// ABOUTME: Handler for the update_tiddler MCP tool
// ABOUTME: Updates existing tiddlers with diff preview and custom field support
import { createTwoFilesPatch } from 'diff';
import {
getTiddler,
putTiddler,
updateTiddlerObject,
getAuthUser,
type Tiddler,
} from '../tiddlywiki-http.js';
import type { ToolResult } from './types.js';
import { UpdateTiddlerInput } from './types.js';
/**
* Generate a readable diff between two tiddlers
*/
function generateTiddlerDiff(oldTiddler: Tiddler, newTiddler: Tiddler): string {
const lines: string[] = [];
// Text diff
const oldText = oldTiddler.text || '';
const newText = newTiddler.text || '';
if (oldText !== newText) {
const patch = createTwoFilesPatch(
oldTiddler.title,
newTiddler.title,
oldText,
newText,
'Before',
'After',
{ context: 1 } // Reduce context to 1 line for more compact diffs
);
// Add a concise summary
const oldLines = oldText.split('\n').length;
const newLines = newText.split('\n').length;
const delta = newLines - oldLines;
const summary =
delta > 0
? `+${delta} line${delta === 1 ? '' : 's'}`
: delta < 0
? `${delta} line${delta === -1 ? '' : 's'}`
: 'modified';
lines.push(`**Content:** ${summary}`);
lines.push('```diff');
lines.push(patch);
lines.push('```');
}
// Metadata changes
const metadataChanges: string[] = [];
if (oldTiddler.tags !== newTiddler.tags) {
metadataChanges.push(` tags: "${oldTiddler.tags || ''}" → "${newTiddler.tags || ''}"`);
}
if (oldTiddler.type !== newTiddler.type) {
metadataChanges.push(` type: "${oldTiddler.type}" → "${newTiddler.type}"`);
}
if (metadataChanges.length > 0) {
lines.push('');
lines.push('**Metadata:**');
lines.push(...metadataChanges);
}
return lines.join('\n');
}
/**
* Handle update_tiddler tool requests.
* Gets the current tiddler, applies updates, generates a diff, and saves.
*/
export async function handleUpdateTiddler(args: unknown): Promise<ToolResult> {
const input = UpdateTiddlerInput.parse(args);
// Get current tiddler
const current = await getTiddler(input.title);
if (!current) {
return {
content: [
{
type: 'text',
text: JSON.stringify({ error: `Tiddler not found: ${input.title}` }, null, 2),
},
],
isError: true,
};
}
// Build updated tiddler - include all custom fields from input
const { title: _title, text, tags, type, ...customFields } = input;
const updates: Partial<Tiddler> = { ...customFields };
if (text !== undefined) updates.text = text;
if (tags !== undefined) updates.tags = tags;
if (type !== undefined) updates.type = type;
const updated = updateTiddlerObject(current, updates, getAuthUser());
// Generate diff
const diff = generateTiddlerDiff(current, updated);
// Apply the change
await putTiddler(updated);
return {
content: [
{
type: 'text',
text: `## Updated: "${input.title}"\n\n${diff}`,
},
],
};
}
// Re-export the input schema for use in tool registration
export { UpdateTiddlerInput };
