import { includes, has, get, map, first, isFunction, isEmpty, startsWith } from "lodash";
import { useEffect, useState, useMemo, useCallback, useRef } from "react";
import notification from "@/services/notification";
import DatabricksDataSource from "@/services/databricks-data-source";

function getDatabases(dataSource, refresh = false) {
  if (!dataSource) {
    return Promise.resolve([]);
  }

  return DatabricksDataSource.getDatabases(dataSource, refresh).catch(() => {
    notification.error("Failed to load Database list.", "Please try again later.");
    return Promise.reject();
  });
}

function getSchema(dataSource, databaseName, refresh = false) {
  if (!dataSource || !databaseName) {
    return Promise.resolve([]);
  }

  return DatabricksDataSource.getDatabaseTables(dataSource, databaseName, refresh).catch(() => {
    notification.error(`Failed to load tables for ${databaseName}.`, "Please try again later.");
    return Promise.reject();
  });
}

function addDisplayNameWithoutDatabaseName(schema, databaseName) {
  if (!databaseName) {
    return schema;
  }
  // add display name without {databaseName} + "."
  return map(schema, table => {
    const databaseNamePrefix = databaseName + ".";
    let displayName = table.name;
    if (startsWith(table.name, databaseNamePrefix)) {
      displayName = table.name.slice(databaseNamePrefix.length);
    }
    return { ...table, displayName };
  });
}

export default function useDatabricksSchema(dataSource, options = null, onOptionsUpdate = null) {
  const [databases, setDatabases] = useState([]);
  const [loadingDatabases, setLoadingDatabases] = useState(true);
  const [currentDatabaseName, setCurrentDatabaseName] = useState();
  const [schemas, setSchemas] = useState({});
  const [loadingSchema, setLoadingSchema] = useState(false);
  const [refreshing, setRefreshing] = useState(false);

  const setCurrentSchema = useCallback(
    schema =>
      setSchemas(currentSchemas => ({
        ...currentSchemas,
        [currentDatabaseName]: schema,
      })),
    [currentDatabaseName]
  );

  const currentDatabaseNameRef = useRef();
  currentDatabaseNameRef.current = currentDatabaseName;
  const loadTableColumns = useCallback(
    tableName => {
      // remove [databaseName.] from the tableName
      DatabricksDataSource.getTableColumns(
        dataSource,
        currentDatabaseName,
        tableName.substring(currentDatabaseName.length + 1)
      ).then(columns => {
        if (currentDatabaseNameRef.current === currentDatabaseName) {
          setSchemas(currentSchemas => {
            const schema = get(currentSchemas, currentDatabaseName, []);
            const updatedSchema = map(schema, table => {
              if (table.name === tableName) {
                return { ...table, columns, loading: false };
              }
              return table;
            });
            return {
              ...currentSchemas,
              [currentDatabaseName]: updatedSchema,
            };
          });
        }
      });
    },
    [dataSource, currentDatabaseName]
  );

  const schema = useMemo(() => {
    const currentSchema = get(schemas, currentDatabaseName, []);
    return addDisplayNameWithoutDatabaseName(currentSchema, currentDatabaseName);
  }, [schemas, currentDatabaseName]);

  const refreshAll = useCallback(() => {
    if (!refreshing) {
      setRefreshing(true);
      const getDatabasesPromise = getDatabases(dataSource, true).then(setDatabases);
      const getSchemasPromise = getSchema(dataSource, currentDatabaseName, true).then(({ schema }) =>
        setCurrentSchema(schema)
      );

      Promise.all([getSchemasPromise.catch(() => {}), getDatabasesPromise.catch(() => {})]).then(() =>
        setRefreshing(false)
      );
    }
  }, [dataSource, currentDatabaseName, setCurrentSchema, refreshing]);

  const schemasRef = useRef();
  schemasRef.current = schemas;
  useEffect(() => {
    let isCancelled = false;
    if (currentDatabaseName && !has(schemasRef.current, currentDatabaseName)) {
      setLoadingSchema(true);
      getSchema(dataSource, currentDatabaseName)
        .catch(() => Promise.resolve({ schema: [], has_columns: true }))
        .then(({ schema, has_columns }) => {
          if (!isCancelled) {
            if (!has_columns && !isEmpty(schema)) {
              schema = map(schema, table => ({ ...table, loading: true }));
              getSchema(dataSource, currentDatabaseName, true).then(({ schema }) => {
                if (!isCancelled) {
                  setCurrentSchema(schema);
                }
              });
            }
            setCurrentSchema(schema);
          }
        })
        .finally(() => {
          if (!isCancelled) {
            setLoadingSchema(false);
          }
        });
    }
    return () => {
      isCancelled = true;
    };
  }, [dataSource, currentDatabaseName, setCurrentSchema]);

  const defaultDatabaseNameRef = useRef();
  defaultDatabaseNameRef.current = get(options, "selectedDatabase", null);
  useEffect(() => {
    let isCancelled = false;
    setLoadingDatabases(true);
    setCurrentDatabaseName(undefined);
    setSchemas({});
    getDatabases(dataSource)
      .catch(() => Promise.resolve([]))
      .then(data => {
        if (!isCancelled) {
          setDatabases(data);

          // We set the database using this order:
          // 1. Currently selected value.
          // 2. Last used stored in localStorage.
          // 3. default database.
          // 4. first database in the list.
          let lastUsedDatabase =
            defaultDatabaseNameRef.current || localStorage.getItem(`lastSelectedDatabricksDatabase_${dataSource.id}`);

          if (!lastUsedDatabase) {
            lastUsedDatabase = includes(data, "default") ? "default" : first(data) || null;
          }

          setCurrentDatabaseName(lastUsedDatabase);
        }
      })
      .finally(() => {
        if (!isCancelled) {
          setLoadingDatabases(false);
        }
      });
    return () => {
      isCancelled = true;
    };
  }, [dataSource]);

  const setCurrentDatabase = useCallback(
    databaseName => {
      if (databaseName) {
        try {
          localStorage.setItem(`lastSelectedDatabricksDatabase_${dataSource.id}`, databaseName);
        } catch (e) {
          // `localStorage.setItem` may throw exception if there are no enough space - in this case it could be ignored
        }
      }
      setCurrentDatabaseName(databaseName);
      if (isFunction(onOptionsUpdate) && databaseName !== defaultDatabaseNameRef.current) {
        onOptionsUpdate({
          ...options,
          selectedDatabase: databaseName,
        });
      }
    },
    [dataSource.id, options, onOptionsUpdate]
  );

  return {
    databases,
    loadingDatabases,
    schema,
    loadingSchema,
    currentDatabaseName,
    setCurrentDatabase,
    loadTableColumns,
    refreshAll,
    refreshing,
  };
}