import { Injectable } from "@nestjs/common";
import type { EmotionTag, EmotionState } from "@kokorone/shared";
import { PrismaService } from "../prisma/prisma.service.js";
import { RuleBasedEmotionTagger } from "./emotion-tagger.js";
import { nextEmotionState, type TransitionContext } from "./emotion-state-machine.js";
import { toResponseStyle, type ResponseStyle } from "./response-style.js";
import { getArchetypeParams } from "../personality/archetype-params.js";

// D-2 時間衰減：預設半衰期 2 小時，實際速度由角色參數（G 群組）覆寫。
const DEFAULT_HALF_LIFE_MS = 2 * 60 * 60 * 1000;
// 低於此值視為「沒有明顯情緒」，dominantState 回報平靜。
const DOMINANT_EPSILON = 5;
// 標記強度低於此值視為刺激太弱，不足以真正觸發情緒轉移（高情緒觸發閾值的原型因此「難觸發」）。
const MIN_TRIGGER_INTENSITY = 0.25;

interface Dimensions {
  calm: number;
  joy: number;
  sad: number;
  alert: number;
  shy: number;
  grumpy: number;
}

const NON_CALM_TAGS: Exclude<EmotionTag, "CALM">[] = ["JOY", "SAD", "ALERT", "SHY", "GRUMPY"];

function fieldFor(tag: Exclude<EmotionTag, "CALM">): "joy" | "sad" | "alert" | "shy" | "grumpy" {
  return tag.toLowerCase() as "joy" | "sad" | "alert" | "shy" | "grumpy";
}

function dominantState(dims: Dimensions): EmotionTag {
  let best: EmotionTag = "CALM";
  let bestValue = DOMINANT_EPSILON;
  for (const tag of NON_CALM_TAGS) {
    const value = dims[fieldFor(tag)];
    if (value > bestValue) {
      best = tag;
      bestValue = value;
    }
  }
  return best;
}

function decayDimensions(dims: Dimensions, elapsedMs: number, halfLifeMs: number): Dimensions {
  const factor = elapsedMs > 0 ? Math.pow(0.5, elapsedMs / halfLifeMs) : 1;
  const joy = dims.joy * factor;
  const sad = dims.sad * factor;
  const alert = dims.alert * factor;
  const shy = dims.shy * factor;
  const grumpy = dims.grumpy * factor;
  const calm = Math.max(0, Math.min(100, 100 - (joy + sad + alert + shy + grumpy)));
  return { calm, joy, sad, alert, shy, grumpy };
}

export interface ProcessInputOptions extends TransitionContext {
  triggerThreshold?: number;
  halfLifeMs?: number;
  now?: Date;
  // I-5：本輪對話沒有明確情緒訊號時，套用作息驅動的基線情緒（不覆蓋文字本身觸發的訊號）。
  baselineSignal?: { tag: EmotionTag; intensity: number };
}

function toDomain(characterId: string, dims: Dimensions, updatedAt: Date): EmotionState {
  return {
    characterId,
    calm: dims.calm,
    joy: dims.joy,
    sad: dims.sad,
    alert: dims.alert,
    shy: dims.shy,
    grumpy: dims.grumpy,
    updatedAt: updatedAt.toISOString(),
  };
}

@Injectable()
export class EmotionService {
  constructor(
    private readonly prisma: PrismaService,
    private readonly tagger: RuleBasedEmotionTagger,
  ) {}

  async getState(characterId: string, now: Date = new Date()): Promise<EmotionState> {
    const { dims, updatedAt } = await this.decayedDimensions(characterId, now);
    await this.persist(characterId, dims, now);
    return toDomain(characterId, dims, now);
  }

  async getResponseStyle(characterId: string, now: Date = new Date()): Promise<ResponseStyle> {
    const state = await this.getState(characterId, now);
    return toResponseStyle(dominantState(state));
  }

  async processInput(
    characterId: string,
    text: string,
    options: ProcessInputOptions = {},
  ): Promise<{ state: EmotionState; style: ResponseStyle }> {
    const now = options.now ?? new Date();
    const { dims: decayed } = await this.decayedDimensions(characterId, now, options.halfLifeMs);
    const currentDominant = dominantState(decayed);

    // G-1：情緒觸發閾值預設由角色性格原型決定，呼叫端仍可明確覆寫。
    const character = await this.prisma.client.character.findUniqueOrThrow({ where: { id: characterId } });
    const archetypeParams = getArchetypeParams(character.personalityArchetype);
    const triggerThreshold = options.triggerThreshold ?? archetypeParams.emotionTriggerThreshold;

    const rawSignal = this.tagger.tag({ text, triggerThreshold });
    // 情緒觸發閾值除了縮放強度，也要能讓「難觸發」原型對弱刺激完全不觸發（而不只是觸發得比較小力）。
    let signal = rawSignal.intensity < MIN_TRIGGER_INTENSITY ? { tag: "CALM" as const, intensity: 0 } : rawSignal;
    if (signal.tag === "CALM" && options.baselineSignal) {
      signal = options.baselineSignal;
    }
    const next = nextEmotionState(currentDominant, signal, options);

    let updated: Dimensions;
    if (next === currentDominant) {
      updated = decayed;
    } else if (next === "CALM") {
      updated = { calm: 100, joy: 0, sad: 0, alert: 0, shy: 0, grumpy: 0 };
    } else {
      const intensityValue = Math.max(20, signal.intensity * 100);
      updated = { calm: Math.max(0, 100 - intensityValue), joy: 0, sad: 0, alert: 0, shy: 0, grumpy: 0 };
      updated[fieldFor(next)] = intensityValue;
    }

    await this.persist(characterId, updated, now);
    return { state: toDomain(characterId, updated, now), style: toResponseStyle(next) };
  }

  private async decayedDimensions(
    characterId: string,
    now: Date,
    halfLifeMs = DEFAULT_HALF_LIFE_MS,
  ): Promise<{ dims: Dimensions; updatedAt: Date }> {
    const row = await this.prisma.client.emotionState.upsert({
      where: { characterId },
      update: {},
      create: { characterId },
    });

    const elapsedMs = now.getTime() - row.updatedAt.getTime();
    const dims = decayDimensions(row, elapsedMs, halfLifeMs);
    return { dims, updatedAt: row.updatedAt };
  }

  private async persist(characterId: string, dims: Dimensions, now: Date): Promise<void> {
    await this.prisma.client.emotionState.update({
      where: { characterId },
      data: { ...dims, updatedAt: now },
    });
  }
}

export { dominantState };