import {Memory} from './memory/memory.ts';

export function cosineDistance(a: number[], b: number[]): number {
	let dot = 0, normA = 0, normB = 0;
	for(let i = 0; i < a.length; i++) {
		dot += a[i] * b[i];
		normA += a[i] * a[i];
		normB += b[i] * b[i];
	}
	const denom = Math.sqrt(normA) * Math.sqrt(normB);
	return denom === 0 ? 1 : 1 - dot / denom;
}

export async function embedMemoryFields(node: Memory, llm: any): Promise<void> {
	const body = stripHeader(node.content);
	const [titleE] = await llm.embedding(node.name.split('/').pop() || node.name);
	const [descE] = await llm.embedding(node.description || '');
	const bodyChunks = body ? await llm.embedding(body) : [];
	if(titleE) node.titleEmbedding = titleE.embedding;
	if(descE) node.embedding = descE.embedding;
	node.bodyEmbeddings = bodyChunks.map((c: any) => c.embedding).filter(Boolean);
}

export function euclideanDistance(a: number[], b: number[]): number {
	let sum = 0;
	for(let i = 0; i < a.length; i++) {
		const d = a[i] - b[i];
		sum += d * d;
	}
	return Math.sqrt(sum);
}

function getWeekStart(date: Date = new Date()): string {
	const d = new Date(Date.UTC(date.getFullYear(), date.getMonth(), date.getDate()));
	const day = d.getUTCDay();
	const diff = day === 0 ? -6 : 1 - day;
	d.setUTCDate(d.getUTCDate() + diff);
	return d.toISOString().slice(0, 10);
}

export function journalDescription(journalName?: string): string {
	const start = journalName?.split('/').pop() || getWeekStart();
	const d = new Date(`${start}T00:00:00Z`);
	d.setUTCDate(d.getUTCDate() + 6);
	const end = d.toISOString().slice(0, 10);
	return `Log from ${start} - ${end}`;
}

function parseFrontmatter(content: string): {fm: Map<string, string>, body: string} {
	const match = content.match(/^---\n([\s\S]*?)\n---\n?([\s\S]*)$/);
	if(!match) return {fm: new Map(), body: content};
	const fm = new Map<string, string>();
	for(const line of match[1].split('\n')) {
		const i = line.indexOf(':');
		if(i === -1) continue;
		const key = line.slice(0, i).trim();
		const raw = line.slice(i + 1).trim();
		let value = raw;
		try { value = JSON.parse(raw); } catch { }
		fm.set(key, value);
	}
	return {fm, body: match[2]};
}

export function writeFrontmatter(fm: Map<string, string>, body: string): string {
	const lines = [...fm.entries()].map(([k, v]) =>
		`${k}: ${JSON.stringify(String(v).replace(/\s+/g, ' ').trim())}`);
	return `---\n${lines.join('\n')}\n---\n\n${body.trimStart()}`;
}

export function stripHeader(content: string): string {
	return content.replace(/^---[\s\S]*?\n---\n?/, '').trimStart();
}

export function touchHeader(node: Memory, body: string): string {
	const {fm} = parseFrontmatter(node.content);
	fm.set('name', node.name);
	fm.set('description', (node.name.startsWith('Journal/') ? journalDescription(node.name) : node.description)
		|| 'Persistent memory document');
	fm.set('modified', new Date().toISOString());
	return writeFrontmatter(fm, stripHeader(body));
}