import { unzipSync } from 'fflate';
import type { SkillFileEntry } from '$lib/api';

/** Mirror hub/src/agent/skillStore.ts limits (ADR-0018). */
const MAX_SKILL_FILES = 512;
const MAX_SKILL_BYTES = 16 * 1024 * 1024;
const SKILL_NAME_PATTERN = /^[a-z0-9][a-z0-9-]{0,63}$/;

export interface ParsedSkillZip {
	readonly name: string;
	readonly description: string | null;
	readonly files: readonly SkillFileEntry[];
}

/**
 * Parse a skill package zip. Root of the archive IS the skill directory
 * (must contain SKILL.md directly — no wrapping folder).
 */
export function parseSkillZip(data: Uint8Array): ParsedSkillZip {
	let entries: Record<string, Uint8Array>;
	try {
		entries = unzipSync(data, {
			filter: (file) => !file.name.endsWith('/'),
		});
	} catch {
		throw new Error('无法解析 zip 文件');
	}

	const files: SkillFileEntry[] = [];
	let totalBytes = 0;

	for (const [rawPath, bytes] of Object.entries(entries)) {
		const path = normalizeZipPath(rawPath);
		if (path === null) continue;
		totalBytes += bytes.byteLength;
		if (totalBytes > MAX_SKILL_BYTES) {
			throw new Error(`技能总大小超过 ${MAX_SKILL_BYTES / (1024 * 1024)} MiB 上限`);
		}
		if (files.length >= MAX_SKILL_FILES) {
			throw new Error(`技能文件数超过 ${MAX_SKILL_FILES} 上限`);
		}
		// Text-only alpha path — API encodes content as UTF-8 strings.
		try {
			files.push({ path, content: decodeUtf8Strict(bytes) });
		} catch {
			throw new Error(`文件不是合法 UTF-8 文本：${path}`);
		}
	}

	if (files.length === 0) {
		throw new Error('zip 为空或不含可用文件');
	}

	const manifest = files.find((f) => f.path === 'SKILL.md');
	if (!manifest) {
		throw new Error('zip 根目录必须包含 SKILL.md（根即 skill 目录，不要多包一层文件夹）');
	}

	const name = parseFrontmatterField(manifest.content, 'name');
	if (name === null || name === '') {
		throw new Error('SKILL.md frontmatter 缺少 name');
	}
	if (!SKILL_NAME_PATTERN.test(name)) {
		throw new Error('技能名称仅允许小写字母、数字和连字符，且以字母或数字开头');
	}

	const description = parseFrontmatterField(manifest.content, 'description');
	files.sort((a, b) => a.path.localeCompare(b.path));
	return { name, description, files };
}

function normalizeZipPath(raw: string): string | null {
	let path = raw.replace(/\\/g, '/');
	// Drop zip noise and absolute/parent escapes before other checks.
	if (path.startsWith('__MACOSX/') || path.includes('/__MACOSX/')) return null;
	const base = path.split('/').pop() ?? '';
	if (base === '.DS_Store' || base.startsWith('._')) return null;
	if (path.startsWith('/') || path.includes('\0')) {
		throw new Error(`非法文件路径：${raw}`);
	}
	// Strip a single leading "./"
	if (path.startsWith('./')) path = path.slice(2);
	const parts = path.split('/').filter((p) => p !== '' && p !== '.');
	if (parts.length === 0 || parts.some((p) => p === '..')) {
		throw new Error(`非法文件路径：${raw}`);
	}
	return parts.join('/');
}

function parseFrontmatterField(manifest: string, key: string): string | null {
	const match = new RegExp(`^${key}:\\s*['"]?([^'"\\r\\n]+)['"]?\\s*$`, 'm').exec(manifest);
	return match ? match[1]!.trim() : null;
}

function decodeUtf8Strict(bytes: Uint8Array): string {
	return new TextDecoder('utf-8', { fatal: true }).decode(bytes);
}