import { Subject } from "./Subject"
import { DateUtils } from "../util/DateUtils"
import { ObjectLiteral } from "../common/ObjectLiteral"
import { OrmUtils } from "../util/OrmUtils"
import { ApplyValueTransformers } from "../util/ApplyValueTransformers"
import { ObjectUtils } from "../util/ObjectUtils"

/**
 * Finds what columns are changed in the subject entities.
 */
export class SubjectChangedColumnsComputer {
    // -------------------------------------------------------------------------
    // Public Methods
    // -------------------------------------------------------------------------

    /**
     * Finds what columns are changed in the subject entities.
     */
    compute(subjects: Subject[]) {
        subjects.forEach((subject) => {
            this.computeDiffColumns(subject)
            this.computeDiffRelationalColumns(subjects, subject)
        })
    }

    // -------------------------------------------------------------------------
    // Protected Methods
    // -------------------------------------------------------------------------

    /**
     * Differentiate columns from the updated entity and entity stored in the database.
     */
    protected computeDiffColumns(subject: Subject): void {
        // if there is no persisted entity then nothing to compute changed in it
        if (!subject.entity) return

        subject.metadata.columns.forEach((column) => {
            // ignore special columns
            if (
                column.isVirtual ||
                column.isDiscriminator // ||
                // column.isUpdateDate ||
                // column.isVersion ||
                // column.isCreateDate
            )
                return

            const changeMap = subject.changeMaps.find(
                (changeMap) => changeMap.column === column,
            )
            if (changeMap) {
                subject.changeMaps.splice(
                    subject.changeMaps.indexOf(changeMap),
                    1,
                )
            }

            // get user provided value - column value from the user provided persisted entity
            const entityValue = column.getEntityValue(subject.entity!)

            // we don't perform operation over undefined properties (but we DO need null properties!)
            if (entityValue === undefined) return

            // if there is no database entity then all columns are treated as new, e.g. changed
            if (subject.databaseEntity) {
                // skip transform database value for json / jsonb for comparison later on
                const shouldTransformDatabaseEntity =
                    column.type !== "json" && column.type !== "jsonb"

                // get database value of the column
                let databaseValue = column.getEntityValue(
                    subject.databaseEntity,
                    shouldTransformDatabaseEntity,
                )

                // filter out "relational columns" only in the case if there is a relation object in entity
                if (column.relationMetadata) {
                    const value = column.relationMetadata.getEntityValue(
                        subject.entity!,
                    )
                    if (value !== null && value !== undefined) return
                }
                let normalizedValue = entityValue
                // normalize special values to make proper comparision
                if (entityValue !== null) {
                    switch (column.type) {
                        case "date":
                            normalizedValue =
                                DateUtils.mixedDateToDateString(entityValue)
                            break

                        case "time":
                        case "time with time zone":
                        case "time without time zone":
                        case "timetz":
                            normalizedValue =
                                DateUtils.mixedDateToTimeString(entityValue)
                            break

                        case "datetime":
                        case "datetime2":
                        case Date:
                        case "timestamp":
                        case "timestamp without time zone":
                        case "timestamp with time zone":
                        case "timestamp with local time zone":
                        case "timestamptz":
                            normalizedValue =
                                DateUtils.mixedDateToUtcDatetimeString(
                                    entityValue,
                                )
                            databaseValue =
                                DateUtils.mixedDateToUtcDatetimeString(
                                    databaseValue,
                                )
                            break

                        case "json":
                        case "jsonb":
                            // JSON.stringify doesn't work because postgresql sorts jsonb before save.
                            // If you try to save json '[{"messages": "", "attribute Key": "", "level":""}] ' as jsonb,
                            // then postgresql will save it as '[{"level": "", "message":"", "attributeKey": ""}]'
                            if (
                                OrmUtils.deepCompare(entityValue, databaseValue)
                            )
                                return
                            break

                        case "simple-array":
                            normalizedValue =
                                DateUtils.simpleArrayToString(entityValue)
                            databaseValue =
                                DateUtils.simpleArrayToString(databaseValue)
                            break
                        case "simple-enum":
                            normalizedValue =
                                DateUtils.simpleEnumToString(entityValue)
                            databaseValue =
                                DateUtils.simpleEnumToString(databaseValue)
                            break
                        case "simple-json":
                            normalizedValue =
                                DateUtils.simpleJsonToString(entityValue)
                            databaseValue =
                                DateUtils.simpleJsonToString(databaseValue)
                            break
                    }

                    if (column.transformer) {
                        normalizedValue = ApplyValueTransformers.transformTo(
                            column.transformer,
                            entityValue,
                        )
                    }
                }

                // if value is not changed - then do nothing
                if (
                    Buffer.isBuffer(normalizedValue) &&
                    Buffer.isBuffer(databaseValue)
                ) {
                    if (normalizedValue.equals(databaseValue)) {
                        return
                    }
                } else {
                    if (normalizedValue === databaseValue) return
                }
            }

            if (!subject.diffColumns.includes(column))
                subject.diffColumns.push(column)

            subject.changeMaps.push({
                column: column,
                value: entityValue,
            })
        })
    }

    /**
     * Difference columns of the owning one-to-one and many-to-one columns.
     */
    protected computeDiffRelationalColumns(
        allSubjects: Subject[],
        subject: Subject,
    ): void {
        // if there is no persisted entity then nothing to compute changed in it
        if (!subject.entity) return

        subject.metadata.relationsWithJoinColumns.forEach((relation) => {
            // get the related entity from the persisted entity
            let relatedEntity = relation.getEntityValue(subject.entity!)

            // we don't perform operation over undefined properties (but we DO need null properties!)
            if (relatedEntity === undefined) return

            // if there is no database entity then all relational columns are treated as new, e.g. changed
            if (subject.databaseEntity) {
                // here we cover two scenarios:
                // 1. related entity can be another entity which is natural way
                // 2. related entity can be just an entity id
                // if relation entity is just a relation id set (for example post.tag = 1)
                // then we create an id map from it to make a proper comparision
                let relatedEntityRelationIdMap: ObjectLiteral = relatedEntity
                if (
                    relatedEntityRelationIdMap !== null &&
                    ObjectUtils.isObject(relatedEntityRelationIdMap)
                )
                    relatedEntityRelationIdMap = relation.getRelationIdMap(
                        relatedEntityRelationIdMap,
                    )!

                // get database related entity. Since loadRelationIds are used on databaseEntity
                // related entity will contain only its relation ids
                const databaseRelatedEntityRelationIdMap =
                    relation.getEntityValue(subject.databaseEntity)

                // if relation ids are equal then we don't need to update anything
                const areRelatedIdsEqual = OrmUtils.compareIds(
                    relatedEntityRelationIdMap,
                    databaseRelatedEntityRelationIdMap,
                )
                if (areRelatedIdsEqual) {
                    return
                } else {
                    subject.diffRelations.push(relation)
                }
            }

            // if there is an inserted subject for the related entity of the persisted entity then use it as related entity
            // this code is used for related entities without ids to be properly inserted (and then updated if needed)
            const valueSubject = allSubjects.find(
                (subject) =>
                    subject.mustBeInserted && subject.entity === relatedEntity,
            )
            if (valueSubject) relatedEntity = valueSubject

            // find if there is already a relation to be changed
            const changeMap = subject.changeMaps.find(
                (changeMap) => changeMap.relation === relation,
            )
            if (changeMap) {
                // and update its value if it was found
                changeMap.value = relatedEntity
            } else {
                // if it wasn't found add a new relation for change
                subject.changeMaps.push({
                    relation: relation,
                    value: relatedEntity,
                })
            }
        })
    }
}