from collections.abc import Sequence

from sqlalchemy import RowMapping, text
from sqlalchemy.ext.asyncio import AsyncSession

from backend.common.enums import DataBaseType
from backend.core.conf import settings


class CRUDCodeGen:
    """代码生成 CRUD 类"""

    @staticmethod
    async def get_all_tables(db: AsyncSession, table_schema: str) -> Sequence[RowMapping]:
        """
        获取所有表名

        :param db: 数据库会话
        :param table_schema: 数据库 schema 名称
        :return:
        """
        if DataBaseType.mysql == settings.DATABASE_TYPE:
            sql = """
            select
              table_name as table_name,
              table_comment as table_comment
            from
              information_schema.tables
            where
              table_name not like 'gen_%'
              and table_schema = :table_schema;
            """
            stmt = text(sql).bindparams(table_schema=table_schema)
        else:
            sql = """
            select
              c.relname as table_name,
              obj_description (c.oid) as table_comment
            from
              pg_class c
              left join pg_namespace n on n.oid = c.relnamespace
            where
              c.relkind = 'r'
              and c.relname not like 'gen_%'
              and n.nspname = :table_schema;
            """
            stmt = text(sql).bindparams(table_schema='public')
        result = await db.execute(stmt)
        return result.mappings().all()

    @staticmethod
    async def get_table(db: AsyncSession, table_schema: str, table_name: str) -> RowMapping | None:
        """
        获取表信息

        :param db: 数据库会话
        :param table_schema: 数据库 schema 名称
        :param table_name: 表名
        :return:
        """
        if DataBaseType.mysql == settings.DATABASE_TYPE:
            sql = """
            select
              table_name as table_name,
              table_comment as table_comment
            from
              information_schema.tables
            where
              table_name not like 'gen_%'
              and table_name = :table_name
              and table_schema = :table_schema;
            """
            stmt = text(sql).bindparams(table_schema=table_schema, table_name=table_name)
        else:
            sql = """
            select
              c.relname as table_name,
              obj_description (c.oid) as table_comment
            from
              pg_class c
              left join pg_namespace n on n.oid = c.relnamespace
            where
              c.relkind = 'r'
              and c.relname not like 'gen_%'
              and c.relname = :table_name
              and n.nspname = :table_schema;
            """
            stmt = text(sql).bindparams(table_schema='public', table_name=table_name)
        result = await db.execute(stmt)
        row = result.fetchone()
        return row._mapping if row else None

    @staticmethod
    async def get_all_columns(db: AsyncSession, table_schema: str, table_name: str) -> Sequence[RowMapping]:
        """
        获取所有列信息

        :param db: 数据库会话
        :param table_schema: 数据库 schema 名称
        :param table_name: 表名
        :return:
        """
        if DataBaseType.mysql == settings.DATABASE_TYPE:
            sql = """
            select
              column_name as column_name,
              case
                when column_key = 'pri' then
                  1
                else
                  0
              end as is_pk,
              case
                when is_nullable = 'no'
                  or column_key = 'pri' then
                  0
                else
                  1
              end as is_nullable,
              ordinal_position as sort,
              column_comment as column_comment,
              column_type as column_type
            from
              information_schema.columns
            where
              column_name <> 'id'
              and column_name <> 'created_time'
              and column_name <> 'updated_time'
              and column_name <> 'deleted'
              and column_name <> 'deleted_time'
              and table_name = :table_name
              and table_schema = :table_schema
            order by
              sort;
            """
            stmt = text(sql).bindparams(table_schema=table_schema, table_name=table_name)
        else:
            sql = """
            select
              a.attname as column_name,
              case
                when exists (
                    select
                      1
                    from
                      pg_constraint c
                    where
                      c.conrelid = t.oid
                      and c.contype = 'p'
                      and a.attnum = any (c.conkey)
                  ) then
                  1
                else
                  0
              end as is_pk,
              case
                when a.attnotnull
                  or exists (
                    select
                      1
                    from
                      pg_constraint c
                    where
                      c.conrelid = t.oid
                      and c.contype = 'p'
                      and a.attnum = any (c.conkey)
                  ) then
                  0
                else
                  1
              end as is_nullable,
              a.attnum as sort,
              col_description (t.oid, a.attnum) as column_comment,
              pg_catalog.format_type (a.atttypid, a.atttypmod) as column_type
            from
              pg_attribute a
              join pg_class t on a.attrelid = t.
              oid join pg_namespace n on n.oid = t.relnamespace
            where
              a.attnum > 0
              and not a.attisdropped
              and a.attname <> 'id'
              and a.attname <> 'created_time'
              and a.attname <> 'updated_time'
              and a.attname <> 'deleted'
              and a.attname <> 'deleted_time'
              and t.relname = :table_name
              and n.nspname = :table_schema
            order by
              sort;
            """
            stmt = text(sql).bindparams(table_schema='public', table_name=table_name)
        result = await db.execute(stmt)
        return result.mappings().all()


code_gen_dao: CRUDCodeGen = CRUDCodeGen()