import { ObjectLiteral } from "../common/ObjectLiteral"
import { SaveOptions } from "../repository/SaveOptions"
import { RemoveOptions } from "../repository/RemoveOptions"
import { MustBeEntityError } from "../error/MustBeEntityError"
import { SubjectExecutor } from "./SubjectExecutor"
import { CannotDetermineEntityError } from "../error/CannotDetermineEntityError"
import { QueryRunner } from "../query-runner/QueryRunner"
import { DataSource } from "../data-source/DataSource"
import { Subject } from "./Subject"
import { OneToManySubjectBuilder } from "./subject-builder/OneToManySubjectBuilder"
import { OneToOneInverseSideSubjectBuilder } from "./subject-builder/OneToOneInverseSideSubjectBuilder"
import { ManyToManySubjectBuilder } from "./subject-builder/ManyToManySubjectBuilder"
import { SubjectDatabaseEntityLoader } from "./SubjectDatabaseEntityLoader"
import { CascadesSubjectBuilder } from "./subject-builder/CascadesSubjectBuilder"
import { OrmUtils } from "../util/OrmUtils"

/**
 * Persists a single entity or multiple entities - saves or removes them.
 */
export class EntityPersistExecutor {
    // -------------------------------------------------------------------------
    // Constructor
    // -------------------------------------------------------------------------

    constructor(
        protected connection: DataSource,
        protected queryRunner: QueryRunner | undefined,
        protected mode: "save" | "remove" | "soft-remove" | "recover",
        protected target: Function | string | undefined,
        protected entity: ObjectLiteral | ObjectLiteral[],
        protected options?: SaveOptions & RemoveOptions,
    ) {}

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

    /**
     * Executes persistence operation ob given entity or entities.
     */
    async execute(): Promise<void> {
        // check if entity we are going to save is valid and is an object
        if (!this.entity || typeof this.entity !== "object")
            return Promise.reject(new MustBeEntityError(this.mode, this.entity))

        // we MUST call "fake" resolve here to make sure all properties of lazily loaded relations are resolved
        await Promise.resolve()

        // if query runner is already defined in this class, it means this entity manager was already created for a single connection
        // if its not defined we create a new query runner - single connection where we'll execute all our operations
        const queryRunner =
            this.queryRunner || this.connection.createQueryRunner()

        // save data in the query runner - this is useful functionality to share data from outside of the world
        // with third classes - like subscribers and listener methods
        let oldQueryRunnerData = queryRunner.data
        if (this.options && this.options.data) {
            queryRunner.data = this.options.data
        }

        try {
            // collect all operate subjects
            const entities: ObjectLiteral[] = Array.isArray(this.entity)
                ? this.entity
                : [this.entity]
            const entitiesInChunks =
                this.options && this.options.chunk && this.options.chunk > 0
                    ? OrmUtils.chunk(entities, this.options.chunk)
                    : [entities]

            // console.time("building subject executors...");
            const executors = await Promise.all(
                entitiesInChunks.map(async (entities) => {
                    const subjects: Subject[] = []

                    // create subjects for all entities we received for the persistence
                    entities.forEach((entity) => {
                        const entityTarget = this.target
                            ? this.target
                            : entity.constructor
                        if (entityTarget === Object)
                            throw new CannotDetermineEntityError(this.mode)

                        let metadata = this.connection
                            .getMetadata(entityTarget)
                            .findInheritanceMetadata(entity)

                        subjects.push(
                            new Subject({
                                metadata,
                                entity: entity,
                                canBeInserted: this.mode === "save",
                                canBeUpdated: this.mode === "save",
                                mustBeRemoved: this.mode === "remove",
                                canBeSoftRemoved: this.mode === "soft-remove",
                                canBeRecovered: this.mode === "recover",
                            }),
                        )
                    })

                    // console.time("building cascades...");
                    // go through each entity with metadata and create subjects and subjects by cascades for them
                    const cascadesSubjectBuilder = new CascadesSubjectBuilder(
                        subjects,
                    )
                    subjects.forEach((subject) => {
                        // next step we build list of subjects we will operate with
                        // these subjects are subjects that we need to insert or update alongside with main persisted entity
                        cascadesSubjectBuilder.build(subject, this.mode)
                    })
                    // console.timeEnd("building cascades...");

                    // load database entities for all subjects we have
                    // next step is to load database entities for all operate subjects
                    // console.time("loading...");
                    await new SubjectDatabaseEntityLoader(
                        queryRunner,
                        subjects,
                    ).load(this.mode)
                    // console.timeEnd("loading...");

                    // console.time("other subjects...");
                    // build all related subjects and change maps
                    if (
                        this.mode === "save" ||
                        this.mode === "soft-remove" ||
                        this.mode === "recover"
                    ) {
                        new OneToManySubjectBuilder(subjects).build()
                        new OneToOneInverseSideSubjectBuilder(subjects).build()
                        new ManyToManySubjectBuilder(subjects).build()
                    } else {
                        subjects.forEach((subject) => {
                            if (subject.mustBeRemoved) {
                                new ManyToManySubjectBuilder(
                                    subjects,
                                ).buildForAllRemoval(subject)
                            }
                        })
                    }
                    // console.timeEnd("other subjects...");
                    // console.timeEnd("building subjects...");
                    // console.log("subjects", subjects);

                    // create a subject executor
                    return new SubjectExecutor(
                        queryRunner,
                        subjects,
                        this.options,
                    )
                }),
            )
            // console.timeEnd("building subject executors...");

            // make sure we have at least one executable operation before we create a transaction and proceed
            // if we don't have operations it means we don't really need to update or remove something
            const executorsWithExecutableOperations = executors.filter(
                (executor) => executor.hasExecutableOperations,
            )
            if (executorsWithExecutableOperations.length === 0) return

            // start execute queries in a transaction
            // if transaction is already opened in this query runner then we don't touch it
            // if its not opened yet then we open it here, and once we finish - we close it
            let isTransactionStartedByUs = false
            try {
                // open transaction if its not opened yet
                if (!queryRunner.isTransactionActive) {
                    if (
                        this.connection.driver.transactionSupport !== "none" &&
                        (!this.options || this.options.transaction !== false)
                    ) {
                        // start transaction until it was not explicitly disabled
                        isTransactionStartedByUs = true
                        await queryRunner.startTransaction()
                    }
                }

                // execute all persistence operations for all entities we have
                // console.time("executing subject executors...");
                for (const executor of executorsWithExecutableOperations) {
                    await executor.execute()
                }
                // console.timeEnd("executing subject executors...");

                // commit transaction if it was started by us
                // console.time("commit");
                if (isTransactionStartedByUs === true)
                    await queryRunner.commitTransaction()
                // console.timeEnd("commit");
            } catch (error) {
                // rollback transaction if it was started by us
                if (isTransactionStartedByUs) {
                    try {
                        await queryRunner.rollbackTransaction()
                    } catch (rollbackError) {}
                }
                throw error
            }
        } finally {
            queryRunner.data = oldQueryRunnerData

            // release query runner only if its created by us
            if (!this.queryRunner) await queryRunner.release()
        }
    }
}