import { composeAssistantSystemPrompt } from './toolkit/AssistantPromptComposer';
import type { KnowledgeRepository } from './KnowledgeRepository';

const SAMPLE_FILE_LIMIT = 8;
const SAMPLE_CHARS_PER_FILE = 1_200;

export interface KnowledgeTopicSample {
  path: string;
  title: string;
  excerpt: string;
}

/**
 * 知识库工具包贡献的提示词能力段：由资料主题归纳可答范围，用户不可见具体文件。
 * 无可检索资料时返回 undefined —— 本包此刻没有能力，不该占一段提示词。
 */
export function describeKnowledgeCapability(
  repository: KnowledgeRepository,
  signal?: AbortSignal,
): string | undefined {
  const samples = collectKnowledgeSamples(repository, signal);
  const topics = uniqueTitles(samples.map((sample) => sample.title));
  if (topics.length === 0) {
    return undefined;
  }
  return [
    '- 查阅工作资料并回答下列主题相关的问题：',
    ...topics.map((topic) => `  · ${topic}`),
  ].join('\n');
}

/**
 * @deprecated 仅知识库一种能力时的旧入口，保留给存量调用方；
 * 新代码走 AssistantToolRegistry 的能力段 + composeAssistantSystemPrompt。
 */
export function resolveAssistantSystemPrompt(
  repository: KnowledgeRepository,
  configuredPrompt: string | undefined,
  signal?: AbortSignal,
): string {
  const capability = describeKnowledgeCapability(repository, signal);
  return composeAssistantSystemPrompt(configuredPrompt, capability ? [capability] : []);
}

export function collectKnowledgeSamples(
  repository: KnowledgeRepository,
  signal?: AbortSignal,
): KnowledgeTopicSample[] {
  const files = repository.listFiles(undefined, signal).files
    .slice()
    .sort((left, right) => right.mtime.localeCompare(left.mtime) || left.path.localeCompare(right.path))
    .slice(0, SAMPLE_FILE_LIMIT);
  const samples: KnowledgeTopicSample[] = [];
  for (const file of files) {
    signal?.throwIfAborted();
    let excerpt = '';
    try {
      excerpt = repository.readFile(file.path, 0, signal).content.slice(0, SAMPLE_CHARS_PER_FILE);
    } catch {
      continue;
    }
    samples.push({
      path: file.path,
      title: extractTitle(file.path, excerpt),
      excerpt: excerpt.replace(/\s+/g, ' ').trim(),
    });
  }
  return samples;
}

export function extractTitle(logicalPath: string, content: string): string {
  const heading = content.match(/^\s{0,3}#{1,3}\s+(.+?)\s*$/m);
  if (heading?.[1]) {
    return sanitizeTitle(heading[1]);
  }
  const base = logicalPath.split('/').pop() ?? logicalPath;
  return sanitizeTitle(base.replace(/\.[^.]+$/, '').replace(/[-_]+/g, ' '));
}

export function uniqueTitles(titles: string[]): string[] {
  const seen = new Set<string>();
  const result: string[] = [];
  for (const title of titles) {
    const key = title.toLocaleLowerCase();
    if (seen.has(key)) {
      continue;
    }
    seen.add(key);
    result.push(title);
  }
  return result;
}

function sanitizeTitle(value: string): string {
  return value
    .replace(/[`*_~\[\]]/g, '')
    .replace(/\s+/g, ' ')
    .trim()
    .slice(0, 32) || '工作资料';
}