) ?? null;
}

function resolveActiveChapterBlueprint(params: {
  customWorldProfile?: CustomWorldProfile | null;
  sceneId?: string | null;
  chapterState?: unknown;
  storyEngineMemory?: unknown;
}) {
  const chapters = getChapterBlueprints(params.customWorldProfile);
  if (chapters.length <= 0) {
    return null;
  }

  const runtimeActState = readStoryEngineMemoryActState(params.storyEngineMemory);
  if (runtimeActState) {
    const matchedByActState = chapters.find(
      (chapter) =>
        chapter.id === runtimeActState.chapterId &&
        chapter.sceneId === runtimeActState.sceneId,
    );
    if (matchedByActState) {
      return matchedByActState;
    }
  }

  const requestedSceneId =
    readString(params.sceneId) ||
    readChapterState(params.chapterState)?.sceneId ||
    readStoryEngineMemoryChapter(params.storyEngineMemory)?.sceneId ||
    '';
  if (requestedSceneId) {
    const matchedByScene = chapters.find(
      (chapter) =>
        chapter.sceneId === requestedSceneId ||
        chapter.linkedLandmarkIds.includes(requestedSceneId),
    );
    if (matchedByScene) {
      return matchedByScene;
    }
  }

  const explicitChapterId =
    readChapterState(params.chapterState)?.id ||
    readStoryEngineMemoryChapter(params.storyEngineMemory)?.id ||
    '';
  if (explicitChapterId) {
    const matchedById = chapters.find((chapter) => chapter.id === explicitChapterId);
    if (matchedById) {
      return matchedById;
    }
  }

  return chapters[0] ?? null;
}

function resolveActiveActBlueprint(params: {
  activeChapter: SceneChapterBlueprint;
  explicitStage?: SceneActStage | null;
  storyEngineMemory?: unknown;
}) {
  const runtimeActState = readStoryEngineMemoryActState(params.storyEngineMemory);
  if (
    runtimeActState &&
    runtimeActState.chapterId === params.activeChapter.id &&
    runtimeActState.sceneId === params.activeChapter.sceneId
  ) {
    const matchedById = params.activeChapter.acts.find(
      (act) => act.id === runtimeActState.currentActId,
    );
    if (matchedById) {
      return matchedById;
    }

    const matchedByIndex = params.activeChapter.acts[runtimeActState.currentActIndex];
    if (matchedByIndex) {
      return matchedByIndex;
    }
  }

  if (params.explicitStage) {
    const matchedByStage = params.activeChapter.acts.find((act) =>
      act.stageCoverage.includes(params.explicitStage!),
    );
    if (matchedByStage) {
      return matchedByStage;
    }
  }

  return params.activeChapter.acts[0] ?? null;
}

function resolveTerminalStoryLevel(totalChapters: number) {
  return Math.max(
    MIN_TERMINAL_STORY_LEVEL,
    Math.min(
      DEFAULT_TERMINAL_STORY_LEVEL,
      Math.round(3 + Math.max(1, totalChapters) * 2.4),
    ),
  );
}

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

function resolvePseudoLevelXp(pseudoLevel: number) {
  const normalizedLevel = Math.max(1, pseudoLevel);
  const lowerLevel = Math.floor(normalizedLevel);
  let lowerLevelXp = 0;

  for (let level = 1; level < lowerLevel; level += 1) {
    lowerLevelXp += computeXpToNextLevel(level);
  }

  return (
    lowerLevelXp +
    computeXpToNextLevel(lowerLevel) * (normalizedLevel - lowerLevel)
  );
}

function resolveChapterBoundaryPseudoLevel(params: {
  boundaryIndex: number;
  totalChapters: number;
}) {
  if (params.boundaryIndex <= 0 || params.totalChapters <= 0) {
    return 1;
  }

  const progress = Math.min(
    1,
    Math.max(0, params.boundaryIndex / params.totalChapters),
  );
  const terminalStoryLevel = resolveTerminalStoryLevel(params.totalChapters);

  return (
    1 +
    Math.pow(progress, PSEUDO_LEVEL_CURVE_EXPONENT) *
      Math.max(0, terminalStoryLevel - 1)
  );
}

function resolveEncounterNpcIds(chapter: SceneChapterBlueprint) {
  return [...new Set(chapter.acts.flatMap((act) => act.encounterNpcIds))];
}

function isLikelyHostileNpc(
  profile: CustomWorldProfile,
  npcId: string,
) {
  const matchedNpc = profile.storyNpcs.find((npc) => npc.id === npcId);
  if (!matchedNpc) {
    return /hostile|enemy|monster|bandit|boss|elite|敌|怪|匪|兽/u.test(npcId);
  }

  if (matchedNpc.initialAffinity < 0) {
    return true;
  }

  const fingerprint = [
    matchedNpc.role,
    matchedNpc.name,
    matchedNpc.title,
    matchedNpc.description,
    ...matchedNpc.tags,
  ].join(' ');

  return /hostile|enemy|monster|bandit|boss|elite|敌|怪|匪|兽|袭击|追猎/u.test(
    fingerprint,
  );
}

function resolveHostileShare(params: {
  totalEncounterCount: number;
  hostileEncounterCount: number;
}) {
  if (params.hostileEncounterCount <= 0) {
    return 0;
  }

  const hostileRatio =
    params.hostileEncounterCount / Math.max(1, params.totalEncounterCount);

  if (hostileRatio >= 0.55) {
    return 0.45;
  }

  if (hostileRatio <= 0.2) {
    return 0.25;
  }

  return 0.35;
}

function resolveChapterPaceBand(params: {
  chapterIndex: number;
  totalChapters: number;
  hostileShare: number;
}) {
  if (params.chapterIndex <= 1) {
    return 'opening_fast' as const;
  }

  if (params.chapterIndex >= params.totalChapters) {
    return 'finale_dense' as const;
  }

  if (params.hostileShare >= 0.45) {
    return 'pressure' as const;
  }

  return 'steady' as const;
}

function buildChapterPlan(params: {
  profile: CustomWorldProfile;
  chapter: SceneChapterBlueprint;
  chapterIndex: number;
  totalChapters: number;
}) {
  const entryPseudoLevel = resolveChapterBoundaryPseudoLevel({
    boundaryIndex: params.chapterIndex - 1,
    totalChapters: params.totalChapters,
  });
  const exitPseudoLevel = resolveChapterBoundaryPseudoLevel({
    boundaryIndex: params.chapterIndex,
    totalChapters: params.totalChapters,
  });
  const totalXpBudget = Math.max(
    40,
    roundToNearestFive(
      resolvePseudoLevelXp(exitPseudoLevel) -
        resolvePseudoLevelXp(entryPseudoLevel),
    ),
  );
  const encounterNpcIds = resolveEncounterNpcIds(params.chapter);
  const hostileEncounterCount = encounterNpcIds.filter((npcId) =>
    isLikelyHostileNpc(params.profile, npcId),
  ).length;
  const hostileShare = resolveHostileShare({
    totalEncounterCount: encounterNpcIds.length,
    hostileEncounterCount,
  });
  const expectedHostileDefeatCount =
    hostileEncounterCount > 0
      ? Math.max(hostileEncounterCount, Math.min(encounterNpcIds.length, 3))
      : 0;
  const hostileXpBudget =
    expectedHostileDefeatCount > 0
      ? Math.max(5, roundToNearestFive(totalXpBudget * hostileShare))
      : 0;
  const questXpBudget = Math.max(0, totalXpBudget - hostileXpBudget);

  return {
    chapterId: params.chapter.id,
    chapterIndex: params.chapterIndex,
    totalChapters: params.totalChapters,
    entryPseudoLevel: Number(entryPseudoLevel.toFixed(3)),
    exitPseudoLevel: Number(exitPseudoLevel.toFixed(3)),
    entryLevel: Math.max(1, Math.floor(entryPseudoLevel)),
    exitLevel: Math.max(1, Math.round(exitPseudoLevel)),
    totalXpBudget,
    questXpBudget,
    hostileXpBudget,
    expectedHostileDefeatCount,
    paceBand: resolveChapterPaceBand({
      chapterIndex: params.chapterIndex,
      totalChapters: params.totalChapters,
      hostileShare,
    }),
  } satisfies ChapterProgressionPlan;
}

export function buildChapterProgressionPlans(
  customWorldProfile: CustomWorldProfile | null | undefined,
) {
  const chapters = getChapterBlueprints(customWorldProfile);
  if (!customWorldProfile || chapters.length <= 0) {
    return [];
  }

  return chapters.map((chapter, index) =>
    buildChapterPlan({
      profile: customWorldProfile,
      chapter,
      chapterIndex: index + 1,
      totalChapters: chapters.length,
    }),
  );
}

export function resolveCurrentChapterProgressionContext(params: {
  customWorldProfile?: CustomWorldProfile | null;
  sceneId?: string | null;
  chapterState?: unknown;
  storyEngineMemory?: unknown;
}) {
  const activeChapter = resolveActiveChapterBlueprint(params);
  if (!activeChapter || !params.customWorldProfile) {
    return null;
  }

  const plans = buildChapterProgressionPlans(params.customWorldProfile);
  const plan = plans.find((entry) => entry.chapterId === activeChapter.id);
  if (!plan) {
    return null;
  }

  const explicitStage = resolveExplicitStage(params);
  const activeAct = resolveActiveActBlueprint({
    activeChapter,
    explicitStage,
    storyEngineMemory: params.storyEngineMemory,
  });

  return {
    plan,
    activeChapter,
    activeAct,
    stage: explicitStage ?? pickActStage(activeAct) ?? DEFAULT_STAGE,
  } satisfies ChapterProgressionContext;
}