import { type SchemaMetadata, sql } from "kysely";
import { BaseIntrospector } from "bknd";

type PostgresSchemaSpec = {
   name: string;
   type: "VIEW" | "BASE TABLE";
   columns: {
      name: string;
      type: string;
      notnull: number;
      dflt: string;
      pk: boolean;
   }[];
   indices: {
      name: string;
      origin: string;
      partial: number;
      sql: string;
      columns: { name: string; seqno: number }[];
   }[];
};

export class PostgresIntrospector extends BaseIntrospector {
   async getSchemas(): Promise<SchemaMetadata[]> {
      const rawSchemas = await this.db
         .selectFrom("pg_catalog.pg_namespace")
         .select("nspname")
         .$castTo<{ nspname: string }>()
         .execute();

      return rawSchemas.map((it) => ({ name: it.nspname }));
   }

   async getSchemaSpec() {
      const query = sql`
         WITH tables_and_views AS (
            SELECT table_name AS name,
               table_type AS type
            FROM information_schema.tables
            WHERE table_schema = 'public'
              AND table_type IN ('BASE TABLE', 'VIEW')
              AND table_name NOT LIKE 'pg_%'
              AND table_name NOT IN (${this.getExcludedTableNames().join(", ")})
         ),

            columns_info AS (
               SELECT table_name AS name,
                  json_agg(json_build_object(
                     'name', column_name,
                     'type', data_type,
                     'notnull', (CASE WHEN is_nullable = 'NO' THEN true ELSE false END),
                     'dflt', column_default,
                     'pk', (SELECT COUNT(*) > 0
                        FROM information_schema.table_constraints tc
                        INNER JOIN information_schema.key_column_usage kcu
                          ON tc.constraint_name = kcu.constraint_name
                        WHERE tc.table_name = c.table_name
                          AND tc.constraint_type = 'PRIMARY KEY'
                          AND kcu.column_name = c.column_name)
                     )) AS columns
               FROM information_schema.columns c
               WHERE table_schema = 'public'
               GROUP BY table_name
            ),

            indices_info AS (
               SELECT
                  t.relname AS table_name,
                  json_agg(json_build_object(
                     'name', i.relname,
                     'origin', pg_get_indexdef(i.oid),
                     'partial', (CASE WHEN ix.indisvalid THEN false ELSE true END),
                     'sql', pg_get_indexdef(i.oid),
                     'columns', (
                        SELECT json_agg(json_build_object(
                           'name', a.attname,
                           'seqno', x.ordinal_position
                         ))
                        FROM unnest(ix.indkey) WITH ORDINALITY AS x(attnum, ordinal_position)
                            JOIN pg_attribute a ON a.attnum = x.attnum AND a.attrelid = t.oid
                     ))) AS indices
               FROM pg_class t
                  LEFT JOIN pg_index ix ON t.oid = ix.indrelid
                  LEFT JOIN pg_class i ON i.oid = ix.indexrelid
               WHERE t.relkind IN ('r', 'v')  -- r = table, v = view
                 AND t.relname NOT LIKE 'pg_%'
               GROUP BY t.relname
            )

         SELECT
            tv.name,
            tv.type,
            ci.columns,
            ii.indices
         FROM tables_and_views tv
            LEFT JOIN columns_info ci ON tv.name = ci.name
            LEFT JOIN indices_info ii ON tv.name = ii.table_name;
      `;

      const tables = await this.executeWithPlugins<PostgresSchemaSpec[]>(query);

      return tables.map((table) => ({
         name: table.name,
         isView: table.type === "VIEW",
         columns: table.columns.map((col) => {
            return {
               name: col.name,
               dataType: col.type,
               isNullable: !col.notnull,
               // @todo: check default value on 'nextval' see https://www.postgresql.org/docs/17/datatype-numeric.html#DATATYPE-SERIAL
               isAutoIncrementing: true, // just for now
               hasDefaultValue: col.dflt != null,
               comment: undefined,
            };
         }),
         indices: table.indices.map((index) => ({
            name: index.name,
            table: table.name,
            isUnique: index.sql?.match(/unique/i) != null,
            columns: index.columns.map((col) => ({
               name: col.name,
               order: col.seqno,
            })),
         })),
      }));
   }
}