import { ObjectLiteral } from "../common/ObjectLiteral"
import { EntityMetadata } from "../metadata/EntityMetadata"
import { SubjectChangeMap } from "./SubjectChangeMap"
import { OrmUtils } from "../util/OrmUtils"
import { RelationMetadata } from "../metadata/RelationMetadata"
import { ColumnMetadata } from "../metadata/ColumnMetadata"
import { ObjectUtils } from "../util/ObjectUtils"
import { InstanceChecker } from "../util/InstanceChecker"

/**
 * Subject is a subject of persistence.
 * It holds information about each entity that needs to be persisted:
 * - what entity should be persisted
 * - what is database representation of the persisted entity
 * - what entity metadata of the persisted entity
 * - what is allowed to with persisted entity (insert/update/remove)
 *
 * Having this collection of subjects we can perform database queries.
 */
export class Subject {
    readonly "@instanceof" = Symbol.for("Subject")

    // -------------------------------------------------------------------------
    // Properties
    // -------------------------------------------------------------------------

    /**
     * Entity metadata of the subject entity.
     */
    metadata: EntityMetadata

    /**
     * Subject identifier.
     * This identifier is not limited to table entity primary columns.
     * This can be entity id or ids as well as some unique entity properties, like name or title.
     * Insert / Update / Remove operation will be executed by a given identifier.
     */
    identifier: ObjectLiteral | undefined = undefined

    /**
     * Copy of entity but with relational ids fulfilled.
     */
    entityWithFulfilledIds: ObjectLiteral | undefined = undefined

    /**
     * If subject was created by cascades this property will contain subject
     * from where this subject was created.
     */
    parentSubject?: Subject

    /**
     * Gets entity sent to the persistence (e.g. changed entity).
     * If entity is not set then this subject is created only for the entity loaded from the database,
     * or this subject is used for the junction operation (junction operations are relying only on identifier).
     */
    entity?: ObjectLiteral

    /**
     * Database entity.
     * THIS IS NOT RAW ENTITY DATA, its a real entity.
     */
    databaseEntity?: ObjectLiteral

    /**
     * Indicates if database entity was loaded.
     * No matter if it was found or not, it indicates the fact of loading.
     */
    databaseEntityLoaded: boolean = false

    /**
     * Changes needs to be applied in the database for the given subject.
     */
    changeMaps: SubjectChangeMap[] = []

    /**
     * Generated values returned by a database (for example generated id or default values).
     * Used in insert and update operations.
     * Has entity-like structure (not just column database name and values).
     */
    generatedMap?: ObjectLiteral

    /**
     * Inserted values with updated values of special and default columns.
     * Has entity-like structure (not just column database name and values).
     */
    insertedValueSet?: ObjectLiteral

    /**
     * Indicates if this subject can be inserted into the database.
     * This means that this subject either is newly persisted, either can be inserted by cascades.
     */
    canBeInserted: boolean = false

    /**
     * Indicates if this subject can be updated in the database.
     * This means that this subject either was persisted, either can be updated by cascades.
     */
    canBeUpdated: boolean = false

    /**
     * Indicates if this subject MUST be removed from the database.
     * This means that this subject either was removed, either was removed by cascades.
     */
    mustBeRemoved: boolean = false

    /**
     * Indicates if this subject can be soft-removed from the database.
     * This means that this subject either was soft-removed, either was soft-removed by cascades.
     */
    canBeSoftRemoved: boolean = false

    /**
     * Indicates if this subject can be recovered from the database.
     * This means that this subject either was recovered, either was recovered by cascades.
     */
    canBeRecovered: boolean = false

    /**
     * Relations updated by the change maps.
     */
    updatedRelationMaps: {
        relation: RelationMetadata
        value: ObjectLiteral
    }[] = []

    /**
     * List of updated columns
     */
    diffColumns: ColumnMetadata[] = []

    /**
     * List of updated relations
     */
    diffRelations: RelationMetadata[] = []

    // -------------------------------------------------------------------------
    // Constructor
    // -------------------------------------------------------------------------

    constructor(options: {
        metadata: EntityMetadata
        parentSubject?: Subject
        entity?: ObjectLiteral
        canBeInserted?: boolean
        canBeUpdated?: boolean
        mustBeRemoved?: boolean
        canBeSoftRemoved?: boolean
        canBeRecovered?: boolean
        identifier?: ObjectLiteral
        changeMaps?: SubjectChangeMap[]
    }) {
        this.metadata = options.metadata
        this.entity = options.entity
        this.parentSubject = options.parentSubject
        if (options.canBeInserted !== undefined)
            this.canBeInserted = options.canBeInserted
        if (options.canBeUpdated !== undefined)
            this.canBeUpdated = options.canBeUpdated
        if (options.mustBeRemoved !== undefined)
            this.mustBeRemoved = options.mustBeRemoved
        if (options.canBeSoftRemoved !== undefined)
            this.canBeSoftRemoved = options.canBeSoftRemoved
        if (options.canBeRecovered !== undefined)
            this.canBeRecovered = options.canBeRecovered
        if (options.identifier !== undefined)
            this.identifier = options.identifier
        if (options.changeMaps !== undefined)
            this.changeMaps.push(...options.changeMaps)

        this.recompute()
    }

    // -------------------------------------------------------------------------
    // Accessors
    // -------------------------------------------------------------------------

    /**
     * Checks if this subject must be inserted into the database.
     * Subject can be inserted into the database if it is allowed to be inserted (explicitly persisted or by cascades)
     * and if it does not have database entity set.
     */
    get mustBeInserted() {
        return this.canBeInserted && !this.databaseEntity
    }

    /**
     * Checks if this subject must be updated into the database.
     * Subject can be updated in the database if it is allowed to be updated (explicitly persisted or by cascades)
     * and if it does have differentiated columns or relations.
     */
    get mustBeUpdated() {
        return (
            this.canBeUpdated &&
            this.identifier &&
            (this.databaseEntityLoaded === false ||
                (this.databaseEntityLoaded && this.databaseEntity)) &&
            // ((this.entity && this.databaseEntity) || (!this.entity && !this.databaseEntity)) &&
            this.changeMaps.length > 0
        )
    }

    /**
     * Checks if this subject must be soft-removed into the database.
     * Subject can be updated in the database if it is allowed to be soft-removed (explicitly persisted or by cascades)
     * and if it does have differentiated columns or relations.
     */
    get mustBeSoftRemoved() {
        return (
            this.canBeSoftRemoved &&
            this.identifier &&
            (this.databaseEntityLoaded === false ||
                (this.databaseEntityLoaded && this.databaseEntity))
        )
    }

    /**
     * Checks if this subject must be recovered into the database.
     * Subject can be updated in the database if it is allowed to be recovered (explicitly persisted or by cascades)
     * and if it does have differentiated columns or relations.
     */
    get mustBeRecovered() {
        return (
            this.canBeRecovered &&
            this.identifier &&
            (this.databaseEntityLoaded === false ||
                (this.databaseEntityLoaded && this.databaseEntity))
        )
    }

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

    /**
     * Creates a value set needs to be inserted / updated in the database.
     * Value set is based on the entity and change maps of the subject.
     * Important note: this method pops data from this subject's change maps.
     */
    createValueSetAndPopChangeMap(): ObjectLiteral {
        const changeMapsWithoutValues: SubjectChangeMap[] = []
        const changeSet = this.changeMaps.reduce((updateMap, changeMap) => {
            let value = changeMap.value
            if (InstanceChecker.isSubject(value)) {
                // referenced columns can refer on values both which were just inserted and which were present in the model
                // if entity was just inserted valueSets must contain all values from the entity and values just inserted in the database
                // so, here we check if we have a value set then we simply use it as value to get our reference column values
                // otherwise simply use an entity which cannot be just inserted at the moment and have all necessary data
                value = value.insertedValueSet
                    ? value.insertedValueSet
                    : value.entity
            }
            // value = changeMap.valueFactory ? changeMap.valueFactory(value) : changeMap.column.createValueMap(value);

            let valueMap: ObjectLiteral | undefined
            if (this.metadata.isJunction && changeMap.column) {
                valueMap = changeMap.column.createValueMap(
                    changeMap.column.referencedColumn!.getEntityValue(value),
                )
            } else if (changeMap.column) {
                valueMap = changeMap.column.createValueMap(value)
            } else if (changeMap.relation) {
                // value can be a related object, for example: post.question = { id: 1 }
                // or value can be a null or direct relation id, e.g. post.question = 1
                // if its a direction relation id then we just set it to the valueMap,
                // however if its an object then we need to extract its relation id map and set it to the valueMap
                if (ObjectUtils.isObject(value) && !Buffer.isBuffer(value)) {
                    // get relation id, e.g. referenced column name and its value,
                    // for example: { id: 1 } which then will be set to relation, e.g. post.category = { id: 1 }
                    const relationId =
                        changeMap.relation!.getRelationIdMap(value)

                    // but relation id can be empty, for example in the case when you insert a new post with category
                    // and both post and category are newly inserted objects (by cascades) and in this case category will not have id
                    // this means we need to insert post without question id and update post's questionId once question be inserted
                    // that's why we create a new changeMap operation for future updation of the post entity
                    if (relationId === undefined) {
                        changeMapsWithoutValues.push(changeMap)
                        this.canBeUpdated = true
                        return updateMap
                    }
                    valueMap = changeMap.relation!.createValueMap(relationId)
                    this.updatedRelationMaps.push({
                        relation: changeMap.relation,
                        value: relationId,
                    })
                } else {
                    // value can be "null" or direct relation id here
                    valueMap = changeMap.relation!.createValueMap(value)
                    this.updatedRelationMaps.push({
                        relation: changeMap.relation,
                        value: value,
                    })
                }
            }

            OrmUtils.mergeDeep(updateMap, valueMap)
            return updateMap
        }, {} as ObjectLiteral)
        this.changeMaps = changeMapsWithoutValues
        return changeSet
    }

    /**
     * Recomputes entityWithFulfilledIds and identifier when entity changes.
     */
    recompute(): void {
        if (this.entity) {
            this.entityWithFulfilledIds = Object.assign({}, this.entity)
            if (this.parentSubject) {
                this.metadata.primaryColumns.forEach((primaryColumn) => {
                    if (
                        primaryColumn.relationMetadata &&
                        primaryColumn.relationMetadata.inverseEntityMetadata ===
                            this.parentSubject!.metadata
                    ) {
                        const value =
                            primaryColumn.referencedColumn!.getEntityValue(
                                this.parentSubject!.entity!,
                            )
                        primaryColumn.setEntityValue(
                            this.entityWithFulfilledIds!,
                            value,
                        )
                    }
                })
            }
            this.identifier = this.metadata.getEntityIdMap(
                this.entityWithFulfilledIds,
            )
        } else if (this.databaseEntity) {
            this.identifier = this.metadata.getEntityIdMap(this.databaseEntity)
        }
    }
}