opencode prompt shortcuts plugin

prompt-shortcuts.ts

import { fmt } from 'llm-tools'

import type { Plugin } from '@opencode-ai/plugin'

const PROMPT_SHORTCUTS = {
	'#explore': fmt.oneLine(`
		Use explore agents to get a better understanding of
		relevant systems before you dive into the details yourself.
	`),
	'#plan': fmt.oneLine(`
		Make a plan and then ask me to review before you make any changes.
	`),
} as const satisfies Record<string, string>

function escapeForRegExp(text: string): string {
	return text.replace(/[.*+?^${}()|[\]\\]/g, '\\$&')
}

function endsSentence(text: string): boolean {
	const trimmed = text.trimEnd()
	if (!trimmed) return true

	return ['.', '!', '?'].includes(trimmed.at(-1) ?? '')
}

function replaceShortcut(text: string, trigger: string, replacement: string): string {
	const pattern = new RegExp(`(\\s*)${escapeForRegExp(trigger)}`, 'g')

	return text.replace(pattern, (_match, whitespace: string, offset: number, source: string) => {
		const prefix = source.slice(0, offset)
		if (endsSentence(prefix)) return `${whitespace}${replacement}`

		return `.${whitespace || ' '}${replacement}`
	})
}

export function replacePromptShortcuts(text: string): string {
	let nextText = text

	for (const [trigger, replacement] of Object.entries(PROMPT_SHORTCUTS)) {
		nextText = replaceShortcut(nextText, trigger, replacement)
	}

	return nextText
}

export const PromptShortcutsPlugin: Plugin = async () => {
	return {
		'chat.message': async (_input, output) => {
			for (const part of output.parts) {
				// Synthetic parts are OpenCode-generated context, not literal user input.
				if (part.type !== 'text' || part.synthetic) continue

				const replaced = replacePromptShortcuts(part.text)
				if (replaced === part.text) continue

				part.text = replaced
			}
		},
	}
}