import {Inject, Injectable} from '../../di'
import {Migrator} from './Migrator'
import {DatabaseService} from '../DatabaseService'
import {FieldType} from '../types'
import {Migration} from './Migration'
import {Builder} from '../builder/Builder'

/**
 * Migrator implementation that tracks applied migrations in a database table.
 * @todo allow configuring more of this
 */
@Injectable()
export class DatabaseMigrator extends Migrator {
    @Inject()
    protected readonly db!: DatabaseService

    /** True if we've initialized the migrator. */
    protected initialized = false

    public async initialize(): Promise<void> {
        await super.initialize()

        if ( this.initialized ) {
            return
        }

        const schema = this.db.get().schema()
        if ( !(await schema.hasTable('migrations')) ) {
            const table = await schema.table('migrations')

            table.primaryKey('id', FieldType.serial).required()

            table.column('identifier')
                .type(FieldType.varchar)
                .required()

            table.column('applygroup')
                .type(FieldType.integer)
                .required()

            table.column('applydate')
                .type(FieldType.timestamp)
                .required()

            await schema.commit(table)
        }

        this.initialized = true
    }

    async has(migration: Migration): Promise<boolean> {
        return this.builder()
            .connection('default')
            .select('id')
            .from('migrations')
            .where('identifier', '=', migration.identifier)
            .exists()
    }

    async markApplied(migrations: Migration | Migration[], applyDate: Date = new Date()): Promise<void> {
        if ( !Array.isArray(migrations) ) {
            migrations = [migrations]
        }

        const applyGroup = await this.getNextGroupIdentifier()
        const rows = migrations.map(migration => {
            return {
                applygroup: applyGroup,
                applydate: applyDate,
                identifier: migration.identifier,
            }
        })

        await this.builder()
            .connection('default')
            .table('migrations')
            .insert(rows)
    }

    async unmarkApplied(migrations: Migration | Migration[]): Promise<void> {
        if ( !Array.isArray(migrations) ) {
            migrations = [migrations]
        }

        const identifiers = migrations.map(migration => migration.identifier)

        await this.builder()
            .connection('default')
            .table('migrations')
            .whereIn('identifier', identifiers)
            .delete()
    }

    async getLastApplyGroup(): Promise<string[]> {
        const applyGroup = await this.builder()
            .connection('default')
            .select('applygroup')
            .from('migrations')
            .get()
            .max<number>('applygroup')

        return this.builder()
            .connection('default')
            .select('identifier')
            .from('migrations')
            .where('applygroup', '=', applyGroup)
            .get()
            .asyncPipe()
            .tap(coll => {
                return coll.pluck<string>('identifier')
            })
            .tap(coll => {
                return coll.all()
            })
            .resolve()
    }

    /**
     * Helper method to look up the next `applygroup` that should be used.
     * @protected
     */
    protected async getNextGroupIdentifier(): Promise<number> {
        const current = await this.builder()
            .connection('default')
            .select('applygroup')
            .from('migrations')
            .get()
            .max<number>('applygroup')

        return (current ?? 0) + 1
    }

    /**
     * Given a list of migration identifiers, filter out those that have been applied.
     * @override to make this more efficient
     * @param identifiers
     * @protected
     */
    protected async filterAppliedMigrations(identifiers: string[]): Promise<string[]> {
        const existing = (await this.builder()
            .connection('default')
            .select('identifier')
            .from('migrations')
            .whereIn('identifier', identifiers)
            .get()
            .collect())
            .pluck<string>('identifier')

        return identifiers.filter(id => !existing.includes(id))
    }

    /**
     * Given a list of migration identifiers, filter out those that have not been applied.
     * @override to make this more efficient
     * @param identifiers
     * @protected
     */
    protected async filterPendingMigrations(identifiers: string[]): Promise<string[]> {
        const existing = await this.builder()
            .connection('default')
            .select('identifier')
            .from('migrations')
            .whereIn('identifier', identifiers)
            .get()
            .pluck<string>('identifier')

        return existing.all()
    }

    /**
     * Get a query builder instance.
     * @protected
     */
    protected builder(): Builder {
        return this.injector.make<Builder>(Builder)
    }
}