import { promises as fs } from "node:fs";
import path from "node:path";
import { fileURLToPath } from "node:url";
import { type DatabaseIntrospector, type Kysely, sql, type TableMetadata } from "kysely";
import { FileMigrationProvider, type MigrationResultSet, Migrator } from "kysely/migration";

/** 迁移目录:packages/db/migrations,文件名 NNNN_name.ts,导出 up/down */
export const MIGRATIONS_DIR = fileURLToPath(new URL("../migrations", import.meta.url));

export interface MigratorOptions {
  /**
   * kysely_migration 表所在 schema。默认不指定(走 search_path)。
   * 在非 public schema 里迁移(如测试隔离 schema)时必须显式指定,
   * 否则 Kysely 会把 public 下已存在的迁移表当成当前库的迁移记录。
   */
  migrationTableSchema?: string;
}

/**
 * 只看一个 schema 的内省器。Kysely 迁移器判断迁移表是否存在时会调用 introspection.getTables(),
 * 默认实现反射全库所有 schema,并对每个 schema 调 has_schema_privilege / pg_get_serial_sequence;
 * 同一个库里别的进程恰好 drop schema 时,这两个函数会报 "schema … does not exist"(并行测试共用开发库时的偶发失败)。
 * 迁移器只需要知道迁移表 / 锁表在不在目标 schema,这里只查目标 schema(未指定时取 current_schema())的表名。
 */
// biome-ignore lint/suspicious/noExplicitAny: 同上
function scopedIntrospector(db: Kysely<any>, schema: string | undefined): DatabaseIntrospector {
  const getTables = async (): Promise<TableMetadata[]> => {
    const rows = await sql<{ name: string; schema: string; kind: string }>`
      select c.relname as name, n.nspname as schema, c.relkind as kind
      from pg_catalog.pg_class c join pg_catalog.pg_namespace n on n.oid = c.relnamespace
      where n.nspname = coalesce(${schema ?? null}::text, current_schema())
        and c.relkind in ('r', 'v', 'p', 'f')`.execute(db);
    return rows.rows.map((r) => ({
      name: r.name,
      schema: r.schema,
      isView: r.kind === "v",
      isForeign: r.kind === "f",
      columns: [],
    }));
  };
  return {
    async getSchemas() {
      const rows = await sql<{ name: string }>`
        select nspname as name from pg_catalog.pg_namespace
        where nspname = coalesce(${schema ?? null}::text, current_schema())`.execute(db);
      return rows.rows;
    },
    getTables,
  };
}

/** 把 db.introspection 换成只看目标 schema 的实现,其余成员原样转发(方法绑回原实例,Kysely 用了私有字段) */
// biome-ignore lint/suspicious/noExplicitAny: 同上
function withScopedIntrospection(db: Kysely<any>, schema: string | undefined): Kysely<any> {
  const introspection = scopedIntrospector(db, schema);
  return new Proxy(db, {
    get(target, prop) {
      if (prop === "introspection") return introspection;
      const v = Reflect.get(target, prop, target);
      return typeof v === "function" ? v.bind(target) : v;
    },
  });
}

// biome-ignore lint/suspicious/noExplicitAny: 迁移器不关心具体表类型
export function createMigrator(db: Kysely<any>, opts: MigratorOptions = {}): Migrator {
  return new Migrator({
    db: withScopedIntrospection(db, opts.migrationTableSchema),
    provider: new FileMigrationProvider({ fs, path, migrationFolder: MIGRATIONS_DIR }),
    ...(opts.migrationTableSchema ? { migrationTableSchema: opts.migrationTableSchema } : {}),
  });
}

/** 迁移到最新;失败时抛出 */
// biome-ignore lint/suspicious/noExplicitAny: 同上
export async function migrateToLatest(db: Kysely<any>, opts: MigratorOptions = {}): Promise<MigrationResultSet> {
  const result = await createMigrator(db, opts).migrateToLatest();
  if (result.error) throw result.error;
  return result;
}

/** 清空 public schema(仅开发/测试用) */
// biome-ignore lint/suspicious/noExplicitAny: 同上
export async function resetSchema(db: Kysely<any>): Promise<void> {
  await sql`drop schema if exists public cascade`.execute(db);
  await sql`create schema public`.execute(db);
}