import type { Kysely } from "kysely";

import type { Database } from "../types.js";
import { getExactMigrationStatus, runMigrations } from "./runner.js";

export type RuntimeMigrationMode = "auto" | "check" | "manual";

export interface RuntimeMigrationConfig {
	runtime: RuntimeMigrationMode;
	dev?: RuntimeMigrationMode;
}

function parseMigrationMode(value: unknown, source: string): RuntimeMigrationMode {
	if (value === "auto" || value === "check" || value === "manual") {
		return value;
	}
	throw new Error(
		`Invalid ${source} value ${JSON.stringify(value)}; expected "auto", "check", or "manual"`,
	);
}

export function normalizeMigrationConfig(value: unknown): RuntimeMigrationConfig {
	if (value === undefined) return { runtime: "auto" };
	if (typeof value !== "object" || value === null || Array.isArray(value)) {
		throw new Error("Invalid migrations configuration; expected an object");
	}

	const runtimeValue = Reflect.get(value, "runtime");
	const devValue = Reflect.get(value, "dev");
	const runtime = parseMigrationMode(runtimeValue, "migrations.runtime");
	const dev = devValue === undefined ? undefined : parseMigrationMode(devValue, "migrations.dev");
	return dev === undefined ? { runtime } : { runtime, dev };
}

export function resolveRuntimeMigrationMode(
	config: RuntimeMigrationConfig | undefined,
	options: { dev: boolean; override?: unknown },
): RuntimeMigrationMode {
	if (options.override !== undefined) {
		return parseMigrationMode(options.override, "EMDASH_MIGRATIONS_MODE");
	}
	if (options.dev) return config?.dev ?? "auto";
	return config?.runtime ?? "auto";
}

export class PendingMigrationsError extends Error {
	readonly pending: string[];

	constructor(pending: readonly string[]) {
		super(`Database has pending EmDash migrations: ${pending.join(", ")}`);
		this.name = "PendingMigrationsError";
		this.pending = [...pending];
	}
}

export async function enforceRuntimeMigrationPolicy(
	db: Kysely<Database>,
	mode: RuntimeMigrationMode,
): Promise<void> {
	if (mode === "manual") return;
	if (mode === "auto") {
		await runMigrations(db);
		return;
	}

	const status = await getExactMigrationStatus(db);
	if (status.pending.length > 0) {
		throw new PendingMigrationsError(status.pending);
	}
}