import {Relation, RelationNotLoadedError} from './Relation'
import {TreeModel} from '../TreeModel'
import {RelationBuilder} from './RelationBuilder'
import {raw} from '../../dialect/SQLDialect'
import {AbstractBuilder} from '../../builder/AbstractBuilder'
import {ModelBuilder} from '../ModelBuilder'
import {Collection, Maybe} from '../../../util'

export class HasTreeParent<T extends TreeModel<T>> extends Relation<T, T, Maybe<T>> {

    protected parentInstance?: T

    protected loaded = false

    protected constructor(
        protected model: T,
        protected readonly leftTreeField: string,
        protected readonly parentIdField: string,
    ) {
        super(model, model)
    }

    protected get parentValue(): any {
        return this.model.key()
    }

    public query(): RelationBuilder<T> {
        return this.builder()
            .tap(b => this.model.applyScopes(b))
            .select(raw('*'))
            .orderByAscending(this.leftTreeField)
    }

    public applyScope(where: AbstractBuilder<T>): void {
        const parentId = this.model.parentId()
        if ( !parentId ) {
            where.whereMatchNone()
            return
        }

        where.where(this.parentIdField, '=', parentId)
    }

    public buildEagerQuery(parentQuery: ModelBuilder<T>, result: Collection<T>): ModelBuilder<T> {
        const parentIds = result.map(model => model.parentId()).whereDefined()
        return this.model.query()
            .without('subtree')
            .whereIn(this.parentIdField, parentIds)
    }

    public matchResults(possiblyRelated: Collection<T>): Collection<T> {
        return possiblyRelated.filter(related => related.key() === this.model.parentId())
    }

    public setValue(related: Maybe<T>): void {
        this.loaded = true
        this.parentInstance = related
    }

    public getValue(): Maybe<T> {
        if ( !this.loaded && this.model.parentId() ) {
            throw new RelationNotLoadedError()
        }

        return this.parentInstance
    }

    public isLoaded(): boolean {
        return this.loaded || !this.model.parentId()
    }

    public async get(): Promise<Maybe<T>> {
        return this.fetch().first()
    }
}