projectContinuousExcerpt

KIT · function · 运行时值

Project a continuous excerpt of a body by binary-searching the longest prefix that fits.

Binary-search a continuous prefix and keep an existing surrogate pair intact. render receives the prefix length, not the text, so the caller decides how the excerpt is framed.

导入

TypeScript

import { projectContinuousExcerpt } from '@jangts/agent-core/kits/projection';

JavaScript

import { projectContinuousExcerpt } from '@jangts/agent-core/kits/projection';

其他公开入口：@jangts/agent-core/types、@jangts/agent-core/kits/projection、@jangts/agent-core/kits。

定义

调用

projectContinuousExcerpt(body: string, limit: number, render: (length: number) => string): ContentProjection | undefined

Project a continuous excerpt of a body by binary-searching the longest prefix that fits.

Binary-search a continuous prefix and keep an existing surrogate pair intact. render receives the prefix length, not the text, so the caller decides how the excerpt is framed.

参数	类型	传递	说明
body	string	必需	—
limit	number	必需	—
render	(length: number) => string	必需	—

返回： ContentProjection \| undefined。

返回值的可选结构： 选择其中一种结构，各分支的字段要求分别列出。

分支 1

undefined

分支 2

字段	类型	必需	说明
text	string	必需	只读。Rendered text that fits the requested budget.
truncated	boolean	必需	只读。True when anything was shortened or replaced by the fallback.

使用示例

• Projection：按预算投影内容：先缩短文本，再减少条目；源数据、投影结果和预算由 App 显式区分。

为同一份查询结果准备紧凑 JSON

入门 · Node.js

TypeScript

import { Projection } from '@jangts/agent-core/kits/projection';
const projection = Projection.defineContentProjection({
  counts: [10, 3, 1], lengths: [200, 80, 20],
  render: value => JSON.stringify(value), fallback: () => '{}',
});
const result = projection.project({ value: { items: [{ title: '配置说明', body: '正文'.repeat(100) }] }, maxChars: 120 });
console.log(result.text, result.truncated);

JavaScript

import { Projection } from '@jangts/agent-core/kits/projection';
const projection = Projection.defineContentProjection({
    counts: [10, 3, 1], lengths: [200, 80, 20],
    render: value => JSON.stringify(value), fallback: () => '{}',
});
const result = projection.project({ value: { items: [{ title: '配置说明', body: '正文'.repeat(100) }] }, maxChars: 120 });
console.log(result.text, result.truncated);

相同数据先移除私有字段，再按预算投影

配置 · Node.js

TypeScript

import { Projection } from '@jangts/agent-core/kits/projection';
const tree = Projection.defineTreeProjection({
  maxDepth: 4,
  visitRecord(record) { delete record.privateNote; },
});
const source = { items: [{ title: '配置说明', body: '正文'.repeat(100), privateNote: '不向模型提供' }] };
// 调用者明确选择副本所有权；visitor 不会碰原记录。
const publicData = tree.visit(structuredClone(source), undefined);
const compact = Projection.defineContentProjection({ counts: [10, 3, 1], lengths: [200, 80, 20], render: JSON.stringify, fallback: () => '{}' });
console.log(compact.project({ value: publicData, maxChars: 120 }));

JavaScript

import { Projection } from '@jangts/agent-core/kits/projection';
const tree = Projection.defineTreeProjection({
    maxDepth: 4,
    visitRecord(record) { delete record.privateNote; },
});
const source = { items: [{ title: '配置说明', body: '正文'.repeat(100), privateNote: '不向模型提供' }] };
// 调用者明确选择副本所有权；visitor 不会碰原记录。
const publicData = tree.visit(structuredClone(source), undefined);
const compact = Projection.defineContentProjection({ counts: [10, 3, 1], lengths: [200, 80, 20], render: JSON.stringify, fallback: () => '{}' });
console.log(compact.project({ value: publicData, maxChars: 120 }));

保留连续正文而非拆散段落

扩展 · Node.js

render 的输出长度须随前缀长度单调增长，二分搜索才有意义。

TypeScript

import { Projection } from '@jangts/agent-core/kits/projection';
const body = '一段连续的资料正文。'.repeat(100);
const excerpt = Projection.projectContinuousExcerpt(body, 120, length => JSON.stringify({ excerpt: body.slice(0, length) }));
if (excerpt) console.log(JSON.parse(excerpt.text));

JavaScript

import { Projection } from '@jangts/agent-core/kits/projection';
const body = '一段连续的资料正文。'.repeat(100);
const excerpt = Projection.projectContinuousExcerpt(body, 120, length => JSON.stringify({ excerpt: body.slice(0, length) }));
if (excerpt)
    console.log(JSON.parse(excerpt.text));

相关策略源码

• 缩减顺序与树遍历

相关定义

• ContentProjection