import * as yaml from "js-yaml";
import { err, ok, Result } from "neverthrow";
import { appError, AppError, AppErrorVariant } from "@/error";
import {
	EMPTY_PROJECT_CONFIG,
	normalizeTag,
	type ProjectConfig,
} from "@/model/projectConfig";

/**
 * Parse task-folder config.yml content.
 * Accepts missing/empty tags → [].
 */
export function parseProjectConfig(
	content: string,
): Result<ProjectConfig, AppError> {
	if (content.trim() === "") {
		return ok({ ...EMPTY_PROJECT_CONFIG });
	}

	let data: unknown;
	try {
		data = yaml.load(content);
	} catch (error) {
		const detail = error instanceof Error ? error.message : "invalid YAML";
		return err(appError(AppErrorVariant.INVALID_PROJECT_CONFIG, { detail }));
	}

	if (data === null || data === undefined) {
		return ok({ ...EMPTY_PROJECT_CONFIG });
	}

	if (typeof data !== "object" || Array.isArray(data)) {
		return err(
			appError(AppErrorVariant.INVALID_PROJECT_CONFIG, {
				detail: "root must be a mapping",
			}),
		);
	}

	const record = data as Record<string, unknown>;
	if (record.tags === undefined) {
		return ok({ tags: [] });
	}

	if (!Array.isArray(record.tags)) {
		return err(
			appError(AppErrorVariant.INVALID_PROJECT_CONFIG, {
				detail: "tags must be an array of strings",
			}),
		);
	}

	const tags: string[] = [];
	const seen = new Set<string>();
	for (const item of record.tags) {
		if (typeof item !== "string") {
			return err(
				appError(AppErrorVariant.INVALID_PROJECT_CONFIG, {
					detail: "tags must be an array of strings",
				}),
			);
		}
		const tag = normalizeTag(item);
		if (!tag || seen.has(tag)) continue;
		seen.add(tag);
		tags.push(tag);
	}

	return ok({ tags });
}