import { DataSource } from "../data-source/DataSource"
import { ObjectLiteral } from "../common/ObjectLiteral"
import { QueryRunner } from "../query-runner/QueryRunner"
import { RelationMetadata } from "../metadata/RelationMetadata"
import { FindOptionsUtils } from "../find-options/FindOptionsUtils"
import { SelectQueryBuilder } from "./SelectQueryBuilder"

/**
 * Wraps entities and creates getters/setters for their relations
 * to be able to lazily load relations when accessing these relations.
 */
export class RelationLoader {
    // -------------------------------------------------------------------------
    // Constructor
    // -------------------------------------------------------------------------

    constructor(private connection: DataSource) {}

    // -------------------------------------------------------------------------
    // Public Methods
    // -------------------------------------------------------------------------

    /**
     * Loads relation data for the given entity and its relation.
     */
    load(
        relation: RelationMetadata,
        entityOrEntities: ObjectLiteral | ObjectLiteral[],
        queryRunner?: QueryRunner,
        queryBuilder?: SelectQueryBuilder<any>,
    ): Promise<any[]> {
        // todo: check all places where it uses non array
        if (queryRunner && queryRunner.isReleased) queryRunner = undefined // get new one if already closed
        if (relation.isManyToOne || relation.isOneToOneOwner) {
            return this.loadManyToOneOrOneToOneOwner(
                relation,
                entityOrEntities,
                queryRunner,
                queryBuilder,
            )
        } else if (relation.isOneToMany || relation.isOneToOneNotOwner) {
            return this.loadOneToManyOrOneToOneNotOwner(
                relation,
                entityOrEntities,
                queryRunner,
                queryBuilder,
            )
        } else if (relation.isManyToManyOwner) {
            return this.loadManyToManyOwner(
                relation,
                entityOrEntities,
                queryRunner,
                queryBuilder,
            )
        } else {
            // many-to-many non owner
            return this.loadManyToManyNotOwner(
                relation,
                entityOrEntities,
                queryRunner,
                queryBuilder,
            )
        }
    }

    /**
     * Loads data for many-to-one and one-to-one owner relations.
     *
     * (ow) post.category<=>category.post
     * loaded: category from post
     * example: SELECT category.id AS category_id, category.name AS category_name FROM category category
     *              INNER JOIN post Post ON Post.category=category.id WHERE Post.id=1
     */
    loadManyToOneOrOneToOneOwner(
        relation: RelationMetadata,
        entityOrEntities: ObjectLiteral | ObjectLiteral[],
        queryRunner?: QueryRunner,
        queryBuilder?: SelectQueryBuilder<any>,
    ): Promise<any> {
        const entities = Array.isArray(entityOrEntities)
            ? entityOrEntities
            : [entityOrEntities]

        const joinAliasName = relation.entityMetadata.name
        const qb = queryBuilder
            ? queryBuilder
            : this.connection
                  .createQueryBuilder(queryRunner)
                  .select(relation.propertyName) // category
                  .from(relation.type, relation.propertyName)

        const mainAlias = qb.expressionMap.mainAlias!.name
        const columns = relation.entityMetadata.primaryColumns
        const joinColumns = relation.isOwning
            ? relation.joinColumns
            : relation.inverseRelation!.joinColumns
        const conditions = joinColumns
            .map((joinColumn) => {
                return `${relation.entityMetadata.name}.${
                    joinColumn.propertyName
                } = ${mainAlias}.${joinColumn.referencedColumn!.propertyName}`
            })
            .join(" AND ")

        qb.innerJoin(
            relation.entityMetadata.target as Function,
            joinAliasName,
            conditions,
        )

        if (columns.length === 1) {
            qb.where(
                `${joinAliasName}.${columns[0].propertyPath} IN (:...${
                    joinAliasName + "_" + columns[0].propertyName
                })`,
            )
            qb.setParameter(
                joinAliasName + "_" + columns[0].propertyName,
                entities.map((entity) =>
                    columns[0].getEntityValue(entity, true),
                ),
            )
        } else {
            const condition = entities
                .map((entity, entityIndex) => {
                    return columns
                        .map((column, columnIndex) => {
                            const paramName =
                                joinAliasName +
                                "_entity_" +
                                entityIndex +
                                "_" +
                                columnIndex
                            qb.setParameter(
                                paramName,
                                column.getEntityValue(entity, true),
                            )
                            return (
                                joinAliasName +
                                "." +
                                column.propertyPath +
                                " = :" +
                                paramName
                            )
                        })
                        .join(" AND ")
                })
                .map((condition) => "(" + condition + ")")
                .join(" OR ")
            qb.where(condition)
        }

        FindOptionsUtils.joinEagerRelations(
            qb,
            qb.alias,
            qb.expressionMap.mainAlias!.metadata,
        )

        return qb.getMany()
        // return qb.getOne(); todo: fix all usages
    }

    /**
     * Loads data for one-to-many and one-to-one not owner relations.
     *
     * SELECT post
     * FROM post post
     * WHERE post.[joinColumn.name] = entity[joinColumn.referencedColumn]
     */
    loadOneToManyOrOneToOneNotOwner(
        relation: RelationMetadata,
        entityOrEntities: ObjectLiteral | ObjectLiteral[],
        queryRunner?: QueryRunner,
        queryBuilder?: SelectQueryBuilder<any>,
    ): Promise<any> {
        const entities = Array.isArray(entityOrEntities)
            ? entityOrEntities
            : [entityOrEntities]
        const columns = relation.inverseRelation!.joinColumns
        const qb = queryBuilder
            ? queryBuilder
            : this.connection
                  .createQueryBuilder(queryRunner)
                  .select(relation.propertyName)
                  .from(
                      relation.inverseRelation!.entityMetadata.target,
                      relation.propertyName,
                  )

        const aliasName = qb.expressionMap.mainAlias!.name

        if (columns.length === 1) {
            qb.where(
                `${aliasName}.${columns[0].propertyPath} IN (:...${
                    aliasName + "_" + columns[0].propertyName
                })`,
            )
            qb.setParameter(
                aliasName + "_" + columns[0].propertyName,
                entities.map((entity) =>
                    columns[0].referencedColumn!.getEntityValue(entity, true),
                ),
            )
        } else {
            const condition = entities
                .map((entity, entityIndex) => {
                    return columns
                        .map((column, columnIndex) => {
                            const paramName =
                                aliasName +
                                "_entity_" +
                                entityIndex +
                                "_" +
                                columnIndex
                            qb.setParameter(
                                paramName,
                                column.referencedColumn!.getEntityValue(
                                    entity,
                                    true,
                                ),
                            )
                            return (
                                aliasName +
                                "." +
                                column.propertyPath +
                                " = :" +
                                paramName
                            )
                        })
                        .join(" AND ")
                })
                .map((condition) => "(" + condition + ")")
                .join(" OR ")
            qb.where(condition)
        }

        FindOptionsUtils.joinEagerRelations(
            qb,
            qb.alias,
            qb.expressionMap.mainAlias!.metadata,
        )

        return qb.getMany()
        // return relation.isOneToMany ? qb.getMany() : qb.getOne(); todo: fix all usages
    }

    /**
     * Loads data for many-to-many owner relations.
     *
     * SELECT category
     * FROM category category
     * INNER JOIN post_categories post_categories
     * ON post_categories.postId = :postId
     * AND post_categories.categoryId = category.id
     */
    loadManyToManyOwner(
        relation: RelationMetadata,
        entityOrEntities: ObjectLiteral | ObjectLiteral[],
        queryRunner?: QueryRunner,
        queryBuilder?: SelectQueryBuilder<any>,
    ): Promise<any> {
        const entities = Array.isArray(entityOrEntities)
            ? entityOrEntities
            : [entityOrEntities]
        const parameters = relation.joinColumns.reduce(
            (parameters, joinColumn) => {
                parameters[joinColumn.propertyName] = entities.map((entity) =>
                    joinColumn.referencedColumn!.getEntityValue(entity, true),
                )
                return parameters
            },
            {} as ObjectLiteral,
        )

        const qb = queryBuilder
            ? queryBuilder
            : this.connection
                  .createQueryBuilder(queryRunner)
                  .select(relation.propertyName)
                  .from(relation.type, relation.propertyName)

        const mainAlias = qb.expressionMap.mainAlias!.name
        const joinAlias = relation.junctionEntityMetadata!.tableName
        const joinColumnConditions = relation.joinColumns.map((joinColumn) => {
            return `${joinAlias}.${joinColumn.propertyName} IN (:...${joinColumn.propertyName})`
        })
        const inverseJoinColumnConditions = relation.inverseJoinColumns.map(
            (inverseJoinColumn) => {
                return `${joinAlias}.${
                    inverseJoinColumn.propertyName
                }=${mainAlias}.${
                    inverseJoinColumn.referencedColumn!.propertyName
                }`
            },
        )

        qb.innerJoin(
            joinAlias,
            joinAlias,
            [...joinColumnConditions, ...inverseJoinColumnConditions].join(
                " AND ",
            ),
        ).setParameters(parameters)

        FindOptionsUtils.joinEagerRelations(
            qb,
            qb.alias,
            qb.expressionMap.mainAlias!.metadata,
        )

        return qb.getMany()
    }

    /**
     * Loads data for many-to-many not owner relations.
     *
     * SELECT post
     * FROM post post
     * INNER JOIN post_categories post_categories
     * ON post_categories.postId = post.id
     * AND post_categories.categoryId = post_categories.categoryId
     */
    loadManyToManyNotOwner(
        relation: RelationMetadata,
        entityOrEntities: ObjectLiteral | ObjectLiteral[],
        queryRunner?: QueryRunner,
        queryBuilder?: SelectQueryBuilder<any>,
    ): Promise<any> {
        const entities = Array.isArray(entityOrEntities)
            ? entityOrEntities
            : [entityOrEntities]

        const qb = queryBuilder
            ? queryBuilder
            : this.connection
                  .createQueryBuilder(queryRunner)
                  .select(relation.propertyName)
                  .from(relation.type, relation.propertyName)

        const mainAlias = qb.expressionMap.mainAlias!.name
        const joinAlias = relation.junctionEntityMetadata!.tableName
        const joinColumnConditions = relation.inverseRelation!.joinColumns.map(
            (joinColumn) => {
                return `${joinAlias}.${
                    joinColumn.propertyName
                } = ${mainAlias}.${joinColumn.referencedColumn!.propertyName}`
            },
        )
        const inverseJoinColumnConditions =
            relation.inverseRelation!.inverseJoinColumns.map(
                (inverseJoinColumn) => {
                    return `${joinAlias}.${inverseJoinColumn.propertyName} IN (:...${inverseJoinColumn.propertyName})`
                },
            )
        const parameters = relation.inverseRelation!.inverseJoinColumns.reduce(
            (parameters, joinColumn) => {
                parameters[joinColumn.propertyName] = entities.map((entity) =>
                    joinColumn.referencedColumn!.getEntityValue(entity, true),
                )
                return parameters
            },
            {} as ObjectLiteral,
        )

        qb.innerJoin(
            joinAlias,
            joinAlias,
            [...joinColumnConditions, ...inverseJoinColumnConditions].join(
                " AND ",
            ),
        ).setParameters(parameters)

        FindOptionsUtils.joinEagerRelations(
            qb,
            qb.alias,
            qb.expressionMap.mainAlias!.metadata,
        )

        return qb.getMany()
    }

    /**
     * Wraps given entity and creates getters/setters for its given relation
     * to be able to lazily load data when accessing this relation.
     */
    enableLazyLoad(
        relation: RelationMetadata,
        entity: ObjectLiteral,
        queryRunner?: QueryRunner,
    ) {
        const relationLoader = this
        const dataIndex = "__" + relation.propertyName + "__" // in what property of the entity loaded data will be stored
        const promiseIndex = "__promise_" + relation.propertyName + "__" // in what property of the entity loading promise will be stored
        const resolveIndex = "__has_" + relation.propertyName + "__" // indicates if relation data already was loaded or not, we need this flag if loaded data is empty

        const setData = (entity: ObjectLiteral, value: any) => {
            entity[dataIndex] = value
            entity[resolveIndex] = true
            delete entity[promiseIndex]
            return value
        }
        const setPromise = (entity: ObjectLiteral, value: Promise<any>) => {
            delete entity[resolveIndex]
            delete entity[dataIndex]
            entity[promiseIndex] = value
            value.then(
                // ensure different value is not assigned yet
                (result) =>
                    entity[promiseIndex] === value
                        ? setData(entity, result)
                        : result,
            )
            return value
        }

        Object.defineProperty(entity, relation.propertyName, {
            get: function () {
                if (
                    this[resolveIndex] === true ||
                    this[dataIndex] !== undefined
                )
                    // if related data already was loaded then simply return it
                    return Promise.resolve(this[dataIndex])

                if (this[promiseIndex])
                    // if related data is loading then return a promise relationLoader loads it
                    return this[promiseIndex]

                // nothing is loaded yet, load relation data and save it in the model once they are loaded
                const loader = relationLoader
                    .load(relation, this, queryRunner)
                    .then((result) =>
                        relation.isOneToOne || relation.isManyToOne
                            ? result.length === 0
                                ? null
                                : result[0]
                            : result,
                    )
                return setPromise(this, loader)
            },
            set: function (value: any | Promise<any>) {
                if (value instanceof Promise) {
                    // if set data is a promise then wait for its resolve and save in the object
                    setPromise(this, value)
                } else {
                    // if its direct data set (non promise, probably not safe-typed)
                    setData(this, value)
                }
            },
            configurable: true,
            enumerable: false,
        })
    }
}