import { redactSecrets } from './secrets.ts'

export const BUDGET = { card: 400, mood: 100, memory: 800, care: 200 } as const
export type Section = keyof typeof BUDGET

/** 粗估 token：CJK 一字約一 token，其餘約四字元一 token */
export function estimateTokens(text: string): number {
  let cjk = 0
  for (const ch of text) if (/[⺀-鿿＀-￯　-〿]/.test(ch)) cjk++
  return cjk + Math.ceil((text.length - cjk) / 4)
}

export type Item = { text: string; score: number }

/** 在預算內保留高分項目，維持原順序；超出時先丟低分 */
export function fitBudget(items: Item[], budget: number): string[] {
  const kept = new Set(items.map((_, i) => i))
  const order = items.map((it, i) => ({ i, score: it.score })).sort((a, b) => a.score - b.score || b.i - a.i)
  let total = items.reduce((n, it) => n + estimateTokens(it.text), 0)
  for (const { i } of order) {
    if (total <= budget) break
    total -= estimateTokens(items[i]!.text)
    kept.delete(i)
  }
  return items.filter((_, i) => kept.has(i)).map(it => it.text)
}

export type Sections = Record<Section, Item[]>

/** 穩定內容（角色卡）在前，變動內容（心情、記憶、關心情境）在後 */
export function assemble(s: Sections): string {
  const part = (title: string, key: Section) => {
    const lines = fitBudget(s[key], BUDGET[key]).map(redactSecrets)
    return lines.length ? `## ${title}\n${lines.join('\n')}` : ''
  }
  const body = [part('角色', 'card'), part('互動記憶', 'memory'), part('目前心情', 'mood'), part('關心情境', 'care')]
    .filter(Boolean)
    .join('\n\n')
  return body ? `<companion>\n${body}\n</companion>` : ''
}