import pg from 'pg';
import { PrismaPg } from '@prisma/adapter-pg';
import { PrismaClient } from '$lib/generated/prisma/client';
import { env } from '$env/dynamic/private';
import { getAuditContext } from '$lib/server/audit-context';
import { describeAction, entityIdFor, sanitizeAuditValue, shouldAudit } from '$lib/server/audit';

let _prisma: PrismaClient | undefined;
let _base: PrismaClient | undefined;
let _pool: pg.Pool | undefined;

function getBase(): { base: PrismaClient; pool: pg.Pool } {
	if (!_base || !_pool) {
		_pool = new pg.Pool({ connectionString: env.DATABASE_URL });
		const adapter = new PrismaPg(_pool);
		_base = new PrismaClient({ adapter });
	}
	return { base: _base, pool: _pool };
}

const roleNameCache = new Map<number, string>();

async function resolveRoleName(base: PrismaClient, roleId: number | null): Promise<string | null> {
	if (roleId === null) return null;
	const cached = roleNameCache.get(roleId);
	if (cached) return cached;
	try {
		const role = await base.userRole.findUnique({
			where: { id: roleId },
			select: { name: true }
		});
		if (role?.name) {
			roleNameCache.set(roleId, role.name);
			return role.name;
		}
	} catch (e) {
		console.error('Failed to resolve role name for audit log:', e);
	}
	return null;
}

type Delegate = {
	findFirst?: (args: unknown) => Promise<unknown>;
	findMany?: (args: unknown) => Promise<unknown>;
};

function delegateFor(base: PrismaClient, model: string): Delegate | undefined {
	const key = model.charAt(0).toLowerCase() + model.slice(1);
	return (base as unknown as Record<string, unknown>)[key] as Delegate | undefined;
}

async function readBefore(
	base: PrismaClient,
	model: string,
	operation: string,
	args: unknown
): Promise<unknown> {
	if (operation.startsWith('create')) return null;
	const delegate = delegateFor(base, model);
	if (!delegate) return null;
	const where = (args as { where?: unknown } | null)?.where;
	try {
		if (operation === 'updateMany' || operation === 'deleteMany') {
			return delegate.findMany ? await delegate.findMany({ where, take: 50 }) : null;
		}
		return delegate.findFirst ? await delegate.findFirst({ where }) : null;
	} catch {
		return null;
	}
}

async function writeAuditRow(
	pool: pg.Pool,
	base: PrismaClient,
	entry: {
		userId: string | null;
		email: string | null;
		roleId: number | null;
		page: string;
		action: string;
		entity: string;
		entityId: string | null;
		before: unknown;
		after: unknown;
		ip: string | null;
	}
): Promise<void> {
	const roleName = await resolveRoleName(base, entry.roleId);
	await pool.query(
		`INSERT INTO "AuditLog"
		 ("id", "createdAt", "userId", "email", "roleId", "roleName", "page", "action", "entity", "entityId", "before", "after", "ip")
		 VALUES ($1, now(), $2, $3, $4, $5, $6, $7, $8, $9, $10::jsonb, $11::jsonb, $12)`,
		[
			crypto.randomUUID(),
			entry.userId,
			entry.email,
			entry.roleId,
			roleName,
			entry.page,
			entry.action,
			entry.entity,
			entry.entityId,
			entry.before === null ? null : JSON.stringify(entry.before),
			entry.after === null ? null : JSON.stringify(entry.after),
			entry.ip
		]
	);
}

function getPrisma(): PrismaClient {
	if (_prisma) return _prisma;

	const { base, pool } = getBase();

	const extended = base.$extends({
		query: {
			$allModels: {
				async $allOperations({ model, operation, args, query }) {
					if (!shouldAudit(model, operation)) {
						return query(args);
					}

					const before = await readBefore(base, model, operation, args);
					const result = await query(args);

					try {
						const ctx = getAuditContext();
						const res = result as { id?: unknown; email?: string; roleId?: number | null } | null;

						let userId = ctx?.userId ?? null;
						let email = ctx?.email ?? null;
						let roleId = ctx?.roleId ?? null;

						// Self-signup: attribute the new user to itself since no session exists yet.
						if (!userId && model === 'User' && operation === 'create' && res) {
							userId = (res.id as string | undefined) ?? null;
							email = res.email ?? null;
							roleId = res.roleId ?? null;
						}

						const after =
							operation === 'updateMany' || operation === 'deleteMany'
								? { count: (result as { count?: number } | null)?.count ?? null }
								: operation.startsWith('delete')
									? null
									: result;

						await writeAuditRow(pool, base, {
							userId,
							email,
							roleId,
							page: ctx?.page ?? '/system',
							action: describeAction(operation),
							entity: model,
							entityId: entityIdFor(args, result, before),
							before: sanitizeAuditValue(before),
							after: sanitizeAuditValue(after),
							ip: ctx?.ip ?? null
						});
					} catch (e) {
						console.error('Failed to write audit log:', e);
					}

					return result;
				}
			}
		}
	});

	_prisma = extended as unknown as PrismaClient;
	return _prisma;
}

export const prisma = new Proxy({} as PrismaClient, {
	get(_, prop) {
		return (getPrisma() as unknown as Record<string | symbol, unknown>)[prop];
	}
});