from sqlalchemy import create_engine
from sqlalchemy import types
from sqlalchemy.engine import reflection
from gometa.metadata.com.linkedin.pegasus2avro.mxe import MetadataChangeEvent
from gometa.metadata.com.linkedin.pegasus2avro.metadata.snapshot import DatasetSnapshot
from gometa.metadata.com.linkedin.pegasus2avro.schema import SchemaMetadata, MySqlDDL
from gometa.metadata.com.linkedin.pegasus2avro.common import AuditStamp

from gometa.ingestion.api.source import WorkUnit
from pydantic import BaseModel
import logging
import time
from typing import Optional
from dataclasses import dataclass

logger = logging.getLogger(__name__)


class SQLAlchemyConfig(BaseModel):
    username: str
    password: str
    host_port: str
    database: str = ""
    scheme: str
    options: Optional[dict] = {}

    def get_sql_alchemy_url(self):
        url=f'{self.scheme}://{self.username}:{self.password}@{self.host_port}/{self.database}'
        logger.debug('sql_alchemy_url={url}')
        return url


@dataclass
class SqlWorkUnit(WorkUnit):
    mce: MetadataChangeEvent 
    
    def get_metadata(self):
        return {'mce': self.mce}
    

def get_schema_metadata(dataset_name, platform, columns) -> SchemaMetadata:

    canonical_schema = [ {
            "fieldPath": column["name"],
            "nativeDataType": repr(column["type"]),
            "type": { "type":get_column_type(column["type"]) },
            "description": column.get("comment", None)
        } for column in columns ]

 
    actor, sys_time = "urn:li:corpuser:etl", int(time.time()) * 1000
    schema_metadata = SchemaMetadata(
        schemaName=dataset_name,
        platform=f'urn:li:dataPlatform:{platform}',
        version=0,
        hash="",
        #TODO: this is bug-compatible with existing scripts. Will fix later
        platformSchema=MySqlDDL(tableSchema = ""),
        created = AuditStamp(time=sys_time, actor=actor),
        lastModified = AuditStamp(time=sys_time, actor=actor),
        fields = canonical_schema
        )
    return schema_metadata



def get_column_type(column_type):
    """
    Maps SQLAlchemy types (https://docs.sqlalchemy.org/en/13/core/type_basics.html) to corresponding schema types
    """
    if isinstance(column_type, (types.Integer, types.Numeric)):
        return ("com.linkedin.pegasus2avro.schema.NumberType", {})

    if isinstance(column_type, (types.Boolean)):
        return ("com.linkedin.pegasus2avro.schema.BooleanType", {})

    if isinstance(column_type, (types.Enum)):
        return ("com.linkedin.pegasus2avro.schema.EnumType", {})

    if isinstance(column_type, (types._Binary, types.PickleType)):
        return ("com.linkedin.pegasus2avro.schema.BytesType", {})

    if isinstance(column_type, (types.ARRAY)):
        return ("com.linkedin.pegasus2avro.schema.ArrayType", {})

    if isinstance(column_type, (types.String)):
        return ("com.linkedin.pegasus2avro.schema.StringType", {})

    return ("com.linkedin.pegasus2avro.schema.NullType", {})

def get_sql_workunits(sql_config:SQLAlchemyConfig, platform: str, env: str = "PROD"):
    url = sql_config.get_sql_alchemy_url()
    engine = create_engine(url, **sql_config.options)
    inspector = reflection.Inspector.from_engine(engine)
    database = sql_config.database
    for schema in inspector.get_schema_names():
        for table in inspector.get_table_names(schema):
            columns = inspector.get_columns(table, schema)
            mce = MetadataChangeEvent()
            if database != "":
                dataset_name = f'{database}.{schema}.{table}'
            else:
                dataset_name = f'{schema}.{table}'

            dataset_snapshot = DatasetSnapshot()
            dataset_snapshot.urn=(
                f"urn:li:dataset:(urn:li:dataPlatform:{platform},{dataset_name},{env})"
            )
            schema_metadata = get_schema_metadata(dataset_name, platform, columns)
            dataset_snapshot.aspects.append(schema_metadata)
            mce.proposedSnapshot = dataset_snapshot
            yield SqlWorkUnit(id=dataset_name, mce = mce)