import { Knex, knex } from "knex"
import { Table } from "../../definitions/common"
import { Operation, QueryJson } from "../../definitions/datasource"
import { breakExternalTableId } from "../utils"
import SchemaBuilder = Knex.SchemaBuilder
import CreateTableBuilder = Knex.CreateTableBuilder
const { FieldTypes, RelationshipTypes } = require("../../constants")

function generateSchema(
  schema: CreateTableBuilder,
  table: Table,
  tables: Record<string, Table>,
  oldTable: null | Table = null
) {
  let primaryKey = table && table.primary ? table.primary[0] : null
  const columns = Object.values(table.schema)
  // all columns in a junction table will be meta
  let metaCols = columns.filter(col => col.meta)
  let isJunction = metaCols.length === columns.length
  // can't change primary once its set for now
  if (primaryKey && !oldTable && !isJunction) {
    schema.increments(primaryKey).primary()
  } else if (!oldTable && isJunction) {
    schema.primary(metaCols.map(col => col.name))
  }

  // check if any columns need added
  const foreignKeys = Object.values(table.schema).map(col => col.foreignKey)
  for (let [key, column] of Object.entries(table.schema)) {
    // skip things that are already correct
    const oldColumn = oldTable ? oldTable.schema[key] : null
    if ((oldColumn && oldColumn.type) || (primaryKey === key && !isJunction)) {
      continue
    }
    switch (column.type) {
      case FieldTypes.STRING:
      case FieldTypes.OPTIONS:
      case FieldTypes.LONGFORM:
        schema.string(key)
        break
      case FieldTypes.NUMBER:
        // if meta is specified then this is a junction table entry
        if (column.meta && column.meta.toKey && column.meta.toTable) {
          const { toKey, toTable } = column.meta
          schema.integer(key).unsigned()
          schema.foreign(key).references(`${toTable}.${toKey}`)
        } else if (foreignKeys.indexOf(key) === -1) {
          schema.float(key)
        }
        break
      case FieldTypes.BOOLEAN:
        schema.boolean(key)
        break
      case FieldTypes.DATETIME:
        schema.datetime(key)
        break
      case FieldTypes.ARRAY:
        schema.json(key)
        break
      case FieldTypes.LINK:
        // this side of the relationship doesn't need any SQL work
        if (
          column.relationshipType !== RelationshipTypes.MANY_TO_ONE &&
          column.relationshipType !== RelationshipTypes.MANY_TO_MANY
        ) {
          if (!column.foreignKey || !column.tableId) {
            throw "Invalid relationship schema"
          }
          const { tableName } = breakExternalTableId(column.tableId)
          // @ts-ignore
          const relatedTable = tables[tableName]
          if (!relatedTable) {
            throw "Referenced table doesn't exist"
          }
          schema.integer(column.foreignKey).unsigned()
          schema
            .foreign(column.foreignKey)
            .references(`${tableName}.${relatedTable.primary[0]}`)
        }
        break
    }
  }

  // need to check if any columns have been deleted
  if (oldTable) {
    const deletedColumns = Object.entries(oldTable.schema)
      .filter(
        ([key, schema]) =>
          schema.type !== FieldTypes.LINK && table.schema[key] == null
      )
      .map(([key]) => key)
    deletedColumns.forEach(key => {
      if (oldTable.constrained && oldTable.constrained.indexOf(key) !== -1) {
        schema.dropForeign(key)
      }
      schema.dropColumn(key)
    })
  }

  return schema
}

function buildCreateTable(
  knex: Knex,
  table: Table,
  tables: Record<string, Table>
): SchemaBuilder {
  return knex.schema.createTable(table.name, schema => {
    generateSchema(schema, table, tables)
  })
}

function buildUpdateTable(
  knex: Knex,
  table: Table,
  tables: Record<string, Table>,
  oldTable: Table
): SchemaBuilder {
  return knex.schema.alterTable(table.name, schema => {
    generateSchema(schema, table, tables, oldTable)
  })
}

function buildDeleteTable(knex: Knex, table: Table): SchemaBuilder {
  return knex.schema.dropTable(table.name)
}

class SqlTableQueryBuilder {
  private readonly sqlClient: string

  // pass through client to get flavour of SQL
  constructor(client: string) {
    this.sqlClient = client
  }

  getSqlClient(): string {
    return this.sqlClient
  }

  /**
   * @param json the input JSON structure from which an SQL query will be built.
   * @return {string} the operation that was found in the JSON.
   */
  _operation(json: QueryJson): Operation {
    return json.endpoint.operation
  }

  _tableQuery(json: QueryJson): any {
    const client = knex({ client: this.sqlClient })
    let query
    if (!json.table || !json.meta || !json.meta.tables) {
      throw "Cannot execute without table being specified"
    }
    switch (this._operation(json)) {
      case Operation.CREATE_TABLE:
        query = buildCreateTable(client, json.table, json.meta.tables)
        break
      case Operation.UPDATE_TABLE:
        if (!json.meta || !json.meta.table) {
          throw "Must specify old table for update"
        }
        query = buildUpdateTable(
          client,
          json.table,
          json.meta.tables,
          json.meta.table
        )
        break
      case Operation.DELETE_TABLE:
        query = buildDeleteTable(client, json.table)
        break
      default:
        throw "Table operation is of unknown type"
    }
    return query.toSQL()
  }
}

export default SqlTableQueryBuilder
module.exports = SqlTableQueryBuilder