import type { SuixinBaseThemeId, SuixinThemeStateV1, UserProfileScoring } from '@/src/storage/appStorage';

import { getThemeTriplet, NEUTRAL_THEME_COLORS } from './palette';
import { lerpHex } from './colorMath';
import { computeTFromStep } from './progress';
import { pickSuixinBaseThemeId } from './pickTheme';

export { NEUTRAL_THEME_COLORS } from './palette';
export { pickSuixinBaseThemeId } from './pickTheme';

/**
 * 根据 base theme 与 step 计算当前背景纯色
 */
export function computeSuixinSolidColor(args: {
  baseThemeId: SuixinBaseThemeId;
  stepIndex: number;
  seed: string;
}): string {
  const [top, _mid, bottom] = getThemeTriplet(args.baseThemeId);
  const t = computeTFromStep({ stepIndex: args.stepIndex, segments: 12, seed: args.seed });
  return lerpHex(top, bottom, t, NEUTRAL_THEME_COLORS[1]);
}

/**
 * 初始化一份随心状态（在冷启动会话内锁定 base theme）
 */
export function buildInitialSuixinState(args: {
  bootId: string;
  profile: UserProfileScoring | null;
  now?: Date;
}): SuixinThemeStateV1 {
  const now = args.now ?? new Date();
  const baseThemeId = pickSuixinBaseThemeId(args.profile);
  const seed = args.bootId;
  const step_index = 0;
  const last_color = computeSuixinSolidColor({ baseThemeId, stepIndex: step_index, seed });
  return {
    schema_version: 1,
    saved_at: now.toISOString(),
    boot_id: args.bootId,
    base_theme_id: baseThemeId,
    seed,
    step_index,
    last_color,
  };
}

/**
 * 切换文案时推进一步（不跨主题）
 */
export function advanceSuixinState(prev: SuixinThemeStateV1, now?: Date): SuixinThemeStateV1 {
  const nextStep = (Number.isFinite(prev.step_index) ? prev.step_index : 0) + 1;
  const last_color = computeSuixinSolidColor({
    baseThemeId: prev.base_theme_id,
    stepIndex: nextStep,
    seed: prev.seed,
  });
  return {
    ...prev,
    saved_at: (now ?? new Date()).toISOString(),
    step_index: nextStep,
    last_color,
  };
}